CN105845018A - Highway tunnel ventilation system simulation platform building method and highway tunnel ventilation system simulation platform - Google Patents

Abstract

The invention discloses a method for constructing a simulation platform of a highway tunnel ventilation system. The steps of the method include determining the geometric similarity ratio, the kinematic similarity ratio and the dynamic similarity ratio S1 of the tunnel prototype p and the simulation model m based on the flow similarity principle. The simulation goal is to set the initial condition S2 of the tunnel prototype ventilation system, establish the similarity boundary condition S3 of the simulation platform based on steps S1 and S2, analyze the simulation platform and the tunnel prototype based on the critical Reynolds number, and build the simulation platform S4. The invention further discloses a simulation platform for a highway tunnel ventilation system. The technical scheme of the invention solves the problem that the current road tunnel ventilation physical model platform does not have universality and versatility, and at the same time, the expandable function can effectively carry out the road tunnel fire physical model test under the above ventilation mode.

Description

A simulation platform construction method and simulation platform for a highway tunnel ventilation system

technical field

The invention relates to the simulation application of highway tunnels, in particular to a method for constructing a simulation platform and a simulation platform for a single inclined shaft ventilation system of a large-section and extra-long highway tunnel.

Background technique

The Fenshuiling Tunnel of Zhangzhuo Expressway is a separated two-way six-lane extra-long mountain road tunnel. The pile number K46+618～K53+416 on the right line of the tunnel has a total length of 6798 meters. The pile number ZK46+539.29～ZK53+430 on the left line of the tunnel has a total length of 6890.71 meters. The longitudinal sections of the left and right lines are designed such that the slope/length of the left line is -3.12%/30.71m and 1.5%/6890.71m, and the slope/length of the right line is -1.5%/6789m. The left line of the tunnel uses the construction inclined shaft as a ventilation shaft, and the vertical ventilation of the ventilation shaft is adopted; the right line uses a pure jet fan for longitudinal ventilation, as shown in Figures 7-1 to 7-3.

Since the left and right lines of the Watershed Tunnel are close to 7000m, the tunnel mileage is long, and the traffic conditions vary greatly before and after. In addition, there is not much experience in the operation and ventilation of super-long highway tunnels in my country, especially the research on multi-unit supply and discharge longitudinal ventilation is still lacking. Therefore, it is very necessary to carry out model test research work on the operation ventilation and fire protection system around the project. Carry out model test research on the operation ventilation technology and ventilation and fire protection of Fenshuiling Tunnel on Zhangzhuo Expressway. By studying the ventilation conditions at different positions and different wind speeds, the flow field velocity in the tunnel and the diffusion range of smoke temperature, different fire locations and different wind speeds are simulated at the same time. Based on the temperature field, smoke flow concentration distribution and spread range in the lower tunnel, a reasonable ventilation configuration scheme for the Watershed Tunnel is proposed.

Compared with the numerical calculation and simulation of highway tunnel ventilation and fire protection, there are few researches on physical model tests of tunnel ventilation and fire protection. Although numerical calculation and simulation have made great progress, they are still insufficient to replace physical model tests. In addition, numerical calculation and simulation still require physical model tests and field tests to provide basic calculation parameters and verify the analysis results.

Therefore, it is necessary to provide a simulation platform construction method and simulation platform for a single inclined shaft ventilation system of a large cross-section extra-long highway tunnel with stronger versatility and better simulation effects.

Contents of the invention

The technical problem to be solved by the present invention is to provide a simulation platform construction method and a simulation platform for a single inclined shaft ventilation system of a large-section and extra-long highway tunnel, so as to solve the problem that the simulation of highway tunnels in the prior art does not have universality and Versatility, the problem that it is impossible to accurately simulate the situation of the actual road tunnel.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A method for constructing a simulation platform of a highway tunnel ventilation system, the steps of the method comprising

Step S1, based on the flow similarity principle, determine the geometric similarity ratio, kinematic similarity ratio and dynamic similarity ratio between the tunnel prototype p and the simulation model m;

Step S2, based on the simulation target, setting the initial conditions of the tunnel prototype ventilation system;

Step S3, based on step S1 and step S2, establish the similarity boundary condition of the simulation platform;

Step S4, analyzing the simulation platform and the tunnel prototype based on the critical Reynolds number, and constructing the simulation platform.

Preferably, said step S1 includes

S11. Express the infinite ratio between the tunnel prototype p and the simulation model m as C _q , that is, the scale $C_q=\frac{q_p}{q_m};$

S12. Establish a geometric similarity scale between the tunnel prototype p and the simulation model m, the geometric similarity scale includes a length l scale: Sectional area A scale: Volume V scale: Among them, l is a certain linear length in the tunnel prototype;

S13. Establish a motion similarity scale between the tunnel prototype p and the simulation model m, and the motion similarity scale includes a motion pixel u scale: Time t scale: Acceleration a scale: $C_a=\frac{a_p}{a_m}=\frac{C_u}{C_t}=\frac{C_u^2}{C_l};$

S14. Establish the scales of the force F with the same name at the corresponding points of the tunnel prototype p and the simulation model m, and the scales of the forces satisfying the same physical properties at the corresponding points of the tunnel prototype p and the simulation model m are all the same.

Preferably, the homonymous force F includes gravity F _G , viscous force F _μ , pressure F _p , elastic force F _E , surface tension F _T ,

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Im</span>}}}<span\; class="notranslate">\; .</span>$

Preferably, the initial conditions in step S2 include

1) The fluid is incompressible;

2) The fluid is isothermal flow, and the fluid density and viscosity are fixed values;

3) The fluid flow is a steady flow, that is, during the fluid flow process, the pressure and flow velocity at any point do not change with time, that is, the pressure and flow velocity are only functions of point coordinates;

4) The fluid is a continuous medium;

5) Fluid flow obeys the law of energy conservation.

Preferably, during the simulation process, it is ensured that the tunnel prototype and the simulation platform are in the same self-modeling area.

A simulation platform for the ventilation system of a highway tunnel, the simulation platform includes a shaft air supply section, a shaft exhaust section, a combustion section, a standard section and a jet section that can be disassembled/joined in proportion to the actual tunnel;

The air supply section of the shaft, the exhaust section of the shaft, the combustion section and the standard section are plexiglass pipes filled with cement mortar in 3.19% of the lower half of the interior space;

An air supply shaft and an air exhaust shaft are respectively provided on the air supply section of the shaft and the air exhaust section of the shaft, and the air intake shaft and the air exhaust shaft form an air supply and exhaust system of an air flow channel;

Adhesive tapes are arranged every 1 meter on the inner walls of the shaft air supply section, shaft exhaust section and standard section in the axial direction; the combustion section is sequentially pasted with flexible asbestos boards on the inner wall of the pipeline that has not been filled with cement mortar and thin iron sheets;

The combustion section, the shaft air supply section and the shaft exhaust section are all 0.5 meters long; the standard sections include three standard sections of 0.5m, 1m and 2m in length;

The length of the jet flow section is 2m, and fans are arranged on it and placed at both ends of the simulation platform.

Preferably, there are 24 cross-sections for measuring the simulation environment parameters inside the simulation platform at the non-combustion section of the simulation platform lapped by the simulated working conditions; the simulation environment parameters include fluid flow rate, pressure, CO concentration and temperature .

Preferably, the total length of the platform is 15m, the geometric ratio of the transverse section is 1:50, and the geometric ratio of the axial direction is 1:100;

The adhesive tape is stuck on the inner wall of the plexiglass pipeline filled with non-cement mortar along the axial direction every 1m in a circumferential direction, and the width of the adhesive tape is 3-6cm.

Preferably, the 24 measurement sections include

5 velocity and pressure measurement sections, which are equipped with total pressure gauges 3;

2 CO concentration measurement sections, which are equipped with CO gas detection and alarm devices;

There are 17 temperature measurement sections, and 32 temperature measurement points are set in the 17 sections, among which, 17 measurement points are set at the vault of the plexiglass pipeline 1 upstream and downstream of the fire source, and 15 measurement points are fixed at the fire source At different heights in the middle of the upstream and downstream tunnels.

Preferably, the 15 measurement points are fixed in 3 of the 17 temperature measurement sections by using 3 thermocouple trees.

The beneficial effects of the present invention are as follows:

The technical solution described in the present invention adopts a general-purpose test platform developed with an advanced combined design concept. The platform can carry out pure jet flow, centralized feeding, Tunnel ventilation model tests of multiple longitudinal ventilation methods such as shaft pressure, shaft suction, and shaft delivery and discharge. In addition, through the movable combustion section set in the model tunnel, tunnel fire tests at different positions and different heat release rates can be carried out, which solves the problem of The current road tunnel ventilation physical model platform does not have the problem of universality and versatility, and at the same time, the scalable function can effectively carry out the road tunnel fire physical model test under the above ventilation mode.

Description of drawings

Below in conjunction with accompanying drawing, specific embodiment of the present invention is described in further detail;

Fig. 1 shows the schematic diagram of simulation platform construction method of the present invention;

Fig. 2 shows the schematic diagram of the overall structure principle of the simulation platform of the present invention;

Fig. 3 shows the outline diagram of the simulation platform of the present invention;

Fig. 4 shows the profile diagram of simulation platform of the present invention;

Fig. 5 shows the axial sectional sketch of simulation platform of the present invention

Fig. 6 shows the layout schematic diagram of thermocouple tree of the present invention;

Fig. 7 shows the schematic diagram of Zhangzhuo Expressway Watershed Tunnel;

Fig. 8 shows an overlapping example of the simulation platform of the present invention.

1. Plexiglass pipeline, 2. Cement mortar filling, 3. Total pressure gauge, 4. Air supply well, 5. Exhaust well, 6. Air supply well, 7. Combustion section, 8. Cement mortar filling and organic Glass pipe crossing line, 9. CO sensor straw and thermocouple tree, 10. Flexible asbestos board + thin iron protective layer, 11. Fire source, 12. Thermocouple tree, 13. Shaft air supply section, 14. Shaft exhaust section , 15, standard section, 16, jet section.

detailed description

In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

As shown in Figure 1, the present invention discloses a method for constructing a simulation platform for a single inclined shaft ventilation system of a large cross-section and extra-long highway tunnel. The method utilizes the principle of flow similarity to obtain physical quantities with the same name on two flow corresponding points, For example, linear length, velocity, pressure, various pressures, etc., should have their own proportional relationship, satisfying the geometric similarity, motion similarity and dynamic similarity of two flows, as well as the similarity of initial conditions and boundary conditions. The steps of the method include

Step S1, based on the principle of flow similarity, determine the geometric similarity ratio, kinematic similarity ratio and dynamic similarity ratio between the tunnel prototype p and the simulation model m; the step S1 includes

S11. Express the infinite ratio between the tunnel prototype p and the simulation model m as C _q , that is, the scale $C_q=\frac{q_p}{q_m};$

S12. Establish a geometric similarity scale between the tunnel prototype p and the simulation model m, the geometric similarity scale includes a length l scale: Sectional area A scale: Volume V scale: Among them, l is a certain linear length in the tunnel prototype;

S13. Establish a motion similarity scale between the tunnel prototype p and the simulation model m, and the motion similarity scale includes a motion pixel u scale: Time t scale: Acceleration a scale: $C_a=\frac{a_p}{a_m}=\frac{C_u}{C_t}=\frac{C_u^2}{C_l};$

S14. Establish the scales of the force F with the same name at the corresponding points of the tunnel prototype p and the simulation model m, and the scales of the forces satisfying the same physical properties at the corresponding points of the tunnel prototype p and the simulation model m are all the same.

Preferably, the homonymous force F includes gravity F _G , viscous force F _μ , pressure F _p , elastic force F _E , surface tension F _T ,

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Im</span>}}}<span\; class="notranslate">\; .</span>$

Step S2, based on the simulation target, set the initial conditions of the tunnel prototype ventilation system; the initial conditions in step S2 include

1) The fluid is incompressible;

2) The fluid is isothermal flow, and the fluid density and viscosity are fixed values;

3) The fluid flow is a steady flow, that is, during the fluid flow process, the pressure and flow velocity at any point do not change with time, that is, the pressure and flow velocity are only functions of point coordinates;

4) The fluid is a continuous medium;

5) Fluid flow obeys the law of energy conservation.

5. The method for constructing a simulation platform according to claim 1, characterized in that, during the simulation process, it is ensured that the tunnel prototype and the simulation platform are in the same self-modeling area.

Step S3, based on step S1 and step S2, establish the similarity boundary condition of the simulation platform;

Step S4, analyzing the simulation platform and the tunnel prototype based on the critical Reynolds number, and constructing the simulation platform.

The specific analysis is as follows:

1. Flow similarity

Define C _q to represent the ratio of the physical quantity q corresponding to the prototype and the model, which is called the scale, namely:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

1), geometric similarity

There is a fixed proportional relationship between the linear variables of the two flows, that is, the ratio of the corresponding linear lengths of the prototype and the model is equal, then the two flows are geometrically similar.

To express a certain linear length, there is a length scale:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

From this, the scale and volume scale of the cross-sectional area of the tunnel prototype and the model tunnel can be deduced, respectively:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; V</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

After the geometric similarity ratio is selected, the cross-sectional area and volume of the model tunnel can be determined according to the cross-sectional area of the tunnel prototype.

2), movement is similar

Motion pixels mean that the velocity of the fluid (wind flow and smoke flow) is similar. That is to say, the size of each corresponding point of the two flows is a fixed ratio C _u .

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Flow is the derivative dl/dt of displacement with respect to time t, and the time scale is:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Similarly, under the condition of similar motion, the acceleration scale of the corresponding fluid particle in the wind flow field is:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

3), the power is similar

The direction of the force F of the same name on the fluid particles at the corresponding points of the two flows is the same, and the ratio of their magnitudes is a fixed scale C _F , then the two flows are said to be dynamically similar. Homonymous forces are forces that have the same physical properties. There are mainly gravity F _G , viscous force F _μ , pressure F _p , elastic force F _E , surface tension F _T , inertial force F _I and so on.

If the resultant force acting on the fluid particle is not equal to zero, according to Newton’s second law, the fluid particle produces a velocity, and according to D’Alembert’s theorem in theoretical mechanics, if the inertial force of the fluid particle is introduced, then the inertial force and the forces on the particle are in balance, the form In this way, the dynamic similarity can be characterized as the similarity of the closing force polygons of the corresponding particles of two similar flows. Assuming that the two flows are similar in flow, and the forces acting on any particle on the fluid include gravity F _G , viscous force F _μ , pressure F _p , elastic force F _E , surface tension F _T , inertial force F _I , etc., then the dynamics of the two flows are similar The following formula is required to be established:

$\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Im</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

In the formula, the subscripts p and m represent the prototype and the model, respectively.

If the two flows are similar, the physical quantities of the same name (such as linear length, velocity, pressure, various forces, etc.) at the corresponding points of the two flows should have a proportional relationship, and the geometric similarity, motion similarity and dynamic similarity of the two flows should be satisfied, as well as the initial conditions. Similar to the boundary conditions. Geometric similarity is the premise and basis of motion similarity and dynamic similarity, dynamic similarity is the dominant factor determining the similarity of two flows, and motion similarity is the performance of geometric similarity and dynamic similarity. Therefore, under the premise of geometric similarity, to ensure the similarity of flow, it mainly depends on the similarity of dynamics.

2. Initial conditions of tunnel prototype ventilation system

In the simulation model test design, according to the nature of the phenomenon under study, it is necessary to grasp the decisive factors affecting the overall situation, and take the factors that are in a secondary position and do not affect the overall situation as similar guarantees or ignore them, so that the model design results No large error occurs. For the road tunnel ventilation simulation model test, most of the similar conditions may not be the main factors, so the following assumptions are made:

(1) The fluid is incompressible

(2) The fluid is isothermal flow, and the fluid density and viscosity are fixed values.

(3) The fluid flow is a steady flow

In the process of fluid flow, the pressure and flow velocity at any point do not change with time, that is, the pressure and flow velocity are only functions of point coordinates.

(4) The fluid is a continuous medium

(5) Fluid flow obeys the law of energy conservation

When the incompressible steady flow fluid flows gradually in the pipeline, the changes of its pressure and velocity along each section of the process (including friction loss) obey the law of energy conservation, which is called Bernoulli's theorem, and it is expressed as the Bernoulli equation .

3. Selection of similarity criteria, similarity boundary conditions

Through the above assumptions, highway tunnel ventilation can be idealized as an incompressible fluid with constant viscosity moving under pressure in a gravity field. The dynamic similarity condition of two flow systems can be derived from the Navier-Stokes equation in dimensionless form, as shown in the following formula:

$\left\{\begin{array}{c}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}\\ \frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Fr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>\\ \frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; Fr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>\\ \frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; Fr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

The above formula does not lead to additional similar conditions.

If the dimensionless coefficients of two geometrically similar systems have the same value, then Equation (9) will give the same solution for the two systems. Therefore, it is generally required that the two systems have The same Froude number (Fr) and Reynolds number (Re).

In the equation of motion, the change in pressure is the combined result of the dynamic effects of acceleration, viscosity, and gravity. For an isopycnic fluid in a closed system, the action of gravity simply causes an excess static pressure distribution, superimposed on the variable pressure caused by other forces. A closed system is defined as a system in which the fluid is completely surrounded by fixed boundaries or a system in which the fluid range can be considered infinite. The former may be a closed pipe, and the latter may be the low-speed motion of an object immersed in gas. The highway tunnel ventilation belongs to immersion and low-speed motion in the gas. For a flow in a closed system, if the motion suddenly turns to rest, the pressure should be distributed according to the laws of hydrostatics. At this point, the pressure can be expressed as the sum of two parts:

p=p _d +p _s (10)

Among them, p _s is determined by hydrostatics (p _s +γh) = constant, and p _d is the part that embodies the "dynamic effect". Constant values are only relevant for datum selection. Substitute formula (10) into the Navier-Stokes equation, eliminate the gravity term, and convert the pressure term into Then formula (9) can be rewritten as:

$\left\{\begin{array}{c}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}\\ \frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>\\ \frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>\\ \frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; \&part;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&part;</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

The above formula shows that in order to make the incompressible fluid dynamics similar in two geometrically similar closed systems, only the Reynolds numbers of the two systems need to be the same. Unique sizing criterion for similar airflow within the model.

For incompressible fluids in geometrically similar closed systems, all the conditions of similarity can be satisfied as long as the Reynolds numbers of the two systems are the same. For the road tunnel ventilation simulation model test, the fluid medium of the two systems is air, and the temperature difference between the two systems is small, which has little influence on the test results. Therefore, the temperature difference between the two systems is ignored, and the temperature of the two systems is considered to be equal, that is:

ρ _p = ρ _m = ρ (12)

μ _p = μ _m = μ (13)

Let the Reynolds numbers of the model and prototype systems be equal:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Substitute formula (12) and formula (13) into the above formula to get:

v _0p L _p =v _0m L _m (15)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; m</span>}}}{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

The subscripts p and m in the formula represent prototype and model respectively.

From formula (16), if the Reynolds coefficients of the model and the prototype are equal, the speed ratio between the model and the prototype is the reciprocal of the length ratio of the model prototype. When the model is n times smaller than the prototype, the wind speed in the model is n times that of the prototype. When the Reynolds coefficient in the prototype is large, it is very difficult to achieve the same Reynolds coefficient in the model. In the case of high Reynolds number, the flow velocity of the model reaches a very objective value, and it is difficult for the fan in the laboratory to achieve this flow velocity. Even if the fan power is increased to meet the flow velocity requirement, the fluid compressibility may have reached a non-negligible level at this time. In order to make the prototype and model similar simulation proceed smoothly, the method of approximate modeling is usually adopted. According to the results of the fluid flow test carried out by Nicholas in 1933 on artificial pipes (six kinds of relative roughness) coated with different sand particles on the inner wall of the pipe, it is shown that the viscous fluid has self-modeling properties. When the Reynolds number Re is large enough to a certain extent When the Reynolds number Re of the prototype is within the self-modeling area, the similar resistance does not require the Reynolds number Re to be equal, then the model Reynolds number Re does not have to be equal to the prototype Reynolds number Re, that is, the Reynolds number Re has nothing to do with the flow characteristic. "Self-Modeling State". In this area, since the drag coefficient is not affected by the Reynolds number Re, the model Reynolds number Re does not have to be equal to the Reynolds number Re, as long as it is in the same self-modeling area as the prototype, the flow can be automatically guaranteed to be similar.

For viscous fluid flow, according to the value of its critical Reynolds number Re, it is divided into the first self-modeling area and the second self-modeling area. When the viscous fluid flows, the range where the Reynolds number Re is greater than the first critical value is called the first self-mode region. When the viscous fluid flows, when the Reynolds number Re is greater than the second critical value, the fluid velocity distribution and flow state no longer change, and are similar to each other, independent of the Reynolds number Re, which is called the second self-modulus region. When the Reynolds number Re of the prototype is in the self-modeling area during the test, as long as the model and the prototype are in the same self-modeling area, there is no need to require the Reynolds number Re of the model and the prototype to be equal, which can greatly reduce the power of the fan, reduce the cost of the model and meet the Similar requirements bring convenience to the study of road tunnel ventilation simulation model tests.

As shown in Figure 2, the present invention further discloses a simulation platform for a single inclined shaft ventilation system of a large-section and extra-long highway tunnel. Section 13, shaft exhaust section 14, combustion section 7, standard section 15 and jet section 16; the shaft air supply section 13, shaft exhaust section 14, combustion section 7 and standard section 15 are all 3.19% of the lower part of the inner space 1% of the space is filled with plexiglass pipes with cement mortar. The air supply section 13 of the shaft and the exhaust section 14 of the shaft are respectively provided with an air supply shaft 4 and an air exhaust shaft 5, and the standard section 15 is symmetrically arranged on the air supply section 13 of the shaft with the air supply shaft 4 and has an exhaust shaft. The short track section center of the vertical shaft exhaust section 14 of well 5, that is, the whole model is symmetrical to the short track center, wherein the short track center is the center of the tunnel section between the air supply shaft 4 and the exhaust shaft 5; 4 and the exhaust shaft 5 form the air supply and exhaust system of the air passage. The jet section 16 is arranged at both ends of the model, on which fans are installed. Along the shaft air supply section 13, shaft exhaust section 14 and standard section 7, adhesive tapes are arranged every 1 meter on the inner wall in the axial direction, and are pasted on the inner wall of the plexiglass pipeline filled with non-cement mortar for a week , the width of the tape is 3-6cm, the sticky surface of the tape faces the air supply channel of the plexiglass pipe, away from the inner wall of the plexiglass pipe, the purpose of setting the tape is to roughen the surface of the tunnel, so that the resistance of the model along the way The coefficient increases to 0.025, which is consistent with the resistance coefficient along the tunnel prototype; the preferred tape width in this scheme is 4cm. In the combustion section 7, flexible asbestos boards and thin iron sheets are sequentially pasted on the inner wall of the plexiglass glass pipe not filled with cement mortar, so as to avoid high-temperature deformation of the plexiglass glass in the combustion section 7. In this solution, the inner wall of the combustion section 7 does not need to be taped, and the flexible asbestos board and the thin iron sheet are arranged along the entire axial length of the combustion section, with the asbestos board on top and the thin iron sheet on the bottom. The combustion section 7, the shaft air supply section 13 and the shaft exhaust section 14 are all 0.5 meters long; the standard section 15 includes three splicable sections of 0.5m, 1m and 2m; the jet section 16 The length is 2m, and fans are arranged on it and placed at both ends of the simulation platform to meet the splicing of the tunnel model and form the air supply source. In this scheme, the positions of the shaft air supply section 13 and the shaft exhaust section 14 in the model platform are determined according to the ratio of the simulation platform to the actual tunnel, and the shaft air supply section 13 and the shaft exhaust section 14 are located according to the ratio of the actual tunnel size. The corresponding air supply shaft 4 and exhaust shaft 5 are designed on the upper processing. The length of the plexiglass pipe 1 is 15m, the geometric ratio of the transverse section is 1:50, and the geometric ratio of the axial direction is 1:100. As shown in Figure 8, in this scheme, according to the actual fire conditions to be imitated, the combustion section 7 can be flexibly assembled with the shaft air supply section 13, the shaft exhaust section 14 and the standard section 15 to form a new fire at the required position. When there is no need to imitate the fire conditions, the position of the combustion section 7 can be replaced by the standard section 15, so that the simulation platform can form a tunnel simulation platform in a normal ventilation state. The present invention adopts a circular oil pan as a test fire source, and each test controls the fire scale by increasing or decreasing 93# gasoline. The black dots in the figure are thermocouple test points, and the rectangular squares in the figure are CO test points and CO sensors are arranged.

On the plexiglass pipeline 1 of the non-combustion section of the simulation platform of the present invention, 24 measuring sections are arranged along the longitudinal non-cement mortar filling place, wherein, 5 sections utilize the total pressure gauge 3 to measure speed and pressure, and these The total pressure gauge 3 is located in the center of the tunnel 0.5m, 3.0m, 5.5m downstream of the fire source and 2.5m, 5m upstream respectively, and the height from the tunnel floor is 5cm; two CO concentration monitoring points are respectively arranged at 15cm downstream and 5cm downstream of the fire source. 30cm in the center of the tunnel, 3.6cm from the tunnel floor; 32 temperature monitoring points are distributed on 17 measurement sections, 17 of which are arranged on the vault above and downstream of the fire source, that is, 17 measurement points along the vault For the measurement sections, 15 are arranged at different heights in the middle of the tunnel above and downstream of the fire source, and are arranged in three galvanic couple trees. The 3 measurement sections belong to the 17 measurement sections.

The present invention selects the JCYB-2000A total pressure meter 3 (intelligent pressure anemometer and air volume meter) produced by Shanghai Renault Instrument Technology Co., Ltd. to match the Pitot tube test bench plexiglass pipe 1 internal flow field wind speed and pressure, and the design is very delicate, inside the physical model The influence of the layout on the internal flow field of the physical similarity test system is negligible, and the test instrument can be used normally in an environment with a high temperature below 800 degrees Celsius, thus ensuring normal readings during the fire test; , choose the GT901 series intelligent gas detection and alarm instrument (CO) produced by Shenzhen Kernuo Electronic Technology Co., Ltd. to test the CO concentration of the flue gas flow inside the plexiglass pipe 1; Set scales at equal intervals to measure the height of the smoke layer, and set up a special person to record the fire smoke diffusion with a camera every 30s; select a section upstream of the fire source in the left (right) line model tunnel, and two sections downstream, specially made Three thermocouple trees measure the vertical distribution of the temperature of the hot smoke layer. Each thermocouple tree is equipped with different numbers of thermocouple probes, and the distance between the probes is 0.03m or 0.05m. They are all bonded and fixed on a measuring rod with a diameter of 2mm by using high-temperature-resistant tinfoil tape. The measuring rod is vertically fixed on the model tunnel invert through a small hole prefabricated in the vault. The diameter of the thermocouple is

2mm, 15mm in length, using a special wire with a high temperature resistance of 400 degrees Celsius; a certain number of thermocouples are arranged at a certain distance from the fire source on the vault of the model tunnel to measure the temperature, as shown in Figure 6, the ports of each thermocouple Connect with the 16-way temperature inspection collector, and collect the temperature of each point through the inspection collector.

In this simulation model test bench, one fan is arranged in the air supply shaft 4, the exhaust shaft 5 of the inclined shaft, and the jet section 16 of the entrance and exit of the tunnel, and each fan is equipped with the same power fan produced by Nanjing Oulu Electric Transmission Co., Ltd. The EV500 magnetic flux vector inverter is used to realize the precise control of the air volume and air pressure of the four fans, and achieve a high degree of similarity between the power and movement of the model and the prototype.

The present invention will be further described below by a group of embodiment:

Taking the watershed extra-long highway tunnel ventilation system and fire protection as the selection ratio of the scene in this embodiment is shown in Table 1:

Table 1 The similarity ratio of each physical quantity of the tunnel simulation model test system

A total of 24 measurement sections are arranged longitudinally on the simulation platform, of which 5 sections are measured by using the total pressure gauge 3 for speed measurement and pressure measurement (located at 0.5m, 3.0m, 5.5m downstream of the fire source and 2.5m, 5m upstream of the tunnel respectively). At the center of the tunnel, the height from the tunnel floor is 5cm), two CO concentration monitoring points (arranged in the middle of the tunnel at 15cm and 30cm downstream of the fire source respectively, and the height from the tunnel floor is 3.6cm), 32 temperature monitoring points are distributed in 17 17 measurement sections, 17 of which are arranged on the vault above and downstream of the fire source (that is, 17 measurement sections along the vault), and 15 are arranged at different heights in the middle of the tunnel above and downstream of the fire source (divided into Three galvanic tree layouts, 3 measurement sections belong to 17 measurement sections). In addition, in order to ensure that the resistance loss coefficient along the physical simulation platform is the same as that of the prototype, the inner surface of the plexiglass pipe 1 is roughened at equal intervals of 1 meter along the longitudinal direction of the tunnel. The dimensions of the tunnel body of the prototype and simulation platforms are shown in Table 2.

Table 2 The main geometric dimensions of the watershed tunnel prototype and simulation platform

The test instrument system is mainly composed of JCYB-2000A total pressure gauge 3 (intelligent pressure anemometer), GT901 series intelligent gas detection and alarm instrument (carbon monoxide), thermocouple and XMD-100 temperature monitoring and inspection instrument, etc. Applicable test instruments for ventilation and fire simulation platform research.

(1) JCYB-2000A full pressure gauge 3

The internal flow field wind speed and pressure test instrument of the tunnel ventilation physics and fire physics simulation platform selects the JCYB-2000A total pressure gauge 3 (intelligent pressure anemometer) produced by Shanghai Renault Instrument Technology Co., Ltd. The measuring instrument is suitable for the measurement of positive pressure, negative pressure and differential pressure of air velocity and volume of gas. It is an ideal instrument for various environmental monitoring stations, laboratories, medicine and health, building air conditioning, heating, ventilation, clean room testing or calibration pressure. Pitot tube can directly measure gas flow velocity and air volume. What needs to be emphasized is that the diameter of the JCYB-2000A total pressure gauge 3 supporting pitot tube produced by the company is only 6mm, which is very small. When it is arranged inside the simulation platform, the influence on the internal flow field of the physical similarity test system can be ignored. The test instrument can be used normally in the environment with a high temperature below 800 degrees Celsius, thus ensuring that it can also be used normally in the fire condition test.

(2) GT901 series intelligent gas detection alarm (carbon monoxide CO)

The concentration of carbon monoxide in the flue gas flow inside the physical simulation platform is selected from Shenzhen Kernuo Electronic Technology Co., Ltd.

GT901 series intelligent gas detection alarm (carbon monoxide) test produced by Co., Ltd. The alarm is an intrinsically safe device that continuously detects the concentration of carbon monoxide in the surrounding air. The instrument adopts carbon monoxide sensor and microcontroller technology imported from world-renowned sensor manufacturers , fast response, high measurement accuracy, good stability and repeatability, the performance of the whole machine is at the leading level in the industry, various parameters can be customized by the user, and the operation is simple. Internal use of large-capacity Ni-MH rechargeable lithium battery, super long standby time; SMD packaging, reliable and beautiful; digital LCD backlight LCD screen display, clear and intuitive; with secondary sound and light alarm function, the preset alarm concentration can be timely and accurately , Intuitive alarm prompt; the appearance of the instrument is made of special high-strength ABS engineering plastics, with fashionable appearance design, beautiful appearance, good hand feeling and durability. The instrument has the function of restoring factory default settings, which is easy to use and maintain, and greatly meets the requirements for high reliability of equipment in industrial field and indoor experiment safety monitoring. GT901 series intelligent gas detector (CO) has a built-in powerful suction pump that can be turned on and off, and is equipped with connecting hoses, probes and condenser tubes (for measuring high-temperature gases).

(3) Measurement of fire smoke diffusion velocity and smoke layer thickness

To measure the height of the smoke layer, set a scale at a key or concerned position. After the fire occurs, use a camera to record the spread of the fire smoke, and at the same time set up a special person to visually record the fire according to the set mark every 30s. The spread of smoke.

(4) Temperature test system

In the fire test, three thermocouple trees were specially made in the vertical distribution test for measuring the temperature of the hot smoke layer, that is, three sections in the tunnel were selected for measurement, one section was set up upstream of the fire source, and one section was set up downstream of the fire source.

Two sections. Because the scale of the fire in this test is small and the scope of the impact on the tunnel is limited, the change of the temperature field around the fire source is mainly studied in the test, and the three selected measurement sections are all near the fire source. Each thermocouple tree is equipped with different numbers of thermocouple probes, and the distance between the probes is 0.03m or 0.05m according to the position of the section from the fire source. Each thermocouple is bonded with high temperature resistant tinfoil tape except for the position of the probe. It is fixed on an iron bar with a diameter of 2mm, and the iron bar passes through the small hole prefabricated in the tunnel vault and is vertically fixed on the tunnel invert. All the thermocouples in the test are specially made by the manufacturer. The diameter of the thermocouple is 2mm and the length is 15mm. In addition, in order to prevent the high temperature from causing adverse effects on the thermocouple wires during the test, which will affect the temperature data collection, special wires with a high temperature resistance of 400 degrees Celsius are used. In order to study the distribution of temperature along the longitudinal direction of the tunnel under fire conditions, a certain number of thermocouples are arranged at a certain distance from the fire source on the tunnel vault to measure the temperature, so as to study the distribution of temperature. In the test, the port of each thermocouple is connected with 16 inspection collectors, and the temperature of each point is collected by the inspection collector.

(5) Power system

A total of 4 fans are installed in the physical simulation test system, and the vertical shaft air supply shaft 4, the vertical shaft exhaust shaft 5, and the exit and entrance of the tunnel model are respectively arranged as axial flow fans, exhaust fans and jet fans. In the test system, two main fans arranged at both ends of the tunnel simulation platform are used to simulate the boosting effect of the jet fans arranged at the exit and entrance of the tunnel. The speed of these two fans can be adjusted after the frequency conversion transformation, so the simulation of the number of start-up groups of the same jet fan can be realized. In addition, in order to study the distribution of wind pressure, wind speed, temperature field and smoke flow field in the tunnel simulation platform under different working conditions, as well as the flow field of the short section, it is also necessary to transform the frequency conversion of the fan for the simulation shaft air supply and exhaust. In order to accurately control the air volume and air pressure of the four fans, each of them is equipped with the same power EV500 flux vector inverter produced by Nanjing Oulu Electric Transmission Co., Ltd. The frequency adjustment of the inverter can be accurate to two decimal places.

(6) Combustion section 7 and fire source setting

This test platform adopts the design concept of assembly and assembly, that is, the combustion section 7 simulating the fire source in the tunnel can be placed at any position in the entire simulation platform to form a new working condition. According to the heat released by the fire source in the previous test, the top of section 1 of the plexiglass pipe can be thermally deformed. Therefore, the combustion section 7 needs to be protected during the test. The protective layer is made of flexible asbestos board and thin iron sheet after several exploratory tests. A circular oil pan was used as the test fire source, and 6 ml of 93# gasoline was added to each test.

According to the requirements of the shape and lining characteristics of the watershed super-long highway tunnel, a watershed tunnel simulation platform with a reduced scale of 1:50 is established. The platform is composed of one segment of organic glass pipes with different functions. It can be divided into the following four categories, namely the standard ventilation section, the jet fan equivalent pressure boost section, the shaft air supply function section, the shaft exhaust air function section, and the combustion section7. When simulating the joint action of the vertical shaft and the jet fan, when the tunnel is in normal operation, ventilation and fire conditions, the plexiglass pipe with the above three functions is used to form a tunnel ventilation and fire simulation platform. When simulating the left line, the ventilation function of the shaft is simultaneously Enabled, when simulating the right line, the shaft air supply and exhaust function section will not be enabled. In order to facilitate the observation of the smoke spread, the tunnel simulation platform mainly adopts a plexiglass pipe to simulate the first section. The inside of the pipe is laid with a cushion, which is approximately close to the cross-sectional shape of the actual tunnel. Four variable frequency fans are provided at the exit and entrance of the tunnel, so that the research on the influence of air supply position and air supply volume on the flow field, temperature field and smoke flow field in the tunnel can be realized. Set up thermocouples, gas detectors and total pressure gauges 3 at different positions inside the pipe section, and conduct physical simulations in fire and non-fire conditions. The watershed tunnel fire simulation platform under different working conditions can be formed by replacing a standard ventilation section with a length of 0.5m in the short section of the tunnel ventilation physical simulation platform with the combustion section 7 or placing the combustion section 7 in other positions.

After the assembly of the physical simulation platform for ventilation and fire protection of the super-long highway tunnel in the watershed, in order to test the stability and reliability of the overall test system of the physical simulation platform under actual working conditions, according to the test requirements of the highway tunnel ventilation simulation platform, a physical simulation platform was specially developed. The basic performance test tests include total pressure gauge 3 test, wind speed stability test, resistance loss coefficient test along the way, jet fan equivalent effect test, power system test, etc.

(1) Total pressure gauge 3 test wind speed stabilization time test

In order to avoid disturbance of the wind flow field in the tunnel simulation platform by the wind speed test instrument and ensure accurate measurement of the wind speed, the JCYB-2000A total pressure gauge 3 equipped with a miniature pitot tube is specially selected for this test to measure the wind speed at a specific point in the simulation platform. When the vertical shaft supply and exhaust fans and the jet fans at both ends of the tunnel work according to the predetermined power, the wind speed of point 1, that is, the distance from the tunnel entrance to the short track center model is 2m, and point 5, that is, the distance from the tunnel exit is short The road center model distance is 2.5m. 15 seconds after passing the test, the reading of the total pressure gauge 3 is basically stable. In this test, the wind speed measured by the total pressure gauge 3 is generally read 30 seconds after the fan frequency conversion adjustment. At this time, the airflow field inside the tunnel simulation platform has fully developed and can Accurately reflect the changes in the power system, so the selection of the reading time of the total pressure gauge 3 in this test is reasonable.

(2) Friction coefficient test along the simulation platform

The friction coefficient along the wall of the watershed tunnel simulation platform fluctuates slightly around 0.025. The test result of the friction coefficient along the way between No. 1 and No. 2 measuring points selected in the simulation platform is 0.02538, and the along-way friction between No. 4 and No. 5 measuring points The coefficient test result is 0.02497. According to the above test results, there is little difference in the resistance coefficient along the ventilation and fire protection simulation platform of the watershed super-long highway tunnel, and there is no need to adjust it. It shows that the resistance along the simulation platform of the tunnel has reached the requirement of similar resistance, and the flow similarity between the tunnel simulation platform and the prototype can be guaranteed.

(3) Equivalent effect test of jet fan

Considering the actual situation that the number of jet fans at the entrance and exit of the tunnel is almost equal, the wind speed caused by the natural wind pressure and the traffic piston wind pressure is determined by the air volume generated in the simulation platform by the coaxial fans at both ends at a certain speed in the tunnel simulation platform. It shows that the coaxial fans at both ends of the tunnel simulation platform are responsible for the boosting effect of 1.4m/s. In the test, when the fan frequency at the outlet end of the simulation platform is running at full speed of 50 Hz, and the coaxial fan and the fan in the supply and exhaust pipeline at the inlet section of the simulation platform are all shut down, the cross-sectional wind speed at the measuring point is 5.262m/s, which is the same as that of the 26 jets in this section. The wind speed 5.28m/s in the tunnel caused by the superposition of fan boost pressure, natural wind pressure and traffic piston wind pressure is relatively close. Therefore, it can be considered that the coaxial fan at the exit end of the simulation platform can more realistically simulate the situation of the tunnel prototype. The coaxial fan at the inlet section of the simulation platform can also realize the superposition of the boost pressure, natural wind pressure and traffic piston wind pressure of 24 jet fans through frequency conversion control.

(4) Power system test

From the outlet of the fan to the air supply channel 6 on the ceiling of the tunnel simulation platform, the two-stage different-diameter constriction neck and the friction along the air duct are applied. It is only 19.8m/s, and then filled with plasticine and pasted with smooth single-sided tape to reduce the local resistance of different diameters, the wind speed at the outlet of air supply duct 6 is increased to 23.7m/s, which is close to the original air supply duct 6 of the tunnel Outlet speed, the choice of YWR2E-200 coaxial pipeline fan to simulate the tunnel air supply inclined shaft axial fan can meet the requirements of the tunnel ventilation simulation platform test. The wind speed at the exhaust outlet of the tunnel simulation platform is 9.56m/s when the air supply coaxial duct fan is running at full speed. Therefore, the selection of YWR2E-160 coaxial duct fan with frequency converter to simulate tunnel exhaust inclined shaft axial fan can meet the requirements of tunnel ventilation simulation platform test. In order to accurately control the air volume of the four fans in the simulation platform test system, two duct fans (simulating the jet flow fan group at both ends of the tunnel) and two coaxial duct fans (simulating the inclined shaft supply and discharge axial flow fans) were respectively used with corresponding power Inverter control, basic property test and follow-up ventilation simulation platform test show that the inverter can change the wind speed of the fan between 0m/s and the maximum wind speed, and can stabilize the wind speed and air volume at any point, so all four inverters can Meet the test requirements of tunnel ventilation simulation platform.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those of ordinary skill in the art can also make It is impossible to exhaustively list all the implementation modes here, and any obvious changes or changes derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims (10)

1. the emulation platform construction method of a Highway Tunnel Ventilation System, it is characterised in that the method Step includes

Step S1, based on Similarity of Flow principle, determine the geometric similarity of tunnel prototype p and phantom m Ratio, kinematic similitude ratio and dynamic similarity ratio；

Step S2, based on simulation objectives, set the initial condition of tunnel prototype ventilating system；

Step S3, based on step S1 and step S2, set up the similarity boundary condition of emulation platform；

Step S4, based on critical Reynolds number, emulation platform and tunnel prototype are analyzed, build emulation flat Platform.

Emulation platform construction method the most according to claim 1, it is characterised in that described step S1 Including

S11, corresponding with phantom m for tunnel prototype p immeasurable schedule of proportion is shown as C_q, i.e. scale $C_q=\frac{q_p}{q_m};$

S12, set up the geometric similarity scale of tunnel prototype p and phantom m, geometric similarity sex ratio Chi includes length l scale:Cross-sectional area A scale:Volume V ratio Example chi:Wherein, l a certain lineal measure in being tunnel prototype；

S13, set up the kinematic similarity scale of tunnel prototype p and phantom m, kinematic similitude sex ratio Chi includes motion pixel u scale:Time t scale:Acceleration a ratio Example chi: $C_a=\frac{a_p}{a_m}=\frac{C_u}{C_t}=\frac{C_u^2}{C_l};$

S14, set up the scale of power F of the same name of the corresponding point of tunnel prototype p and phantom m, simultaneously Meet tunnel prototype p the most identical with the scale of the power of the Same Physical character of the corresponding point of phantom m.

Emulation platform construction method the most according to claim 2, it is characterised in that described power F of the same name Including gravity F_G, viscous force F_μ, pressure F_p, elastic force F_E, surface tension F_T,

$C_F=\frac{F_{Gp}}{F_{Gm}}=\frac{F_{pp}}{F_{pm}}=\frac{F_{\mathrm{\&mu;}p}}{F_{\mathrm{\&mu;}m}}=\frac{F_{Ep}}{F_{Em}}=\frac{F_{Tp}}{F_{Tm}}=\frac{F_{Ip}}{F_{\mathrm{Im}}}.$

Emulation platform construction method the most according to claim 1, it is characterised in that in institute's step S2 Initial condition includes

1) fluid is incompressible；

2) fluid be isothermal Flow of Single, fluid density and viscosity be definite value；

3) fluid flowing is in stationary flow, i.e. process fluid flow, and the pressure of any point and flow velocity are the most at any time Between and change, i.e. pressure and flow velocity is the function of point coordinates；

4) fluid is continuous media；

5) law of conservation of energy is observed in fluid flowing.

Emulation platform construction method the most according to claim 1, it is characterised in that in simulation process, Ensure that tunnel prototype and emulation platform are in same from mould district.

6. the emulation platform of a Highway Tunnel Ventilation System, it is characterised in that this emulation platform include with What actual tunnel was proportional can the split dismounting/vertical shaft air supply section of splicing, vertical shaft exhaustion section, burning zone, mark Quasi-section and jet segment；

Described vertical shaft air supply section, vertical shaft exhaustion section, burning zone and standard paragraphs are the latter half, inner space The Lucite pipe of cement mortar is filled in the space of 3.19%；

Blowing shaft and air draft well, described downcast is offered respectively on described vertical shaft air supply section and vertical shaft exhaustion section With the supply and exhaust system that air draft well forms gas channel；

Every 1 meter of cloth along the inwall of described vertical shaft air supply section, vertical shaft exhaustion section and the equal axial direction of standard paragraphs Put adhesive tape；Described burning zone has been applied ointment or plaster flexible asbestos board on the inner-walls of duct that cement mortar is not filled successively And sheet iron；

Described burning zone, vertical shaft air supply section and vertical shaft air draft segment length are 0.5 meter；Described standard paragraphs wraps respectively Include the standard paragraphs of tri-kinds of length of 0.5m, 1m and 2m；

The a length of 2m of described jet segment, is provided with blower fan and is placed in this emulation platform two ends.

Emulation platform the most according to claim 6, it is characterised in that overlapping by simulated condition Emulation platform non-burning section at be provided with 24 for measuring the disconnected of the internal simulated environment parameter of emulation platform Face；Described simulated environment parameter includes rate of flow of fluid, pressure, CO concentration and temperature.

Emulation platform the most according to claim 7, it is characterised in that

The total length of this platform is 15m, and horizontal section geometric proportion is 1:50, axial geometric proportion 1:100；

Described adhesive tape is pasted every 1m hoop vertically and is filled in the non-cement mortar of described Lucite pipe Inwall one week, described tape width is 3-6cm.

Emulation platform the most according to claim 7, it is characterised in that described 24 Measure section bags Include

5 are tested the speed and pressure measurement section, and this section is provided with total head meter 3；

2 CO measurement of concetration sections, this section is provided with CO gas detecting and alarming instrument；

17 temperature survey sections, arrange 32 temperature measuring points, wherein, 17 in 17 sections Measure point and be arranged at the vault in Lucite pipe 1 road of burning things which may cause a fire disaster upstream and downstream, measure point for 15 and fix At the differing heights of the tunnel center position of burning things which may cause a fire disaster upstream and downstream.

Emulation platform the most according to claim 9, it is characterised in that measure some profit for described 15 It is fixed in 3 in described 17 temperature survey sections with 3 thermocouple trees.