CN116735148A - Water tunnel experimental device, system and method based on injection principle - Google Patents
Water tunnel experimental device, system and method based on injection principle Download PDFInfo
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
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Abstract
The invention relates to a water tunnel experimental device, a system and a method based on an injection principle, belonging to the technical field of hydrodynamic experimental study; the experimental device comprises a front reflux section, an experimental section, a static section, a rear reflux section, a bottom rectifying section and a power system, wherein the front reflux section, the experimental section, the rear reflux section and the bottom rectifying section are sequentially connected through a flange plate to form a closed water hole; the stationary section is a pipeline with two open ends and is connected in parallel with the experimental section, one end of the stationary section is connected with the outlet end of the front reflux section, and the other end of the stationary section is connected with the inlet end of the rear reflux section; when the high-speed fluid flowing in from the front backflow section enters the experimental section, the high-speed fluid contacts with the fluid of the static section to generate momentum exchange, and the high-speed fluid can drive the low-speed fluid of the static section to move, so that a low-Reynolds-number flow space is formed in the experimental section.
Description
Technical Field
The invention belongs to the technical field of hydrodynamic force experiment research, in particular relates to a water tunnel experiment device, system and method based on an injection principle, and provides a circulating type free-adjustment water tunnel experiment platform capable of realizing low Reynolds number and low turbulence.
Background
The blunt body bypass problem is widely existed in the fields of aeronautics engineering, ocean engineering and the like, such as supporting structures of wings, cooling towers and ocean platforms and the like. The flow field around these blunt structures involves rich flow phenomena such as flow separation, vortex generation and shedding, etc. The vortex which alternately falls off from the two sides of the blunt body can cause the blunt body to receive larger flow resistance and lifting force. When the blunt body is elastically connected, vortex-induced vibration phenomenon is induced if the vortex shedding frequency approaches the natural frequency of the system. When the structure is in vortex induced vibration, fatigue and failure of the structure are further caused.
The experimental method is an important means for exploring the hydrodynamic problem, and designing an experimental device with good performance is a precondition for effectively acquiring the flow information. The water tunnel is a common and effective experimental device for hydrodynamics research, which generates adjustable water flow by means of a power device according to a set pipeline, and simulates the interaction of an experimental object and a water flow field in a test section for experimental research. In contrast to the model moving in still water, the test model is fixed in a water tunnel experiment, the experimental setup creates a relative velocity by controlling the water flow. The current water tunnel device can be divided into two types according to the structural form: one is a vertical water tunnel, which is a water tunnel powered by gravity, and the water flow is pressed into a test section at a certain speed, so that a power system is not required to be additionally arranged, and the vertical water tunnel is also called a gravity water tunnel. The second is a circulating water tunnel, which is powered by a water pump to push water flow to circulate in the pipeline in a reciprocating way. The circulating water tunnel is often provided with a control system for controlling the flow rate and pressure in the pipe, and is a sealed experimental device for collecting and processing data in high-speed flow. Because the occupation space of the gravity type water tunnel is large, and the flow velocity of the test section is related to the water level line, the control and the observation are not facilitated, and therefore, the circulating water tunnel is commonly used.
The existing water tunnel experiment system mostly adopts the design of large channel, large flow and high flow velocity, so that long-term operation not only can bring loss to the experiment section, the contraction section and the expansion section, but also can only carry out hydrodynamic study under high Reynolds number due to the structural characteristics (generally, the Reynolds number is more than 3900 and is understood as high Reynolds number), and hydrodynamic basic study under low Reynolds number can not be carried out. For example, the Chinese patent 'a low-disturbance high-flow high-speed circulating water tunnel experiment system', wherein the water tunnel experiment system has the advantages of large cross-sectional area of an experiment section, high flow speed and flow rate, small along-distance disturbance and the like; for example, the experimental water tunnel is convenient to detach and move, and can simulate flow fields with different temperatures, water depths, pressures and flow rates. The water tunnel experimental apparatus described in both of the above patents is not convenient for hydrodynamic basic studies at low reynolds numbers.
The current numerical means, namely 'direct numerical simulation', can solve a relatively real flow field environment, the numerical simulation can be calculated more accurately under the condition that the Reynolds number is about 1000 or less, and for the condition that the Reynolds number is greater than 1000, the direct numerical simulation means is used for accurately solving the flow field environment with relatively large time cost, if an additional error is brought by using a Reynolds averaging method or a large vortex simulation method, and the result between a coupling experiment and the numerical simulation can be better through an experiment with a low Reynolds number. Meanwhile, an effective active flow control means can be formulated under the condition of low Reynolds number to reduce resistance and vibration, and the current mainstream is to solve the Reynolds number of 100-1000 in numerical simulation to perform active flow control, so that the feasibility of the flow control means is verified in experiments, and the experiments with the low Reynolds number of 100-1000 are needed. In the current circulating water tunnel, when the problem of flow around a blunt body is studied, the Reynolds number is usually about 7000, and the experiment of the bottom Reynolds number cannot be performed, so we propose a circulating water tunnel device suitable for low Reynolds number.
Disclosure of Invention
The technical problems to be solved are as follows:
in order to avoid the defects of the prior art, the water hole experimental device, the system and the method based on the injection principle are characterized in that a front backflow section, an experimental section 6, a rear backflow section and a bottom rectification section are sequentially connected through flanges to form a closed water hole, the two ends of the static section 5 are respectively connected into a contraction section of the front backflow section and a contraction section of the rear backflow section through parallel connection of the experimental section 5, the fluid speed of the experimental section 6 is reduced based on the injection principle, disturbance is not added additionally, and an experimental environment with low Reynolds number and low turbulence degree is provided for observing and measuring relevant hydrodynamic parameters under the lower Reynolds number. The water tunnel experimental device has the advantages of small occupied area, simple structure, compact design, small disturbance along the path of the experimental observation section, low and stable water flow velocity.
The technical scheme of the invention is as follows: the water tunnel experimental device based on the injection principle comprises a front backflow section, an experimental section 6, a static section 5, a rear backflow section, a bottom rectification section and a power system, wherein the front backflow section, the experimental section, the rear backflow section and the bottom rectification section are sequentially connected through a flange plate to form a closed water tunnel;
the stationary section 5 is a pipeline with two open ends, is connected with the experimental section 6 in parallel, one end of the pipeline is connected with the outlet end of the front reflux section, and the other end of the pipeline is connected with the inlet end of the rear reflux section; when the fluid moves through the power system and the high-speed fluid flowing in from the front backflow section enters the experimental section 6, the high-speed fluid contacts with the fluid of the static section 5 to generate momentum exchange, and the high-speed fluid drives the low-speed fluid of the static section 5 to move, so that a low-Reynolds-number flow space is formed in the experimental section 6.
The invention further adopts the technical scheme that: the front reflux section comprises a front bending section and a contraction section which are connected in sequence, and the total length is L1; the rear reflux section comprises an expansion section, a transition section 10 and a rear bending section which are sequentially connected, the total length is L2, and L1 is more than L2; the bottom rectifying section comprises a power section 13 and a rectifying section 17 which are sequentially connected; the cross sections of the front bending section, the transition section, the rear bending section and the bottom rectifying section are circular, the cross section area is S1, the cross section of the experimental section 6 is circular, and the cross section area is S2; the section of the contraction section is circular, and the contraction angle is between 5 and 10 degrees; the section of the expansion section is circular, and the expansion angle is 8-12 degrees; the contraction section realizes the transition from S1 to S2, and the expansion section realizes the transition from S2 to S1;
the upper end of the side wall of the power section 13 is provided with a water inlet 14, the power section 13 is provided with a power system, the power system comprises a motor 15 and a propeller 16, and the motor 15 is connected with the propeller 16 through a coupling; the rectifying section 17 is provided with a pressure and flow regulating system 19 for regulating the flow rate and the internal pressure, and the side wall of the rectifying section 17 is provided with a water outlet 18.
The invention further adopts the technical scheme that: the convergent section comprises an end radius ratio of 4:3: the first contraction section 1, the second contraction section 3 and the third contraction section 4 of the device 2 are sequentially and coaxially arranged, and are connected through a flange; the specific position of the static section 5 connected with the contraction section is in the third contraction section 4;
the expansion section comprises a first expansion section 7 and a second expansion section 8, wherein the first expansion section 7 and the second expansion section 8 are sequentially arranged and are connected through a flange plate; the end radius ratio of the first expansion section 7, the second expansion section 8 and the transition section 10 is 1:2:4, a step of; the specific position of the stationary segment 5 to be connected to the expansion segment is the first expansion segment 7.
The invention further adopts the technical scheme that: the first contraction section 1 is provided with a first rectifying net 2, the transition section 10 is internally provided with a second rectifying net 9, and the rectifying section 17 is internally provided with a rectifier 20 near the front bending section; the rectifier 20 is a multi-layer fine rectifying net, and the net surface of the fine rectifying net is provided with a plurality of small cylindrical holes with the diameter of 8 mm.
The invention further adopts the technical scheme that: the experimental section 6 is divided into two area sections, a mixing deceleration section 61 is arranged close to the contraction section, and the fluid in the section is subjected to mixing deceleration; the near expansion section is an experimental observation section 62, where a low Reynolds number flow space is formed; the inner wall of the experiment observation section 62 is connected with the flowmeter 24 and the pressure sensor 25 for water hole measurement and control.
The invention further adopts the technical scheme that: the front bending section comprises a first bending section 21 and a second bending section 22, and the rear bending section comprises a third bending section 11 and a fourth bending section 12; the bending angles of the first bending section 21, the second bending section 22, the third bending section 11 and the fourth bending section 12 are 90 degrees, the first bending section 21 and the second bending section 22 are connected through a flange, and the third bending section 11 and the fourth bending section 12 are connected through a flange; the horizontal sections of the second bending section 22, the contraction section, the experiment section 6, the expansion section, the transition section 10 and the third bending section 11 are all coaxial, and the horizontal sections of the first bending section 21, the bottom rectifying section and the fourth bending section 12 are all coaxial.
The invention further adopts the technical scheme that: the first bending section 21, the second bending section 22, the third bending section 11 and the fourth bending section 12 are internally provided with flow guiding devices for reducing the impact loss of fluid.
The invention further adopts the technical scheme that: a pressure regulating valve 51 is installed in the middle of the stationary section 5.
An experimental system using a water tunnel experimental device based on an injection principle comprises the water tunnel experimental device based on the injection principle, a laser 28, a synchronizer 27, a computer 29 and a high-speed camera 30, wherein the laser 28 is provided with a light arm 26, and a light source of the light arm 26 is positioned above an experimental observation section 62; the high speed camera 30 is used to take photographs of the fluid in the experimental observation section 62; the synchronizer 27 is connected with the laser 28 and is used for synchronously triggering the laser 28 and the high-speed camera 30; the computer 29 is connected to the synchronizer 27, the laser 28, the high-speed camera 30 and the motor 15 for controlling the motor 15, the high-speed camera 30, the synchronizer 27 and the laser 28, and for collecting and processing data transferred from the high-speed camera 30.
The operation method of the experimental system comprises the following specific implementation steps:
step one: injecting water into the water tunnel experimental device, adding a proper amount of PIV special tracer particles during water injection, and regulating a pressure and flow regulating system 19 until water is filled;
step two: starting an experimental system, starting a circulating water tunnel device, and fully mixing the PIV special trace particles with water in the rectifier 20;
step three: the blunt body 23 is arranged inside the experimental observation section 62, and the plane tracer particles are illuminated by the sheet light source 31 generated by the laser;
step four: the movement of the trace particles in the experimental observation section 62 is understood as movement of the fluid, the trace particle movement process is acquired by the high-speed camera 30, and the acquired information is transmitted to the computer 29 for processing;
fifth step: the low Reynolds number data of the experiment is processed by the computer 29 to verify the results of the direct numerical simulation in the computer 29.
Advantageous effects
The invention has the beneficial effects that: according to the water tunnel experimental device based on the injection principle, the experimental section is connected with the static section in parallel, the two ends of the static section are respectively connected with the contraction section and the expansion section, fluid flowing into the experimental section from the front backflow section has higher speed, when the fluid enters the mixed deceleration section, the fluid with speed and the static fluid connected with the static section into the contraction section can be sheared, and due to the existence of intermolecular interaction force in the fluid, the fluid can be prevented from being accelerated. Thus, under viscous forces, the fast fluid will interact with the stationary fluid, creating a momentum exchange, creating a steady low-velocity flow in the region of the central axis of the experimental section tubing, resulting in a low reynolds number, low turbulence, low disturbance, high quality flow space in the experimental observation section. The low-Reynolds number circulating water tunnel can maintain the flow velocity of an observation section at 10mm/s by adjusting the rotating speed of a motor, is more suitable for the mechanistic research of observing the blunt body wake flow, and can ensure that the flow field is not more than 3%.
The contraction section is composed of three sections, and the contraction angle of the contraction section can be changed according to specific experimental requirements, so that a larger range of speed change is realized; by setting the contraction angle between 5 degrees and 10 degrees, the proper fluid flow rate can be effectively ensured, and the fluid with the speed and the fluid at the static section can generate better shearing effect. Each section of the contraction section is connected by a standard flange plate, so that the method is more economical and practical; the gradual shrinkage section can effectively reduce disturbance and energy loss caused by abrupt change of the section, and can ensure that velocity vectors are in the same direction when fluid flows to the experimental section; the design of the contraction section can effectively reduce the input of initial power under the premise of low Reynolds number.
According to the invention, the variable frequency motor is used for inputting power in a manner of connecting the propeller, when the input power needs to be changed, the variable frequency motor can stably change the current flow field environment, and the extra disturbance caused by the design of the traditional flow valve is avoided; meanwhile, the rotation of the propeller can reduce the initial turbulence intensity to a certain extent, which is beneficial to providing a good initial environment for the whole experimental system and realizing the stepless speed change with the speed range of 0.01m/s to 1.0 m/s.
According to the experimental observation section, a Particle Image Velocimetry (PIV) experimental measurement device and a model pulsation pressure measurement device can be added according to specific requirements, and the whole adaptability of the part is very strong; because of the low Reynolds number experimental environment, the experimental data and the data of the high-fidelity direct numerical simulation can be coupled, and the mechanistic problems related to the fluid can be explored.
The experimental device can realize two modes of vertical installation and horizontal installation, and under the vertical installation, the space occupation can be saved, and other measuring systems can be conveniently equipped; the invention has the advantages of convenient assembly and disassembly of each part and convenient processing.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a water tunnel experimental device based on the injection principle;
FIG. 2 is a schematic diagram of the experimental section according to the present invention;
FIG. 3 is a schematic diagram of an experimental system according to the present invention;
FIG. 4 is a schematic view of a constriction according to the present invention;
fig. 5 is a schematic view of an expansion section according to the present invention.
Reference numerals illustrate: 1. first constriction 2, first rectifier 3, second constriction 4, third constriction 5, stationary stage 51, pressure regulating valve 52, stationary stage piping 6, experimental stage 61, hybrid deceleration stage 62, experimental observation stage 7, first expansion stage 8, second expansion stage 9, second rectifier 10, transition stage 11, third bend 12, fourth bend 13, power stage 14, water inlet 15, motor 16, propeller 17, rectifier stage 18, water outlet 19, pressure and flow regulating system 20, rectifier 21, first bend 22, second bend 23, blunt 24, flow meter 25, pressure sensor 26, light arm 27, synchronizer 28, laser 29, computer 30, high speed camera 31, sheet light source.
Detailed Description
The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
Referring to fig. 1, the water tunnel experimental device based on the injection principle comprises a first bending section 21, a second bending section 22, a first contraction section 1, a second contraction section 3, a third contraction section 4, an experimental section 6, a first expansion section 7, a second expansion section 8, a transition section 10, a third bending section 11, a fourth bending section 12, a power section 13 and a rectifying section 17 which are sequentially connected through a flange plate to form a closed water tunnel. The water tunnel experimental device is vertically arranged, the overall height of the shape of the water tunnel experimental device is 1600mm, the overall width of the water tunnel experimental device is 3370mm, the height of the experimental observation section 62 from the bottom is 1500mm, and the water tunnel experimental device is convenient to observe and debug in a short distance.
Referring to fig. 1, the water tunnel experimental device further includes a stationary section 5, the stationary section 5 includes a pressure regulating valve 51 and a stationary section pipeline 52, two ends of the stationary section pipeline 52 are opened, one end of the stationary section pipeline 52 is connected to the third contraction section 4, the other end is connected to the first expansion section 7, the pressure regulating valve 51 is installed in the middle of the stationary section pipeline 52 and used for regulating the fluid pressure in the stationary section pipeline 52, and the stationary section 5 is connected in parallel with the experimental section 6.
Referring to fig. 1, a circular water inlet 14 is provided at the upper end of the side wall of the power section 13, a circular water outlet 18 is provided on the side wall of the rectifying section 17, and a pressure and flow regulating system 19 is installed on the rectifying section 17 for regulating the flow rate and the internal pressure; the motor 15 and the propeller 16 are installed in the power section 13, the motor 15 is specifically a variable frequency motor, the variable frequency motor is connected with the propeller 16 through a coupling, the variable frequency motor drives the propeller 16 to enable fluid to move, when fluid with speed enters the inlet of the experiment section 6, the fluid with speed is connected with the fluid of the third contraction section 4 to be contacted with the static section 5, the fluid with speed and the static fluid can be sheared, and due to intermolecular interaction force in the fluid, acceleration of the fluid can be hindered, so that the fluid with speed interacts with the static fluid under the action of viscous force to generate momentum exchange, and the fluid with high speed can drive the fluid with low speed of the static section 5 to move, so that a flowing space with low Reynolds number is formed in the experiment section 6.
Referring to fig. 1, in the present invention, the cross sections of the first bending section 21, the second bending section 22, the transition section 10, the third bending section 11, the fourth bending section 12, the power section 13 and the rectifying section 17 are all circular, the inner diameters of the cross sections are all 400mm, the wall thickness of each bending section is 10mm, and the lengths of the power section 13, the rectifying section 17 and the like are all 950mm; the section of the experimental section 6 is round, and the diameter of the section is 100mm; the bending angles of the first bending section 21, the second bending section 22, the third bending section 11 and the fourth bending section 12 are 90 degrees, and guide vanes are arranged in the four bending sections and used for relieving the centrifugal force of fluid turning and reducing impact loss.
Referring to fig. 1 and 4, the sections of the first contraction section 1, the second contraction section 3 and the third contraction section 4 are circular, and the lengths of the contraction sections are equal and are 320mm; the end radius ratio of the first contraction section 1, the second contraction section 3 and the third contraction section 4 is 4:3:2, the maximum inner diameter of the first contraction section 1 is 400mm; the total contraction angle of each contraction section is between 5 and 10 degrees, which is favorable for the uniform increase of the fluid speed, thereby reducing the turbulence in the incoming flow.
Referring to fig. 1 and 5, the sections of the first expansion section 7 and the second expansion section 8 are circular, the total length of the two expansion sections is 520mm, and the end radius ratio of the first expansion section 7, the second expansion section 8 and the transition section 10 is 1:2:4, the minimum diameter of the first expansion section 7 is 100mm, wherein the radius ratio of the two ends of the first expansion section 7 is 1:2, the radius ratio of the two ends of the second expansion section 8 is 2:4, the transition section 10 is a straight bore, serving to connect the second diverging section 8 and the third curved section 11. When the fluid flows out from the experimental section 6, the fluid has a certain speed, and in order to effectively reduce the flowing-out speed, a larger expansion angle is required according to the law of mass conservation, so that the total expansion angle of the expansion section is designed to be between 8 and 12 degrees; in the invention, the total length of the first bending section 21, the second bending section 22, the first contraction section 1, the second contraction section 3 and the third contraction section 4 is 1460mm, and the total length of the first expansion section 7, the second expansion section 8, the transition section 10, the third bending section 11 and the fourth bending section 12 is 1260mm.
Referring to fig. 1, the horizontal sections of the second bending section 22, the first contraction section 1, the second contraction section 3, the third contraction section 4, the experimental section 6, the first expansion section 7, the second expansion section 8, the transition section 10 and the third bending section 11 are all coaxial; the horizontal section of the first bending section 21, the rectifying section 17, the power section 13 and the horizontal section of the fourth bending section 12 are all coaxial.
Referring to fig. 1, the first contraction section 1 is provided with a first rectifying net 2 for breaking the vortex in the water flow introduced by the first bending section 21 and the second bending section 22 to ensure the flow field quality of the inflow of the contraction section; the transition section 10 is internally provided with a second rectifying net 9 for reducing the turbulence in the fluid; the rectifier 20 is installed in the rectifying section 17 near the first bending section 21, the rectifier 20 is a multi-layer fine rectifying net, a plurality of small cylindrical holes with the diameter of 8mm are distributed on the net surface of the fine rectifying net, and vortex formed in the fluid with speed is broken through the rectifier 20, so that the turbulence of the fluid entering the first bending section 21 is reduced. In order to reduce the pulsating force caused by the fluctuation of the fluid velocity, a pressure and flow regulating valve 19 is arranged before the rectifying net 20, i.e. in a direction close to the power section 13. According to the invention, through arranging the rectifying nets or rectifiers with different specifications in the first contraction section 1, the transition section 10 and the rectifying section 17, the instability of fluid flow can be reduced, and the method is beneficial to providing a good initial environment for the whole experimental system.
Referring to fig. 1 and 2, the experimental section 6 is divided into two area sections, and the section 4 near the third contraction section is a mixed deceleration section 61, where the incoming flow performs mixed deceleration; the experimental observation section 62 is close to the first expansion section 7, a low Reynolds number flow space is formed in the experimental observation section, and the test model blunt body 23 is arranged in the experimental observation section; the reynolds number is defined as re=ρvd/μ, where ρ is the density of the fluid, v is the flow rate of the fluid, d is the characteristic length, μ is the viscosity coefficient; when the size of the measured object is fixed, if the low Reynolds number is to be ensured, the flow rate of the experiment observation section 62 needs to be reduced; according to the invention, the incoming flow speed can be effectively reduced through the mixed speed reduction section 61, the fluid flowing in from the third contraction section 4 has relatively high speed, when the fluid enters the mixed speed reduction section 61 and is in contact with the fluid of the static section 5, momentum exchange is generated, and the high-speed fluid can drive the low-speed fluid of the static section 5 to move, so that a low-Reynolds-number flow space is formed in the central axis area of the experimental observation section 62, and the method is particularly suitable for research on observation and measurement of relevant hydrodynamic parameters under low Reynolds number and low turbulence; the experimental observation section 62 can be customized according to different experimental requirements, and if visual experimental study is required to be performed on the section of fluid, the section is made of high-strength and optical-resistant organic glass so as to facilitate close-range observation of experimenters or Particle Image Velocimetry (PIV) experimental measurement. If the pressure applied by the experimental model needs to be measured, a pressure sensor can be arranged on the surface or in the experimental model, and a lead is led out from the upper side of the experimental section to implement measurement and monitoring. The inner wall surface of the experimental observation section 62 is connected with the flowmeter 24 and the pressure sensor 25 for flow and pressure measurement and control of the section. The experimental observation section 62 has a total length of 300mm and a diameter of 100mm.
The experimental testing process of the water tunnel experimental device based on the injection principle comprises the following steps:
step one: opening the water inlet 14, injecting water into the circulating water tunnel device, and adjusting the pressure and flow adjusting system 19 until the whole device is filled with water;
step two: starting a variable frequency motor, and driving the propeller 16 to rotate at a low speed by the variable frequency motor, so that fluid in the pipeline moves along with the variable frequency motor;
step three: the accelerated fluid passes through rectifying section 17, wherein irregular vortex structures are broken by dense cylindrical holes of rectifier 20, thereby reducing the turbulence of the fluid entering first curved section 21;
step four: after the regular fluid rectified by the rectifier 20 passes through the second bending section 22, new interference may be brought, so that the first rectifying net 2 is installed in the first contraction section 1 to weaken the disturbance, and the fluid passes through the first contraction section 1, the second contraction section 3 and the third contraction section 4 to shear the fluid passing through the static section 5 at a higher speed;
step five: the high-speed incoming flow interacts with the low-speed fluid of the static section 5, and the high-speed incoming flow is decelerated in the mixed deceleration section 61 based on the injection principle, so that a low-Reynolds-number and low-turbulence flow field environment is formed in the experimental observation section 62;
step six: according to the experiment requirement, the output power of the variable frequency motor is adjusted to enable the fluid in the experiment observation section 62 to reach the flow rate meeting the requirement, so that the experiment observation is carried out on the test model installed in the experiment observation section 62.
Step seven: the observed flow of fluid through the first and second expansion sections 7, 8 will drop faster as the expansion angle of the expansion section is greater than the contraction angle of the contraction section, so as not to impact the third and fourth bending sections 11, 12.
Referring to fig. 3, if more refined experiments need to be performed on the water tunnel experimental device based on the injection principle, such as observing complex phenomena of wake condition of a blunt body, formation and falling off of karman vortex street, vortex induced vibration and the like, a Particle Image Velocimetry (PIV) experimental measurement device can be added to measure dynamic parameters related to fluid. Based on the above, the invention provides an experimental system using a water tunnel experimental device based on an injection principle, which comprises the water tunnel experimental device based on the injection principle, a laser 28, a synchronizer 27, a computer 29 and a high-speed camera 30, wherein the laser 28 is provided with a light arm 26, and a light source of the light arm 26 is positioned above an experimental observation section 62; high speed camera 30 is used to take photographs of the fluid in experimental observation section 62; the synchronizer 27 is connected with the laser 28 and is used for synchronously triggering the laser 28 and the high-speed camera 30; the computer 29 is connected to the synchronizer 27, the laser 28, the high-speed camera 30 and the motor 15 for controlling the motor 15, the high-speed camera 30, the synchronizer 27 and the laser 28, and for collecting and processing data transferred from the high-speed camera 30.
The application method of the experimental system comprises the following specific implementation steps:
step one: injecting water into the water tunnel experimental device, adding a proper amount of PIV special tracer particles during water injection, wherein the sphericity of the tracer particles is more than 95%, the main chemical components are SiO2 more than 65%, and regulating the pressure and flow regulating system 19 until the water is filled;
step two: starting an experimental system, starting a circulating water tunnel device, and fully mixing the PIV special trace particles with water in the rectifier 20;
step three: the blunt body 23 is arranged in the experimental observation section 62, the model of the laser 28 is MGL-N-532A-4W, the optical arm 26 is adjusted, a proper observation surface is found, the laser intensity is adjusted, and the chip light source 31 generated by the laser 28 illuminates the trace particles on the plane;
step four: the movement of the trace particles in the experimental observation section 62 is understood as movement of the fluid, the trace particle movement process is acquired by the high-speed camera 30, and the acquired information is transmitted to the computer 29 for processing;
fifth, the computer 29 processes the collected information using a "cross-correlation algorithm" to obtain experimental low Reynolds number data for verifying the results of direct numerical simulation in the computer.
The blunt body bypass flow environment with low Reynolds number has strong periodicity, is very suitable for fundamental research of hydrodynamics, and can be used for discussing the mechanism problem. The existing numerical simulation technology has higher solving precision in a low Reynolds number environment, and the water tunnel experimental device can effectively couple experimental data by combining the numerical simulation technology.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made in the above embodiments by those skilled in the art without departing from the spirit and principles of the invention.
Claims (10)
1. Water tunnel experimental apparatus based on draw and penetrate principle, its characterized in that: the device comprises a front reflux section, an experimental section (6), a static section (5), a rear reflux section, a bottom rectification section and a power system, wherein the front reflux section, the experimental section, the rear reflux section and the bottom rectification section are sequentially connected through a flange plate to form a closed water tunnel;
the static section (5) is a pipeline with two open ends, is connected with the experimental section (6) in parallel, one end of the pipeline is connected with the outlet end of the front backflow section, and the other end of the pipeline is connected with the inlet end of the rear backflow section; when the high-speed fluid flowing in from the front backflow section enters the experimental section (6) through the power system, the high-speed fluid is in contact with the fluid of the static section (5) to generate momentum exchange, and the high-speed fluid can drive the low-speed fluid of the static section (5) to move, so that a low-Reynolds-number flow space is formed in the experimental section (6).
2. The water tunnel experimental device based on the injection principle according to claim 1, wherein: the front reflux section comprises a front bending section and a contraction section which are connected in sequence, and the total length is L1; the rear reflux section comprises an expansion section, a transition section (10) and a rear bending section which are sequentially connected, the total length is L2, and L1 is more than L2; the bottom rectifying section comprises a power section (13) and a rectifying section (17) which are connected in sequence; the cross sections of the front bending section, the transition section, the rear bending section and the bottom rectifying section are circular, the cross section area is S1, the cross section of the experimental section (6) is circular, and the cross section area is S2; the section of the contraction section is circular, and the contraction angle is between 5 and 10 degrees; the section of the expansion section is circular, and the expansion angle is 8-12 degrees; the contraction section realizes the transition from S1 to S2, and the expansion section realizes the transition from S2 to S1;
the upper end of the side wall of the power section (13) is provided with a water inlet (14), the power section (13) is provided with a power system, the power system comprises a motor (15) and a propeller (16), and the motor (15) is connected with the propeller (16) through a coupling; the rectifying section (17) is provided with a pressure and flow regulating system (19) for regulating flow speed and internal pressure, and the side wall of the rectifying section (17) is provided with a water outlet (18).
3. The water tunnel experimental device based on the injection principle according to claim 2, wherein: the convergent section comprises an end radius ratio of 4:3: the first contraction section (1), the second contraction section (3) and the third contraction section (4) of the device 2 are coaxially arranged in sequence, and are connected through a flange; the specific position of the static section (5) connected to the front backflow section is in the third contraction section (4);
the expansion section comprises a first expansion section (7) and a second expansion section (8), wherein the first expansion section (7) and the second expansion section (8) are sequentially arranged and are connected through a flange plate; the end radius ratio of the first expansion section (7), the second expansion section (8) and the transition section (10) is 1:2:4, a step of; the specific position of the stationary section (5) connected to the rear-mounted reflux section is in the first expansion section (7).
4. A water tunnel experimental device based on the injection principle according to claim 3, characterized in that: the first contraction section (1) is provided with a first rectifying net (2), the transition section (10) is internally provided with a second rectifying net (9), and the rectifying section (17) is internally provided with a rectifier (20) close to the front bending section; the rectifier (20) is a multi-layer fine rectifying net, and a net surface of the fine rectifying net is provided with a plurality of small cylindrical holes with the diameter of 8 mm.
5. The water tunnel experimental device based on the injection principle according to claim 2, wherein: the experimental section (6) is divided into two area sections, a mixed deceleration section (61) is arranged close to the contraction section, and fluid in the section is subjected to mixed deceleration; the near expansion section is an experimental observation section (62), and a low Reynolds number flow space is formed in the experimental observation section; the inner wall of the experiment observation section (62) is connected with the flowmeter (24) and the pressure sensor (25) and is used for water hole measurement and control.
6. The water tunnel experimental device based on the injection principle according to claim 2, wherein: the front bending section comprises a first bending section (21) and a second bending section (22), and the rear bending section comprises a third bending section (11) and a fourth bending section (12); the bending angles of the first bending section (21), the second bending section (22), the third bending section (11) and the fourth bending section (12) are 90 degrees, the first bending section (21) and the second bending section (22) are connected through a flange plate, and the third bending section (11) and the fourth bending section (12) are connected through a flange plate; the horizontal sections of the second bending section (22), the contraction section, the experiment section (6), the expansion section, the transition section (10) and the third bending section (11) are coaxial, and the horizontal sections of the first bending section (21), the bottom rectifying section and the fourth bending section (12) are coaxial.
7. The water tunnel experimental device based on the injection principle according to claim 6, wherein: the first bending section (21), the second bending section (22), the third bending section (11) and the fourth bending section (12) are internally provided with flow guiding devices for reducing impact loss of fluid.
8. The water tunnel experimental device based on the injection principle according to claim 1, wherein: a pressure regulating valve (51) is arranged in the middle of the static section (5).
9. An experimental system of a water tunnel experimental device based on injection principle as claimed in claim 1, characterized in that: the water tunnel experimental device based on the injection principle, comprises a water tunnel experimental device based on the injection principle, a laser (28), a synchronizer (27), a computer (29) and a high-speed camera (30), wherein the laser (28) is provided with an optical arm (26), and a light source of the optical arm (26) is positioned above an experimental observation section (62); the high speed camera (30) is used for acquiring photographs of fluid in the experimental observation section (62); the synchronizer (27) is connected with the laser (28) and is used for synchronously triggering the laser (28) and the high-speed camera (30); the computer (29) is connected with the synchronizer (27), the laser (28), the high-speed camera (30) and the motor (15) and used for controlling the motor (15), the high-speed camera (30), the synchronizer (27) and the laser (28) and collecting and processing data transmitted by the high-speed camera (30).
10. A method of operating an experimental system according to claim 9, comprising the steps of:
step one: injecting water into the water tunnel experimental device, adding a proper amount of PIV special tracer particles during water injection, and regulating a pressure and flow regulating system (19) until water is filled;
step two: starting an experimental system, starting a circulating water tunnel device, and fully mixing the PIV special trace particles with water in a rectifier (20);
step three: installing a blunt body (23) inside the experimental observation section (62), and illuminating the planar tracer particles by a sheet light source (31) generated by a laser;
step four: collecting the trace particle moving process in the experiment observation section (62) through a high-speed camera (30), and transmitting collected information to a computer (29) for processing;
fifth step: the low Reynolds number data of the experiment is obtained by processing in the computer (29) and is used for verifying the results of direct numerical simulation in the computer (29).
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| CN117405354A (en) * | 2023-12-13 | 2024-01-16 | 中国人民解放军海军工程大学 | Flow excitation resonance suppression method for cavitation water hole corner segment guide vane |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117405354A (en) * | 2023-12-13 | 2024-01-16 | 中国人民解放军海军工程大学 | Flow excitation resonance suppression method for cavitation water hole corner segment guide vane |
| CN117405354B (en) * | 2023-12-13 | 2024-02-23 | 中国人民解放军海军工程大学 | Flow excitation resonance suppression method for cavitation water hole corner segment guide vane |
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