CN116907790A - Wind wave flow generation system for simulating towing process of immersed tube joint - Google Patents
Wind wave flow generation system for simulating towing process of immersed tube joint Download PDFInfo
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- CN116907790A CN116907790A CN202310577151.2A CN202310577151A CN116907790A CN 116907790 A CN116907790 A CN 116907790A CN 202310577151 A CN202310577151 A CN 202310577151A CN 116907790 A CN116907790 A CN 116907790A
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Abstract
The invention discloses a wind wave current generation system for simulating a towing process of a immersed tube joint, which relates to the technical field of ocean engineering and comprises the following components: the test pool is used for generating waves required by a test; the trailer system is used for realizing longitudinal towing of the pipe joint; and the flow generating system is used for simulating cross flow encountered in the towing process of the pipe joint. The wind wave current generation system for simulating the towing process of the immersed tube joint is simple and reasonable in structure, the test pool meets the test requirements of simple longitudinal towing and transverse towing (which can be called vertical towing), and simultaneously meets the test requirements of longitudinal and transverse simultaneous towing (which can be called oblique towing), the power condition can be the combined action of pure current, pure wave or wave current, the maximum hydrostatic towing speed in the test is 2.1m/s, the towing time can reach more than 100s under the model scale of 1:50, the constant-speed towing duration meets the requirement of resistance measurement, the controllable accuracy of the running speed of the trailer system is 0.1cm/s, and the accuracy completely meets the accuracy requirement of the towing speed, so that the accuracy of a simulation experiment is improved.
Description
Technical Field
The invention relates to the technical field of ocean engineering, in particular to a wind wave current generation system for simulating a towing process of a immersed tube joint.
Background
Along with urban integration and global economic trade globalization, convenient transportation directly drives the economic development of the region, various novel hydraulic structures play an extremely important role in the world cross-sea and cross-river transportation, a immersed tube tunnel is taken as a special cross-sea and cross-river engineering, more and more remarkable advantages are played in the world underwater tunnel engineering construction in a unique construction mode, the immersed tube tunnel takes immersed tube pipe joints as units, and the underwater tunnel is formed through series of construction such as prefabrication, undocking, floating, sinking and splicing;
because the marine environment is relatively bad, the immersed tube joint is influenced by environmental factors such as wind and wave currents in the ocean in the construction process, and the complex environmental load is very likely to cause damage and breakage caused by the load exceeding the bearing capacity of the mooring rope in the system; the floating process of the pipe joint is used as a stage of complex environmental conditions encountered in immersed tube construction, and the configuration of a towing cable and the research on the towing cable force borne by a towing cable have very important practical significance.
Therefore, we propose a wind wave current generation system for simulating the towing process of a immersed tube joint so as to solve the problems set forth above.
Disclosure of Invention
The invention aims to provide a wind wave current generation system for simulating the towing process of a immersed tube joint so as to solve the problems in the current market proposed by the background technology.
In order to achieve the above object, the present invention provides a wind wave current generation system for simulating a towing process of a immersed tube section, comprising:
the test pool is used for generating waves required by a test;
the trailer system is used for realizing longitudinal towing of the pipe joint;
the flow generating system is used for simulating cross flow encountered in the towing process of the pipe joint;
a wave generating system for generating a desired wave;
the measuring instrument mainly comprises a wave height measuring instrument, a flow velocity measuring instrument, a water level measuring instrument and a tension measuring instrument.
As a preferable technical scheme of the invention, the test pool is scaled according to the geometric scale at the center of the pool according to the actual towing channel topography, a north-south model channel is established through sand bedding cement plastering, the model channel length is 40m, a north-south trailer system is established along the model channel and used for longitudinal towing of pipe joints, a flow-making system is arranged along the east-west direction and used for making transverse flow, and a wave-making system is established at the south side of the pool and used for generating waves required by the test.
As the preferable technical scheme of the invention, the trailer system consists of two parts of guide rails and a trailer, wherein the guide rails are arranged on two sides of a model channel, the guide rails run in the north-south direction, the flatness in the vertical direction and the horizontal direction meet the test requirements, the trailer is erected on the guide rails, the trailer is in meshing transmission, the movement is controlled by a variable-frequency servo motor, the running speed and the acceleration parameters of the trailer can be accurately set through an automatic program, and the remote control of the start-stop operation of the trailer is realized through wireless remote control;
the length of the trailer track is 36m, the maximum hydrostatic towing speed in the test is 2.1m/s, the towing time can reach more than 100s under a model scale of 1:50, the constant-speed towing duration meets the requirement of resistance measurement, the running speed controllable precision of the trailer system is 0.1cm/s, and the precision completely meets the precision requirement of the towing speed.
As a preferred technical solution of the present invention, the flow generating system includes: 9 reversible pumps are distributed on the western side of the water pool at equal intervals, the forward and reverse rotation and the rotating speed of the reversible pumps are controlled by a frequency converter to obtain the required flow velocity, and the maximum flow velocity can reach 40cm/s, so that the requirement of test cross flow is completely met.
As a preferable technical scheme of the invention, the wave generating system is a movable rocking plate type irregular wave generating machine, the wave generating machine consists of a wave generating plate, a servo driver, a servo motor, an encoder, a server, a computer and other peripherals, the calculation of wave generating control signals is completed by the computer according to parameters corresponding to required waves, the signals are transmitted to the servo driver through an interface circuit, the servo driver controls the rotation of the servo motor, and the ball screw converts the rotation of the motor into linear motion and generates expected waves through the wave generating plate.
As a preferred embodiment of the present invention, the measuring instrument includes:
the wave height measuring instrument adopts a DS30 wave height acquisition system;
the flow velocity measuring instrument adopts a Vectrino acoustic Doppler three-dimensional flow velocity meter;
the water level measuring instrument adopts an ultrasonic water level meter;
the tension measuring instrument adopts a 2013 type tension comprehensive measuring system.
In order to achieve the above purpose, the invention also provides a test method of a wind wave current generation system for simulating the towing process of a immersed tube joint, which is characterized by comprising the following steps:
step one, calibrating a water flow field in a water tank/pool according to flow speed requirements corresponding to different water levels, and storing control parameters of a flow making system;
step two, mounting the pipe joint model in place according to the specified requirement, and mounting the tension meter in place;
starting a flow making system, monitoring water flow through a flow velocity meter, and after a flow field is stable, starting resistance measurement, wherein all tension instruments are synchronously collected by using an AD converter and a computer, the collection rate is 50Hz, and considering that unstable wake vortexes possibly exist at the downstream of a pipe joint under a large flow velocity, and the length of a sampling record is 10 minutes;
and fourthly, synthesizing the collected tensile force according to the angle in a time process, obtaining the maximum resistance Fd of the pipe joint in the corresponding direction, and calculating the resistance coefficient Cd value corresponding to the action angle of the water flow according to the Morrison formula.
As a preferable technical scheme of the invention, the width of the pool needs to meet the following conditions: the distance from the structural object to the side wall of the water tank is more than 3 times of the projection width of the structural object in the water flow direction, and in the resistance characteristic test research, 2 dynamic conditions of flow direction angles are simulated altogether;
when the water flow is arranged at 0 degree, the width of the pool exceeds (3+3+1) ×width (0.92 m) =6.44 m;
when the water flow is arranged at 90 degrees, the width of the water pool exceeds (3+3+1) x-type length (3.3 m) =23.1 m;
considering the conditions of the test site and the requirements of the test flow rate comprehensively, the 0-degree water flow action test is carried out in a water tank with the width of 7m, the maximum flow making capacity of the test is met with the requirements of the maximum flow rate of the test, the 90-degree water flow action test is carried out in a water tank with the width of 24m, and the maximum flow making capacity of the test is met with the requirements of the flow rate equivalent to 0.8m/s of the prototype.
In order to achieve the above purpose, the invention also provides a test model for a test method of a wind wave current generation system for simulating a tube section towing process of a immersed tube, which is characterized in that the test model comprises a tube section model, a sinking barge model and a measuring tower model.
As the preferable technical scheme of the invention, the shell of the mould pipe joint is made of high-strength PVC plastic plates, the end sealing door is made of transparent acrylic plates, and three pore canals in the immersed tube are made of light wood-plastic plates, so that a very small space capable of balancing weight exists between the shell and the inner wood-plastic plates, and the weight of the pipe joint is completed by balancing high-density lead sheets due to the small space;
the sinking barge body is of a rectangular hollow shell structure, the model manufacturing material is wood, waterproof paint is adopted for external protection, and cement blocks are adopted for counterweight in the rectangular shell to meet the requirement that the gravity center position and the mass distribution are similar;
the structure of the measuring tower model is complex, and because the weight of the measuring tower is small relative to the weight of the immersed tube, the weight and the gravity center position of the measuring tower model are mainly guaranteed to be similar when the measuring tower model is manufactured, the measuring tower structure is manufactured by adopting light aluminum materials, and the weighing is performed by adopting small lead sheets.
Compared with the prior art, the invention has the beneficial effects that:
1. the wind wave flow generation system for simulating the towing process of the immersed tube joint is simple and reasonable in structure, the test pool meets the test requirements of simple longitudinal towing and transverse towing (which can be called vertical towing), and simultaneously meets the test requirements of longitudinal and transverse simultaneous towing (which can be called oblique towing). The power condition can be the combined action of pure flow, pure wave or wave flow, the maximum hydrostatic towing speed in the test is 2.1m/s, the towing time can reach more than 100s under a model scale of 1:50, the constant-speed towing duration meets the requirement of resistance measurement, the controllable precision of the running speed of a trailer system is 0.1cm/s, and the precision completely meets the precision requirement of the towing speed, so that the accuracy of a simulation experiment is improved;
2. the wind wave flow generation system for simulating the pipe joint towing process of the immersed pipe is mainly used for simulating cross flow encountered in the pipe joint towing process. 9 reversible pumps are distributed on the western side of the water tank at equal intervals, the forward and reverse rotation and the rotating speed of the reversible pumps are controlled by a frequency converter to obtain the required flow speed, the maximum flow speed can reach 40cm/s, and the requirements of test cross flow are completely met;
3. the wave generating system of the wind wave flow generating system for simulating the towing process of the immersed tube joint is a movable rocking plate type irregular wave generating machine, the wave generating machine consists of a wave generating plate, a servo driver, a servo motor, an encoder, a server, a computer and other peripherals, the calculation of wave generating control signals is completed by the computer according to parameters corresponding to required waves, the signals are transmitted to the servo driver through an interface circuit, the servo driving controls the rotation of the servo motor, and the ball screw converts the rotation of the motor into linear motion and can generate expected waves through the wave generating plate.
Drawings
FIG. 1 is a schematic cross-sectional view of a pipe joint floating channel;
FIG. 2 is a plan view of a standard pipe joint tow boat configuration;
FIG. 3 is a plan view of a non-pipe section tow boat configuration;
FIG. 4 is a table of longitudinal and transverse towing conditions of a pipe joint;
FIG. 5 is a diagram of the hydraulic characteristics of the blunt body flow-around plane;
FIG. 6 is a schematic diagram of a shape resistance formula;
FIG. 7 is a schematic diagram of a frictional resistance formula;
FIG. 8 is a schematic diagram of the structure of the present invention;
FIG. 9 is a schematic illustration of a pipe joint counterweight;
FIG. 10 is a schematic diagram of a standard pipe joint towing four-side mooring scheme;
FIG. 11 is a table of standard pipe section full wet hauling tug layout;
FIG. 12 is a table of non-pipe section full wet tow floating tow boat layout;
FIG. 13 is a table of main parameters for the pipe section and the sink barge model;
FIG. 14 is a table of water depth, draft and slack water depth relationships;
FIG. 15 is a table of pipe joint transverse towing conditions.
FIG. 16 is a schematic illustration of a towing test pool;
fig. 17 is a schematic diagram of a trailer system with pipe section longitudinal movement traction.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
Referring to fig. 1-17, the present invention provides a technical solution: a stormy wave current generating system for simulating a towing process of a immersed tube joint, comprising:
the test pool is used for generating waves required by a test; the test pool is 50m long and 30m wide, scaling is carried out according to the geometric scale at the center of the pool according to the actual towing channel terrain, a north-south model channel is established through sand bedding cement plastering, the model channel is 40m long, a north-south trailer system is established along the model channel and used for longitudinal towing of pipe joints, a flow-making system is arranged along the east-west direction and used for making transverse flow, and in addition, a wave-making system is established at the south side of the pool and used for generating waves required by the test;
the trailer system is used for realizing longitudinal towing of the pipe joint; the trailer system consists of two parts, namely a guide rail and a trailer, wherein the guide rail is arranged on two sides of a model channel, the south and north directions and the vertical and horizontal planeness meet test requirements, the trailer is arranged on the guide rail, the meshing transmission is realized, the movement is controlled by a variable-frequency servo motor, the running speed and the acceleration parameters of the trailer can be accurately set through an automatic program, and the remote control of the start and stop operation of the trailer is realized through wireless remote control;
the length of a trailer track is 36m, the maximum hydrostatic towing speed in the test is 2.1m/s, the towing time can reach more than 100s under a model scale of 1:50, the constant-speed towing duration meets the requirement of resistance measurement, the controllable accuracy of the running speed of a trailer system is 0.1cm/s, and the accuracy completely meets the accuracy requirement of the towing speed;
the flow generating system is used for simulating cross flow encountered in the towing process of the pipe joint; the flow making system comprises: 9 reversible pumps are distributed on the western side of the water pool at equal intervals, the forward and reverse rotation and the rotating speed of the reversible pumps are controlled by a frequency converter to obtain the required flow speed, the maximum flow speed can reach 40cm/s, and the requirements of test cross flow are completely met;
a wave generating system for generating a desired wave; the wave generating system is a movable rocking plate type irregular wave generator, the wave generator consists of a wave generating plate, a servo driver, a servo motor, an encoder, a server, a computer and other peripherals, the computer finishes the calculation of wave generating control signals according to the parameters corresponding to the needed waves, the signals are transmitted to the servo driver through an interface circuit, the servo driver controls the rotation of the servo motor, and the ball screw converts the rotation of the motor into linear motion and generates expected waves through the wave generating plate;
the measuring instrument mainly comprises a wave height measuring instrument, a flow velocity measuring instrument, a water level measuring instrument and a tension measuring instrument; the measuring instrument includes: the wave height measuring instrument adopts a DS30 wave height acquisition system; the flow velocity measuring instrument adopts a Vectrino acoustic Doppler three-dimensional flow velocity meter; the water level measuring instrument adopts an ultrasonic water level instrument; the tension measuring instrument adopts a 2013 type tension comprehensive measuring system;
a test method for a wind wave current generation system for simulating a towing process of a immersed tube joint is characterized by comprising the following steps:
step one, calibrating a water flow field in a water tank/pool according to flow speed requirements corresponding to different water levels, and storing control parameters of a flow making system;
step two, mounting the pipe joint model in place according to the specified requirement, and mounting the tension meter in place;
starting a flow making system, monitoring water flow through a flow velocity meter, and after a flow field is stable, starting resistance measurement, wherein all tension instruments are synchronously collected by using an AD converter and a computer, the collection rate is 50Hz, and considering that unstable wake vortexes possibly exist at the downstream of a pipe joint under a large flow velocity, and the length of a sampling record is 10 minutes;
step four, synthesizing the collected tensile force according to the angle in a time process, obtaining the maximum resistance Fd of the pipe joint in the corresponding direction, and calculating the resistance coefficient Cd value corresponding to the action angle of the water flow according to the Morrison formula;
the width of the pool needs to meet: the distance from the structural object to the side wall of the water tank is more than 3 times of the projection width of the structural object in the water flow direction, and in the resistance characteristic test research, 2 dynamic conditions of flow direction angles are simulated altogether;
when the water flow is arranged at 0 degree, the width of the pool exceeds (3+3+1) ×width (0.92 m) =6.44 m;
when the water flow is arranged at 90 degrees, the width of the water pool exceeds (3+3+1) x-type length (3.3 m) =23.1 m;
considering the conditions of the test site and the requirements of the test flow rate comprehensively, the 0-degree water flow action test is carried out in a water tank with the width of 7m, the maximum flow making capacity of the test is met with the requirements of the maximum flow rate of the test, the 90-degree water flow action test is carried out in a water tank with the width of 24m, and the maximum flow making capacity of the test is met with the requirements of the flow rate equivalent to 0.8m/s of the prototype.
The experimental model is used for simulating the experimental method of the wind wave current generation system in the towing process of the immersed tube joint, and is characterized by comprising a tube joint model, a sinking barge model and a measuring tower model; the shell of the pipe joint of the model is made of high-strength PVC plastic plates, the end sealing door is made of transparent acrylic plates, three pore canals in the sinking pipe are made of light wood-plastic plates, so that a very small space capable of balancing weight exists between the shell and the inner wood-plastic plates, and the pipe joint is made of high-density lead sheets by balancing weight of the pipe joint due to small space;
the sinking barge body is of a rectangular hollow shell structure, the model manufacturing material is wood, waterproof paint is adopted for external protection, and cement blocks are adopted for counterweight in the rectangular shell to meet the requirement that the gravity center position and the mass distribution are similar;
the structure of the measuring tower model is complex, and because the weight of the measuring tower is small relative to the weight of the immersed tube, the weight and the gravity center position of the measuring tower model are mainly guaranteed to be similar when the measuring tower model is manufactured, the measuring tower structure is manufactured by adopting light aluminum materials, and the weighing is performed by adopting small lead sheets.
Test conditions:
1. pipe joint parameter
After the pipe joint prefabrication and outfitting operation are considered, the pipe joint is moved out of the harbor pool to float to the tunnel address. The pipe joint is subjected to towing object model test research in a heavy load (the concrete pouring of the pipe joint is finished, and the measurement control tower and the sinking barge outfitting are finished).
The floating haulage test study object comprises a standard pipe joint and a non-standard pipe joint.
1.2. Test water level
Tube joint towing test considers two water levels (national 1985 altimeter):
(1) Designing a high water level: +2.02m;
(2) Designing a low water level: -0.72m.
1.3. Test flow rate
The relative motion speed of the following four pipe joints and water flow is considered in the longitudinal towing of the pipe joints:
(1)0.5144m/s；
(2)1.0288m/s；
(3)1.5432m/s；
(4)2.0576m/s。
the relative motion speed of the pipe joint and the water flow is considered by the following four pipe joints:
(1)0.5m/s；
(2)0.6m/s；
(3)0.7m/s；
(4)0.8m/s。
the towing resistance of the pipe joint under the condition that the longitudinal relative movement speed of the pipe joint and the water flow is 0.5144m/s and 1.0288m/s and the transverse relative movement speeds of the pipe joint and the water flow are coupled is considered.
1.4. Wave element
According to the hydrological actual measurement data and calculation analysis results of the engineering area, the wave elements for the test are taken as follows: the wave height is 0.8m and the period is 6s.
1.5. Working condition group times
The external environmental power conditions of the pipe joint channel floating are mainly water flow and waves, and the power elements and the pipe joint have longitudinal opposite and transverse opposite movements. Consider the relative movement of the water flow and the pipe joint in the longitudinal direction and the transverse direction; in view of the space constraints of the test field, it is difficult to arrange a transverse wave generator, which only considers the longitudinal relative movement of the wave with the pipe section.
2 model design and test method
The longitudinal relative movement of the pipe joint and the water flow is realized by dragging the pipe joint through a dragging system, and the transverse relative movement of the pipe joint and the water flow is realized by making transverse flow. The model follows the gravity similarity criteria with a model scale of 1:50.
2.1 resistance characteristics of pipe joints
The hydrodynamic characteristics of the pipe joint in floating transportation are important technical indexes for manufacturing a pipe joint towing and mooring scheme. The hydrodynamic characteristic parameters of the pipe joint can be used for calculating the force for controlling the movement of the pipe joint, so that the parameters and the quantity of external equipment for restraining the movement of the pipe joint can be further estimated.
The problem of floating force of the box-type immersed tube in water is theoretically the problem of viscous wave making of a blunt body in a limited area. The water resistance experienced by the pipe joint while towing near the free surface of the fluid includes viscous resistance, which is related to the reynolds number, and wave making resistance, which is related to the friedel number. Because the pipe joint is a square blunt body, the main component in the viscous resistance is shape resistance, and the specific gravity of the friction resistance is relatively small. Because the speed is lower when towing, the wave making resistance is also lower.
2.1.1 shape resistance
In actual flow, when water flow acts on the flow-facing surface of the pipe joint, flow is depressurized, the thickness of a boundary layer on the flow-facing surface is smaller, and the thickness of the boundary layer on the flow-facing surface is continuously and slowly increased due to a forward pressure gradient generated after the upstream water flow is depressurized. The water flow spreads from the forward flow surface to the forward flow surface, and therefore the kinetic energy of the water particles is insufficient to just overcome the counter-pressure gradient from the forward flow surface to the back flow surface. In fact, during the movement of the water particles on the downstream surface, the fluid particles in the boundary layer are not only affected by the friction resistance of the wall surface, but also by the deceleration action of the counter-pressure gradient, and the kinetic energy left by the fluid particles is insufficient for the other fluid particles to reach the back flow surface. Thus, fluid particles within the downstream boundary layer near the wall will have a nearly zero flow velocity just downstream of the downstream surface.
In the deceleration process of the forward boundary layer, the water particles closer to the wall surface are subjected to higher viscous resistance and more severely decelerated. Under the action of a larger back pressure gradient, a point with zero flow velocity gradient and wall shear stress appears on the wall, which is a boundary layer separation point. A backflow occurs downstream of the separation point, which backflow forms a lateral compression of the incoming flow flowing up the separation point, so that the incoming flow is pressed towards the main flow zone, thus forming a boundary layer separation phenomenon.
After the wall boundary layer is separated, the flow structure of the back flow surface of the pipe joint can be changed greatly. The change pattern is closely related to the speed of the incoming flow, and in general, a large-scale backflow region is formed on the back flow surface, or a periodic oscillation state characterized by non-constant large-scale vortex shedding is generated.
Since the boundary layer friction and swirling motion consume a lot of energy, the pressure on the back flow side is lowered, and is much lower than the pressure on the upstream side, thereby generating shape resistance. The size of the flow path depends on the position of the separation point of the wall boundary layer, and the smaller the wake area or the closer the separation point is to the downstream, the smaller the shape resistance. In combination with morphological parameters of the pipe section (form width B, form length L), B/L is an important parameter affecting the boundary layer separation point.
The above was an analysis of the flow characteristics of the blunt body in the horizontal plane. In fact, the blunt body of the pipe joint has the same type of flow around characteristic in the vertical direction, so that the draft D and the floating depth D of the pipe joint are also important parameters for influencing the stress of the pipe joint.
2.1.2 frictional resistance
Frictional resistance is mainly generated upstream of the separation point, compared to shape resistance, and within a boundary layer where the wall surface is very thin. In general, frictional resistance is associated with wet surface finish of the pipe joint.
2.1.3 wave making resistance
When a floating body such as a ship moves on the water surface, the surrounding water can be disturbed, so that the distribution of the fluid pressure around the ship body is changed, and waves are further raised. The pressure difference acting in the opposite direction of the floating body movement, which is generated by the asymmetric front-back pressure distribution of the floating body due to the floating body wave making, is called wave making resistance.
2.2 stress pattern analysis of pipe joints
After the water flow acts stably, the gravity FG of the pipe joint and the buoyancy FB, the dragging force FT and the resistance Fd which are received form a balanced state, and due to the fact that the positions of the acting points of all the forces are different, when the dragging force FT and the resistance Fd exist and are combined with the posture (stability) of the pipe joint, the pipe joint can deflect around the gravity center (the flow facing end is sunk), and therefore the moment formed by the dragging force FT and the resistance Fd is offset by the restoring moment generated by the change of the buoyancy and the adjustment of the position of the floating center, and therefore, the pipe joint is sunk at the flow facing end when water flow exists. In the force and moment balancing process, the shape length L and the shape width B of the pipe joint are important variables affecting the stress and the posture of the pipe joint.
In addition, when water flow acts on the pipe joint, the surplus water depth at the bottom of the pipe joint is also an important parameter affecting the stress of the pipe joint. At the same flow rate, the water flow force obviously increases with the decrease of the rich water depth, and the influence variable can be analyzed by the ratio of the water depth D to the draft D.
2.3 similarity criteria
When floating bodies such as immersed tubes float on the sea, the floating bodies are mainly subjected to comprehensive acting forces such as water flow, waves, wind and the like. These forces affecting the pipe section can be divided into two categories according to the actual effect: one is the fluid inertial force, which is related to acceleration, and the other is the viscous force, which is related to velocity.
In fact, when the inertial force similarity is satisfied, the similarity criterion adopted is Fu Rude similarity, i.e. the prototype and model are required to have equal Fr numbers; when the resistance similarity is satisfied, the Reynolds numbers (Re) between the prototype and the model are required to be equal;
in fact, when the reynolds number is large, after the flow enters the turbulent flow roughness region (i.e., the resistance square region), the flow resistance is independent of the reynolds number and only dependent on the relative roughness, so long as the similarity of Fu Rude between the prototype and the model is ensured.
Because the immersed tube joint is a regular rectangular box, the shape of the immersed tube joint is called a blunt body in the fluid mechanics, the separation point of a boundary layer is easy to stabilize, and the immersed tube joint is easy to enter a resistance square region, and the resistance square region can be carried out at a lower Reynolds number.
Thus, combining the above analysis with conventional marine engineering hydrodynamic test experience, the model test needs to meet Fu Rude similarity criteria. According to the test content, the similarity criteria are refined as follows:
(1) Geometric similarity
Ensure that the pipe joint, the sinking barge, the measuring tower, the water depth and the like are all reduced according to the same proportion. According to the field conditions and the current making capacity of a laboratory, the geometric ratio of the experimental study model is 1:50.
(2) Similar movement and power
The forces of any corresponding points in the model and prototype dimensions have corresponding directions, and the sizes of the forces are correspondingly proportional, namely the motions of the two water flows are similar.
In the similar motion, the weight and the gravity center position of the pipe joint, the sinking barge and the measuring tower need to meet similar conditions.
The center of gravity, roll and pitch cycles of the immersed tube satisfy similar conditions at the same time.
3 traction mode
In the pipe section channel towing resistance test, two pipe section towing traction schemes are adopted: a four-corner traction scheme and a four-corner traction scheme.
3.1 four corner traction
Four corner points of the pipe joint are used as mooring rope points and are obliquely stretched to a traction column of the trailer system through four mooring ropes.
When four corners traction towing uniform motion, two cables at the towing side are stressed, two cables at the rear side are basically unstressed, and the tension force of the two cables at the rear side is not strictly 0 due to the asymmetry of the flow and vortex shedding of the blunt body.
3.2 four-side traction
The center of each of the two short sides (i.e., two ends) of the pipe section is provided with a mooring line point, two mooring line points on each of the two long sides, and the direction of the mooring line is perpendicular to the sides, and the mooring line points are connected to the traction column of the trailer system through 6 mooring lines in total. And after the cable force vectors of the cables are synthesized, projecting the synthesized cable force vectors to the towing direction to calculate towing resistance and resistance coefficients. Only the standard pipe joint adopts the traction scheme, and the aim is to analyze the sensitivity degree of the test result to different traction towing schemes.
When four sides pull and tow at uniform motion, the cable on the towing side is mainly stressed, the cable on the rear side is basically unstressed, and the stress of the cable vertical to the towing direction is basically caused by asymmetric vortex shedding.
Test procedure
And in the test preparation stage, the working performance of the trailer system is subjected to system test, the traction advancing speed of the trailer is rated, and relevant setting parameters are stored. And calibrating the flow velocity of the cross flow, and storing corresponding flow control parameters. And the instrument for the test is used for checking and testing, so that the instrument and the equipment can work normally.
(1) Longitudinal towing test process of pipe joint
(a) The trailer runs to a starting point position;
(b) The water level is adjusted to the test water level;
(c) According to the traction scheme, connecting the pipe joint to a trailer system through a cable and a tension meter;
(d) Standing for a period of time, and setting the tension meter to zero after the pipe joint reaches an equilibrium state;
(e) Setting relevant control parameters corresponding to the traction speed of the trailer, and starting to collect the cable tension;
(f) Starting the trailer after 50s, running the traction pipe joint at a specific working condition speed until the tail end of the trailer track, and ending data acquisition after the trailer stops for a period of time;
(g) And (3) data are derived, tension synthesis is carried out according to the angle, the maximum longitudinal resistance of the pipe joint is obtained, and the longitudinal resistance coefficient is calculated according to a Morrison formula.
(2) Longitudinal and transverse towing test process of pipe joint
(a) The trailer runs to a starting point position;
(b) The water level is adjusted to the test water level;
(c) According to the traction scheme, connecting the pipe joint to a trailer system through a cable and a tension meter;
(d) Standing for a period of time, and setting the tension meter to zero after the pipe joint reaches an equilibrium state;
(e) Synchronously collecting tension data of all cables, and starting a flow making system to make cross flow after one minute;
(f) Monitoring water flow through a flow velocity meter, and continuously collecting data for 1 minute after the flow field is stable;
(g) And starting the trailer system, and advancing the pipe joint under the traction of the trailer until the end of the track is reached, stopping the trailer, and ending the data acquisition after a period of time.
And (3) data are derived, the collected tensile force is synthesized in a time process according to an angle, so that the longitudinal resistance and the transverse resistance of the pipe joint are obtained, and the transverse and longitudinal resistance coefficients of the pipe joint under the corresponding water level and flow velocity are calculated according to Morrison formula.
To complete a series of work, and what is not described in detail in this specification is prior art that is well known to those skilled in the art.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (10)
1. A stormy wave current generation system for simulating a tube section towing process of a immersed tube, comprising:
the test pool is used for generating waves required by a test;
the trailer system is used for realizing longitudinal towing of the pipe joint;
the flow generating system is used for simulating cross flow encountered in the towing process of the pipe joint;
a wave generating system for generating a desired wave;
the measuring instrument mainly comprises a wave height measuring instrument, a flow velocity measuring instrument, a water level measuring instrument and a tension measuring instrument.
2. The wind wave flow generating system for simulating the towing process of the immersed tube joint according to claim 1, wherein the test pool is arranged in the center of the pool, scaled according to the actual towing channel topography and geometric scale, a north-south model channel is established through sand bedding cement plastering, the model channel is 40m long, a north-south trailer system is established along the model channel and used for longitudinal towing of the tube joint, a flow system is arranged along the east-west direction and used for transverse flow, and a wave system is established on the south side of the pool and used for generating waves required by the test.
3. The wind wave flow generating system for simulating the towing process of the immersed tube pipe joint according to claim 1, wherein the trailer system consists of two parts of a guide rail and a trailer, the guide rail is arranged on two sides of a model channel, the south-north trend, the vertical and horizontal flatness meet test requirements, the trailer is arranged on the guide rail, meshing transmission is carried out, the movement is controlled by a variable frequency servo motor, the running speed and the acceleration parameters of the trailer can be accurately set through an automatic program, and the remote control of the start-stop operation of the trailer is realized through wireless remote control;
the length of the trailer track is 36m, the maximum hydrostatic towing speed in the test is 2.1m/s, the towing time can reach more than 100s under a model scale of 1:50, the constant-speed towing duration meets the requirement of resistance measurement, the running speed controllable precision of the trailer system is 0.1cm/s, and the precision completely meets the precision requirement of the towing speed.
4. The wind wave current generation system for simulating a tube-in-tube towing process of claim 1, wherein the current generation system comprises: 9 reversible pumps are distributed on the western side of the water pool at equal intervals, the forward and reverse rotation and the rotating speed of the reversible pumps are controlled by a frequency converter to obtain the required flow velocity, and the maximum flow velocity can reach 40cm/s, so that the requirement of test cross flow is completely met.
5. The wind wave current generation system for simulating the towing process of the immersed tube joint according to claim 1, wherein the wave generation system is a movable swing plate type irregular wave generator, the wave generator consists of a wave generator plate, a servo driver, a servo motor, an encoder, a server, a computer and other peripherals, the calculation of wave generation control signals is completed by the computer according to parameters corresponding to required waves, the signals are transmitted to the servo driver through an interface circuit, the servo driver controls the rotation of the servo motor, and the ball screw converts the rotation of the motor into linear motion and generates expected waves through the wave generator plate.
6. The wind wave current generation system for simulating a tube-in-tube towing process of claim 1, wherein the measuring instrument comprises:
the wave height measuring instrument adopts a DS30 wave height acquisition system;
the flow velocity measuring instrument adopts a Vectrino acoustic Doppler three-dimensional flow velocity meter;
the water level measuring instrument adopts an ultrasonic water level meter;
the tension measuring instrument adopts a 2013 type tension comprehensive measuring system.
7. A test method for a wind wave current generation system for simulating a towing process of a immersed tube joint is characterized by comprising the following steps:
step one, calibrating a water flow field in a water tank/pool according to flow speed requirements corresponding to different water levels, and storing control parameters of a flow making system;
step two, mounting the pipe joint model in place according to the specified requirement, and mounting the tension meter in place;
starting a flow making system, monitoring water flow through a flow velocity meter, and after a flow field is stable, starting resistance measurement, wherein all tension instruments are synchronously collected by using an AD converter and a computer, the collection rate is 50Hz, and considering that unstable wake vortexes possibly exist at the downstream of a pipe joint under a large flow velocity, and the length of a sampling record is 10 minutes;
and fourthly, synthesizing the collected tensile force according to the angle in a time process, obtaining the maximum resistance Fd of the pipe joint in the corresponding direction, and calculating the resistance coefficient Cd value corresponding to the action angle of the water flow according to the Morrison formula.
8. The test method of claim 7, wherein the width of the pool is required to satisfy: the distance from the structural object to the side wall of the water tank is more than 3 times of the projection width of the structural object in the water flow direction, and in the resistance characteristic test research, 2 dynamic conditions of flow direction angles are simulated altogether;
when the water flow is arranged at 0 degree, the width of the pool exceeds (3+3+1) ×width (0.92 m) =6.44 m;
when the water flow is arranged at 90 degrees, the width of the water pool exceeds (3+3+1) x-type length (3.3 m) =23.1 m;
considering the conditions of the test site and the requirements of the test flow rate comprehensively, the 0-degree water flow action test is carried out in a water tank with the width of 7m, the maximum flow making capacity of the test is met with the requirements of the maximum flow rate of the test, the 90-degree water flow action test is carried out in a water tank with the width of 24m, and the maximum flow making capacity of the test is met with the requirements of the flow rate equivalent to 0.8m/s of the prototype.
9. A test model for use in a test method of the wind wave current generation system for simulating a tube section towing process of a immersed tube as claimed in claim 7, wherein the test model comprises a tube section model, a sinking barge model and a measuring tower model.
10. The test model of the test method for simulating the wind wave current generation system of the immersed tube joint towing process according to claim 9, wherein,
the shell of the pipe joint of the model is made of high-strength PVC plastic plates, the end sealing door is made of transparent acrylic plates, three pore canals in the sinking pipe are made of light wood-plastic plates, so that a very small space capable of balancing weight exists between the shell and the inner wood-plastic plates, and the pipe joint is made of high-density lead sheets by balancing weight of the pipe joint due to small space;
the sinking barge body is of a rectangular hollow shell structure, the model manufacturing material is wood, waterproof paint is adopted for external protection, and cement blocks are adopted for counterweight in the rectangular shell to meet the requirement that the gravity center position and the mass distribution are similar;
the structure of the measuring tower model is complex, and because the weight of the measuring tower is small relative to the weight of the immersed tube, the weight and the gravity center position of the measuring tower model are mainly guaranteed to be similar when the measuring tower model is manufactured, the measuring tower structure is manufactured by adopting light aluminum materials, and the weighing is performed by adopting small lead sheets.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117554029A (en) * | 2024-01-11 | 2024-02-13 | 中铁四局集团有限公司 | Open caisson floating transportation towing simulation test device and method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117554029A (en) * | 2024-01-11 | 2024-02-13 | 中铁四局集团有限公司 | Open caisson floating transportation towing simulation test device and method thereof |
| CN117554029B (en) * | 2024-01-11 | 2024-04-05 | 中铁四局集团有限公司 | Open caisson floating transportation towing simulation test device and method thereof |
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