Measuring platform for generating incoming flow with low Reynolds number and low turbulivity based on ejection principle

Abstract

The invention discloses a measuring platform for generating incoming flow with low Reynolds number and low turbulivity based on an injection principle, and belongs to the field of hydrodynamic experiment technology research. The measuring platform comprises a high-speed water inlet section, a convergence section, an experiment section and a water outlet section which are connected in sequence to form a linear non-closed measuring platform. The high-speed water inlet section introduces high-speed water flow with the controllable flow speed through a high-speed water pump, and a flow guiding device is arranged in the high-speed water inlet section to guide the water flow to the two sides to enter the convergence section. The two sides of the convergence section are connected with height-adjustable still water tanks, and pressure regulation control over still water in the convergence section is achieved. The speed-adjustable high-speed water flow and the pressure-adjustable still water are mixed in the convergence section on the basis of the ejection principle, finally, low-Reynolds-number low-turbulence incoming flow is generated in the experiment section, and a hydrodynamic experiment is carried out in the experiment section. The water outlet section is used for discharging water flow flowing out of the experiment section. The problem that an existing traditional water tunnel device cannot generate incoming flow with the low Reynolds number and the stable flow speed is solved, and the water tunnel device has the advantages of being simple in structure and convenient to disassemble and assemble.

Description

Technical Field

[0001] The invention belongs to the research field of hydrodynamic experimental technology, and in particular relates to a measurement platform for generating low Reynolds number and low turbulence incoming flow based on the ejection principle. Background Art

[0002] In the process of hydrodynamic research, a good experimental device is the prerequisite for effectively obtaining accurate flow information. Water tunnel is a common and effective experimental device for studying hydrodynamics. It has a set pipeline and simulates the interaction between the experimental object and the water flow field in the test section for experimental research. Unlike the movement of the model in still water, the model in the water tunnel experiment is generally fixed, and the experiment is carried out by controlling the relative velocity of the water flow. At present, the commonly used water tunnel devices are divided into two types according to the structure: vertical water tunnel and circulating water tunnel. Among them, the vertical water tunnel is powered by gravity, and the water flow flows from a water tank with a certain height into the pipeline. No additional power device is required, which is also called a gravity water tunnel. The circulating water tunnel is powered by a water pump to drive the water flow to circulate in the pipeline. The flow rate of the circulating water tunnel can be accurately adjusted, and the circulating water flow in the pipeline enables the experimenter to conduct long-term observations. The gravity water tunnel is limited by the large space occupied and the limited adjustable flow rate range, so the circulating water tunnel is often used in general experiments.

[0003] Water tunnel experiments under low Reynolds numbers are an important means to conduct research on the design, optimization, and active and passive control mechanisms of aircraft. However, existing water tunnel test systems, whether vertical or circulating, mostly adopt large-channel, large-flow, and high-velocity designs, with a general Reynolds number higher than 3900. In the current circulating water tunnels, the Reynolds number reaches more than 7000 in blunt-body flow experiments. Long-term use of such designs will not only damage the device itself, but also, due to its structural characteristics, generally only high-Reynolds number experiments can be carried out, making it difficult to carry out basic research on hydrodynamics under low Reynolds numbers.

[0004] The Chinese patent "A low-water-level gravity water tunnel with high flow rate and low turbulence" has the advantages of reduced loss and turbulence, but it is still a high-flow water tunnel and it is difficult to produce low Reynolds number inflow. In addition, most conventional water tunnels are driven by pressure difference, which makes it difficult to ensure that the inflow is stable and uniform. At the same time, conventional water tunnel devices are large and bulky, with high device consumption, inconvenient to assemble and use, and poor experimental flexibility. Therefore, it is necessary to design a measurement platform that is different from the traditional water tunnel experimental device, has a simple structure, is easy to disassemble and assemble, and can produce low Reynolds number and low turbulence inflow. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a measurement platform for generating low Reynolds number and low turbulence inflow based on the principle of ejection. The platform is a non-closed measurement platform formed by sequentially connecting a high-speed water inlet section, a convergence section, an experimental section, and a water outlet section. A flow guide device is provided in the high-speed water inlet section, and a still water tank with adjustable height is connected on both sides of the convergence section. The adjustable speed high-speed water flow and the adjustable pressure still water are mixed in the convergence section based on the principle of ejection, and finally a low Reynolds number and low turbulence inflow is generated in the experimental section. The present invention solves the problem that the existing traditional water tunnel device cannot generate low Reynolds number and stable flow rate inflow, and has the characteristics of simple structure and easy disassembly and assembly.

[0007] The technical solution of the present invention is: a measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle, comprising a high-speed water inlet section, a convergence section, a test section and a water outlet section which are sequentially connected in a straight line;

[0008] The high-speed water inlet section has one end away from the convergent section as a water inlet, which is connected to a high-speed water pump for introducing high-speed water flow; a flow guide device is installed inside the high-speed water inlet section for shrinking and guiding the high-speed water flow to both sides of the internal channel of the high-speed water inlet section and entering the convergent section; the flow rate of the high-speed water flow is adjustable;

[0009] Two still water tanks are symmetrically arranged on both sides of the convergent section. The still water tanks are connected to the still water inlets on both sides of the convergent section through hoses. The still water tanks are used to inject still water into the convergent section. The height of the still water tanks is adjustable, and is used to adjust the still water pressure in the convergent section.

[0010] A water flow space with low Reynolds number and low turbulence is formed in the experimental section for conducting hydrodynamic experiments; and the water outlet section is used to discharge the water flowing out of the experimental section.

[0011] A further technical solution of the present invention is that: the main body of the high-speed water entry section is a shell structure with a rectangular cross section and open ends, and is divided into a front contraction section and a transition section by a flow guide device;

[0012] The flow guide device is coaxially installed in the inner cavity of the high-speed water inlet section shell, and the flow guide device includes a flow guide front end, a contraction part and a transition part which are coaxially connected in sequence; the flow guide front end is hemispherical, and its spherical surface faces the water inlet; the contraction part transitionally connects the flow guide front end and one end of the transition part, and is used to guide the water flowing through the flow guide front end to the transition part; the cross-section of the transition part is rectangular, and its top wall and bottom wall are respectively in contact with and fixedly connected to the top wall and bottom wall of the inner cavity of the high-speed water inlet section, and its side walls on both sides respectively form high-speed water flow channels with the same spacing with the side walls on both sides of the inner cavity of the high-speed water inlet section, and the other end of the transition part is flush with one end of the high-speed water inlet section facing the convergence section;

[0013] The connection between the water inlet and the contraction section and the transition section is the front contraction section of the high-speed water entry section, and the section where the transition section is located is the transition section of the high-speed water entry section.

[0014] A further technical solution of the present invention is: the contraction angle of the contraction portion to both sides is 10° to 15°, and the width of the high-speed water flow channel on one side formed by the outer wall of the transition portion and the side wall of the inner cavity of the high-speed water entry section is 1 / 4 of the total width of the cross-section of the inner cavity of the high-speed water entry section.

[0015] A further technical solution of the present invention is that a honeycomb is installed in the inner cavity of the high-speed water inlet section near the convergence section to reduce the turbulence of the high-speed water flow.

[0016] A further technical solution of the present invention is: the convergent section is a shell structure with a rectangular cross-section and open ends; the side walls on both sides of the convergent section are symmetrically provided with static water inlets that penetrate the inner cavity; the static water boxes on both sides of the convergent section are watertightly connected to the static water inlets through hoses; the horizontal height of the static water box relative to the convergent section is adjustable, which is used to adjust the static water pressure in the convergent section.

[0017] A further technical solution of the present invention is: the high-speed water flow inlet end of the convergent section forms a still water area and a high-speed water flow area, the still water area is located at the center of the cross-section of the high-speed water flow inlet end of the convergent section, and the high-speed water flow area is located on both sides of the cross-section of the high-speed water flow inlet end of the convergent section, and after the high-speed water flow in the high-speed water flow area contacts the still water flow in the still water area, momentum exchange is generated in the convergent section based on the action of viscous force.

[0018] A further technical solution of the present invention is: the experimental section is a shell structure with a rectangular cross-section and open ends; a removable cover is provided on the top wall of the experimental section for placing the experimental model into the inner cavity of the experimental section; the side panels on both sides of the experimental section are transparent for observing the experimental conditions inside the experimental section; a model bracket is fixed to the bottom wall of the inner cavity of the experimental section for installing the experimental model; a hot wire anemometer is installed in the inner cavity of the experimental section for monitoring the quality of the incoming flow.

[0019] A further technical solution of the present invention is: the water outlet section adopts a linear gradually expanding channel, one end of which is connected to the water outlet of the experimental section, and the other end of the expanded end is connected to the water tank.

[0020] A further technical solution of the present invention is that the high-speed water inlet section, the convergence section, the experimental section and the water outlet section are all connected by connecting flanges, and watertight treatment is performed at the connection points.

[0021] A further technical solution of the present invention is that the rectangular cross-sections of the high-speed water entry section, the convergence section and the experimental section perpendicular to the water flow direction have the same size.

[0022] Beneficial Effects

[0023] The beneficial effects of the present invention are as follows: the present invention is a measurement platform for generating low Reynolds number and low turbulence incoming flow based on the ejection principle, which is provided with a high-speed water inlet section, a convergence section, an experimental section and an outlet section, and each section is connected in sequence by a flange plate, so as to form a straight-line non-closed measurement platform as a whole. The present invention connects a static water tank on both sides of the convergence section, connects the static water tank and the inner cavity of the convergence section through a hose, adjusts the height of the static water tank on both sides to adjust the pressure of the static water area, and adjusts the water flow velocity of the high-speed incoming water through a high-speed water pump, so that the static water and the high-speed water flow are mixed in the convergence section based on the ejection principle. Under the action of the viscous force, the speed-carrying fluids on both sides will interact with the central static fluid to generate momentum exchange without adding additional disturbances, thereby providing a low Reynolds number, low turbulence and easy-to-observe visual experimental environment in the experimental section, so that the incoming flow velocity can be controlled at 1-10 mm / s, and the Reynolds number is below 300, so as to realize the experimental study of hydrodynamics at a lower Reynolds number and lower turbulence.

[0024] The present invention abandons the conventional pressure difference drive to generate incoming flow, and instead generates low Reynolds number and low turbulence incoming flow through shear drive. According to the specific situation, by adjusting the high-speed water flow velocity and hydrostatic pressure in the convergent section, the contraction angle of the water flow to both sides of the contraction section in the high-speed water entry section, and the ratio of the width of the water flow channels on both sides of the transition section to the total width of the inner cavity of the high-speed water entry section, a large range and high-precision water flow speed control can be achieved, effectively ensuring the effect of the mixed shear of high-speed fluid and static fluid, and obtaining a high-quality low Reynolds number and low turbulence flow field space in the experimental section.

[0025] The present invention provides a measuring platform that is different from the traditional water tunnel device. The overall structure is a straight-through I-shaped horizontal structure. Each group of sections is connected by a standard flange, which has the advantages of simple structure and low device loss. The static water tank is innovatively set on both sides of the convergent section and connected to the inner cavity of the convergent section, which is convenient for adjusting the water pressure of the static water. The static water pressure can be adjusted by moving the static water tank up and down to obtain better shearing effect and speed adjustment, and can also have a better study on the essence of the ejection principle. The I-shaped non-circulating configuration of the present invention occupies a small area, has a longer service life, and is lower in cost. Compared with the large and bulky conventional water tunnels, the segmented structure of the measuring platform device is easy to disassemble and install, and is also easier to process and has a lower cost. In addition, visual plexiglass is used on both sides of the experimental section to facilitate flow field experimental observations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the overall structure of the measurement platform of the present invention;

[0027] Figure 2 It is a schematic diagram of the internal structure of the contraction section and the transition section of the high-speed water inlet section of the present invention;

[0028] Figure 3It is a plan view of the convergence section, the experimental section, and the water outlet section in the present invention;

[0029] Figure 4 This is a schematic diagram of the principle of generating a low Reynolds number and low turbulence incoming flow based on the ejection principle of the present invention.

[0030] Explanation of the reference numerals: 1. high-speed water inlet section, 11. water inlet, 12. front contraction section, 13. transition section, 2. convergence section, 21. still water inlet, 22. high-speed water flow inlet of the convergence section, 23. still water area, 24. high-speed water flow area, 3. experimental section, 31. cover plate, 32. model bracket, 33. visualization glass, 4. water outlet section, 5. flow guide device, 51. flow guide front end, 52. contraction part, 53. transition part, 6. still water tank, 7. honeycomb, 8. experimental model, 9. hot wire anemometer. DETAILED DESCRIPTION

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] See also Figure 1 , this embodiment provides a measurement platform for generating low Reynolds number and low turbulence inflow based on the principle of ejection. It is a horizontal straight-through non-closed hydrodynamic experimental device. The measurement platform includes a high-speed water inlet section 1, a convergent section 2, an experimental section 3 and a water outlet section 4, which are connected in sequence in a straight line. Each section is connected by a flange to form a water flow channel inside, and the joints are all watertight. The measurement platform introduces high-speed water flow through the left water inlet 11 of the high-speed water inlet section 1, and the high-speed water flow is contracted and diverted to both sides in the water flow channel of the high-speed water inlet section 1 before entering the convergent section 2. Still water is added to the convergent section 2, and the high-speed water flow and the still water are mixed and sheared in the convergent section 2, thereby generating a low Reynolds number and low turbulence inflow in the experimental section 3 to conduct hydrodynamic experiments, and then the water flow in the experimental section 3 is discharged through the outlet section 4. The specific technical solution of this embodiment is described as follows:

[0034] See also Figure 1The main body of the high-speed water inlet section 1 is a shell structure with a rectangular cross-section and open ends. The left end of the high-speed water inlet section 1, that is, the end away from the convergence section 2, is a water inlet 11. The water inlet 11 is connected to a high-speed water pump for introducing a high-speed water flow into the high-speed water inlet section 1. The flow rate of the high-speed water flow can be adjusted by the high-speed water pump. A flow guide device 5 is installed inside the high-speed water inlet section 1, which is used to shrink and guide the high-speed water flow entering the high-speed water inlet section 1 from the water inlet 11 to both sides of the internal water flow channel of the high-speed water inlet section before entering the convergence section 2. The high-speed water inlet section 1 is divided into a front shrinking section 12 and a transition section 13 by the flow guide device 5. The front shrinking section 12 is used to shrink the high-speed water flow entering the high-speed water inlet section 1, and the transition section 13 realizes a buffering transition of the shrunken high-speed water flow.

[0035] See also Figure 1 , 2 The flow guide device 5 is coaxially fixedly installed in the inner cavity of the shell of the high-speed water entry section 1. The flow guide device 5 includes a flow guide front end 51, a contraction portion 52 and a transition portion 53 which are coaxially connected in sequence. The section from the water inlet 11 to the connection between the contraction portion 52 and the transition portion 53 is the front contraction section 12 of the high-speed water entry section 1, and the section where the transition portion 53 is located is the transition section 13 of the high-speed water entry section 1.

[0036] The front end 51 of the diversion is hemispherical, and its spherical surface faces the water inlet 11 to achieve preliminary diversion. The contraction portion 52 transitionally connects the front end 51 of the diversion and one end of the transition portion 53, and is used to guide the water flow passing through the front end 51 to the transition portion 53. The cross-section of the transition portion 53 is rectangular, and its top wall and bottom wall are respectively in contact with and fixedly connected to the top wall and bottom wall of the inner cavity of the high-speed water entry section 1, and its side walls respectively form high-speed water flow channels with the same spacing with the side walls of the inner cavity of the high-speed water entry section. The other end of the transition portion 53 is flush with one end of the high-speed water entry section 1 facing the convergence section 2. The contraction portion 52 guides the water flow to the water flow channels on both sides formed by the transition portion 53 and the inner wall of the high-speed water entry section 1, so that the high-speed water flows through the water flow channels on both sides of the transition section 13 into the convergence section 2. In order to reduce the turbulence of the high-speed water flow, the present embodiment is provided with a honeycomb 7 installed in the inner cavity of the high-speed water entry section 1 near the convergence section 2, and the honeycomb 7 can be selected from conventional honeycombs.

[0037] In this embodiment, the contraction angle of the contraction portion 52 to both sides is 10° to 15°, and the width of the high-speed water flow channel on one side formed by the outer wall of the transition portion 53 and the inner cavity side wall of the high-speed water entry section 1 is 1 / 4 of the total width of the inner cavity cross section of the high-speed water entry section 1. The high-speed water flow channels on both sides of the transition section 13 are of equal width and are symmetrically arranged relative to the central axis of the high-speed water entry section 1.

[0038] See also Figure 1 , 3The convergent section 2 is a shell structure with a rectangular cross-section and open ends. Its left end is watertightly connected to the transition section 13 of the high-speed water entry section 1, and its right end is watertightly connected to the water inlet section of the experimental section. The side walls on both sides of the convergent section 2 are symmetrically provided with still water inlets 21 that penetrate the inner cavity of the convergent section 2, which are used to connect the still water tank 6. Two still water tanks 6 are symmetrically provided on both sides of the convergent section 2. The still water tanks 6 are connected to the still water inlets 21 on both sides of the convergent section 2 through hoses. The still water tanks 6 are used to inject still water flow into the convergent section 2. The still water tank 6 can move up and down, that is, the height relative to the convergent section 2 is adjustable, and is used to adjust the water pressure of the still water area in the convergent section 2. The adjustable high-speed water flow and the still water with adjustable hydrostatic pressure are mixed and decelerated in the convergent section 2, and the convergent section 2 provides an environment for studying the principle and method of ejection.

[0039] See also Figure 3 , 4 , the left side of the convergent section 2 is the high-speed water flow inlet 22 of the convergent section, and the high-speed water flow enters the convergent section 2 from here and mixes with the still water in the convergent section 2. Therefore, a still water area 23 and a high-speed water flow area 24 are formed at the high-speed water flow inlet end of the convergent section 2. The still water area 23 is located at the center of the cross section of the high-speed water flow inlet end of the convergent section 2, and the high-speed water flow area 24 is located on both sides of the cross section of the high-speed water flow inlet end of the convergent section 2. After the high-speed water flow in the high-speed water flow area 24 contacts the still water flow in the still water area 23, momentum exchange is generated in the convergent section based on the viscous force, thereby forming a water flow space with low Reynolds number and low turbulence in the experimental section 3.

[0040] See also Figure 1 , 3 The experimental section 3 is a shell structure with a rectangular cross section and open ends. The left end of the experimental section 3 is watertightly connected to the convergent section 2, and the right end is watertightly connected to the inlet end of the outlet section 4. A water flow space with low Reynolds number and low turbulence is formed in the experimental section 3 for conducting hydrodynamic experiments. A cover plate 31 is provided on the top wall of the experimental section 3, and the cover plate 31 is detachably fixedly connected to the top wall by screws. The cover plate 31 is used to place the experimental model 8 into the inner cavity of the experimental section 3. The side panels on both sides of the experimental section 3 are transparent, and a visual glass 33 is installed in the middle of the side panels. In this embodiment, transparent organic glass is used to observe the experimental conditions inside the experimental section 8. A model bracket 32 ​​is fixed to the bottom wall of the inner cavity of the experimental section 3 for installing the experimental model 8. The experimental model 8 adopts a model of an aircraft reduced according to the similarity criterion or a wing shape with hydrodynamic performance test value. A hot wire anemometer 9 is installed at one end of the inner cavity of the experimental section 3 close to the convergent section 2 to monitor the flow rate and stability of the fluid generated in the experimental section 3 under different conditions.

[0041] The water outlet section 4 is used to discharge the water flowing out of the experimental section 3. The water outlet section 4 adopts a linear gradually expanding channel, the left end of which is connected to the experimental section 3, and the other end of the expanded end is connected to the water tank. The water in the water tank can be re-introduced into the high-speed water inlet section 1 through a high-speed water pump for recycling.

[0042] The measurement platform for generating low Reynolds number and low turbulence flow based on the ejection principle provided in this embodiment is horizontally arranged, with an apparent total length of 1600mm and an apparent total height of 250mm. The total length of the high-speed water entry section 1 is L1, which is 400mm, and the cross-sectional area perpendicular to the water flow direction is 250*250mm. 2 The contraction angle of the contraction part 52 in the front contraction section 12 is 10°, the length L2 of the transition section 13 is 150mm, the ratio of the high-speed water flow channel width on one side of the cross section of the transition section 13 to the total width of the cross section of the transition section 13 is 1:4, and the two sides are symmetrical. The total length L3 of the convergence section 2 is 500mm, and the cross-sectional area perpendicular to the water flow direction is 250*250mm 2 The total length of the experimental section L4 is 350mm, and the cross-sectional area perpendicular to the water flow direction is 250*250mm 2 The rectangular cross-sections of the high-speed water entry section 1, the convergent section 2 and the experimental section 3 perpendicular to the water flow direction have the same size, which is convenient for connection and fixation through flanges.

[0043] The present invention adjusts the speed of the high-speed incoming water flow through a high-speed water pump, and the pressure of the static water flow in the convergent section 2 can be adjusted by adjusting the height of the static water tank 6. The high-speed water flow and the static water shear drive, the high-speed water flow entering the convergent section 2 on both sides interacts with the central static water flow to produce momentum exchange, and the central static fluid is driven to produce speed under the action of shear force, and sufficient shear occurs in the convergent section 2, and finally the required low Reynolds number and low turbulence visual experimental environment is generated in the experimental section 3 for experimental research on hydrodynamics. The present invention has a novel method for exploring the ejection principle and high adjustability. The measurement platform finally realized has a small footprint, low cost, simple structural design, and generates a low and relatively stable incoming flow velocity. The experimental section 3 can achieve a flow velocity of 1-10 mm / s and an incoming flow of Reynolds number within 300, which is conducive to the design, optimization and active and passive control mechanism research of underwater vehicles.

[0044] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle, characterized in that: It includes a high-speed water inlet section, a convergence section, a test section and a water outlet section which are connected in sequence in a straight line; The high-speed water inlet section has one end away from the convergent section as a water inlet, which is connected to a high-speed water pump for introducing high-speed water flow; a flow guide device is installed inside the high-speed water inlet section for shrinking and guiding the high-speed water flow to both sides of the internal channel of the high-speed water inlet section and entering the convergent section; the flow rate of the high-speed water flow is adjustable; Two still water tanks are symmetrically arranged on both sides of the convergent section. The still water tanks are connected to the still water inlets on both sides of the convergent section through hoses. The still water tanks are used to inject still water into the convergent section. The height of the still water tanks is adjustable, and is used to adjust the still water pressure in the convergent section. A water flow space with low Reynolds number and low turbulence is formed in the experimental section for conducting hydrodynamic experiments; and the water outlet section is used to discharge the water flowing out of the experimental section.

2. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1 is characterized in that: The main body of the high-speed water entry section is a shell structure with a rectangular cross section and open ends, and is divided into a front contraction section and a transition section by a flow guide device; The flow guide device is coaxially installed in the inner cavity of the high-speed water inlet section shell, and the flow guide device includes a flow guide front end, a contraction part and a transition part which are coaxially connected in sequence; the flow guide front end is hemispherical, and its spherical surface faces the water inlet; the contraction part transitionally connects the flow guide front end and one end of the transition part, and is used to guide the water flowing through the flow guide front end to the transition part; the cross-section of the transition part is rectangular, and its top wall and bottom wall are respectively in contact with and fixedly connected to the top wall and bottom wall of the inner cavity of the high-speed water inlet section, and its side walls on both sides respectively form high-speed water flow channels with the same spacing with the side walls on both sides of the inner cavity of the high-speed water inlet section, and the other end of the transition part is flush with one end of the high-speed water inlet section facing the convergence section; The connection between the water inlet and the contraction section and the transition section is the front contraction section of the high-speed water entry section, and the section where the transition section is located is the transition section of the high-speed water entry section.

3. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 2 is characterized in that: The contraction angle of the contraction portion to both sides is 10° to 15°, and the width of the high-speed water flow channel on one side formed by the outer wall of the transition portion and the side wall of the inner cavity of the high-speed water inlet section is 1 / 4 of the total width of the cross-section of the inner cavity of the high-speed water inlet section.

4. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1, characterized in that: A honeycomb is installed in the inner cavity of the high-speed water inlet section near the convergence section to reduce the turbulence of the high-speed water flow.

5. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1, characterized in that: The convergent section is a shell structure with a rectangular cross-section and open ends; the side walls on both sides of the convergent section are symmetrically provided with static water inlets that penetrate the inner cavity; the static water boxes on both sides of the convergent section are watertightly connected to the static water inlets through hoses; the horizontal height of the static water box relative to the convergent section is adjustable, which is used to adjust the static water pressure in the convergent section.

6. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 5, characterized in that: The high-speed water flow inlet end of the convergent section forms a still water area and a high-speed water flow area. The still water area is located at the center of the cross-section of the high-speed water flow inlet end of the convergent section, and the high-speed water flow area is located on both sides of the cross-section of the high-speed water flow inlet end of the convergent section. After the high-speed water flow in the high-speed water flow area contacts the still water flow in the still water area, momentum exchange is generated in the convergent section based on the action of viscous force.

7. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1, characterized in that: The experimental section is a shell structure with a rectangular cross-section and open ends; a removable cover is provided on the top wall of the experimental section for placing an experimental model into the inner cavity of the experimental section; the side panels on both sides of the experimental section are transparent for observing the experimental conditions inside the experimental section; a model bracket is fixed on the bottom wall of the inner cavity of the experimental section for installing the experimental model; a hot wire anemometer is installed in the inner cavity of the experimental section for monitoring the quality of the incoming flow.

8. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1, characterized in that: The water outlet section adopts a linear gradually expanding channel, one end of which is connected to the water outlet of the experimental section, and the other end of the expanded end is connected to the water tank.

9. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1, characterized in that: The high-speed water inlet section, the convergence section, the experimental section and the water outlet section are all connected by connecting flanges, and watertight treatment is performed at the connection points.

10. The measurement platform for generating low Reynolds number and low turbulence inflow based on the ejection principle according to claim 1, characterized in that: The rectangular cross-sections of the high-speed water entry section, the convergence section and the experimental section perpendicular to the water flow direction have the same size.

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