A measurement platform for generating low Reynolds number and low turbulence intensity incoming flow based on the ejection principle

Abstract

This invention discloses a measurement platform for generating low Reynolds number and low turbulence flow based on the ejection principle, belonging to the field of hydrodynamic experimental technology research. The measurement platform comprises a high-speed inlet section, a convergence section, an experimental section, and an outlet section connected sequentially, forming a linear, non-closed measurement platform. The high-speed inlet section introduces a high-speed water flow with controllable velocity via a high-speed pump. A flow guide device within the high-speed inlet section directs the water flow to both sides before it enters the convergence section. Adjustable-height stilling water tanks are connected to both sides of the convergence section to regulate the pressure of the still water within the convergence section. The adjustable-speed water flow and the adjustable-pressure still water mix in the convergence section based on the ejection principle, ultimately generating a low Reynolds number and low turbulence flow in the experimental section, where hydrodynamic experiments are conducted. The outlet section is used to discharge the water flowing out of the experimental section. This invention solves the problem that existing traditional water tunnel devices cannot generate low Reynolds number and stable velocity flows, and features a simple structure that is easy to assemble and disassemble.

Description

Technical Field

[0001] This invention belongs to the field of hydrodynamic experimental technology research, specifically involving a measurement platform for generating low Reynolds number and low turbulence intensity incoming flow based on the ejection principle. Background Technology

[0002] In hydrodynamic research, a high-performance experimental setup is essential for obtaining accurate flow information. Water tunnels are a common and effective experimental device in hydrodynamics research. They consist of pre-defined pipes that simulate the interaction between the experimental object and the water flow field within the test section, facilitating experimental research. Unlike models moving in still water, models in water tunnel experiments are generally stationary, and the experiment is conducted by controlling the relative velocity of the water flow. Currently, commonly used water tunnel setups are classified into two types based on their structure: vertical water tunnels and circulating water tunnels. Vertical water tunnels are powered by gravity, drawing water from a tank of a certain height into the pipes, requiring no additional power unit; they are also called gravity water tunnels. Circulating water tunnels, on the other hand, are powered by a water pump, propelling the water flow through the pipes in a cycle. The flow rate in a circulating water tunnel can be precisely adjusted, and the circulating water allows for extended observation by researchers. Gravity water tunnels are limited by their large footprint and limited adjustable flow rate range; therefore, circulating water tunnels are generally more commonly used in experiments.

[0003] Low Reynolds number water tunnel experiments are an important tool for studying the design, optimization, and active / passive control mechanisms of aircraft. However, existing water tunnel test systems, whether vertical or circulating, mostly employ designs with large channels, high flow rates, and high velocities, generally resulting in Reynolds numbers exceeding 3900. In current circulating water tunnels conducting bluff body flow experiments, Reynolds numbers have even reached over 7000. Long-term use of such designs not only damages the equipment itself but also, due to their structural characteristics, generally limits experiments to high Reynolds numbers, making it difficult to conduct fundamental hydrodynamic research at low Reynolds numbers.

[0004] The Chinese patent, "A Gravity-Type Water Tunnel with High Flow Velocity and Low Turbulence," offers advantages in reducing losses and turbulence, but it remains a high-velocity water tunnel, making it difficult to generate low Reynolds number flows. Furthermore, conventional water tunnels mostly rely on pressure differentials, which struggle to ensure stable and uniform flow. Additionally, conventional water tunnel devices are large and bulky, resulting in high energy consumption, inconvenient assembly and use, and poor experimental flexibility. Therefore, there is a need to design a measurement platform that differs from traditional water tunnel experimental devices, featuring a simple structure, easy assembly and disassembly, and the ability to generate low Reynolds number and low turbulence flows. Summary of the Invention

[0005] The technical problem to be solved:

[0006] To overcome the shortcomings of existing technologies, this invention provides a measurement platform for generating low Reynolds number and low turbulence flow based on the ejection principle. This non-closed measurement platform consists of a high-speed inlet section, a convergence section, an experimental section, and an outlet section connected sequentially. A flow guiding device is installed within the high-speed inlet section, and adjustable-height still water tanks are connected to both sides of the convergence section. The adjustable-speed high-speed water flow and adjustable-pressure still water mix in the convergence section based on the ejection principle, ultimately generating a low Reynolds number and low turbulence flow in the experimental section. This invention solves the problem that existing traditional water tunnel devices cannot generate low Reynolds number and stable velocity flows, and features a simple structure that is easy to assemble and disassemble.

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

[0008] The high-speed water inlet section has an inlet at the end furthest from the converging section. The inlet is connected to a high-speed water pump to introduce high-speed water flow. A flow guiding device is installed inside the high-speed water inlet section to guide the high-speed water flow to both sides of the internal channel of the high-speed water inlet section and into the converging section. The flow rate of the high-speed water flow is adjustable.

[0009] Two static water tanks are symmetrically arranged on both sides of the convergence section. The static water tanks are connected to the static water inlets on both sides of the convergence section through hoses. The static water tanks are used to inject static water into the convergence section. The height of the static water tanks is adjustable to regulate the static water pressure in the convergence section.

[0010] The experimental section forms a low Reynolds number and low turbulence space for hydrodynamic experiments; the outlet section is used to discharge the water flowing out of the experimental section.

[0011] A further technical solution of the present invention is: the main body of the high-speed water inlet section is a shell structure with a rectangular cross-section and open at both ends, which is divided into a pre-contraction section and a transition section by a flow guiding device;

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

[0013] The section from the inlet to the junction of the contraction section and the transition section is the pre-contraction section of the high-speed water inlet section, and the section where the transition section is located is the transition section of the high-speed water inlet section.

[0014] A further technical solution of the present invention is: the angle at which the contraction part contracts to both sides is 10° to 15°, and the width of the high-speed water flow channel formed by the outer wall of the transition part and the inner wall 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.

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

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

[0017] A further technical solution of the present invention is: the high-speed water flow inlet end of the convergence section forms a still water zone and a high-speed water flow zone. The still water zone is located at the center of the cross-section of the high-speed water flow inlet end of the convergence section, and the high-speed water flow zone is located on both sides of the cross-section of the high-speed water flow inlet end of the convergence section. After the high-speed water flow in the high-speed water flow zone comes into contact with the still water flow in the still water zone, momentum exchange occurs in the convergence section based on the action of viscous force.

[0018] A further technical solution of the present invention is as follows: the experimental section is a shell structure with a rectangular cross-section and open ends; the top wall of the experimental section is provided with a detachable cover plate for inserting the experimental model into the inner cavity of the experimental section; the side plates of the experimental section are designed to be transparent for observing the experimental conditions inside the experimental section; a model support 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 outlet section adopts a linearly expanding channel, one end of which is connected to the outlet of the experimental section, and the other end of which is expanded and 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 dimensions.

[0022] Beneficial effects

[0023] The beneficial effects of this invention are as follows: This invention provides a measurement platform for generating low Reynolds number and low turbulence flow based on the ejection principle. It comprises a high-speed inlet section, a convergence section, an experimental section, and an outlet section, with each section connected sequentially via flanges to form a single-line, non-closed measurement platform. This invention connects still water tanks to both sides of the convergence section, with flexible hoses connecting the still water tanks to the inner cavity of the convergence section. The pressure in the still water zone is adjusted by regulating the height of the two still water tanks, and the high-speed inlet water velocity is regulated by a high-speed water pump. This allows the still water and high-speed flow to mix in the convergence section based on the ejection principle. Under the action of viscous forces, the velocities on both sides interact with the central still fluid, generating momentum exchange without adding additional disturbance. This provides a low Reynolds number, low turbulence, and easily observable visual experimental environment in the experimental section, allowing the inlet flow velocity to be controlled between 1-10 mm / s and the Reynolds number to be below 300, enabling hydrodynamic experimental research at lower Reynolds numbers and lower turbulence.

[0024] This invention eliminates the conventional pressure difference-driven flow generation method, instead generating a low Reynolds number and low turbulence flow through shear drive. Depending on the specific circumstances, by adjusting the high-speed flow velocity and hydrostatic pressure in the convergence section, the contraction angle of the contraction section in the high-speed inlet section, and the ratio of the width of the flow channels on both sides of the transition section to the total width of the high-speed inlet section's inner cavity, a wide range of high-precision flow velocity control can be achieved. This effectively ensures the effect of shearing between the high-speed fluid and the stationary fluid, resulting in a high-quality low Reynolds number and low turbulence flow field in the experimental section.

[0025] This invention provides a measurement platform that differs from traditional water tunnel devices. It features a horizontal, straight-through structure with standard flange connections between sections, offering advantages such as simple structure and low device wear. Innovatively, the static water tanks are positioned on both sides of the convergence section and connected to its inner cavity, facilitating static water pressure adjustment. The static water pressure can be adjusted by moving the static water tanks up and down, resulting in better shearing effects and variable speed control, and allowing for a better understanding of the ejection principle. The straight, non-circulating configuration of this invention has a small footprint, longer service life, and lower cost. Compared to the large and bulky nature of conventional water tunnels, the segmented structure of this measurement platform facilitates disassembly and installation, is easier to manufacture, and has lower costs. Furthermore, the experimental section uses visible acrylic glass on both sides, facilitating flow field experimental observations. Attached Figure Description

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

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

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

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

[0030] Explanation of reference numerals in the attached diagrams: 1. High-speed water inlet section; 11. Water inlet; 12. Pre-contraction section; 13. Transition section; 2. Converging section; 21. Still water inlet; 22. High-speed water inlet of the convergence section; 23. Still water zone; 24. High-speed water zone; 3. Experimental section; 31. Cover plate; 32. Model support; 33. Visualization glass; 4. Water outlet section; 5. Flow guiding device; 51. Flow guiding front end; 52. Convergence section; 53. Transition section; 6. Still water tank; 7. Honeycomb structure; 8. Experimental model; 9. Hot-wire anemometer. Detailed Implementation

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

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] See Figure 1 This embodiment provides a measurement platform for generating low Reynolds number and low turbulence flow based on the ejection principle. It is a horizontal, straight-through, non-closed hydrodynamic experimental device. The platform includes a high-speed inlet section 1, a convergence section 2, an experimental section 3, and an outlet section 4, connected in a straight line. Each section is connected by flanges, forming an internal water flow channel, and all connections are watertight. The platform introduces high-speed water flow through the left inlet 11 of the high-speed inlet section 1. The high-speed water flow is then guided and contracted to both sides within the water flow channel of the high-speed inlet section 1 before entering the convergence section 2. Still water is added to the convergence section 2. The high-speed water flow and the still water undergo mixing and shearing within the convergence section 2, thereby generating a low Reynolds number and low turbulence flow in the experimental section 3 for hydrodynamic experiments. The water flow from the experimental section 3 is then discharged through the outlet section 4. The specific technical solution of this embodiment is described below:

[0034] See Figure 1The high-speed water inlet section 1 is a rectangular shell structure with open ends. The left end of the high-speed water inlet section 1, away from the converging section 2, is the inlet 11, which is connected to a high-speed water pump to introduce 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 guiding device 5 is installed inside the high-speed water inlet section 1 to guide and contract the high-speed water flow entering the high-speed water inlet section 1 to both sides of the internal water flow channel before entering the converging section 2. The high-speed water inlet section 1 is divided into a pre-contraction section 12 and a transition section 13 by the flow guiding device 5. The pre-contraction section 12 contracts the high-speed water flow entering the high-speed water inlet section 1, and the transition section 13 buffers and transitions the contracted high-speed water flow.

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

[0036] The guide front end 51 is hemispherical, with its spherical surface facing the inlet 11, achieving initial flow guidance. The converging part 52 transitions between the guide front end 51 and one end of the transition part 53, guiding the water flow passing through the guide front end 51 to the transition part 53. The transition part 53 has a rectangular cross-section, with its top and bottom walls contacting and fixedly connected to the top and bottom walls of the inner cavity of the high-speed water inlet section 1, respectively. Its two side walls form high-speed water flow channels with the same spacing as the side walls of the inner cavity of the high-speed water inlet section. The other end of the transition part 53 is flush with the end of the high-speed water inlet section 1 facing the converging section 2. The converging part 52 guides the water flow to the two side water flow channels formed by the transition part 53 and the inner wall of the high-speed water inlet section 1, allowing the high-speed water to flow through the water flow channels on both sides of the transition section 13 into the converging section 2. To reduce the turbulence of the high-speed water flow, in this embodiment, a honeycomb device 7 is installed near the converging section 2 in the inner cavity of the high-speed water inlet section 1. A conventional honeycomb device can be used for the honeycomb device 7.

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

[0038] See Figure 1 , 3The converging section 2 is a rectangular shell structure with open ends. Its left end is watertightly connected to the transition section 13 of the high-speed water inlet section 1, and its right end is watertightly connected to the inlet section of the experimental section. Symmetrically arranged on both side walls of the converging section 2 are static water inlets 21 that penetrate the inner cavity of the converging section 2, used to connect to static water tanks 6. Two static water tanks 6 are symmetrically arranged on both sides of the converging section 2, connected to the static water inlets 21 on both sides of the converging section 2 via flexible hoses. The static water tanks 6 are used to inject static water flow into the converging section 2. The static water tanks 6 are vertically movable, i.e., their height relative to the converging section 2 is adjustable, used to regulate the water pressure in the static water zone within the converging section 2. The adjustable high-speed water flow and the adjustable static water pressure mix and decelerate within the converging section 2, providing an environment suitable for studying the ejection principle method.

[0039] See Figure 3 , 4 The high-speed water flow inlets 22 are located on both sides of the left end of the convergence section 2. The high-speed water flows into the convergence section 2 through these inlets and mix with the still water within it. This creates a still water zone 23 and a high-speed water flow zone 24 at the high-speed water flow inlet of the convergence section 2. The still water zone 23 is located at the center of the cross-section at the high-speed water flow inlet of the convergence section 2, while the high-speed water flow zones 24 are located on both sides of the cross-section at the high-speed water flow inlet of the convergence section 2. After the high-speed water flow in the high-speed water flow zone 24 comes into contact with the still water flow in the still water zone 23, momentum exchange occurs in the convergence section due to viscous forces, thus creating a low Reynolds number, low turbulence flow space within the experimental section 3.

[0040] See Figure 1 , 3 Experimental section 3 is a rectangular shell structure with open ends. The left end of experimental section 3 is watertightly connected to convergent section 2, and the right end is watertightly connected to the inlet end of outlet section 4. A low Reynolds number, low turbulence flow space is formed within experimental section 3 for hydrodynamic experiments. A cover plate 31 is provided on the top wall of experimental section 3, which is detachably fixed to the top wall by screws. The cover plate 31 is used to insert the experimental model 8 into the inner cavity of experimental section 3. The side plates of experimental section 3 are transparent, with a viewing glass 33 installed in the middle of the side plates. In this embodiment, transparent plexiglass is used to observe the experimental conditions inside experimental section 8. A model support 32 is fixed to the bottom wall of the inner cavity of experimental section 3 for mounting the experimental model 8. The experimental model 8 is a scaled-down aircraft model based on similarity criteria or an airfoil with hydrodynamic performance testing value. A hot-wire anemometer 9 is installed near the convergent section 2 inside the inner cavity of experimental section 3 to monitor the flow velocity and stability of the fluid generated in experimental section 3 under different conditions.

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

[0042] The measurement platform provided in this embodiment, which generates a low Reynolds number and low turbulence flow based on the ejection principle, is horizontally set up. Its total length is 1600mm and its total height is 250mm. The high-speed water inlet section 1 has a total length L1 of 400mm and a cross-sectional area perpendicular to the water flow direction of 250*250mm. 2 In the pre-contraction section 12, the contraction angle of the contraction part 52 to both sides is 10°. The length L2 of the transition section 13 is 150mm. The ratio of the width of the high-speed water flow channel 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 is L4, which is 350 mm, and the cross-sectional area perpendicular to the water flow direction is 250 x 250 mm. 2 The high-speed water inlet section 1, the convergence section 2, and the experimental section 3 have the same rectangular cross-sectional dimensions perpendicular to the water flow direction, which facilitates connection and fixation via flanges.

[0043] This invention utilizes a high-speed water pump to regulate the velocity of the high-speed incoming water flow. The pressure of the static water flow in the convergence section 2 can be adjusted by regulating the height of the still water tank 6. Through shear drive between the high-speed water flow and the static water, the high-speed water flow entering from both sides of the convergence section 2 interacts with the central static water flow, generating momentum exchange. Under the action of shear force, the central static fluid generates velocity, and sufficient shearing occurs within the convergence section 2. Ultimately, the desired low Reynolds number and low turbulence visualization experimental environment is generated in the experimental section 3 for hydrodynamic experimental research. This invention offers a novel and highly adjustable method for exploring the ejection principle. The resulting measurement platform has a small footprint, low cost, and simple structural design. It generates a low and stable incoming flow velocity, achieving an incoming flow velocity of 1-10 mm / s and a Reynolds number below 300 in the experimental section 3. This is beneficial for conducting research on the design, optimization, and active / passive control mechanisms of underwater vehicles.

[0044] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A measurement platform for generating low Reynolds number and low turbulence intensity incoming flow based on the ejection principle, characterized in that, It includes a high-speed water inlet section, a convergence section, an experimental section, and a water outlet section that are connected in a straight line. The high-speed water inlet section has an inlet at the end furthest from the converging section. The inlet is connected to a high-speed water pump to introduce high-speed water flow. A flow guiding device is installed inside the high-speed water inlet section to guide the high-speed water flow to both sides of the internal channel of the high-speed water inlet section and into the converging section. The flow rate of the high-speed water flow is adjustable. Two static water tanks are symmetrically arranged on both sides of the convergence section. The static water tanks are connected to the static water inlets on both sides of the convergence section through hoses. The static water tanks are used to inject static water into the convergence section. The height of the static water tanks is adjustable to regulate the static water pressure in the convergence section. The experimental section forms a low Reynolds number and low turbulence space for hydrodynamic experiments; the outlet section is used to discharge the water flowing out of the experimental section. The converging section is a shell structure with a rectangular cross-section and open ends; symmetrical still water inlets communicating with the inner cavity are provided on both side walls of the converging section; still water tanks on both sides of the converging section are watertightly connected to the still water inlets via flexible hoses; the horizontal height of the still water tanks relative to the converging section is adjustable to regulate the still water pressure inside the converging section. The high-speed water flow inlet end of the convergence section forms a still water zone and a high-speed water flow zone. The still water zone is located at the center of the cross-section of the high-speed water flow inlet end of the convergence section, and the high-speed water flow zone is located on both sides of the cross-section of the high-speed water flow inlet end of the convergence section. After the high-speed water flow in the high-speed water flow zone comes into contact with the still water flow in the still water zone, momentum exchange occurs in the convergence section based on the action of viscous force. A honeycomb device is installed in the inner cavity of the high-speed water inlet section near the converging section to reduce the turbulence of the high-speed water flow.

2. The measurement platform for generating low Reynolds number and low turbulence intensity incoming flow based on the ejection principle according to claim 1, characterized in that, The main body of the high-speed water inlet section is a shell structure with a rectangular cross-section and open ends. It is divided into a pre-contraction section and a transition section by a flow guiding device. The flow guiding device is coaxially installed in the inner cavity of the high-speed water inlet section shell. The flow guiding device includes a flow guiding front end, a converging part, and a transition part connected coaxially in sequence. The flow guiding front end is hemispherical, with its spherical surface facing the water inlet. The converging part transitionally connects one end of the flow guiding front end and the transition part, and is used to guide the water flowing through the flow guiding front end to the transition part. The transition part has a rectangular cross-section. Its top wall and bottom wall are in contact with and fixedly connected to the top wall and bottom wall of the inner cavity of the high-speed water inlet section, respectively. Its two side walls form high-speed water flow channels with the same spacing as the two side walls of the inner cavity of the high-speed water inlet section. The other end of the transition part is flush with the end of the high-speed water inlet section facing the converging section. The section from the inlet to the junction of the contraction section and the transition section is the pre-contraction section of the high-speed water inlet section, and the section where the transition section is located is the transition section of the high-speed water inlet section.

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

4. The measurement platform for generating low Reynolds number and low turbulence intensity incoming flow 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. The top wall of the experimental section is equipped with a detachable cover plate for inserting the experimental model into the inner cavity of the experimental section. The side plates of the experimental section are transparent for observing the experimental conditions inside the experimental section. A model support 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.

5. The measurement platform for generating low Reynolds number and low turbulence intensity incoming flow based on the ejection principle according to claim 1, characterized in that, The outlet section adopts a linearly expanding channel, with one end connected to the outlet of the experimental section and the other end flared out to enter the water tank.

6. The measurement platform for generating low Reynolds number and low turbulence intensity incoming flow based on the ejection principle according to claim 1, characterized in that, The high-speed water inlet section, convergence section, experimental section, and outlet section are all connected by connecting flanges, and the connection points are watertight.

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

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