A density stratification creation system

Abstract

The application provides a density stratification system, belonging to the technical field of fluid dynamics experiment. The system comprises a water tank, a salt water tank and a flow generating unit. The water tank comprises a ring channel for containing water. One side of the water tank is a water inlet section, which is connected with the salt water tank and supplies the ring channel with salt water of a set concentration. The other side of the water tank is provided with the flow generating unit, which gives the water flow in the ring channel a set flow rate. The water tank is provided with a detection unit in the water inlet section. The device is used for the research of water flow dynamics such as density and velocity, and has the advantages of simple stratification, controllable velocity and stable hierarchical structure.

Description

Technical Field

[0001] This application relates to a density stratification system, belonging to the field of fluid dynamics experimental technology. Background Technology

[0002] In the fields of natural sciences and engineering, problems involving stratified fluid flow are numerous and increasingly attracting attention. Currently, existing research on stratified fluids mainly employs the drag tank method and wind tunnel experiments.

[0003] In the drag-and-drop method, fluid density stratification is achieved by adjusting salt water of different concentrations. Although density stratification can be controlled relatively precisely, the process of achieving relative fluid flow through a mechanical drag model will seriously affect the original density profile of the fluid, making it impossible to repeat the experiment. Furthermore, the synchronous movement of the data acquisition system for flow field and other data is inconvenient.

[0004] In wind tunnel experiments, density stratification is achieved by heating or cooling a specific wall surface. However, due to the limitations of air thermal properties, density stratification is often ineffective, and a large incoming air velocity can quickly destroy the original stratified structure, making it impossible to achieve a stable stratified flow effect. Summary of the Invention

[0005] In view of this, this application provides a density stratification system that, while maintaining fluid stability, enables precise measurement of velocity field, density field, temperature field, etc., providing a theoretical basis for the observation of related fluid properties and heat and mass transfer phenomena.

[0006] Specifically, this application is implemented through the following scheme:

[0007] A density stratification system includes a water tank, a brine tank, and a flow generation unit.

[0008] The water tank includes a ring channel for holding water;

[0009] One side of the water tank is the water inlet section, which is connected to the brine tank to supply brine of a set concentration into the loop; the other side is equipped with a flow-generating unit to give the water in the loop a set flow rate.

[0010] A detection unit is installed in the water tank of the inlet section;

[0011] Turn on the brine tank and supply water of the set concentration into the loop to the set level; turn off the brine tank and start the flow generation unit. The water flow near the flow generation unit is turbulent. When the inlet section reaches the set velocity, turn off the flow generation unit and start the detection unit to perform dynamic tests on the water flow of the set density and speed.

[0012] Compared to traditional density stratification tanks, this project constructs a specific density profile through a density stratification system, achieving stable stratified flow with the help of a flow-generating unit. It also allows for precise measurement of heat and mass transfer phenomena under certain density stratification and background flow conditions in the test / inlet sections. The flow-generating mechanism is installed in the stratified flow circulating tank, creating a physical scenario where the fluid circulates at a certain velocity while maintaining stable brine density stratification.

[0013] Furthermore, as a preferred option:

[0014] The water tank has a ring-shaped structure formed by the inner wall, outer wall, and bottom.

[0015] An inlet pipe is introduced into the inlet section, and a diffuser float is installed at the end of the inlet pipe located in the water tank. The other end of the inlet pipe is connected to the outlet of the peristaltic pump, and the inlet of the peristaltic pump is connected to the brine tank through a water supply pipe. The peristaltic pump, brine tank, and diffuser float deliver water of a set concentration (set in the brine tank) into the water tank.

[0016] The flow-generating unit is equipped with two flow-generating pumps, each with disc-shaped blades. The two pumps rotate in opposite directions with adjacent blades overlapping, generating flow on one side of the loop. More preferably, the flow-generating pump includes a guide wheel shaft, a coupling, a reducer, a servo motor, and a main shaft. The guide wheel shaft is driven to rotate by the servo motor and the reducer. The main shaft is fitted onto the output end of the guide wheel shaft, and multiple sets of blades are mounted on the main shaft. During installation, at least one fixing plate, such as fixing plate one and fixing plate two, can be installed on the guide wheel shaft above the main shaft. These plates connect the bearings to the tank frame, thus fixing the flow-generating pump and ensuring stable rotation. The bottom of the guide wheel shaft is connected to the bottom of the tank via a bushing. The guide wheel shaft above the main shaft is connected to fixing plate one via a bearing. Fixing plate two is installed above fixing plate one, with both ends mounted on the top of the support frame. Mounting holes are provided on fixing plate two, and a reducer is installed on top of it. The reducer is connected to the guide wheel shaft via a coupling (such as a flexible coupling), and the servo motor is connected above the reducer.

[0017] In the flow-generating unit consisting of two flow-generating pumps, two servo motors drive the corresponding guide wheel shafts to rotate in opposite directions, thereby driving the corresponding main shaft and the blades on it to rotate synchronously.

[0018] In the aforementioned device, a water tank constitutes the simulated construction unit, a brine tank and a peristaltic pump constitute the density stratification unit, and a flow-generating pump works in conjunction with the water tank to form the flow-generating unit. These three components work together to achieve a density stratification construction system, ensuring a stable supply of density and flow rate. When the peristaltic pump is turned on, water from the brine tank is pumped into the water tank. When the set level is reached, the peristaltic pump is turned off, and the flow-generating pump is started. After a certain period of flow generation, the flow-generating pump is turned off, allowing for dynamic testing of the water flow at a set density and velocity on the inlet side.

[0019] It also includes a heated water circulation system, with insulation and heat transfer modules installed within the water tank, which work in conjunction with the heated water circulation system. A physical model with specific thermodynamic boundaries can be constructed in the test section, allowing for precise measurements of the velocity, density, and temperature fields around the model. This device provides the means to observe and measure density stratification flow and related heat and mass transfer phenomena under experimental conditions.

[0020] The above-mentioned scheme presents challenges in the experimental measurement and study of various physical phenomena, such as the occurrence and development of thermal convection boundaries, under specific density stratification and fluid flow background conditions. On the one hand, it requires constructing accurate fluid density stratification conditions and flow velocities; on the other hand, it requires ensuring that the density stratification remains stable for a sufficient period of time, which is difficult to achieve in traditional drag-and-drop water tank experiments. This invention addresses the shortcomings of existing technologies by providing a novel stratified flow circulating water tank to achieve stable stratified horizontal flow and to accurately measure heat and mass transfer phenomena under certain density stratification and background flow conditions in the test section. Attached Figure Description

[0021] Figure 1 A front view of the system constructed for this application;

[0022] Figure 2 A top view of the system created for this application;

[0023] Figure 3 This is a schematic diagram of the flow-generating pump in this application;

[0024] Figure 4 This is a schematic diagram of the guide wheel in this application;

[0025] Figure 5 This is a schematic diagram of the test structure for this application;

[0026] Figure 6 This is a schematic diagram illustrating the usage status of this application;

[0027] Figure 7 This is a schematic diagram of the test status of this application.

[0028] Numbered in the diagram: 1. Water tank; 11. Support frame; 12. Upper beam; 13. Lower beam; 14. Base frame; 15. Tank wall; 16. Tank bottom; 17. Arc-shaped bend; 18. Drain pipe; 2. Brine tank; 21. Agitator; 22. Connecting pipe; 23. Connecting valve; 24. Agitator pump; 3. Peristaltic pump; 31. Water supply pipe; 32. Water inlet pipe; 33. Float diffuser; 4. Clear water tank; 5. Flow pump; 5a. Flow pump one; 5b. Flow pump two; 51. Guide wheel shaft; 52. Bushing; 53. Bearing; 54. Coupling; 541. Flat key; 55. Servo motor; 56. 57. Reducer; 571. Main shaft; 572. Guide wheel shaft hole; 573. Blade; 6. Fixing plate one; 7. Fixing plate two; 8. Heating water circulation system; 81. Insulation module; 82. Heat exchange module; 9. Laser instrument; 10. Camera. Detailed Implementation Example 1

[0029] The density stratification system in this embodiment includes a water tank 1, a brine tank 2, and a flow pump 5.

[0030] The water tank 1 is a ring-shaped structure formed by the inner wall, outer wall and bottom. One side is the water inlet section, through which salt water of a set concentration is introduced; the other side is equipped with a flow pump 5, which makes the water flow through the ring channel on that side turbulent, giving the water flow a specific velocity.

[0031] Combination Figure 1 and Figure 2 A water inlet pipe 32 is introduced into the water inlet section. A diffuser float 33 is installed at the end of the water inlet pipe 32 located in the water tank 1. The other end of the water inlet pipe 32 is connected to the outlet of the peristaltic pump 3. The inlet of the peristaltic pump 3 is connected to the brine tank 2 through the water supply pipe 31. The peristaltic pump 3, the brine tank 2, and the diffuser float 33 deliver water of a set concentration (set in the brine tank 2) into the water tank 1.

[0032] Combination Figure 2 , Figure 3 There are two flow pumps 5, which rotate in opposite directions and have some blades 572 as shown. Figure 3 The overlapping pattern shown completes flow generation on this side of the loop.

[0033] Among them, combined Figure 3 The flow pump 5 includes a guide wheel shaft 51, a coupling 54, a reducer 56, a servo motor 55, and a main shaft 57. The guide wheel shaft 51 is driven to rotate by the servo motor 55 and the reducer 56. The main shaft 57 is mounted on the output end of the guide wheel shaft 51, and multiple sets of blades 572 are arranged on the main shaft 57.

[0034] During installation, the bottom of the guide wheel shaft 51 is connected to the bottom of the groove 16 through the bushing 52. The guide wheel shaft 51 above the main shaft 57 is connected to the first fixing plate 6 through the bearing 53. The second fixing plate 7 is set above the first fixing plate 6. The two ends of the second fixing plate 7 are mounted on the top of the bracket 11. Mounting holes are opened on it, and a reducer 56 is installed on it. The reducer 56 is connected to the guide wheel shaft 51 by a coupling 54 (such as a flexible coupling). The servo motor 55 is connected above the reducer 56.

[0035] In the flow-generating unit consisting of two flow-generating pumps 5, two servo motors 55 drive the corresponding guide wheel shafts 51 to rotate in opposite directions, thereby driving the corresponding main shaft 57 and the blades 572 on it to rotate synchronously.

[0036] In the above-mentioned device, the water tank 1 constitutes the simulated construction work unit, the brine tank 2, the peristaltic pump 3, etc. constitute the density stratification unit, and the flow pump 5, together with the water tank 1, constitutes the flow generation unit. The three work together to realize the density stratification construction system and achieve a stable supply of density and flow rate. Example 2

[0037] This embodiment has the same setup as Embodiment 1, the difference being: [combination of...] Figure 5 It also includes a heating water circulation system 8, with an insulation module 81 and a heat transfer module 82 installed in the water tank 1. The insulation module 81 and the heat transfer module 82 work together with the heating water circulation system 8 to monitor the temperature.

[0038] In the above scheme:

[0039] The main body of the water tank 1 can adopt a ring-shaped structure consisting of a profile frame and a glass outer wall.

[0040] The profile frame includes a support 11, an upper beam 12, a lower beam 13, a base frame 14, and an arc-shaped bend 17. The upper beam 12, lower beam 13, and base frame 14 are arranged from top to bottom and fixed at different heights of the support 11. The upper beam 12 and the upper arc-shaped bend 17 form the first arc-shaped frame, and the lower beam and the lower arc-shaped bend form the second arc-shaped frame. Inner arc-shaped frames are respectively provided on the inner sides of the first and second arc-shaped frames, and the four frames form a loop.

[0041] The outer wall of the glass includes a groove wall 15 and a groove bottom 16. The groove wall 15 is vertically installed between the upper side beam 12 and the lower side beam 13, and between the arc-shaped bend 17 and the lower side beam 13. The groove bottom 16 is horizontally installed between the bottom of the upper side beam 12 and the bottom of the lower side beam 13.

[0042] The first curved frame, the second curved frame, and the groove wall 15 form the outer wall, the inner curved frame and the inner groove wall form the inner wall, and the groove bottom 16 forms the bottom.

[0043] The outer glass wall and the ring channel form a simulated space that accommodates the internal circulation of liquid.

[0044] The effective internal dimensions of the water tank 1 are 12m × 0.6m × 0.6m (length × width × height). The upper beam 12, lower beam 13, base frame 14, and curved corner 17 can all be welded from high-strength 100×60×4mm steel pipes and plates, with a design load of 5 tons to meet the load-bearing requirements of the frame. The lower beam 13 is located 0.6m above the ground to facilitate the installation of drainage pipes 18 and other devices at the bottom of the tank bottom 16 for drainage and the erection of related measurement systems. Both the tank walls 15 and the tank bottom 16 can be made of ultra-clear tempered glass to simultaneously meet the requirements for light transmittance and strength.

[0045] The dual-tank structure of the brine tank 2 and the clear water tank 4 can create the brine stratification fluid conditions required for the experiment in the water tank 1, which can be used to simulate the actual atmospheric background stratification state.

[0046] The brine tank 2 and the clear water tank 4 can be composed of two water tanks with a volume of approximately 3000L, respectively holding brine and clear water of specific concentrations. The brine tank 3 is equipped with an (electric) stirring pump 24 and a stirrer 21 to accelerate the uniform mixing of the brine in the brine tank with the flowing clear water. The brine tank 2 and the clear water tank 4 are connected by a connecting pipe 22 and a connecting valve 23. The peristaltic pump 3 has a flow rate of 0-13L / min. Its inlet end is connected to the brine tank 2 through a water supply pipe 31, and its outlet end is connected to the water tank 1 through an inlet pipe 32, used to inject the uniformly mixed brine into the water tank 1 at a stable flow rate. A diffuser float 33 is installed at the bottom of the inlet pipe 32. As a key component for creating linear density stratification, it is made of foam and porous materials. On the one hand, it can float with the rise of the liquid level; on the other hand, the porous material in contact with the liquid surface allows the flowing brine to be injected into the water tank 1 uniformly and slowly.

[0047] The aforementioned brine tank 2, peristaltic pump 3, and clear water tank 4 can achieve density stratification using a dual-pipe method, maximizing the mixing efficiency of the brine solution and reducing the disturbance of the preceding brine stratification structure by subsequent water injections during continuous water injection.

[0048] After water injection is completed, the brine stratification conditions are established. When a specific flow velocity is generated in water tank 1, the fluid shearing and turbulence will affect the stable stratification structure. Within a certain period of time, under the premise of ensuring relatively stable density stratification, the flow pump 5 achieves the formation of water flow conditions at a specific flow velocity.

[0049] Its specific structure is as follows Figure 3 , 4As shown, two sets of flow-generating pumps 5 are installed in the water tank 1: flow-generating pump 5a and flow-generating pump 5b. Each flow-generating pump includes a guide wheel shaft 51 and a main shaft 57. The bottom of the guide wheel shaft 51 is connected to the tank bottom 16 through a bushing 52. The top of the guide wheel shaft 51 passes through a fixing plate 6 (connected by a bearing 53), and then through a fixing plate 7 mounted on the tank wall 15. It is connected via a coupling 54 (with a flat key), a reducer 56, and a servo motor 55. The main shaft 57 has a guide wheel shaft hole 571 in the middle. The main shaft 57 is installed on the output end of the guide wheel shaft 51 through the guide wheel shaft hole 571 and a long flat key (not shown in the figure). Disc-shaped blades 572 are installed on the main shaft 57. The blades 572 on adjacent sides of flow-generating pump 5a and flow-generating pump 5b form a staggered overlapping structure.

[0050] Page 572 can employ nine disc-shaped structures, each 700mm in diameter, stacked along the height of the main axis 57: Left side (with...) Figure 4 The bottom blade (for standard use) is installed close to the wall of the tank bottom 16, while the right-side flow pump is installed upside down. The bottom blade is 25 mm off the ground. The axial distance between the center of the guide wheel shaft of the left-side flow pump and the center of the guide wheel shaft of the right-side flow pump is 600 mm. The blades of the two flow pumps are staggered in the center of the water tank 1 to form a partial meshing area. The root of the blade 572 (the end connected to the main shaft 57) is 25 mm thick, the edge is 5 mm thick, the distance between two adjacent blades is 25 mm, the diameter of the main shaft 57 is 240 mm, and the diameter of the guide wheel shaft 21 located at its center is 30 mm.

[0051] In the water tank 1, the side where the flow pump 5 is set is the flow generation zone, and the test section is located on the other side away from the flow pump 5, which is used to place various physical models.

[0052] Two flow-generating pumps are driven synchronously by their respective servo motors, but in opposite directions. When the two flow-generating pumps rotate in opposite directions, the water around the flow-generating pump 5 is drawn to the meshing area of ​​the center of the blades 572 by viscous resistance and is ejected, forming a stable horizontal jet between the gaps of the blades 572. The acceleration of the water flow in the flow-generating section also causes a certain turbulence effect, but as the flow moves away from the flow-generating pump 5, stable density stratification will gradually reduce the turbulence, eventually forming a stable stratified flow.

[0053] The glass in the bottom 16 section can be double-layered, with the upper layer (20mm thick) of bottom glass being removable and installed as follows: Figure 5The relevant pipelines are shown. In addition to installing various insulation modules 81, various copper heat exchange modules 82 can be fabricated as needed. After the physical modules made of copper are internally divided into pipelines, they can be connected to the external heating water circulation system 8 through the pipelines to realize the heating of the copper model and the simulation of related convective heat transfer boundary conditions, and the required temperature can be monitored through thermocouples. At the same time, the test section can be equipped with measurement systems such as acoustic Doppler point velocity meters, particle image velocimetry (PIV) systems, and density measurement systems to realize the measurement of various physical scenarios such as flow fields and density stratification.

[0054] The above system constitutes a horizontal circulating water-type construction device. The water tank 1 has a total length of approximately 12 m, a designed water depth of 0.4 m, a maximum water consumption of approximately 3 m³, and an adjustable water flow velocity within the range of 0~0.5 m / s. The rated maximum power is approximately 5 kW. The water tank 1, tank walls 15, and bottom tank 16 are assembled in sections. Key precision indicators include: parallelism and perpendicularity errors ≤ ±1 mm, elliptical corner radius of 1.2 m with an error ≤ ±1 mm, and no leakage.

[0055] The aforementioned density stratification system ensures a stable brine stratification environment for a given time at a specific flow velocity. The system is comprised of a water tank unit (e.g., water tank 1), a density stratification unit (brine tank 2, peristaltic pump 3, clear water tank 4, etc.), a flow generation unit (flow generation pump 5, etc.), and a city model and heating unit (heated water circulation system 8, etc.). Under the premise of meeting requirements for geometric similarity, kinematic similarity, and dynamic similarity, the density stratification unit allows for the establishment of a thermal boundary model of a city or building under a specific temperature stratification in the test section. Simultaneously, the flow generation unit can create stratified brine flow at a specific velocity. Under specific initial and boundary conditions, it ultimately simulates the development of the flow field around physical models such as city buildings and the convective boundary layer formed by heating under specific background stratified flow.

Claims

1. A density stratification system, characterized in that, Includes a water tank, brine tank, flow generation unit, and heated water circulation system: The water tank includes a ring channel for holding water; One side of the water tank is the water inlet section, which is connected to the brine tank to supply brine of a set concentration into the loop; the other side is equipped with a flow-generating unit to give the water in the loop a set flow rate. The water inlet section is equipped with a diffuser float. The water inlet pipe is connected to the brine tank via a peristaltic pump. The inlet of the peristaltic pump is connected to the water supply pipe, which is connected to the brine tank to supply water to the water tank. The outlet of the peristaltic pump is connected to the water inlet pipe, and the diffuser float is installed at the end of the water inlet pipe. A detection unit is installed in the water tank of the inlet section; The flow-generating unit includes two flow-generating pumps. Each flow-generating pump includes a guide wheel shaft, a reducer, a servo motor, and a main shaft. The guide wheel shaft is driven to rotate by the servo motor and the reducer. The main shaft is mounted on the output end of the guide wheel shaft. Multiple sets of disc-type blades are arranged on the main shaft. The two flow-generating pumps rotate in opposite directions and the disc-type blades on the adjacent side form a staggered overlapping structure. The water tank is equipped with an insulation module and a heat transfer module. The insulation module and the heat transfer module work together with the heating water circulation system to construct a physical model with a certain thermal boundary in the water inlet section, so as to realize the measurement of the velocity field, density field and temperature field around the model. Turn on the brine tank and supply water of the set concentration into the loop to the set level; turn off the brine tank and start the flow generation unit. The water flow near the flow generation unit is turbulent. When the inlet section reaches the set velocity, turn off the flow generation unit and start the detection unit to perform dynamic tests on the water flow of the set density and speed.

2. The density stratification system according to claim 1, characterized in that: The brine tank is equipped with a stirring unit.

3. The density stratification system according to claim 2, characterized in that: The stirring unit includes a stirrer and a stirring pump, with the stirring pump driving the stirrer.

4. The density stratification system according to claim 1, characterized in that: It also includes a clean water tank, which is connected to the brine tank by a connecting pipe, and a connecting valve is installed on the connecting pipe.

5. A density stratification system according to claim 1, characterized in that: A fixing plate is also provided on the main shaft, and the fixing plate is located above the main shaft.

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