Experimental Apparatus and Method for Thermal Buoyancy Jet in Stratified Environment

Abstract

The present invention discloses an experimental device and method for thermal buoyant jets in a stratified environment. The experimental device for thermal buoyant jets mainly includes the following three parts: a PIV and thermal imager measurement system, a "double-tank method" stratified water body generation device, and a thermal buoyant jet outflow device. The device includes two water tanks with different solution densities, a test water tank, a PIV and thermal imager system, a constant-temperature heating water tank, and a jet nozzle. A flow pump is equipped at the bottom of the heating water tank, and the flow pump is connected to a thermal buoyant jet nozzle equipped with a three-way pipe through a rubber tube. This system can generate a stratified water body with a consistent refractive index, conduct thermal buoyant jet experiments in an arbitrarily stratified environment, meet the experimental conditions for simultaneously measuring the flow field and water surface temperature field of thermal buoyant jets, has a simple structure, is easy to use, and has good reliability, accuracy, and ease of use.

Description

Technical Field

[0001] The present invention belongs to the technical field of buoyant jets, and particularly relates to an experimental device and method for thermal buoyant jets in a stratified environment. Background Art

[0002] A buoyant jet refers to the phenomenon of columnar fluid motion driven by buoyancy, which widely exists in nature and practical engineering, such as volcanic eruptions, deep-sea hydrothermal plumes, coastal warm water discharges, and factory hot waste gases. In a stratified environment caused by temperature and salinity differences, the dynamic process of a thermal buoyant jet is relatively complex. Under the action of buoyancy, the thermal buoyant jet does not always move upward. In a stratified environment caused by temperature and salinity differences, the thermal buoyant jet will continuously mix with the ambient fluid, resulting in a gradual decrease in the density difference between it and the ambient fluid. After reaching the maximum rising height, it will rebound and stabilize near the neutral buoyancy layer (where the density difference is zero), and then only horizontal diffusion occurs. The long-term accumulation effect of the thermal buoyant jet will significantly affect the energy balance and water chemical components of the region, and have a negative impact on the ecological environment. Therefore, in-depth understanding of the movement law and its action mechanism of thermal buoyant jets in a stratified environment has important scientific significance and practical value for environmental protection, ecological environment assessment, engineering design, etc.

[0003] The water tank experiment is a classic method for studying thermal buoyant jets. The commonly used flow field measurement method is particle image velocimetry (PIV), and the currently adopted high-precision non-invasive temperature measurement method is generally thermal imager temperature measurement (IR). However, in the currently published technical solutions, there is no experimental device system for thermal buoyant jets that can simultaneously measure the flow field and temperature field, can realize the preparation of arbitrarily stratified water bodies, and can achieve refractive index matching. Summary of the Invention

[0004] The present invention overcomes the deficiencies in the prior art and provides an experimental device and method for thermal buoyant jets in a stratified environment.

[0005] One aspect of the present invention provides an experimental device for thermal buoyant jets in a stratified environment. It includes a brine water tank, an ethanol solution water tank, a test water tank, an infrared thermal imager, a PIV system, a heating water tank, and a jet nozzle.

[0006] A water pipe and a first outlet valve are provided at the lower part of the brine water tank, and the first outlet valve is connected to the ethanol solution water tank through the water pipe; a water tank stirrer is provided in the ethanol solution water tank, a second outlet valve is provided at the lower part of the ethanol solution water tank, the second outlet valve is connected to the test water tank through another water pipe, and a disc outflow device is provided at the outlet of the water pipe, and the disc outflow device is located on one side of the test water tank.

[0007] The jet nozzle is fixed on an adjustable bracket on the other side of the test water tank, and the inlet of the jet nozzle is connected to the heating water tank through a solenoid valve; the heating water tank is equipped with a tee structure composed of a main jet pipe, a bypass solenoid valve, a bypass pipe and a third outlet valve.

[0008] The liquid levels of the brine tank and the ethanol solution tank are the same, the solution volumes are the same, and the solution refractive indices are the same. By controlling the flow rate relationship between the second outlet valve and the first outlet valve, a stratified water body with any stratification condition can be generated. When the flow rate of the second outlet valve is twice that of the first outlet valve, a uniform linear stratified water body can be generated. Another aspect of the present invention provides an experimental method for thermal buoyancy jets in a stratified environment. Using the above buoyancy jet experimental device, it includes the following steps:

[0009] a. Install the PIV system and the infrared thermal imager, fix the jet nozzle in the test water tank, and connect the rubber hose between the nozzle and the heating water tank; subsequently, install the laser emitter of the PIV system on the slide rail above the test water tank, adjust the laser plane so that it vertically enters the water surface, place the high-speed camera of the PIV system on the side of the water tank, adjust the height of the camera tripod so that the thermal buoyancy jet nozzle is in the appropriate area of the camera view, and connect the camera to a high-performance computer; install the infrared thermal imager on the slide rail above the test water tank as well, and connect the infrared thermal imager to another computer.

[0010] b. Prepare the stratified water body. Prepare brine and ethanol solutions with different densities and the same refractive index in advance, pump the brine and ethanol solutions into the brine tank and the ethanol solution tank respectively, pump the brine solution from the brine tank into the ethanol solution tank at a rate of A L / h, and after the solution is stirred by the stirrer in the ethanol solution tank, pump it into the test water tank at a rate of 2A L / h, and a linear stratified environment with the same refractive index can be generated; by changing the flow rate relationship between the second outlet valve and the first outlet valve, a non-uniform stratified environment or a two-layer stratified water body with the same refractive index can also be generated as needed.

[0011] c. Heat the thermal buoyancy jet supplementary liquid using the heating water tank, and use a stirrer to stir the heating water tank to eliminate the internal temperature gradient of the solution.

[0012] d. Use the bypass pipe with a bypass solenoid valve to pre-discharge a certain volume of thermal buoyancy jet to preheat the rubber hose under the water; measure the outlet temperature of the bypass pipe using a K-type puncture thermocouple to ensure that the outlet temperature is stable.

[0013] e. Close the bypass pipe and open the third outlet valve to simulate the outflow process of the thermal buoyancy jet in the stratified water body.

[0014] f. Use the PIV system and the infrared thermal imager to record the movement and change process of the fluid in the test water tank, and carry out the measurement of the flow velocity and temperature of the thermal buoyancy jet.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The thermal buoyancy jet experimental device and method of the present invention have a simple structure, are easy to use, and have good reliability, accuracy, and usability.

[0017] 2. The purpose of generating stratified water is to simulate the stratification phenomenon caused by temperature and salinity differences in the actual ocean environment, so it is crucial. The present invention can prepare stratified water under any stratification conditions, and it is proved that when the liquid levels of the two water tanks are kept at the same height and the solution volumes are the same, by considering the water mass conservation theory of the ethanol solution water tank within a certain period of time, through theoretical calculation, when the outflow flow rate of the ethanol water tank is controlled to be twice that of the saline solution water tank, linearly stratified water can be generated; considering that the saline solution water tank is preferentially filled with the solution and pumped into the test water tank, and then the ethanol solution water tank is filled with the solution and pumped into the test water tank, two-layer stratified water can be generated; by changing the outflow flow rate relationship between the two water tanks, non-uniformly stratified water can also be generated. At the same time, the present invention adopts the disk outflow method, thereby reducing the outflow momentum and increasing the outflow area, and further reducing the disturbance of the outflow to the fluid.

[0018] 3. The refractive index difference caused by the density difference between fluids will cause image blurring and noise problems during the PIV measurement process, resulting in pseudo-pulsation velocity in the analysis results and incorrect calculation of turbulence-related parameters. The present invention takes into account the convenience and safety of operation, and selects two solutions with the same refractive index but different densities, namely ethanol solution / saline solution, and prepares an arbitrarily stratified environment with a consistent refractive index through the "double-cylinder method".

[0019] 4. The present invention uses a PIV system and a thermal imager technology. The PIV system mainly consists of a laser emitter, a high-speed camera, and a high-performance computer. It can clearly record the movement trajectory and real-time position image of particles. The thermal imager is placed directly above the test water tank to measure the water surface temperature from top to bottom, and the influence of atmospheric transmission can be ignored, so as to simultaneously obtain high-precision fluid state information.

[0020] 5. In order to ensure that the outflow density of the thermal buoyancy jet is less than that of the ambient water body, the present invention selects ethanol solution as the thermal buoyancy jet replenishing liquid. A heating water tank composed of a temperature control sensor, a temperature control switch, and a heating device is used to heat the replenishing liquid. Before the experiment, a certain volume of the thermal buoyancy jet can be pre-discharged by using a bypass pipe with a solenoid valve, which can reduce the heat loss of the thermal buoyancy jet replenishing liquid during subsequent transmission and improve the experimental accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the present invention;

[0022] Figure 2 This is the right view of the present invention.

[0023] Among them, 1. brine water tank; 2. ethanol solution tank; 3. water tank stirrer; 4. second water outlet valve; 5. water pipe; 6. first water outlet valve; 7. disc outflow device; 8. test water tank; 9. infrared thermal imager; 10. laser emitter; 11. jet nozzle; 12. adjustable bracket; 13. solenoid valve; 14. main jet pipe; 15. bypass solenoid valve; 16. bypass pipe; 17. heating water tank; 18. high-speed camera. Specific embodiments

[0024] The following further elaborates on the specific embodiments of the present invention with reference to the accompanying drawings.

[0025] The present invention includes a brine water tank, an ethanol solution tank, a test water tank, an infrared thermal imager, a PIV system, a heating water tank, and a jet nozzle. A water pipe and a first water outlet valve are provided at the lower part of the brine water tank, and the first water outlet valve is connected to the ethanol solution tank through the water pipe; the ethanol solution tank is provided with a water tank stirrer, a second water outlet valve is provided at the lower part of the ethanol solution tank, and the second water outlet valve is connected to the test water tank through the water pipe, and a disc outflow device is provided at the water pipe outlet. The jet nozzle is fixed on an adjustable bracket on the test water tank, and the inlet of the jet nozzle is connected to the heating water tank after passing through a third water outlet valve; a tee structure composed of a main fluid pipeline, a bypass solenoid valve, a bypass pipe, and a third water outlet valve is provided outside the heating water tank.

[0026] This experimental device is mainly divided into three parts: a PIV and thermal imager measurement system, a "double-cylinder method" stratified water body generation device, and a thermal buoyancy jet outflow device.

[0027] Preferably, the test water tank is made of transparent acrylic board and has good light transmission performance.

[0028] Preferably, the jet nozzle can freely adjust the height and angle, and its nozzle is circular.

[0029] Preferably, the brine water tank and the ethanol solution tank need to have the same liquid level height and the same solution volume. Salt solutions and ethanol solutions with the same refractive index are respectively placed in the brine water tank and the ethanol solution tank, and a disc outflow device is used to pump the mixed liquid into the experimental water tank to generate a stratified water body with the same refractive index.

[0030] Preferably, the PIV system is mainly composed of a laser emitter, a high-speed camera, and a high-performance computer, and uses the image cross-correlation algorithm for post-processing; the infrared thermal imager is placed directly above the test water tank to measure the water surface temperature from top to bottom.

[0031] Preferably, the heating water tank includes a temperature control sensor, a temperature control switch and a heating device, and is connected to the jet nozzle through a rubber hose.

[0032] The present invention also provides an experimental method for thermal buoyancy jet in a stratified environment using the above device, including the following steps:

[0033] a. Install the PIV system and the infrared thermal imager. Fix the jet nozzle in the test water tank and connect the rubber hose between the nozzle and the constant temperature water tank. Subsequently, install the laser of the PIV system on the slide rail above the test water tank and adjust the laser plane to vertically penetrate the water surface; also install the infrared thermal imager on the slide rail above the test water tank and fix it on the right side of the PIV system.

[0034] b. Prepare the stratified water body. Prepare brine and ethanol solutions with different densities and the same refractive index in advance. Pump the brine and ethanol solutions into the brine water tank and the ethanol solution water tank respectively. Pump the salt solution from the brine water tank into the ethanol solution water tank at a rate of A L / h. After being stirred by the stirrer in the ethanol solution water tank, pump it into the test water tank at a rate of 2A L / h, and a linear stratified environment with the same refractive index can be generated; by changing the flow rate relationship between the second outlet valve and the first outlet valve, a non-uniform stratified environment with the same refractive index or a two-layer stratified water body can also be generated as required.

[0035] c. Select ethanol solution as the thermal buoyancy jet supplementary liquid, heat the supplementary liquid using the heating water tank, and use a stirrer to stir the heating water tank to eliminate the internal temperature gradient of the solution.

[0036] d. Use the bypass pipe with a bypass solenoid valve to pre-discharge a certain volume of thermal buoyancy jet in advance and preheat the rubber hose located underwater; measure the outflow temperature of the bypass pipe using a K-type puncture thermocouple to ensure the stability of the outflow temperature.

[0037] e. Close the bypass pipe and open the solenoid valve to simulate the outflow process of the thermal buoyancy jet in the stratified water body.

[0038] f. Inject the required jet fluid into the test water tank and observe or use the PIV system and the infrared thermal imager to record the movement and change process of the fluid in the test water tank.

[0039] Preferably, the laser emitter in the PIV system uses a continuous wave neodymium-doped yttrium aluminum garnet crystal laser source (Nd:YAG Laser) with a wavelength of 532 nm.

[0040] Preferably, the tracer particles of the experimental device are polyethylene with a particle size of 50 μm and a density of 1.04 g / cm 3 , having good fluid following performance.

[0041] Example:

[0042] As shown Figure 1 in the figure, the device of this embodiment specifically includes a brine water tank 1, an ethanol solution tank 2, a test tank 8, an infrared thermal imager 9, a PIV system (which is jointly composed of a laser emitter 10, a high-speed camera 18, and a high-performance computer (not shown in the figure)), a heating tank 17, and a jet nozzle 11. A water pipe 5 and a first outlet valve 6 are provided at the lower part of the brine water tank 1, and the first outlet valve 6 is connected to the ethanol solution tank 2 through a water pipe. The ethanol solution tank 2 is provided with a tank stirrer 3. A second outlet valve 4 is provided at the lower part of the ethanol solution tank 2, and the second outlet valve 4 is connected to the test tank 8 through a water pipe, and a disc outflow device 7 is provided at the water pipe outlet. The jet nozzle 11 is fixed on an adjustable bracket 12 fixed together with the test tank 8, and the inlet of the jet nozzle 11 is connected to the heating tank 17 after passing through a third outlet valve 13; a tee structure jointly composed of a jet main pipe 14, a bypass solenoid valve 15, a bypass pipe 16, and a third outlet valve 13 is provided at the outlet of the heating tank 17. Figure 1 In the figure, the x direction is the horizontal direction, and the positive direction of the z axis is the vertical direction opposite to the direction of the gravitational acceleration.

[0043] The test rectangular tank 8 is made of transparent acrylic board and has good light transmission performance. In the experiment, the brine water tank 1 is filled with a salt solution with a higher density, and the ethanol solution tank 2 is filled with an ethanol solution with a lower density. The liquid levels and solution volumes of the two tanks are the same. The first outlet valve 6 between the two tanks is adjusted. After being fully mixed by the stirrer in the ethanol solution tank 2, the second outlet valve 4 between the ethanol solution tank 2 and the test tank 8 is adjusted, and the disc outflow method of the disc outflow device 7 is adopted to make the mixed solution flow into the test tank 8. The heating tank 17 uses a constant temperature device composed of a temperature control sensor, a temperature control switch, and a heating device to heat the replenishing liquid. The temperature sensor uses a K-type thermocouple, and the heating device uses a heating rod.

[0044] Correspondingly, the experimental method for thermal buoyancy jet in a stratified environment using the above device mainly includes the following steps:

[0045] (1) Install the PIV and thermal imager equipment. Before the experiment, the jet nozzle 11 is fixed in the test tank 8. Subsequently, the laser emitter 10 of the PIV system is installed on the slide rail above the test tank 8, and the laser emitter is adjusted to vertically irradiate the water surface; the high-speed camera 18 of the PIV system is placed on the side of the water tank, see Figure 2 , adjust the height of the camera tripod so that the thermal buoyancy jet nozzle is in the appropriate area of the camera view, connect the camera to the high-performance computer, and adjust the camera frame rate to an appropriate value. The infrared thermal imager 9 is also installed on the slide rail above the test tank 8, and another computer is used to connect the infrared thermal imager 9.

[0046] (2) Prepare stratified water bodies. Prepare brine and ethanol solutions with consistent refractive indices in advance. Pump the brine and ethanol solutions into the brine water tank 1 and the ethanol solution water tank 2 of the "double-tank system" respectively. Place the disc outflow device 7 of the ethanol solution water tank 2 in the area of the test water tank 8 far from the PIV measurement range to reduce the impact of the disc outflow process on the stratification degree of the water body in the measurement area. Adjust the first water outlet valve 6 and pump the salt solution from the brine water tank 1 into the ethanol solution water tank 2 at a rate of A L / h. After the solution is stirred by the stirrer 3 in the ethanol solution water tank 2, it is then pumped into the test water tank 8 at a rate of 2A L / h. When the height of the stratified water body in the test water tank 8 reaches the preset height, turn off the flow pump to complete the preparation of the linear stratified water body. Considering the mass conservation of the water body in the ethanol solution water tank 2:

[0047]

[0048] where ρ A is the density of the brine, Q A is the outflow flow rate of the brine water tank 1, Q B is the outflow flow rate of the ethanol solution water tank 2, ρ B (t) is the density of the solution in the ethanol solution water tank 2 at time t, and V L is the volume of the solution in the ethanol solution water tank 2 (the fluid is incompressible). After combining like terms in Equation (1) and then dividing by Δt, we can get:

[0049]

[0050] Within Δt time, the density change of the solution in the ethanol solution water tank 2 is very small, satisfying ρ B (t)≈ρ B (t + Δt). By transposing Equation (2) and dividing by Q A we can get:

[0051]

[0052] Integrate Equation (3) with respect to time t:

[0053]

[0054] where C ρ is a constant. Considering the initial condition at t = 0, ρ B (t) = ρ B (0) and ρ A >ρ B (0), we can get:

[0055]

[0056] Substitute Equation (5) into Equation (4) to get:

[0057]

[0058] When the outlet flow rate of ethanol solution tank 2 is twice the outlet flow rate of brine tank 1, the density function of the solution in ethanol solution tank 2 is:

[0059]

[0060] Formula (7) shows that the density of the solution in the ethanol solution tank 2 increases linearly with time, so a linear stratified water body can be generated. By changing the flow rate of the first water outlet valve 6 and the second water outlet valve 4, a non-uniform stratified water body can be generated. If a two-layer stratified water body needs to be prepared, an extreme case can be considered, that is, the salt solution tank 1 is first added with the solution and pumped into the test water tank 8, and then the solution is added to the ethanol solution tank 2 and pumped into the test water tank 8.

[0061] The sampling plate installed on the test water tank 8 is used to extract solution samples at different depths in the stratified environment, the refractive index is verified using a refractometer, the density of the solution samples at different depths is measured using a hydrometer, and the stratification function is determined based on the sample data.

[0062] (3) Preparation of thermal buoyancy jet replenishing liquid. In order to ensure that the density of the thermal buoyancy jet is less than that of the stratified water body, an ethanol solution is selected as the thermal buoyancy jet replenishing liquid, and a heating water tank 17 composed of a temperature control sensor, a temperature control switch and a heating device is used to heat the replenishing liquid. The water tank 17 is stirred by a stirrer to eliminate the internal temperature gradient of the solution and ensure that the replenishing liquid temperature is uniform.

[0063] (4) Preheat the underwater pipe. Use an adjustable flow pump to preset the outflow velocity of the heating water tank 17, and use the bypass pipe 16 with the bypass solenoid valve 15 to pre-discharge a certain volume of thermal buoyancy jet to preheat the rubber hose under water; use a K-type piercing thermocouple to measure the outflow temperature of the bypass pipe to ensure that the outflow temperature is stable. Turn on the acquisition mode of the high-speed camera 18 and thermal imager 9 of the PIV system in advance, then close the bypass pipe 16, open the solenoid valve 13, and start the flow velocity and temperature measurement of the thermal buoyancy jet.

[0064] In summary, the jet fluid in the stratified environment of the present invention is stable, which avoids the image blur and noise problems in the PIV measurement process caused by the refractive index difference caused by the density difference between the fluids, greatly reduces the difficulty of experimental data processing and phenomenon analysis, and brings convenience to the observation of thermal buoyancy jets.

Claims

1. Stratified environmental thermal buoyancy jet experimental device, Characterized in that: It includes a brine water tank (1), an ethanol solution water tank (2), a test water tank (8), an infrared thermal imager (9), a PIV system, a heating water tank (17) and a jet nozzle (11); A water pipe (5) and a first water outlet valve (6) are provided at the lower part of the brine water tank (1), and the first water outlet valve (6) is connected to the ethanol solution water tank (2) through the water pipe (5); A water tank stirrer (3) is provided in the ethanol solution water tank (2), a second water outlet valve (4) is provided at the lower part of the ethanol solution water tank (2), and the second water outlet valve (4) is connected to the test water tank (8) through another water pipe, and a disc outflow device (7) is provided at the outlet of this water pipe, and the disc outflow device (7) is located on one side of the test water tank (8); The jet nozzle (11) is fixed on an adjustable bracket (12) on the other side of the test water tank (8), and the inlet of the jet nozzle (11) is connected to the heating water tank (17) through an electromagnetic valve (13); The heating water tank (17) is equipped with a tee structure composed of a jet main pipe (14), a bypass electromagnetic valve (15), a bypass pipe (16) and a third water outlet valve (13); The liquid levels of the brine water tank (1) and the ethanol solution water tank (2) are the same, the solution volumes are the same, and the solution refractive indices are the same. By controlling the flow rate relationship between the second water outlet valve (4) and the first water outlet valve (6), a stratified water body with any stratification can be generated. When the second water outlet valve (4) is controlled to be twice the flow rate of the first water outlet valve (6), a uniform linear stratified water body can be generated; The jet nozzle is fixed in the test water tank (8), and the jet nozzle is connected to the heating water tank (17) through a rubber hose; The laser emitter (10) of the PIV system is installed on the slide rail above the test water tank (8), and the laser plane is adjusted to vertically enter the water surface. The high-speed camera (18) of the PIV system is placed on the side of the test water tank (8), and the height of the camera tripod is adjusted so that the thermal buoyancy jet nozzle is in the appropriate area of the view of the high-speed camera (18), and the high-speed camera (18) is connected to a high-performance computer; The infrared thermal imager (9) is also installed on the slide rail above the test water tank (8), and another computer is used to connect to this infrared thermal imager (9).

2. The thermal buoyancy jet experimental device according to claim 1, Characterized in that: The jet nozzle (11) can be freely adjusted in height and angle.

3. The thermal buoyancy jet experimental device according to claim 1, Characterized in that: The PIV system is mainly composed of a laser emitter (10), a high-speed camera (18) and a high-performance computer, and image cross-correlation algorithm is used for post-processing.

4. The thermal buoyancy jet experimental device according to claim 1, Characterized in that: The infrared thermal imager (9) is placed directly above the test water tank (8) to measure the water surface temperature from top to bottom.

5. The thermal buoyancy jet experimental device according to claim 1, Characterized in that: The heating water tank (17) includes a temperature control sensor, a temperature control switch and a heating device, and the heating water tank (17) is connected to the jet nozzle (11) through a rubber hose.

6. Method for the experiment of thermal buoyant jet in a stratified environment, which is a method using the buoyant jet experimental device described in any one of claims 1 to 5. It is characterized in that it includes the following steps: a. Install the PIV system and the infrared thermal imager (9), fix the jet nozzle in the test water tank (8), and connect the rubber hose between the nozzle and the heating water tank; subsequently, install the laser emitter (10) of the PIV system on the slide rail above the test water tank (8), adjust the laser plane to vertically penetrate the water surface, place the high-speed camera (18) of the PIV system on the side of the test water tank (8), adjust the height of the camera tripod so that the thermal buoyant jet nozzle is in the appropriate area of the camera view, and connect the camera to a high-performance computer; install the infrared thermal imager (9) on the slide rail above the test water tank (8) as well, and connect this infrared thermal imager (9) using another computer; b. Prepare the stratified water body; prepare salt water and ethanol solutions with different densities and the same refractive index in advance, pump the salt water and ethanol solutions into the salt water tank (1) and the ethanol solution tank (2) respectively, pump the salt water solution from the salt water tank (1) into the ethanol solution tank (2) at a rate of A L / h, after the solution is stirred by the stirrer in the ethanol solution tank (2), then pump it into the test water tank (8) at a rate of 2A L / h, and a linear stratified environment with the same refractive index can be generated; by changing the flow rate relationship between the second outlet valve (4) and the first outlet valve (6), a non-uniform stratified environment with the same refractive index or a two-layer stratified water body can also be generated as required; c. Heat the thermal buoyant jet replenishing liquid using the heating water tank (17), and use a stirrer to stir the heating water tank (17) to eliminate the internal temperature gradient of the solution; d. Use the bypass pipe (16) with a bypass solenoid valve (15) to pre-discharge a certain volume of thermal buoyant jet to preheat the rubber hose located underwater; measure the outflow temperature of the bypass pipe (16) using a K-type puncture thermocouple to ensure the stability of the outflow temperature; e. Close the bypass pipe (16), open the third outlet valve (13), and simulate the outflow process of the thermal buoyant jet in the stratified water body; f. Use the PIV system and the infrared thermal imager (9) to record the movement and change process of the fluid in the test water tank (8), and conduct the measurement of the flow velocity and temperature of the thermal buoyant jet.

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