Variable buoyancy propulsion fluid resistance reduction and noise reduction teaching and scientific research comprehensive test platform and method

Abstract

The invention provides a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform and an experiment method. The variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform comprises a deep pool, a variable buoyancy test bed, a model folding and unfolding bearing device, a test model and a data acquisition and display module. A variable buoyancy test bed is fixed at the center of the bottom of a deep pool; the model folding and unfolding bearing device is fixedly connected to the bottom of the variable buoyancy test bed; the test model is slidably and detachably installed on the variable buoyancy test bench. And the data acquisition and display module is fixed on the variable buoyancy test bed. According to the core technology, variable buoyancy propulsion is used for replacing a traditional propulsion device, interference of wake flow and hydrodynamic noise generated by the propulsion device to a flow field and noise is eliminated, the direct relation between the flow speed and the flow resistance borne by the aircraft shell and the generated flow noise is established, and flow resistance and flow noise signals with the low signal-to-noise ratio are obtained; therefore, the resistance reduction and noise reduction performance of the underwater vehicle shell and the surface structure of the underwater vehicle shell can be accurately evaluated.

Description

Technical Field

[0001] The invention belongs to the field of fluid drag reduction and noise reduction, and specifically relates to a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform and experimental method. Background Art

[0002] Improving the maneuverability and acoustic stealth performance of ships is an important research content in the development of marine equipment, and experimental research is one of the main methods for conducting research on fluid drag reduction and noise reduction. Therefore, it is an indispensable task to develop a comprehensive teaching and scientific research test platform for fluid drag reduction and noise reduction that can accurately measure flow resistance and flow noise signals, cultivate high-quality talents in the field of fluid drag reduction and noise reduction, and conduct high-precision fluid drag reduction and noise reduction tests.

[0003] The fluid drag and noise reduction test devices currently used mainly include circulating water tunnels, towing water tanks and gravity water tunnels. For circulating water tunnels and towing water tanks, they can provide flow field conditions close to actual working conditions, but they require an external propulsion system to provide power during operation (such as a water pump for circulating water tunnels and a trailer for towing water tanks). In practical applications, it is difficult to eliminate the influence of the propulsion system, resulting in large environmental noise in the measured fluid resistance and noise results; for gravity water tunnels, the internal fluid moves under the action of gravity, which is relatively quiet and eliminates the influence of the propulsion system, but it requires a large amount of water to be pumped into a water tower (or water tank) during the test preparation stage, which consumes a lot of energy. Therefore, it is very important to design a fluid resistance and noise test device that eliminates the interference of the propulsion system and has low energy consumption for the study of the resistance and noise performance of the vehicle at medium and high speeds. Summary of the invention

[0004] The purpose of the present invention is to provide a comprehensive teaching and scientific research test platform and experimental method for drag and noise reduction of variable buoyancy propulsion fluid.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform, comprising a deep water pool, a variable buoyancy test bench, a model retractable bearing device, a test model and a data acquisition and display module; the variable buoyancy test bench is fixed to the bottom center of the deep water pool; the test model is installed on a guide rail in the variable buoyancy test bench frame; the model retractable bearing device is used to retract and carry the test model; the test model generates variable buoyancy by throwing a heavy object, so that the test model moves along the guide rail in the deep water pool at an adjustable speed; the data acquisition and display module is fixed on the variable buoyancy test bench, and is used to collect flow resistance, flow noise signals and distribution information of vortices in the flow field;

[0007] The model retractable load-bearing device comprises a retractable servo device and a load-bearing release device, the guide rail is installed on the load-bearing release device, the load-bearing release device is further installed at the center position of the bottom plate of the variable buoyancy test bench, and the retractable servo device is installed on the bottom plate of the variable buoyancy test bench; the retractable servo device comprises a retractable servo device housing, a wire arranging guide rod, a wire arranging coupling, a wire arranging motor, a wire arranging nut, a wire arranging wheel, a wire arranging bearing, an I-shaped wire reel, a wire reel shaft, a bushing, a wire reel bearing, a wire reel coupling, a wire reel motor and a wire rope; the wire reel motor is fixed inside the retractable servo device housing and is connected to the wire arranging guide rod through the wire arranging coupling. The wire arranging guide rod is a long straight screw rod, which is rotatably fixed in the housing of the retracting and releasing servo device through a wire arranging bearing; the wire arranging nut is threadedly connected to the wire arranging guide rod, and the wire arranging wheel is fixedly connected to the wire arranging nut; the wire rope is wound around the I-shaped take-up wheel through the wire arranging wheel, and the I-shaped take-up wheel is rotatably fixed in the housing of the model retracting and releasing servo device through a wire taking-up bearing, and the two ends of the take-up coupling are respectively connected to the I-shaped take-up wheel and the output shaft of the take-up motor, and the I-shaped take-up wheel, the take-up coupling and the output shaft of the take-up motor rotate synchronously, and the test model is connected to the retracting and releasing servo device through a wire rope.

[0008] Furthermore, the variable buoyancy test bench is the overall framework of a comprehensive teaching and scientific research test platform for variable buoyancy propulsion fluid drag reduction and noise reduction, including a test bench body and guide rails; the test bench body includes vertical bracket I, vertical bracket II, vertical bracket III, vertical bracket IV, a top frame and a bottom plate, and the guide rail is vertically fixed at the center of the bottom plate.

[0009] Furthermore, the load-releasing device comprises a load-releasing device outer shell, a push rod motor, a slider and a clamping arm; the load-releasing device outer shell is fixed to the bottom of the bottom plate of the variable buoyancy test bench, the push rod motor is fixed in the load-releasing device outer shell, the slider is detachably connected to the push rod motor, and the slider is slidably connected to the model load-releasing device outer shell, and the slider slides along the load-releasing device outer shell under the action of the push rod motor; one end of the clamping arm is rotatably connected to the slider, and the other end is free, and the clamping arm rotates around the load-releasing device outer shell.

[0010] Furthermore, a sample to be tested is installed on the surface of the test model, and the test model includes a buoyancy chamber shell, an electronic chamber and a jettison chamber shell, a jettison chamber battery, a permanent magnet, a powered coil and a load; the buoyancy chamber shell is fixedly connected to the electronic chamber and the jettison chamber shell, and are sealed by a sealing ring; the jettison chamber battery is fixed in the electronic chamber and the jettison chamber shell, the permanent magnet is fixedly connected to the electronic chamber and the jettison chamber shell, the powered coil is wound around the outside of the permanent magnet, and the load is adsorbed on the lower surface of the permanent magnet around which the powered coil is wound.

[0011] Furthermore, the data acquisition and display module includes a pressure sensor, a hydrophone and a PIV test system; the pressure sensor array is arranged inside the guide rail; the hydrophone and the PIV test system are respectively fixed on the inner sides of two vertical brackets opposite to the main body of the variable buoyancy test bench.

[0012] A comprehensive teaching and scientific research test method for drag and noise reduction of variable buoyancy propulsion fluid, the specific steps are as follows:

[0013] 1) Construction of the test bench framework

[0014] Fix the variable buoyancy test bench body at the center of the bottom of the deep water pool, fix the load-releasing device at the center of the bottom plate of the variable buoyancy test bench body, fix the guide rail at the center of the upper surface of the load-releasing device, fix the PIV test system and the hydrophone on any two vertical brackets arranged opposite to each other in the variable buoyancy test bench body, fix the pressure sensor to the guide rail, fix the retractable servo device to the bottom plate, and add a certain height of water into the deep water pool; install the sample to be tested on the surface of the test model, and connect the retractable servo device and the test model with a steel wire rope;

[0015] 2) Start the experiment

[0016] Start the retractable servo device, tighten the wire rope, sink the test model, put the load-bearing release device in the load-bearing condition, and fix the test model; reverse the model retractable servo device and loosen the wire rope;

[0017] When conducting resistance and noise tests:

[0018] The model-carrying release device is placed in the release condition, the test model is released, and the test model floats up. The pressure sensor is used to monitor the time it takes for the test model to reach each sensor. The floating speed of the test model is calculated by the distance between adjacent sensors and the arrival time difference. The hydrophone is used to test the hydrodynamic noise, and the PIV test system is used to observe the fluid boundary layer on the surface of the sample to be tested.

[0019] Furthermore, the buoyancy of the test model is:

[0020] F 浮 =ρ 液 V 排

[0021] Where g is the acceleration due to gravity; is the displacement volume of the test model; the test model’s own gravity is:

[0022] G=ρ 固 V 固

[0023] in, is the volume of the solid part of the test model; therefore, to ensure that F浮 ≥G, in the preferred case (ρ 液 =1000kg / m 3 ρ 固 =7850kg / m 3 ), there is the following relationship:

[0024] V 排 ≥7.85V 固 .

[0026] The beneficial effects of the present invention are:

[0027] 1. The test model in the present invention comprises a buoyancy chamber, an electronic chamber and a jettison chamber, wherein the buoyancy chamber provides a constant buoyancy, and the electronic chamber is used to control the jettison chamber to jettison the load outward, and the gravity exerted on the test model is adjusted by jettisoning the load, thereby controlling the magnitude of the propulsion force exerted on the model, and further controlling the movement speed of the test model;

[0028] 2. The present invention utilizes variable buoyancy propulsion consisting of an electronic cabin and a jettison cabin to replace the traditional propulsion device, thereby eliminating interference from the propulsion system and obtaining purer flow resistance and flow noise signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of a comprehensive experimental platform for fluid drag and noise reduction teaching and scientific research with variable buoyancy propulsion;

[0030] Figure 2 It is a schematic diagram of the structure of the model retracting and extending servo device (top view);

[0031] Figure 3 It is a schematic diagram of the structure of the model retracting and extending servo device (main view);

[0032] Figure 4 is a schematic diagram of the test model structure;

[0033] Figure 5 It is a schematic diagram of the load-bearing condition of the model load-bearing release device;

[0034] Figure 6 It is a schematic diagram of the release condition of the model load-bearing release device;

[0035] Figure 7 It is a schematic diagram of the main body of the variable buoyancy test bench bracket;

[0036] Figure 8 It is a schematic diagram of the cross section of the guide rail.

[0037] In the figure, 1-wire rope; 2-PIV test system; 3-deep water tank; 4-variable buoyancy test bench body; 5-guide rail; 6-test model; 7-sample to be tested; 8-hydrophone; 9-load release device; 10-retractable servo device; 11-cable motor; 12-cable coupling; 13-cable nut; 14-cable guide rod; 15-cable bearing; 16-retractable bearing; 17-sleeve; 18-retractable servo device housing; 19-I-shaped reel; 20-retractable shaft; 21-retractable Wire coupling; 22-wire taking-up motor; 23-wire wheel; 24-buoyancy chamber shell; 25-sealing ring; 26-electronic chamber and jettison chamber shell; 27-jet load battery; 28-permanent magnet; 29-coil; 30-load; 31-support arm; 32 slider; 33-push rod motor; 34-load release device shell; 35-vertical bracket I; 36-vertical bracket II; 37-top frame; 38-vertical bracket III; 39-vertical bracket IV; 40-bottom plate; 41-pressure sensor. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings.

[0039] like Figure 1 and Figure 7 As shown, the working principle of a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform of the present invention is described in detail:

[0040] Before conducting the flow resistance and flow noise tests, the variable buoyancy test bench body 4 is fixed at the bottom center of the deep water pool 3, the model load-bearing and releasing device 9 is fixed at the bottom center of the variable buoyancy test bench body 4, the guide rail 5 is fixed at the upper surface center of the model load-bearing and releasing device 9, the PIV test system 2 and the hydrophone 8 are fixed on any two vertical brackets arranged opposite to each other in the variable buoyancy test bench body 4, the pressure sensor 41 is fixedly connected to the guide rail 5, the model retraction and extension servo device 10 is fixedly connected to the bottom plate 40, and a certain height of water (or seawater) is added into the deep water pool 3, thereby completing the construction of the test bench framework.

[0041] The sample 7 to be tested is selected according to the purpose of the test. For example, if the resistance noise characteristics of the shell need to be tested, the sample 7 to be tested is a shell of different shapes; if the resistance noise characteristics of the surface structure need to be tested, the sample 7 to be tested is a shell of different surface structures. The sample 7 to be tested is installed on the surface of the test model 6, and then the test model 6 is detachably and slidably connected to the guide rail 5, and the model retraction and extension servo device 10 and the test model 6 are connected by the wire rope 1. At this point, the preparations before the test are completed.

[0042] Start the model retracting and releasing servo device 10, tighten the wire rope 1, so that the test model 6 sinks, and then put the model load-bearing and releasing device 9 in the load-bearing condition to fix the test model 6; finally, reverse the model retracting and releasing servo device 10 and relax the wire rope 1.

[0043] When conducting resistance and noise tests, the model-carrying release device 9 is placed in a release state, the test model 6 is released, the test model 6 floats up, the pressure sensor 41 is used to monitor the time when the test model 6 reaches each sensor, the floating speed of the test model 6 is calculated by the distance between adjacent sensors and the arrival time difference, the hydrophone 8 is used to test the hydrodynamic noise, and the PIV test system 2 is used to observe the fluid boundary layer on the surface of the sample to be tested 7. It is worth noting that a certain distance is maintained between the test model 6 and the PIV test system 2, so that the fluid boundary layer on the surface of the sample to be tested 7 will not be affected.

[0044] like Figure 2 and Figure 3 As shown, the model retractable servo device 10 of the present invention comprises a model retractable servo device housing 18, a wire arrangement motor 11, a wire arrangement coupling 12, a wire arrangement guide rod 14, a wire arrangement nut 13, a wire arrangement wheel 23, a wire arrangement bearing 15, an I-shaped wire take-up wheel 19, a wire take-up shaft 20, a wire take-up coupling 21, a wire take-up motor 22, a sleeve 17, and a wire take-up bearing 16. In the test preparation stage, the wire arrangement motor 11 is started, and the wire arrangement guide rod 14 is driven to rotate through the wire arrangement coupling 12, so that the wire arrangement nut 13 moves linearly along the guide rod 14, and then the wire arrangement wheel 23 fixedly connected to the wire arrangement nut 13 moves linearly. At the same time, the wire take-up motor 22 is started, and the wire take-up shaft 20 is driven to rotate through the wire take-up coupling 21, so that the I-shaped wire take-up wheel 19 rotates, so that the wire rope 1 is evenly arranged on the outer surface of the I-shaped wire take-up wheel 19 through the wire arrangement wheel 23. At this time, the test model 6 is subjected to the downward pulling force provided by the steel wire rope 1 and sinks in the deep water pool 3. After the test model 6 sinks to a certain position, the wire arrangement motor 11 and the wire take-up motor 22 stop rotating, and the test model 6 is fixed by the model load-bearing release device 9, and then the wire arrangement motor 11 and the wire take-up motor 22 reverse, so that the steel wire rope 1 is separated from the I-shaped wire take-up wheel 19 and freely falls into the model take-up and release servo device housing 18, so that the test model 6 is not subjected to force, and the preparation work before the experiment is completed.

[0045] like Figure 4As shown, the test model 6 of the present invention comprises a buoyancy chamber shell 24, an electronic chamber and a jettison chamber shell 26, a jettison battery 27, a permanent magnet 28, a power coil 29, a load 30 and a sealing ring 25. The load 30 is a magnetic metal block, and the magnetic pole direction of the load 30 is the same as that of the permanent magnet 28. Therefore, when the power coil 29 is not energized, the load 30 is adsorbed on the lower surface of the permanent magnet 28. When it is necessary to control the movement speed of the test model 6 by jettisoning, the jettison battery 27 supplies power to the power coil 29 to provide a magnetic field in the opposite direction to the permanent magnet 28, and the magnetic field generated by the power coil 29 is much larger than the magnetic field generated by the permanent magnet 28. At this time, the load 30 falls under the action of the magnetic force of the power coil 29 and its own gravity, and the overall mass of the test model 6 is reduced, the gravity it receives is reduced, and the buoyancy provided by the buoyancy chamber remains unchanged, so the total propulsion force received is increased, and the floating speed is accelerated.

[0046] like Figure 5 and Figure 6 As shown, the model carrying and releasing device 9 of the present invention comprises a supporting arm 31, a slider 32, a push rod motor 33 and a model carrying and releasing device housing 34. Before the test starts, the test model 6 sinks to a certain position under the action of the model retracting and releasing servo device 10, and then the model carrying and releasing device 9 starts to work. First, the model carrying and releasing device 9 is in a loading condition, and the slider 32 moves upward along the model carrying device housing 34 under the action of the push rod motor 33, driving the supporting arm 31 to rotate, so that the free end of the supporting arm 31 contacts the lower surface edge of the electronic compartment and the jettisoning compartment housing 26 in the test model 6, thereby fixing the test model 6. At the beginning of the test, the model carrying and releasing device 9 is in a releasing condition, and the slider 32 moves downward along the model carrying and releasing device housing 34 under the action of the push rod motor 33, driving the supporting arm 31 to rotate, so that the free end of the supporting arm 31 leaves the electronic compartment and the jettisoning compartment housing 26 in the test model 6, thereby releasing the test model 6.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A comprehensive teaching and scientific research test platform for variable buoyancy propulsion fluid drag reduction and noise reduction, characterized by: The invention comprises a deep water pool (3), a variable buoyancy test bench, a model retractable bearing device, a test model (6) and a data acquisition and display module; the variable buoyancy test bench is fixed at the bottom center of the deep water pool (3); the test model (6) is installed on a guide rail (5) in the frame of the variable buoyancy test bench; the model retractable bearing device is used to retract and carry the test model (6); the test model (6) generates variable buoyancy by throwing a heavy object, so that the test model (6) moves along the guide rail (5) in the deep water pool (3) at an adjustable speed; the data acquisition and display module is fixed on the variable buoyancy test bench and is used to collect flow resistance, flow noise signals and distribution information of vortices in the flow field; The model retractable bearing device comprises a retractable servo device (10) and a load-bearing release device (9), the guide rail (5) is mounted on the load-bearing release device (9), the load-bearing release device (9) is further mounted at the center of the bottom plate (40) of the variable buoyancy test bench, and the retractable servo device (10) is mounted on the bottom plate (40) of the variable buoyancy test bench; the retractable servo device (10) comprises a retractable servo device housing (18), a wire arrangement guide rod (14), a wire arrangement coupling (12), a wire arrangement motor (11), a wire arrangement nut (13), a wire arrangement wheel (23), a wire arrangement bearing (15), an I-shaped wire take-up wheel (19), a wire take-up shaft (20), a shaft sleeve (17), a wire take-up bearing (16), a wire take-up coupling (21), a wire take-up motor (22) and a steel wire rope (1); the wire arrangement motor (11) is fixed inside the retractable servo device housing (18), and is connected to the wire arrangement guide rod through the wire arrangement coupling (12). The wire arranging guide rod (14) is connected, and the three rotate synchronously; the wire arranging guide rod (14) is a long straight screw, which is rotatably fixed in the housing (18) of the retracting servo device through a wire arranging bearing (15); the wire arranging nut (13) is connected to the wire arranging guide rod (14) through a thread, and the wire arranging wheel (23) is fixedly connected to the wire arranging nut (13); the wire rope (1) is wound around the I-shaped take-up wheel (19) through the wire arranging wheel (23), and the I-shaped take-up wheel (19) is rotated. The wire wheel (19) is rotatably fixed in the housing (18) of the model retractable servo device through a wire retractable bearing (16); the two ends of the wire retractable coupling (21) are respectively connected to the I-shaped wire retractable wheel (19) and the output shaft of the wire retractable motor (22); and the I-shaped wire retractable wheel (19), the wire retractable coupling (21) and the output shaft of the wire retractable motor (22) rotate synchronously; and the test model (6) is connected to the retractable servo device (10) through a steel wire rope (1).

2. According to claim 1, a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform is characterized by: The variable buoyancy test bench is an integral frame constituting a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform, comprising a test bench body (4) and a guide rail (5); the test bench body (4) comprises a vertical bracket I (35), a vertical bracket II (36), a vertical bracket III (38), a vertical bracket IV (39), a top frame (37) and a bottom plate (40), and the guide rail (5) is vertically fixed at the center of the bottom plate (40).

3. According to claim 1, a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform is characterized by: The load-releasing device (9) comprises a load-releasing device housing (34), a push rod motor (33), a slider (32) and a clamping arm (31); the load-releasing device housing (34) is fixed to the bottom of the variable buoyancy test bench bottom plate (40), the push rod motor (33) is fixed in the load-releasing device housing (34), the slider (32) is detachably connected to the push rod motor (33), and the slider (33) is slidably connected to the model load-releasing device housing (34), and the slider (33) slides along the load-releasing device housing (34) under the action of the push rod motor (33); one end of the clamping arm (31) is rotatably connected to the slider (33), and the other end is free, and the clamping arm (31) rotates around the load-releasing device housing (34).

4. According to claim 1, a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform is characterized by: The test model (6) has a sample to be tested (7) installed on its surface. The test model (6) comprises a buoyancy chamber shell (24), an electronic chamber and a jettison chamber shell (26), a jettison chamber battery (27), a permanent magnet (28), an energized coil (29) and a load (30); the buoyancy chamber shell (24) is fixedly connected to the electronic chamber and the jettison chamber shell (26), and a sealing ring is used to seal the two; the jettison chamber battery (27) is fixed in the electronic chamber and the jettison chamber shell (26), the permanent magnet (28) is fixedly connected to the electronic chamber and the jettison chamber shell (26), the energized coil (29) is wound around the outside of the permanent magnet (28), and the load (30) is adsorbed on the lower surface of the permanent magnet (28) around which the energized coil (29) is wound.

5. According to claim 1, a variable buoyancy propulsion fluid drag reduction and noise reduction teaching and scientific research comprehensive test platform is characterized by: The data acquisition and display module comprises a pressure sensor (41), a hydrophone (8) and a PIV test system (2); the pressure sensor (41) array is arranged inside the guide rail (5); the hydrophone (8) and the PIV test system (2) are respectively fixed on the inner sides of two opposite vertical brackets of the variable buoyancy test bench body (4).

6. A teaching and scientific research comprehensive test method for drag and noise reduction of variable buoyancy propulsion fluid according to any one of claims 1 to 5, characterized in that: The specific steps are as follows: 1) Construction of the test bench framework The variable buoyancy test bench body (4) is fixed at the bottom center of the deep water pool (3), the load-releasing device (9) is fixed at the center of the bottom plate (40) of the variable buoyancy test bench body (4), the guide rail (5) is fixed at the center of the upper surface of the load-releasing device (9), the PIV test system (2) and the hydrophone (8) are fixed on any two vertical brackets arranged opposite to each other in the variable buoyancy test bench body (4), the pressure sensor (41) is fixedly connected to the guide rail (5), the retractable servo device (10) is fixedly connected to the bottom plate (40), and a certain height of water is added into the deep water pool (3); the sample to be tested (7) is installed on the surface of the test model (6), and the retractable servo device (10) and the test model (6) are connected by a steel wire rope (1); 2) Start the experiment Start the retractable servo device (10), tighten the steel wire rope (1), make the test model (6) sink, make the load-bearing release device (9) be in the load-bearing condition, and fix the test model (6); reverse the model retractable servo device (10), and loosen the steel wire rope (1); Conduct resistance and noise tests: The model-carrying release device (9) is placed in a release state, the test model (6) is released, the test model (6) floats up, the time when the test model (6) reaches each sensor is monitored by a pressure sensor (41), the floating speed of the test model (6) is calculated by the distance between adjacent sensors and the arrival time difference, the hydrophone (8) is used to test the hydrodynamic noise, and the PIV test system (2) is used to observe the fluid boundary layer on the surface of the sample to be tested (7).

7. A teaching and scientific research comprehensive test method for drag and noise reduction of variable buoyancy propulsion fluid according to claim 6, characterized in that: The buoyancy of the test model (6) is: F 浮 =ρ 液 gV 排 Where g is the acceleration due to gravity; is the displacement volume of the test model (6); the self-weight of the test model (6) is: G=ρ 固 gV 固 in, is the volume of the solid part in the test model (6); therefore, to ensure that F 浮 ≥G, in the preferred case (ρ 液 =1000kg / m 3 ρ 固 =7850kg / m 3 ), there is the following relationship: V 排 ≥7.85V 固 。 8. The teaching and scientific research comprehensive test method for drag and noise reduction of variable buoyancy propulsion fluid according to claim 6 is characterized by: The sample to be tested (7) is adjusted as follows according to the test purpose: when testing the resistance noise characteristics of the shell, the sample to be tested (7) is a shell of different shapes; when testing the resistance noise characteristics of the surface structure, the sample to be tested (7) is a shell of different surface structures.

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