CN112572718B - Bionic flexible fin hydrodynamic performance measurement experimental device and method - Google Patents
Bionic flexible fin hydrodynamic performance measurement experimental device and method Download PDFInfo
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Abstract
The invention belongs to the technical field of bionic hydrodynamics, and particularly relates to an experimental device and method for measuring hydrodynamic performance of a bionic flexible fin. The invention can measure the thrust and hydrodynamic performance of the flexible fin under different strouhal numbers and Reynolds numbers and motion modes by adjusting the motion frequency of the bionic flexible fin, the size of water flow in the water tank and the initial phase difference of the gear set. Pigment release ports are formed in the middle positions of chord lengths on the two sides of the bionic flexible fin and are used for storing pigments with two colors respectively, and when the bionic flexible fin moves, the pigments can diffuse into water, so that the visualization of a flow field around the bionic flexible fin is realized; the wave-absorbing plate can reduce the interference of the free liquid level to a vortex system in the wake flow of the flexible fin, and the accuracy of a measuring result is ensured. The bionic flexible fin device adopts a scheme that a small stepping motor and a gear set are adopted to drive the flexible fin to move, a six-component balance is used for measurement, and pigments are scattered on the surface of the fin, so that the bionic flexible fin device is simple in structure, and is easy to measure the hydrodynamic performance of the bionic flexible fin and visualize the surrounding flow field.
Description
Technical Field
The invention belongs to the technical field of bionic hydrodynamics, and particularly relates to an experimental device and method for measuring hydrodynamic performance of a bionic flexible fin.
Background
Through the natural selection of the fishes for hundreds of millions of years, a propulsion and control system suitable for tour and escape of the fishes is developed. The system mainly comprises a fish body and various fins on the fish body. They are often remarkable and can motivate some innovative designs that greatly improve the way man-made systems operate in water. An example application that would benefit most is Autonomous Underwater Vehicles (AUVs). With the continuous expansion of research and use of the AUV, especially the rise of intelligent navigation and autonomous operation in recent two years, the AUV puts higher requirements on navigation stability and maneuverability of the AUV when performing tasks. Existing systems are inadequate in dexterous manipulation for maneuvering and hovering purposes, and are rough compared to the capabilities of fish. Certain planktonic fishes are efficiently propelled and have excellent operability, and inspiration can be provided for designing a propeller, so that the performance of the propeller exceeds that of the propeller used at present. In addition, the advantages of both noiseless propulsion and less wake vortex generation may have other implications, particularly in military applications. Underwater robotic devices are currently being developed that assess fin-like propeller yield and "transplant" it onto artificial systems.
Due to their wide range of appearance, batfish are all provided with a wide pectoral fin, ranging from a diamond shape to a disk shape. Batfish-like swimming patterns, one in which the propulsive wave swims through the body in the opposite direction to the overall motion and at a speed greater than the overall swimming speed, and one in which the wave propels itself by moving its enlarged pectoral fin in a flapping motion (with considerable edgewise flexion) in conjunction with a rolling motion (a traveling wave moving in a downstream direction). The batfish is excellent in maneuverability and high in propulsion efficiency, and has received wide attention from researchers in recent years.
Rosenberger analyzed the kinematics of eight bat fish species, each with a different swimming motion. Rosenberger identified a continuous spectrum of motion ranging from Rajiform fluctuations (multiple waves of travel through the fins and body) to Mobuliform oscillations (characterized by extensive flapping of the pectoral fins). In this regard, Schaefer & Summers asserts a correlation between the morphology of batfish and its motion strategies.
In addition to the observation of these batfish-like movements, little is known about the fluid dynamics of this complex propulsion mechanism. Lauder & Drucker performed detailed studies on the thrust generated by the flexible pectoral fins, including detailed visualization and speed measurements, but only for fish with fins smaller than their overall size (e.g., sunfish, mackerel, and trout). For batfish, the pectoral fin is the same dimension as the entire body, no thrust and flow measurements are made, and flow visualization is lacking.
The hydrodynamics experiment is an important means for carrying out the research of the bionic flexible fin, and mainly researches the interaction between water and the flexible fin. At present, in the design process of the bionic robot fish, computational fluid dynamics software is mostly adopted to carry out numerical simulation on propulsion of the fish fin, and an actual experimental device is lacked to prove the reliability of the simulation.
Disclosure of Invention
The invention aims to provide an experimental device for measuring the hydrodynamic performance of a bionic flexible fin, which is easy to measure the hydrodynamic performance of the bionic flexible fin and can visualize a surrounding flow field.
The purpose of the invention is realized by the following technical scheme: comprises a flat plate bracket, an experiment table and a water tank; the bottom surface of the flat plate bracket is provided with a six-component balance; the experiment table is positioned below the flat plate bracket and is parallel to the flat plate bracket; the test bench is connected with a six-component balance through a bearing rod, and the six-component balance measures the force and moment values of the test bench in all directions; the water tank is positioned below the experiment table; the experiment table is provided with a gear set and a stepping motor; the gear set consists of a driving wheel and a driven wheel, the driving wheel and the driven wheel are arranged in a row along the length direction of the water tank, the driving wheel is connected with the stepping motor, all the driven wheels are respectively connected with the bionic flexible fins through connecting rods, and the connecting rods are vertically embedded along the cross sections of the bionic flexible fins; the bionic flexible fin is arranged in the water tank, the chord length of the bionic flexible fin is parallel to the length direction of the water tank, and a wave-absorbing plate is arranged above the bionic flexible fin; the wave-absorbing plate is arranged at the free liquid level in the water tank and is close to the cross section of the bionic flexible fin; a water pump is arranged on one side of the water tank; the middle positions of chord lengths on two sides of the bionic flexible fin are provided with pigment release ports for respectively storing pigments with two colors, and when the bionic flexible fin moves, the pigments can diffuse into water, so that the visualization of a flow field around the bionic flexible fin is realized.
The invention also aims to provide an experimental method for measuring the hydrodynamic performance of the bionic flexible fin.
The purpose of the invention is realized by the following technical scheme: the method comprises the following steps:
step 1: installing a bionic flexible fin hydrodynamic performance measurement experiment device, and setting a phase difference in the gear set; setting the rotating speed of a stepping motor according to the motion frequency of the bionic flexible fin in the experimental scheme; supplying power to the six-component balance, the stepping motor and the water pump;
step 2: measuring the power of the bionic flexible fin moving in the air in 10 periods under the Strouhal number and the phase difference; when the bionic flexible fin moves stably, reading the power of the stepping motor within 10 periods, and turning off the stepping motor;
and step 3: calculating the water flow according to the Reynolds number of the bionic flexible fin so as to set the rotating speed of the water pump; after the water flow is stable and the flow field is stable, reading the force and the moment in each direction of the six-component balance within 10 periods;
and 4, step 4: turning on the stepping motor, reading the force and moment in each direction of the six-component balance in 10 periods when the bionic flexible fin moves and the flow field is stable, reading the power in 10 periods on the stepping motor, and turning off the water pump and the stepping motor;
and 5: subtracting the force and moment values of the bionic flexible fin in the static and moving process in water to obtain a thrust time-varying curve under the motion mode, the Strouhal number and the Reynolds number, and further calculating the average thrust; the bionic flexible fin moves in the air and in the water, the power of the stepping motor is subtracted to obtain the hair power, the input power is the hair power and the motor efficiency, the change curve of the input power along with the time is further obtained, and the average input power and the propulsion efficiency are calculated; propulsion efficiency (average thrust force water flow rate)/average input power;
step 6: when the bionic flexible fin moves, the pigments with two colors in the pigment release openings at the two sides of the bionic flexible fin can diffuse into water; by shooting pictures of the flow field around the flexible fin, the function of the vortex system in the bionic flexible fin thrust generation process is further analyzed.
The invention has the beneficial effects that:
the invention provides an experimental device capable of measuring the hydrodynamic performance of a bionic flexible fin and visualizing the surrounding flow field, which can simulate some characteristics of the bionic flexible fin under unsteady flow. Under the drive of the stepping motor, the driven wheel and the horizontal connecting rod in the gear set can convert circular motion into reciprocating linear motion similar to sine and transmit the motion to the bionic flexible fin, so that the periodic motion of the bionic flexible fin is realized, and the motion of the pectoral fin of the mink fish is effectively simulated. The hydrodynamic performance of the flexible fin under a plurality of strouhal numbers can be measured by adjusting the rotating speed of the stepping motor and changing the motion frequency of the bionic flexible fin. The water pump can adjust the rotational speed to the water current's in the control transparent basin size can measure the hydrodynamic force performance of flexible fin under a plurality of reynolds numbers. By setting a phase difference between each link motion, i.e., adjusting the initial phase of the gear set, a sine wave can be propagated along the chord of the flexible fin. The phase of the adjustment is different, as is the motion pattern of the flexible fin, which can range from oscillatory to oscillatory, and the hydrodynamic performance is measured. Pigment release openings are formed in the middle positions of chord lengths of the two sides of the bionic flexible fin, pigments of two colors are stored respectively, and when the bionic flexible fin moves, the pigments can diffuse into water, so that visualization of a flow field around the bionic flexible fin is achieved. The wave-absorbing plate can reduce the interference of the free liquid level to a vortex system in the wake flow of the flexible fin, and the accuracy of a measuring result is ensured. The bionic flexible fin can be replaced by flexible fins in other shapes, and the expansibility of the device is strong.
Drawings
Fig. 1 is a cross-sectional view of an experimental apparatus for measuring hydrodynamic performance of a bionic flexible fin according to the present invention.
Fig. 2 is an axonometric view of the experimental device for measuring hydrodynamic performance of the bionic flexible fin.
Fig. 3 is three views of a bionic flexible fin in the invention.
Fig. 4 is a detail view of the gear set of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
A bionic flexible fin hydrodynamic performance measurement experimental device belongs to the field of bionic hydrodynamics. The device comprises a flat support, an experiment table and a transparent water tank, wherein a six-component balance is arranged below the flat support, the six-component balance is connected with the experiment table through a bearing aluminum rod, and the six-component balance measures force and moment values of the experiment table in all directions. The experiment table is provided with a gear set and a stepping motor which can be accurately controlled. The first gear in the gear set is connected with a stepping motor which is a driving wheel, the other four gears are driven wheels, and the driven wheels are connected with the bionic flexible fins through connecting rods. By controlling the stepper motor, the frequency of motion of the flexible fin can be adjusted. The bionic flexible fin is made of flexible materials. It has the shape of a yellow mink pectoral fin, and the cross section of the yellow mink pectoral fin is of an NACA0020 airfoil. The wave absorbing plate is arranged above the bionic flexible fin, so that the interference of the free liquid level to a vortex system in the wake flow of the flexible fin is reduced, and the accuracy of a measuring result is ensured. The water pump is connected to transparent basin left side, controls the size of rivers through the rotational speed of adjusting the water pump. The invention measures the thrust, the output power and the thrust coefficient of the flexible fin under different strouhal numbers and Reynolds numbers by changing the motion frequency and the water flow speed of the flexible fin. The invention can also adjust the phase difference between the gears, and measure the hydrodynamic performance parameters of the flexible fin under different motion modes (swinging to fluctuation). In addition, the pigment release port is arranged in the middle of the chord length on the two sides of the flexible fin, so that the pigment can diffuse into water when the flexible fin moves, and the visualization of the flow field around the fin is realized. The invention provides the experimental device for measuring the hydrodynamic performance of the bionic flexible fin, which is simple and convenient to operate, low in cost and accurate in measurement. The bionic flexible fin device adopts a scheme that a small stepping motor and a gear set are adopted to drive the flexible fin to move, a six-component balance is used for measurement, and pigments are scattered on the surface of the fin, so that the bionic flexible fin device is simple in structure, and is easy to measure the hydrodynamic performance of the bionic flexible fin and visualize the surrounding flow field.
With reference to fig. 1 and fig. 2, an experimental apparatus for measuring hydrodynamic performance of a bionic flexible fin is arranged as follows: the flat support 1 is a supporting frame, and the whole experimental device is hung. A six-component balance 2 is arranged below the flat support 1, and the six-component balance 2 mainly has the function of measuring the force and moment values of the experiment table in all directions. The experiment table 5 is connected with the six-component balance 2 through the bearing aluminum rod 3, the experiment table 5 must be parallel to the flat support 1, and the measurement accuracy of the six-component balance force and the moment can be obviously improved. The space above the laboratory table 5 is mainly for arranging a gear train 6 and a stepping motor 4. The stepping motor 4 can control its rotation speed accurately and can obtain its input power. A stepping motor 4 and a gear set 6 are arranged on the experiment table 5, and the rotating speed of the stepping motor can be accurately controlled. The gear set 6 comprises five gears, a driving wheel and four driven wheels, the five gears in the gear set 6 are arranged along the direction of the transparent water tank and are sequentially meshed, the driving wheel is connected with the stepping motor 4, and each driven wheel is connected with an aluminum connecting rod 7. The upper edge of the gear set 6 is provided with a bolt which is convenient to be connected with an aluminum connecting rod 7, and the initial phase of the gear is adjustable. The bionic flexible fin 12 is arranged inside the transparent water tank 8. The aluminum tie rod 7 is embedded vertically along the cross section of the biomimetic flexible fin 12. The bionic flexible fin 12 is arranged inside the transparent water tank 8, and the chord length of the flexible fin is parallel to the direction of the transparent water tank 8.
With reference to fig. 1 and 2, the bionic flexible fin hydrodynamic performance measurement experimental device has the following movement modes: under the rotation of the stepping motor 4, the driven wheel and the aluminum horizontal connecting rod in the gear set 6 can convert the circular motion into the reciprocating linear motion which is approximate to sine. The aluminum vertical connecting rod can transmit the movement to the flexible fin 12, so that the periodic movement of the flexible fin is realized, and the motion of the pectoral fin of the mink fish is effectively simulated.
With reference to fig. 2 and 4, the parameter changing manner of the experimental apparatus for measuring hydrodynamic performance of the bionic flexible fin is as follows: the rotation speed of the stepping motor 4 is controlled to adjust the motion frequency of the flexible fin 12, so that the strouhal number of the flexible fin is changed. By changing the phase difference of the gear set, the motion mode of the flexible fin can be adjusted from swing to wave. The flexible fin 12 is in oscillatory mode if the chord length direction is less than one propulsive wavelength and in wave mode if it is greater than one propulsive wavelength. The left side of the transparent water tank 8 is connected with a water pump 11, the right side of the transparent water tank is provided with a drain hole 10, and the water flow can be controlled by adjusting the rotating speed of the water pump 11. The Reynolds number of the flexible fin can be changed by adjusting the water flow.
With reference to fig. 1 and 2, the hydrodynamic parameter reading method of the experimental apparatus for measuring hydrodynamic performance of the bionic flexible fin is as follows: the force and the moment in each direction are obtained through the six-component balance 2, the input power of the stepping motor can be read out to obtain the power, and the water flow can be read out through the water pump.
With reference to fig. 1 and 2, some error elimination manners of the experimental apparatus for measuring hydrodynamic performance of the bionic flexible fin are as follows: the wave eliminating plate 9 is arranged above the bionic flexible fin 12 and is close to the cross section of the bionic flexible fin 12, and the wave eliminating plate 9 can prevent the free liquid level of the transparent water tank 8 from generating waves.
With reference to fig. 2 and 3, the visual flow field mode of the experimental device for measuring hydrodynamic performance of the bionic flexible fin is as follows: pigment release openings are formed in the middle positions of chord lengths on the two sides of the bionic flexible fin 12 and are used for storing red and green pigments respectively, and when the flexible fin moves, the pigments can diffuse into water, so that the visualization of a flow field around the fin is realized.
With reference to fig. 2 and 3, a visual flow field observation mode of the bionic flexible fin hydrodynamic performance measurement experimental device is as follows: and the transparent water tank 8 is transparent and is convenient for observing and shooting the flow field around the flexible fin 12.
The specific process is as follows:
1) the bionic flexible fin hydrodynamic performance measurement experimental device is installed according to the figures 1 and 2.
2) The phase difference in the gear sets is set according to the experimental scheme.
3) And the six-component balance, the stepping motor and the water pump are powered.
4) And setting the rotating speed of the stepping motor according to the motion frequency of the flexible fin in the experimental scheme. After the setting is finished, the whole experimental device is started.
5) The power of the flexible fin moving in the air within 10 cycles under the strouhal number and the phase difference needs to be measured firstly. And when the flexible fin of the device moves stably, reading the power of the stepping motor within 10 periods. The stepper motor is turned off.
6) And then calculating the water flow according to the Reynolds number of the flexible fin in the experimental scheme, setting the rotating speed of the water pump, and reading the force and the moment of the six-component balance in each direction within 10 periods when the water flow is stable and the flow field is stable.
7) The stepper motor is turned on. And when the flexible fin moves and the flow field is stable, reading the force and the moment in each direction of the six-component balance within 10 periods. The power over 10 cycles on the stepper motor is read. The water pump and stepper motor are turned off.
8) And subtracting the force and moment values of the flexible fin in the static and moving processes in the water to obtain a thrust time-varying curve under the motion mode, the Strouhal number and the Reynolds number. Further, the average thrust can be obtained. The flexible fins move in the air and in the water, the power of the stepping motor is subtracted to obtain the hair power, and the input power is the hair power and the motor efficiency. Further, the variation curve of the input power along with the time can be obtained, and the average input power can be obtained. Propulsion efficiency (average thrust force water flow rate)/average input power.
9) And (5) repeating the steps (4) to (8).
10) For the visualization of the flow field under specific parameters, red and green pigments can be released into the fins after the flexible fins move and the flow field is stabilized, and the flow field around the fins can be observed and photographed.
The dynamic performance measurement experimental device for the bionic flexible fin can change the strouhal number, Reynolds number and motion mode of the flexible fin by adjusting the rotating speed of the stepping motor, the flow velocity of water and the phase difference among the gears.
The bionic flexible fin 12 is made of flexible materials, has a shape of a chest fin of a yellow mink fish, and has a cross section of an NACA0020 wing shape.
The six-component balance 2 measures the force and moment values of the experiment table 5 in all directions, and the measured forces are the stress and moment on the whole experiment table 5.
The wave-absorbing plate 9 can reduce the interference of the free liquid level to the vortex system in the wake flow of the flexible fin 12, and the accuracy of the measurement result and the visual image is ensured.
The aluminum connecting rod 7 will perform an approximately sinusoidal motion in a plane perpendicular to the water flow. By setting a phase difference between each link, i.e., adjusting the initial phase of the gear set, a sine wave can be propagated along the chord of the flexible fin, essentially adjusting the oscillatory or undulating motion pattern of the flexible fin. The sine wave wavelength is determined by the phase difference between the first gears in the gear set. Furthermore, because each link is rigid, the amplitude of the flexible fins increases with the distance the link extends downward.
The invention provides an experimental device capable of measuring the hydrodynamic performance of a bionic flexible fin and visualizing a surrounding flow field, which simulates some characteristics of the bionic flexible fin under unsteady flow. The flexible fin motion aspect: driven by the stepping motor, a driven wheel in the gear set and an aluminum horizontal connecting rod can convert circular motion into reciprocating linear motion which is approximate to sine. The vertical connecting rod made of aluminum can transmit the motion to the flexible fin, so that the periodic motion of the flexible fin is realized, and the motion of the pectoral fin of the mink fish is effectively simulated. The hydrodynamic performance of the flexible fin under a plurality of strouhal numbers can be measured by adjusting the rotating speed of the stepping motor and changing the motion frequency of the flexible fin. The water pump can adjust the rotational speed to the size of rivers in the control transparent basin can measure the hydrodynamic force performance of flexible fin under a plurality of reynolds numbers. By setting a phase difference between each link motion, i.e., adjusting the initial phase of the gear set, a sine wave can be propagated along the chord of the flexible fin. The phase of the adjustment is different, as is the motion pattern of the flexible fin, which can range from oscillatory to oscillatory, and the hydrodynamic performance is measured. The bionic flexible fin is provided with pigment release ports in the middle of chord lengths on two sides, the pigments in red and green colors are stored respectively, and when the flexible fin moves, the pigments can diffuse into water, so that the visualization of a flow field around the fin is realized. The wave-absorbing plate can reduce the interference of the free liquid level to a vortex system in the wake flow of the flexible fin, and the accuracy of a measuring result is ensured. The bionic flexible fin can be replaced by flexible fins in other shapes, and the expansibility of the device is strong.
The invention provides an experimental device capable of measuring hydrodynamic performance of a bionic flexible fin and visualizing a surrounding flow field, which comprises a flat support, a six-component balance, a force bearing aluminum rod, a stepping motor, an experimental table, a gear set, an aluminum connecting rod, a transparent water tank, a wave absorbing plate, a water pump and the bionic flexible fin, and simulates some characteristics of the bionic flexible fin under unsteady flow. Driven by the stepping motor, the driven wheel in the gear set and the aluminum horizontal connecting rod can convert circular motion into reciprocating linear motion similar to sine. The aluminum vertical connecting rod can transmit the movement to the flexible fin, so that the periodic movement of the flexible fin is realized. The mechanical design is very exquisite, and the motion of the pectoral fin of the mink can be really simulated. The hydrodynamic performance of the flexible fin under a plurality of strouhal numbers can be measured by adjusting the rotating speed of the stepping motor and changing the motion frequency of the flexible fin. The water pump can adjust the rotational speed to the size of rivers in the control transparent basin can measure the hydrodynamic force performance of flexible fin under a plurality of reynolds numbers. By setting a phase difference between each link motion, i.e., adjusting the initial phase of the gear set, a sine wave can be propagated along the chord of the flexible fin. The phase of the adjustment is different, as is the motion pattern of the flexible fin, which can range from oscillatory to oscillatory, and the hydrodynamic performance is measured. The adjusting parameters are simple and easy to implement, and can be quickly adjusted in an experiment, so that the experiment time is reduced, and the experiment efficiency is improved. And subtracting the force and moment values of the flexible fin in the static and moving processes in the water to obtain a thrust time-varying curve under the motion mode, the Strouhal number and the Reynolds number. Further, the average thrust can be obtained. The flexible fins move in the air and in the water, the power of the stepping motor is subtracted to obtain the hair power, and the input power is the hair power and the motor efficiency. Further, the variation curve of the input power along with the time can be obtained, and the average input power can be obtained. Propulsion efficiency (average thrust force water flow rate)/average input power. The device can accurately and rapidly measure the hydrodynamic performance parameters of the flexible fin under different pairs of Strouhal numbers, Reynolds numbers or phase differences. Pigment release openings are formed in the middle positions of chord lengths of two sides of the flexible fin of the bionic flexible fin and are used for storing red and green pigments respectively, and when the flexible fin moves, the pigments can diffuse into water, so that the visualization of a flow field around the fin is realized. By shooting pictures of the flow field around the flexible fin, the role of the vortex system in the thrust generation process of the flexible fin is further analyzed. The wave-absorbing plate can reduce the interference of the free liquid level to a vortex system in the wake flow of the flexible fin, and the accuracy of a measuring result is ensured. The bionic flexible fin can be replaced by flexible fins of other shapes or sizes, and the expansibility of the device is strong.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (1)
1. A bionic flexible fin hydrodynamic performance measurement experiment method is characterized by comprising the following steps:
step 1: installing a bionic flexible fin hydrodynamic performance measurement experiment device, and setting a phase difference in the gear set; setting the rotating speed of a stepping motor according to the motion frequency of the bionic flexible fin in the experimental scheme; supplying power to the six-component balance, the stepping motor and the water pump;
the experimental device for measuring hydrodynamic performance of the bionic flexible fin comprises a flat plate bracket, an experimental table and a water tank; the bottom surface of the flat plate bracket is provided with a six-component balance; the experiment table is positioned below the flat plate bracket and is parallel to the flat plate bracket; the test bench is connected with a six-component balance through a bearing rod, and the six-component balance measures the force and moment values of the test bench in all directions; the water tank is positioned below the experiment table; the experiment table is provided with a gear set and a stepping motor; the gear set consists of a driving wheel and a driven wheel, the driving wheel and the driven wheel are arranged in a row along the length direction of the water tank, the driving wheel is connected with the stepping motor, all the driven wheels are respectively connected with the bionic flexible fins through connecting rods, and the connecting rods are vertically embedded along the cross sections of the bionic flexible fins; the bionic flexible fin is arranged in the water tank, the chord length of the bionic flexible fin is parallel to the length direction of the water tank, and a wave-absorbing plate is arranged above the bionic flexible fin; the wave-absorbing plate is arranged at the free liquid level in the water tank and is close to the cross section of the bionic flexible fin; a water pump is arranged on one side of the water tank; pigment release ports are formed in the middle positions of chord lengths on the two sides of the bionic flexible fin and are used for storing pigments with two colors respectively, and when the bionic flexible fin moves, the pigments can diffuse into water, so that the visualization of a flow field around the bionic flexible fin is realized;
step 2: measuring the power of the bionic flexible fin moving in the air in 10 periods under the Strouhal number and the phase difference; when the bionic flexible fin moves stably, reading the power of the stepping motor within 10 periods, and turning off the stepping motor;
and step 3: calculating the water flow according to the Reynolds number of the bionic flexible fin so as to set the rotating speed of the water pump; after the water flow is stable and the flow field is stable, reading the force and the moment in each direction of the six-component balance within 10 periods;
and 4, step 4: turning on the stepping motor, reading the force and moment in each direction of the six-component balance in 10 periods when the bionic flexible fin moves and the flow field is stable, reading the power in 10 periods on the stepping motor, and turning off the water pump and the stepping motor;
and 5: subtracting the force and moment values of the bionic flexible fin in the static and moving process in water to obtain a thrust time-varying curve under the motion mode, the Strouhal number and the Reynolds number, and further calculating the average thrust; the bionic flexible fin moves in the air and in the water, the power of the stepping motor is subtracted to obtain the hair power, the input power is the hair power and the motor efficiency, the change curve of the input power along with the time is further obtained, and the average input power and the propulsion efficiency are calculated; propulsion efficiency (average thrust force water flow rate)/average input power;
step 6: when the bionic flexible fin moves, the pigments with two colors in the pigment release openings at the two sides of the bionic flexible fin can diffuse into water; by shooting pictures of the flow field around the flexible fin, the function of the vortex system in the bionic flexible fin thrust generation process is further analyzed.
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| CN112572718A (en) | 2021-03-30 |
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