A method and experimental device for reducing cylindrical radiation noise by rotation control

Abstract

The present invention discloses a method and an experimental device for reducing cylindrical radiation noise by rotation control, which belongs to the fields of fluid mechanics, flow noise and flow; the method steps are as follows: step 1: measuring the lift-drag coefficient by an experimental device, and reading the lift-drag coefficient as a feedback signal into the memory of a host computer in real time; step 2: defining the noise index J according to the instantaneous lift-drag coefficient; step 3: using the feedback signal as input, using the proximal optimization strategy model to train a reinforcement learning agent, interacting with the flow field, and outputting the instantaneous rotation speed, with the goal of reducing the noise index J; step 4: reducing the noise index J through continuous training, and finally achieving noise reduction. The present invention adopts reinforcement learning to generate a control strategy, and uses an adaptive unsteady rotation excitation mechanism to reduce the cylindrical radiation noise; it can use rotation control to reduce the cylindrical radiation noise and achieve the best control effect.

Description

Technical Field

[0001] The invention belongs to the fields of fluid mechanics, flow noise and flow, and in particular relates to a method and an experimental device for reducing cylindrical radiation noise through rotation control. Background Art

[0002] The problem of cylindrical radiation noise is widely present in daily life, such as the harsh noise of wind-blown wires and the huge noise radiated by aircraft landing gear. Therefore, exploring methods to reduce cylindrical radiation noise has important engineering value. Studies have shown that under low Mach number conditions, vortex shedding formed by fluid flowing through the cylinder is the main mechanism for generating noise. This also provides a theoretical basis for reducing radiation noise by controlling the flow field. Existing studies have used flow control to intervene in vortex shedding to change radiation noise and successfully achieved noise reduction. The fluid dynamic changes of the cylinder directly reflect the changes in vortex shedding. Therefore, for closed-loop control, fluid dynamic information can be used as a feedback signal. Among them, the numerical simulation research paper "Noise reduction by feedback rotary oscillation of a three-dimensional circular cylinder" published in the journal "Fluids and Structures" in 2019, Volume 84, Pages 421 to 439, uses the lift coefficient as a feedback signal, and proportional control generates a control law, and the cylindrical flow radiation noise is reduced by 10dB through rotation control. However, its proportional coefficient needs to be specified based on experience and varies with the working conditions, and may not necessarily achieve the best noise reduction effect. Reinforcement learning, which has developed rapidly in recent years, is an effective means to achieve optimal control. Studies have shown that active flow control methods based on reinforcement learning can achieve optimal control effects close to the drag reduction limit. However, the training process requires the use of data in the flow field, which is difficult to apply in engineering practice. In addition, the training method of reinforcement learning is based on flow field goals such as reducing drag and increasing lift, and cannot be directly applied to the sound field.

[0003] Based on this, the present invention provides a method and an experimental device which uses the surface information of the cylinder as feedback, generates a control strategy using reinforcement learning, and reduces the radiated noise of the cylinder through rotation control. Summary of the invention

[0004] Technical issues to be solved:

[0005] In order to avoid the shortcomings of the prior art, the present invention provides a method and experimental device for reducing cylindrical radiation noise through rotation control, adopts reinforcement learning to generate a control strategy, and utilizes an adaptive unsteady rotation excitation mechanism to reduce cylindrical radiation noise; it is possible to utilize rotation control to reduce cylindrical radiation noise and achieve the best control effect.

[0006] The technical solution of the present invention is: a method for reducing cylindrical radiation noise by rotation control, characterized in that the specific steps are as follows:

[0007] Step 1: Measure the lift-drag coefficient through the experimental device, and read the lift-drag coefficient into the host computer memory in real time as a feedback signal;

[0008] Step 2: Define the noise index J according to the instantaneous lift-drag coefficient:

[0009]

[0010] Among them, ω∈(0,1), N represents the total number of moments, i is the i-th moment, Derivative of the lift coefficient at the ith moment, Derivative of the resistance coefficient at the i-th moment;

[0011] Step 3: Take the feedback signal as input, use the proximal optimization strategy model to train the reinforcement learning agent, interact with the flow field, and output the instantaneous speed, with the goal of reducing the noise index J;

[0012] Step 4: Through continuous training, reduce the noise index J and finally achieve noise reduction.

[0013] A further technical solution of the present invention is: in step 1, the instantaneous fluid dynamic information measured by the experimental device, that is, the lift F L (t) and resistance F D (t), and non-dimensionalized using the following formula:

[0014]

[0015]

[0016] Among them, ρ0 is the air density, U0 is the average speed in the wind tunnel, and D0 is the outer diameter of the cylinder of the experimental device. After non-dimensionalization, the instantaneous lift coefficient C is obtained: L (t) and the instantaneous drag coefficient C D (t).

[0017] A further technical solution of the present invention is: in step 3, the proximal optimization strategy model includes an action network and an evaluation network.

[0018] A further technical solution of the present invention is: the input of the evaluation network is the instantaneous fluid dynamic coefficient, and the output is the predicted reward; the actual reward is defined as -J, and the goal of the evaluation network is to reduce the gap between the predicted reward and the actual reward; the input of the action network is the instantaneous fluid dynamic coefficient, and the output is the instantaneous rotational speed, and its goal is to reduce the noise index J.

[0019] An experimental device for reducing cylindrical radiation noise by rotation control, characterized in that it includes an anechoic chamber, a microphone assembly, a three-force balance, a support rod, a coupling, a servo motor, a cylindrical shell, and a rotating connector; the inlet and outlet of the anechoic chamber are respectively connected to the silent wind tunnel pipeline, a partition is provided at the bottom, and other components of the experimental device are installed in the anechoic chamber;

[0020] The servo motor and the three-force balance are installed in the compartment, and the output end of the servo motor is arranged vertically;

[0021] The bottom end of the rotating connector passes through the bottom plate of the muffler chamber and is connected to the servo motor through a coupling; the top end is detachably coaxially connected to the cylindrical housing;

[0022] The top end of the support rod extends into and is closely attached to the inner wall of the cylindrical shell, and the bottom end passes through the bottom plate of the anechoic chamber and is connected to a three-force balance. The three-force balance obtains lift and drag information by measuring the displacement of the support rod;

[0023] The microphone assembly is used to measure instantaneous sound pressure.

[0024] A further technical solution of the present invention is: the anechoic chamber is surrounded by sound-absorbing material; the top plate of the partition is a sound-absorbing partition for eliminating the mechanical noise of the servo motor.

[0025] A further technical solution of the present invention is that the outer circumferential surface of the cylindrical shell is an equal-diameter cylindrical structure, a stepped through hole is opened along the central axis thereof, the inner diameter of the upper end is smaller than the inner diameter of the lower end, and a plurality of radial key grooves are opened on the stepped surface along the circumferential direction.

[0026] A further technical solution of the present invention is: the upper end of the rotating connector is a disc, and a plurality of radial keys are arranged on its upper end surface along the circumferential direction. The number of the radial keys corresponds to that of the radial key slots, and they are installed in cooperation with each other for detachable connection between the cylindrical shell and the rotating connector; the lower end of the rotating connector is a coaxial straight rod, and the bottom end is connected to the servo motor through a coupling; the rotating connector is driven to rotate by the servo motor, thereby driving the cylindrical shell to rotate.

[0027] A further technical solution of the present invention is: the upper end of the support rod is a straight rod, and the lower end is an L-shaped connecting rod; the upper straight rod extends into the cylindrical shell, and its axial direction is perpendicular to the central axis of the cylindrical shell, and its two ends are tightly attached to the inner wall of the large diameter end of the cylindrical shell, and it is only used to measure the displacement of the cylindrical shell and does not play a supporting role; the short arm of the lower L-shaped connecting rod is vertically fixed to the outer circumferential surface of one side of the upper support rod to avoid interference with the rotating connecting piece, and its long arm is horizontally arranged and the end is connected to the three-force balance.

[0028] A further technical solution of the present invention is: the microphone assembly includes a microphone array and a high-precision microphone, and the distance between the microphone array and the cylindrical shell is smaller than the distance between the high-precision microphone and the cylindrical shell;

[0029] The microphone array is a plurality of microphones arranged along an arc, and is used to measure the sound pressure and obtain the directivity of noise radiation;

[0030] The measurement range and sensitivity of the high-precision microphone are both greater than those of the microphone array.

[0031] Beneficial Effects

[0032] The beneficial effects of the present invention are:

[0033] 1. The far-field radiation noise of the cylinder is related to fluid dynamics. Reducing the fluid dynamics pulsation can reduce the radiation noise of the cylinder. The use of rotation control can significantly change the flow field structure and the fluid dynamics of the cylinder, thus reducing the radiation noise of the cylinder.

[0034] 2. Since the size of the rotation control device is determined by the inner diameter of the cylindrical shell, when testing different working conditions, it is only necessary to keep the inner diameter of the cylindrical shell unchanged and change the outer diameter of the cylindrical shell for processing. There is no need to rebuild the experimental device, which improves the experimental efficiency.

[0035] 3. The reinforcement learning method constructed by the present invention uses the fluid dynamics information of the cylindrical surface as input, which is closer to engineering practice and aims at reducing noise, so better noise reduction effect can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a general schematic diagram of an experimental device for reducing cylindrical radiation noise by using rotation control in the present invention;

[0037] Figure 2 It is a schematic diagram of the relative positions of the internal structure of the cylindrical shell and the rotating connector and the support rod;

[0038] Figure 3 It is a schematic diagram of the connection part between the rotating connector and the inside of the cylindrical shell;

[0039] Figure 4 It is a schematic diagram of the support rod;

[0040] Explanation of the reference numerals: 1. Microphone array, 2. High-precision microphone, 3. Anechoic chamber outlet, 4. Three-force balance, 5. Support rod, 6. Coupling, 7. Servo motor, 8. Cylindrical shell, 9. Rotating connector, 10. Anechoic chamber inlet, 11. High-performance computer, 12. Sound-absorbing baffle. DETAILED DESCRIPTION

[0041] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0043] Reference Figure 1 As shown in FIG. 1 , this example is an experimental device for reducing the radiated noise of a cylinder by rotation control.

[0044] The experimental device was built in an open silent wind tunnel, and an anechoic chamber was set up at the opening of the wind tunnel. The main devices are as follows: Figure 1 The inlet 10 and outlet 12 of the anechoic chamber are respectively connected to the silent wind tunnel pipe, so that the airflow flows in from the inlet and all flows out from the outlet. The surroundings and top of the anechoic chamber are all made of split-point type sound-absorbing materials, and the bottom is a partition structure separated by a sound-absorbing partition 12. A servo motor 7 and a three-force balance 4 are arranged inside the partition. Among them, the function of the sound-absorbing partition 12 is to prevent the mechanical noise generated by the servo motor 7 from affecting the measurement results when it is actuated.

[0045] The servo motor 7 can realize forward and reverse rotation according to the specified speed, and drive the rotating connector 9 to rotate through the coupling 6. Further, the rotating connector 9 is connected by a key to rotate the cylindrical shell 8. The displacement change of the cylindrical shell 8 when rotating can be transmitted to the three-force balance 4 by the support rod 5. The three-force balance 4 obtains lift and drag information by measuring the displacement of the support rod.

[0046] The relative positions of the rotating connecting member 9 and the support rod 5 inside the cylindrical housing 8 are as follows: Figure 2 The upper part of the rotating connector 9 is close to the centerline of the cylindrical shell 8. The support rod 5 is slightly lower than the centerline to prevent interference with the rotating connector 9 during rotation. The top view of the connection between the rotating connector 9 and the inner part of the cylindrical shell 8 is shown in FIG. Figure 3. The rotating connector 9 is a customized steel structure, and the upper part is a cross structure with four keyways. The cylindrical shell 8 can be made by 3D printing, and a keyway is opened at the bottom of the thicker part of the shell, corresponding to the position of the cross structure. The keyways are all standard sizes, connected by keys of standard specifications, and tightened by the gravity of the cylindrical shell 8 itself. The end face of the top round tube of the support rod 5 needs to be close to the inner wall of the cylindrical shell 8. In order to avoid excessive friction, the position where the top round tube of the connecting rod 5 contacts the cylindrical shell 8 needs to be processed into a spherical surface and lubricated during the experiment.

[0047] Preferably, the support rod 5 is a lightweight structure that fits tightly with the inner surface of the cylindrical shell. It is welded from two sections of round tubes. The two end faces of the top round tube are spherical and close to the inner surface of the cylindrical shell. Only the displacement of the cylinder is measured, and there is no need to support the cylinder. The inside of the cylindrical shell 8 is separated by half of its total axial length, thick on the top and thin on the bottom. The inner diameter of the thicker part is D1, and the thinner part is D2, and the difference between the thick and thin inner diameters (D2-D1) needs to be greater than 6 times the length of the standard key. The inner diameter of the cylindrical shell 8 is fixed, and the outer diameter D0 can be adjusted according to the experimental requirements. The support rod 5 is installed at the thinner part of the cylindrical shell 8, and the length of the top round tube is half of the diameter of the thinner part of the cylinder, that is, D2 / 2, to ensure that it does not interfere with the rotating connector.

[0048] The lift-drag coefficient measured by the three-force balance 4 is read into the computer memory in real time, and the control signal is output through the reinforcement learning method to adjust the motor speed. The directivity of noise radiation is obtained by using a microphone array arranged along the arc, and a high-precision microphone with a larger measurement range and higher sensitivity can be set up to measure the sound pressure data at key positions. At a position close to the cylinder, a microphone array arranged along the arc is used to measure the sound pressure and obtain the directivity of noise radiation. At the same time, a high-precision microphone with a larger measurement range and higher sensitivity can be set up at a position far away from the cylinder. The noise reduction effect is evaluated by directivity and sound pressure.

[0049] A method of reducing the radiated noise of a cylinder by rotation control in this embodiment:

[0050] First, the cylindrical shell 8 is a hollow shell structure. When processing the inner wall of the cylindrical shell 8, it is necessary to ensure that the upper part is thicker and the lower part is thinner, and a key groove is opened at the bottom of the thicker end of the shell. By changing the outer diameter of the cylindrical shell 8, the experimental working conditions can be quickly changed.

[0051] Then, the rotation control of the cylinder is realized by the servo motor 7, the coupling 6, the rotating connector 9 and the cylindrical shell 8. A key groove is opened on the upper surface of the rotating connector 9, and the cylindrical shell is driven to rotate through the key connection. The connection part between the rotating connector 9 and the cylindrical shell 8 is set near the middle section of the cylinder.

[0052] The feedback signal is the instantaneous lift resistance of the cylinder under the action of the fluid measured by the three-force balance. The three-force balance measures the force on the cylinder through the displacement of the support rod. One end of the support rod is close to the inner surface of the thinner part of the lower side of the cylindrical shell, and the support rod is close to the lower half of the cylinder to ensure that it does not interfere with the rotating connection.

[0053] Finally, the rotation of the cylindrical shell is controlled in real time by the reinforcement learning method. The specific process is to read the lift and drag information measured over a period of time into the memory as a feedback signal through a three-force balance, and use the reinforcement learning method constructed by the present invention with the goal of reducing the radiation noise of the cylinder to calculate and generate the control strategy in real time on a high-performance computer, and use the reinforcement learning method to calculate and generate the control strategy in real time, and finally output it to the servo motor to control the rotation speed of the cylindrical shell. After the rotation speed of the cylinder reaches stability, continue to experiment with 200 characteristic times to measure the noise, where the characteristic time can be calculated by the average speed of the incoming flow and the outer diameter of the cylinder.

[0054] The specific experimental process is:

[0055] At the beginning of the experiment, you need to follow Figure 2 The cylindrical shell 8, the rotating connector 9, the support rod 5 and the coupling 6 are installed in sequence. After the wind tunnel is started, wait for the measurement results of the microphone array 1, the high-precision microphone 2 and the three-force balance 4 to reach stability. The background noise is measured in a stable state, and the three-force balance is calibrated. The instantaneous fluid dynamic information measured by the three-force balance is the lift F L (t) and resistance F D (t), using

[0056]

[0057] Non-dimensionalization is performed, where ρ0 is the air density, U0 is the average speed in the wind tunnel, and D0 is the outer diameter of the cylinder. After non-dimensionalization, the instantaneous lift coefficient C is obtained L (t) and the instantaneous drag coefficient C D (t), and is directly input into the memory of the high-performance computer 11 as a feedback signal. Since the sound pressure is actually related to the pulsating value of the fluid dynamic coefficient, the instantaneous lift and drag coefficient at N moments in a period of time is used as the feedback signal. The feedback signal is processed by the high-performance computer 11 using the reinforcement learning method. The process of using the feedback signal as input and outputting the control signal in real time in the reinforcement learning method is a training of the reinforcement learning agent, which is implemented using the proximal strategy optimization model. According to the instantaneous fluid dynamic coefficient, the noise index can be defined as:

[0058]

[0059] Where ω∈(0,1). ω cannot be 0, because the cylindrical radiation noise is mainly dominated by lift, and ω cannot be 1, otherwise the vortex shedding direction will deviate significantly, causing the sound radiation in the flow direction to be significantly enhanced. N represents the total number of moments, i is the i-th moment, Derivative of the lift coefficient at the ith moment, Derivative of the drag coefficient at the ith moment.

[0060] Noise reduction can be achieved by reducing the size of the noise index J. When using the proximal optimization strategy model to train a reinforcement learning agent, it is necessary to interact with the flow field. The model contains two sets of networks, namely the action network and the evaluation network. The input of the evaluation network is the instantaneous fluid dynamic coefficient, and the output is the predicted reward. The actual reward is defined as -J, and the goal of the evaluation network is to reduce the gap between the predicted reward and the actual reward. The input of the action network is the instantaneous fluid dynamic coefficient, and the output is the instantaneous speed of the servo motor 7. Its goal is to reduce the noise index J. The maximum speed of the servo motor 7 is limited by the cylinder linear speed being less than the average speed U0 of the wind tunnel. When the experimental device is started, the cylinder rotates counterclockwise at the maximum speed. With the training of the reinforcement learning agent, the cylinder speed will gradually stabilize near a fixed value.

[0061] The instantaneous sound pressure can be measured by the microphone array 1 and the high-precision microphone 2. After the reinforcement learning agent training is completed, that is, after the speed of the servo motor 7 reaches a stable state, the sound pressure information can be obtained by measuring for a period of time. The effective value of the sound pressure can be used to evaluate the noise reduction effect.

[0062] If it is necessary to study the cylinder under different working conditions, it is only necessary to change the outer diameter of the cylinder shell and adjust the wind speed of the wind tunnel.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for reducing cylindrical radiation noise by rotation control, characterized in that The specific steps are as follows: Step 1: The lift-drag coefficient is measured by the experimental device, and the lift-drag coefficient is read into the host computer memory in real time as a feedback signal; the instantaneous fluid dynamic information measured by the experimental device, that is, the lift F L (t) and resistance F D (t), and non-dimensionalized using the following formula: Among them, ρ0 is the air density, U0 is the average speed in the wind tunnel, and D0 is the outer diameter of the cylinder of the experimental device. After non-dimensionalization, the instantaneous lift coefficient C is obtained: L (t) and the instantaneous drag coefficient C D (t); Step 2: Define the noise index J according to the instantaneous lift-drag coefficient: in, ω ∈(0,1), N represents the total number of moments, i is the i-th moment, Derivative of the lift coefficient at the ith moment, Derivative of the resistance coefficient at the i-th moment; Step 3: Take the feedback signal as input, use the proximal optimization strategy model to train the reinforcement learning agent, interact with the flow field, and output the instantaneous speed, with the goal of reducing the noise index J; Step 4: Reduce the noise index J through continuous training and finally achieve noise reduction; The experimental device of the method of reducing the radiated noise of a cylinder by rotation control comprises an anechoic chamber, a microphone assembly, a three-force balance, a support rod, a coupling, a servo motor, a cylindrical shell, and a rotating connector; the inlet and outlet of the anechoic chamber are respectively connected to the silent wind tunnel duct, and a partition is arranged at the bottom thereof, and other components of the experimental device are installed in the anechoic chamber; the servo motor and the three-force balance are installed in the partition, and the output end of the servo motor is arranged vertically; the bottom end of the rotating connector passes through the bottom plate of the anechoic chamber and is connected to the servo motor through a coupling; the top end thereof is detachably coaxially connected to the cylindrical shell; the top end of the support rod extends into and is tightly attached to the inner wall of the cylindrical shell, and the bottom end passes through the bottom plate of the anechoic chamber and is connected to the three-force balance, and the three-force balance obtains lift and drag information by measuring the displacement of the support rod; the microphone assembly is used to measure instantaneous sound pressure; The outer circumferential surface of the cylindrical shell is an equal-diameter cylindrical structure, and a stepped through hole is opened along the central axis thereof, the inner diameter of the upper end is smaller than the inner diameter of the lower end, and a plurality of radial key grooves are opened along the circumferential direction on the stepped surface; The upper end of the rotating connector is a disc, and a plurality of radial keys are arranged on its upper end surface along the circumferential direction. The radial keys correspond to the radial key slots in number, and are installed in cooperation with each other for detachable connection between the cylindrical shell and the rotating connector; the lower end of the rotating connector is a coaxial straight rod, and the bottom end is connected to the servo motor through a coupling; the rotating connector is driven to rotate by the servo motor, thereby driving the cylindrical shell to rotate; The upper end of the support rod is a straight rod, and the lower end is an L-shaped connecting rod; the upper straight rod extends into the cylindrical shell, and its axial direction is perpendicular to the central axis of the cylindrical shell, and its two ends are tightly attached to the inner wall of the large diameter end of the cylindrical shell, which is only used to measure the displacement of the cylindrical shell and does not play a supporting role; the short arm of the lower L-shaped connecting rod is vertically fixed to the outer circumference of one side of the upper support rod to avoid interference with the rotating connecting piece, and its long arm is horizontally arranged and its end is connected to a three-force balance.

2. A method for reducing cylindrical radiation noise by rotation control according to claim 1, characterized in that: In step 3, the proximal optimization strategy model includes an action network and an evaluation network.

3. A method for reducing cylindrical radiation noise by rotation control according to claim 2, characterized in that: The input of the evaluation network is the instantaneous fluid dynamic coefficient, and the output is the predicted reward; the actual reward is defined as -J, and the goal of the evaluation network is to reduce the gap between the predicted reward and the actual reward; the input of the action network is the instantaneous fluid dynamic coefficient, and the output is the instantaneous rotation speed, and its goal is to reduce the noise index J.

4. The method of reducing cylindrical radiation noise by rotation control according to claim 1, characterized in that: The anechoic chamber is surrounded by sound-absorbing materials; the top plate of the partition is a sound-absorbing partition, which is used to eliminate the mechanical noise of the servo motor.

5. The method of reducing cylindrical radiation noise by rotation control according to claim 1, characterized in that: The microphone assembly includes a microphone array and a high-precision microphone, and the distance between the microphone array and the cylindrical shell is smaller than the distance between the high-precision microphone and the cylindrical shell; The microphone array is a plurality of microphones arranged along an arc, and is used to measure the sound pressure and obtain the directivity of noise radiation; The measurement range and sensitivity of the high-precision microphone are both greater than those of the microphone array.

Images