Supersonic cavity self-sustaining oscillation loop feedback intensity calculation method and system

Abstract

The invention discloses a supersonic cavity self-sustaining oscillation loop feedback intensity calculation method and system. The method comprises the steps that the noise pressure level of each measuring point is calculated according to pulsating pressure data obtained through measurement; calculating incoming flow turbulence boundary layer noise at a preset position by using linear interpolation according to the noise sound pressure level of each measuring point, and judging the measuring point influenced by the feedback shock wave according to a comparison result of the incoming flow turbulence boundary layer noise and a preset threshold value; and counting the number of the measuring points influenced by the feedback shock wave, and comparing the noise sound pressure levels of all the measuring points influenced by the feedback shock wave to calculate the variable quantity of the feedback shock wave intensity. The pulsating pressure sensor is arranged in the front edge boundary layer of the cavity to measure the pressure disturbance signal caused by the feedback shock wave invading the front edge boundary layer, so that the accurate assessment of the feedback shock wave intensity is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid mechanics, and in particular to a method and system for calculating feedback strength of a supersonic cavity self-sustaining oscillation loop. Background Art

[0002] Under certain geometric and incoming flow conditions, a supersonic cavity will form a self-sustaining oscillation feedback loop of flow-acoustic coupling. The feedback loop of supersonic cavity flow-acoustic coupling consists of four links, namely, the initial disturbance formed by the interaction between the feedback shock wave and the shear layer at the leading edge of the cavity, the development and growth of the disturbance in the shear layer, the collision of the disturbance with the trailing edge of the cavity, and the forward propagation of the feedback shock wave formed by the collision. In this feedback loop, the feedback signal is carried by the feedback shock wave, propagates from the trailing edge of the cavity to the leading edge, and amplifies the initial disturbance by interfering with the leading edge shear flow, thus achieving a positive feedback effect.

[0003] The feedback effect makes the unsteady flow in the cavity more rhythmic and more violent, inducing severe flow oscillations and noise, with a sound pressure level of more than 170dB. People try to weaken the feedback effect of the cavity oscillation loop to achieve effective control of noise. Pereira et al. modified the shape of the trailing edge of the cavity, trying to reduce the intensity of the feedback shock wave by weakening the collision intensity between the disturbance and the trailing edge. Liu Jun et al. developed control measures to interfere with the propagation of feedback shock waves, the purpose of which is to accelerate the attenuation of the forward-propagating feedback shock wave by arranging transverse baffles at the bottom of the cavity. Thangamani et al. proposed the idea of ​​using the leading edge horizontal jet to interfere with the interaction between the feedback shock wave and the shear layer, hoping to suppress the feedback effect in this way.

[0004] In order to verify the control effect of the above control measures on the feedback effect, it is necessary to accurately evaluate the feedback strength of the supersonic cavity self-sustaining oscillation loop. Unfortunately, people can only evaluate the cavity feedback strength indirectly through indirect means such as the sound pressure level of the cavity bottom surface, and there is no effective method to directly evaluate the feedback strength. In addition to the feedback shock wave, there are also many types of shock waves such as small shock waves and front wall reflected shock waves passing through the cavity bottom surface. Therefore, it is not reasonable to use the sound pressure level of the cavity bottom surface to characterize the feedback shock wave intensity.

[0005] Under certain geometric and incoming flow conditions, a supersonic cavity will form a self-sustaining oscillation feedback loop coupled with flow and sound. Accurately evaluating the cavity feedback strength is of great significance for optimizing the performance of the control method and the shape of the cavity. Summary of the invention

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0007] To this end, the present invention proposes a method for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop. By arranging a pulsating pressure sensor in the leading edge boundary layer of the cavity and measuring the pressure disturbance signal caused by the feedback shock wave invading the leading edge boundary layer, an accurate assessment of the feedback shock wave strength can be achieved.

[0008] Another object of the present invention is to provide a supersonic cavity self-sustaining oscillation loop feedback strength calculation system.

[0009] To achieve the above object, the present invention provides a method for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop, comprising:

[0010] Calculate the noise sound pressure level at each measuring point based on the measured pulsating pressure data;

[0011] According to the noise sound pressure levels of the measuring points, the incoming flow turbulent boundary layer noise at the preset position is calculated by linear interpolation, and the measuring point affected by the feedback shock wave is determined by comparing the incoming flow turbulent boundary layer noise with a preset threshold value;

[0012] The number of measuring points affected by the feedback shock wave is counted, and the noise sound pressure levels of all measuring points affected by the feedback shock wave are compared to calculate the change in the intensity of the feedback shock wave.

[0013] The method for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop according to an embodiment of the present invention may also have the following additional technical features:

[0014] In one embodiment of the present invention, before calculating the noise sound pressure level at each measuring point according to the measured pulsating pressure data, the method further includes:

[0015] On the central axis of the leading edge of the supersonic cavity, a number of pulsating pressure sensors are arranged without interval, and the coverage range of the sensors exceeds 0.2 times the cavity depth.

[0016] In one embodiment of the present invention, the pulsating pressure sensor is used to detect feedback shock wave signals and incoming flow turbulent boundary layer noise.

[0017] In one embodiment of the present invention, if the noise sound pressure level SPL of a measuring point satisfies the following inequality, it is considered that the measuring point is affected by the feedback shock wave:

[0018] SPL-SPL turb ≥ΔSPL (1)

[0019] Among them, SPL turb is the incoming turbulent boundary layer noise, and ΔSPL is 5dB.

[0020] In one embodiment of the present invention, SPL turb is the turbulent boundary layer noise at a distance of 0.2 times the cavity depth from the leading edge.

[0021] To achieve the above object, the present invention provides, on the other hand, a supersonic cavity self-sustaining oscillation loop feedback strength calculation system, comprising:

[0022] A noise sound pressure level calculation module is used to calculate the noise sound pressure level of each measuring point according to the measured pulsating pressure data;

[0023] An affected measuring point judgment module is used to calculate the incoming flow turbulent boundary layer noise at a preset position according to the noise sound pressure level of each measuring point by using linear interpolation, and judge the measuring point affected by the feedback shock wave by comparing the incoming flow turbulent boundary layer noise with a preset threshold;

[0024] The shock wave intensity change calculation module is used to count the number of measuring points affected by the feedback shock wave and compare the noise sound pressure levels of all measuring points affected by the feedback shock wave to calculate the change in the feedback shock wave intensity.

[0025] The method and system for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop in an embodiment of the present invention are based on the characteristics of the flow at the leading edge of a supersonic cavity. By arranging a pulsating pressure sensor in the leading edge boundary layer of the cavity, the pressure disturbance signal caused by the feedback shock wave invading the leading edge boundary layer is measured, thereby achieving an accurate evaluation of the feedback shock wave strength and improving the calculation efficiency.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0028] Figure 1 is a flow chart of a method for calculating feedback strength of a supersonic cavity self-sustaining oscillation loop according to an embodiment of the present invention;

[0029] Figure 2 is a diagram of a standard model of a C201 cavity according to an embodiment of the present invention;

[0030] Figure 3 1. It is a schematic diagram of the complex flow structure of the supersonic cavity and the installation position of the leading edge pulsation pressure sensor according to an embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of flow control of a trailing edge cylinder according to an embodiment of the present invention;

[0032] Figure 5 is a schematic diagram of flow control of a trailing edge baffle according to an embodiment of the present invention;

[0033] Figure 6 2 is a schematic diagram of the sound pressure level distribution of the bottom surface of the concave cavity under the basic state and cylindrical control at Mach number 2.0 according to an embodiment of the present invention;

[0034] Figure 7 is a schematic diagram of the sound pressure level distribution of the bottom surface of the concave cavity under the basic state and the diaphragm control at Mach number 2.0 according to an embodiment of the present invention;

[0035] Figure 8 4 is a structural diagram of a supersonic cavity self-sustaining oscillation loop feedback strength calculation system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] The following describes a method and system for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop according to an embodiment of the present invention with reference to the accompanying drawings.

[0039] Embodiment 1:

[0040] Figure 1 FIG. 1 is a flow chart of a method for calculating feedback strength of a supersonic cavity self-sustaining oscillation loop according to an embodiment of the present invention. Figure 1 As shown, the method includes:

[0041] S1, calculate the noise sound pressure level at each measuring point based on the measured pulsating pressure data.

[0042] S2, calculating the incoming flow turbulent boundary layer noise at a preset position according to the noise sound pressure level of each measuring point and using linear interpolation, and judging the measuring point affected by the feedback shock wave by comparing the incoming flow turbulent boundary layer noise with a preset threshold;

[0043] S3, count the number of measuring points affected by the feedback shock wave, and compare the noise sound pressure levels of all measuring points affected by the feedback shock wave to calculate the change in the intensity of the feedback shock wave.

[0044] It can be understood that after the feedback shock wave is formed at the trailing edge of the cavity, it propagates forward along the inside of the cavity and eventually collides with the front wall of the cavity. The root of the feedback shock wave collides with the front wall of the cavity first. During the collision, the contact point between the feedback shock wave and the wall gradually moves from the bottom of the cavity to the corner of the leading edge of the cavity. After the collision is completed, the feedback shock wave will be divided into two parts. One part of the shock wave reflected by the front wall moves downstream along the inside of the cavity. The other part of the shock wave bypasses the leading edge and continues to propagate forward, invading the leading edge boundary layer in the form of pressure disturbance. Since the incoming flow is a supersonic flow, the disturbance can only be pushed forward in the subsonic zone within the boundary layer. Since the energy of the disturbance wave invading the boundary layer is limited, under the sweep of the high-speed flow of the boundary layer, the disturbance energy decays rapidly until it disappears.

[0045] Different from the high-intensity noise environment under the action of complex wave systems in the cavity, the flow at the leading edge of the cavity is only affected by the turbulent boundary layer of the incoming flow and the feedback shock wave. Among them, the boundary layer turbulent pulsation is significantly weaker than the pressure pulsation caused by the feedback shock wave. Therefore, by simply comparing the size of the sound pressure level, it is possible to determine whether the leading edge measurement point is affected by the feedback shock wave.

[0046] Based on the above analysis of the flow at the leading edge of a supersonic cavity, one embodiment of the present invention formulates the following four steps to carry out the evaluation of the feedback strength of the cavity self-sustaining oscillation loop, as follows:

[0047] (1) On the central axis of the front edge of the cavity, there is no spacing. Figure 3 The pulsating pressure sensors shown in the figure need to cover a range of more than 0.2 times the cavity depth. These pulsating pressure sensors will be used to detect feedback shock wave signals and incoming turbulent boundary layer noise. When the measurement range is met, smaller sensors should be selected as much as possible to arrange more sensors, thereby obtaining more detailed noise distribution characteristics in the leading edge boundary layer.

[0048] (2) Calculate the noise sound pressure level at each measuring point based on the measured pulsating pressure data.

[0049] (3) According to the noise sound pressure level of each measuring point, the incoming turbulent boundary layer noise at the preset position is calculated by linear interpolation, and the measuring point affected by the feedback shock wave is determined by comparing the incoming turbulent boundary layer noise with the preset threshold. That is, under the interference of the feedback shock wave, the intensity of the leading edge measuring point noise will be significantly increased. Therefore, if the sound pressure level SPL of the measuring point satisfies the following inequality,

[0050] SPL-SPL turb ≥ΔSPL (1)

[0051] It is considered that the measuring point is affected by the feedback shock wave. In formula (1), SPL turbis the turbulent boundary layer noise of the incoming flow. In general, the distance that the feedback shock wave propagates forward after passing over the leading edge does not exceed 0.2 times the depth of the cavity. Therefore, the present invention takes SPL turb It is the turbulent boundary layer noise at 0.2 times the cavity depth from the leading edge, which can be obtained by interpolating the sound pressure level at the measuring point. ΔSPL is generally taken as 5dB.

[0052] (4) Finally, the number of measuring points affected by the feedback shock wave is counted, and the change in the feedback shock wave intensity is evaluated by comparing the number of measuring points affected by the feedback shock wave and the sound pressure level of the measuring points. First, the more measuring points affected by the feedback shock wave, the greater the feedback shock wave intensity. Generally speaking, the stronger the feedback shock wave intensity, the farther the disturbance will penetrate the boundary layer after bypassing the leading edge of the cavity, and the more measuring points will be affected by the feedback shock wave. Secondly, when the feedback shock wave penetration distance is the same (the same number of measuring points), the greater the sound pressure level of the measuring point (the first measuring point close to the leading edge), the greater the feedback shock wave intensity.

[0053] It is understandable that the prerequisite for evaluating the feedback shock wave intensity under different working conditions is that the input parameters of the incoming flow remain unchanged. In other words, the parameters such as the incoming flow Mach number, velocity pressure, and turbulent boundary layer characteristics are required to remain consistent under different working conditions.

[0054] According to the method for calculating the feedback strength of the self-sustaining oscillation loop of a supersonic cavity in an embodiment of the present invention, the noise sound pressure level of each measuring point is calculated according to the measured pulsating pressure data; the incoming flow turbulent boundary layer noise at a preset position is calculated according to the noise sound pressure level of each measuring point and by using linear interpolation, and the measuring point affected by the feedback shock wave is judged by comparing the incoming flow turbulent boundary layer noise with the preset threshold; the number of measuring points affected by the feedback shock wave is counted, and the noise sound pressure level of all measuring points affected by the feedback shock wave is compared to calculate the change in the feedback shock wave intensity. Based on the characteristics of the leading edge flow of the supersonic cavity, a pulsating pressure sensor is arranged in the leading edge boundary layer of the cavity to measure the pressure disturbance signal caused by the feedback shock wave invading the leading edge boundary layer, so as to achieve an accurate evaluation of the feedback shock wave intensity.

[0055] Embodiment 2:

[0056] Based on the trailing edge cylinder (see Figure 4 ) and trailing edge bulkhead (see Figure 5 ) was conducted in a wind tunnel test of a supersonic cavity noise control. The cavity model was the C201 standard model, and the test Mach number was 2.0. The following analysis of the test results demonstrates how the method of the present invention can be used to evaluate the feedback strength of a supersonic cavity self-sustaining oscillation loop, and the reliability of the method of the present invention is verified by comparing it with the sound pressure level distribution in the cavity.

[0057] The appearance of the standard model of C201 cavity is as follows Figure 2As shown in Figure 1, the cavity length is 200 mm, the depth is 33.3 mm, and the width is 66.7 mm. The pulsating pressure sensors at the front and bottom of the cavity are as follows: Figure 3 As shown, five pulsating pressure sensors with an outer diameter of 1.7 mm are arranged at the front edge of the cavity, covering a range of 8.5 mm.

[0058] Trailing edge cylinder suppression cavity feedback strength test:

[0059] First, based on the measured pulsating pressure data, the noise sound pressure level data of each measuring point are calculated as shown in Table 1.

[0060] Then, the turbulent boundary layer noise at 0.2 times the cavity depth from the leading edge is calculated by linear interpolation. The sound pressure level of the turbulent boundary layer noise under the basic state is:

[0061] The sound pressure level of turbulent boundary layer noise under cylinder control is:

[0062] According to the discriminant formula (1), it can be seen that in both states, only the first measuring point on the leading edge is affected by the feedback shock wave. By comparing the sound pressure level of the first measuring point on the leading edge, it can be found that the sound pressure level under cylinder control is reduced by 5.58dB. Therefore, it is believed that the feedback shock wave intensity under cylinder control is reduced to a certain extent compared with the basic state. As the feedback intensity of the cavity decreases, the noise sound pressure level in the cavity should also decrease. In fact, from Figure 6 From the displayed sound pressure level distribution at the bottom of the cavity, it can be seen that under cylindrical control, the sound pressure level at the bottom of the cavity is indeed shifted downward by 3 to 5 dB as expected.

[0063] Table 1

[0064]

[0065] Embodiment 3:

[0066] Transverse partition to suppress cavity feedback strength test:

[0067] First, based on the measured pulsating pressure data, the noise sound pressure level data of each measuring point is calculated as shown in Table 2.

[0068] Then, the turbulent boundary layer noise at 0.2 times the cavity depth from the leading edge is calculated by linear interpolation. The sound pressure level of the turbulent boundary layer noise under the basic state is:

[0069] The sound pressure level of turbulent boundary layer noise under partition control is:

[0070] According to the discriminant formula (1), it can be seen that in both states, only the first measuring point of the leading edge is affected by the feedback shock wave. Then, by comparing the sound pressure level of the first measuring point of the leading edge, it can be found that the sound pressure level under the partition control is reduced by 10.82dB. Therefore, it is believed that compared with the basic state, the feedback shock wave intensity under the partition control has decreased to a certain extent. In addition, from Figure 7 From the displayed sound pressure level distribution of the cavity bottom, it can be seen that under the control of the partition, the sound pressure level of the cavity bottom is shifted downward by 6 to 9 dB as a whole, indicating that the partition has a good suppression effect on the cavity noise.

[0071] Table 2

[0072]

[0073]

[0074] By comparing Example 2 and Example 3, it can be seen that the sound pressure level at the first measuring point on the leading edge drops by 10.82dB under the control of the baffle, while it only drops by 5.58dB under the control of the cylinder. Therefore, according to the feedback intensity evaluation method proposed in the present invention, the present invention believes that the baffle has a better inhibitory effect on the feedback effect of the cavity than the cylinder. On the other hand, from the sound pressure level distribution of the bottom surface of the cavity, the present invention can see that the sound pressure level of the bottom surface of the cavity drops by 6 to 9dB under the control of the baffle, while the sound pressure level drops by only 3 to 5dB under the control of the cylinder. These sound pressure level data indirectly indicate that the baffle has a better inhibitory effect on the feedback effect of the cavity than the cylinder, and further verify the reliability of the feedback intensity evaluation method proposed in the present invention.

[0075] According to the method for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop in an embodiment of the present invention, starting from the characteristics of the flow at the leading edge of the supersonic cavity, a pulsating pressure sensor is arranged in the leading edge boundary layer of the cavity to measure the pressure disturbance signal caused by the feedback shock wave invading the leading edge boundary layer, thereby achieving an accurate evaluation of the feedback shock wave strength.

[0076] In order to implement the above embodiment, Figure 8 As shown, this embodiment also provides a supersonic cavity self-sustaining oscillation loop feedback strength calculation system 10, including:

[0077] The noise sound pressure level calculation module 100 is used to calculate the noise sound pressure level of each measuring point according to the measured pulsating pressure data;

[0078] An affected measuring point determination module 200 is used to calculate the incoming flow turbulent boundary layer noise at a preset position according to the noise sound pressure level of each measuring point by using linear interpolation, and determine the measuring point affected by the feedback shock wave by comparing the incoming flow turbulent boundary layer noise with a preset threshold;

[0079] The shock wave intensity change calculation module 300 is used to count the number of measuring points affected by the feedback shock wave and compare the noise sound pressure levels of all measuring points affected by the feedback shock wave to calculate the change in the feedback shock wave intensity.

[0080] Furthermore, before the noise sound pressure level calculation module 100, it also includes: a sensor arrangement module, which is used to:

[0081] On the central axis of the leading edge of the supersonic cavity, a number of pulsating pressure sensors are arranged without interval, and the coverage range of the sensors exceeds 0.2 times the cavity depth.

[0082] Furthermore, the pulsating pressure sensor is used to detect the feedback shock wave signal and the incoming flow turbulent boundary layer noise.

[0083] Furthermore, if the noise sound pressure level SPL at the measuring point satisfies the following inequality, it is considered that the measuring point is affected by the feedback shock wave:

[0084] SPL-SPL turb ≥ΔSPL (1)

[0085] Among them, SPL turb is the incoming turbulent boundary layer noise, and ΔSPL is 5dB.

[0086] Furthermore, taking SPL turb is the turbulent boundary layer noise at a distance of 0.2 times the cavity depth from the leading edge.

[0087] According to the supersonic cavity self-sustaining oscillation loop feedback strength calculation system of the embodiment of the present invention, starting from the characteristics of the leading edge flow of the supersonic cavity, a pulsating pressure sensor is arranged in the leading edge boundary layer of the cavity to measure the pressure disturbance signal caused by the feedback shock wave invading the leading edge boundary layer, thereby realizing accurate evaluation of the feedback shock wave strength.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0089] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A method for calculating the feedback strength of a supersonic cavity self-sustaining oscillation loop, characterized in that: include: Calculate the noise sound pressure level at each measuring point based on the measured pulsating pressure data; According to the noise sound pressure levels of the measuring points, the incoming flow turbulent boundary layer noise at the preset position is calculated by linear interpolation, and the measuring point affected by the feedback shock wave is determined by comparing the incoming flow turbulent boundary layer noise with a preset threshold value; The number of measuring points affected by the feedback shock wave is counted, and the noise sound pressure levels of all measuring points affected by the feedback shock wave are compared to calculate the change in the intensity of the feedback shock wave.

2. The method according to claim 1, characterized in that Before calculating the noise sound pressure level at each measuring point according to the measured pulsating pressure data, the method further includes: On the central axis of the leading edge of the supersonic cavity, a number of pulsating pressure sensors are arranged without interval, and the coverage range of the sensors exceeds 0.2 times the cavity depth.

3. The method according to claim 1, characterized in that The pulsating pressure sensor is used to detect feedback shock wave signals and incoming flow turbulent boundary layer noise.

4. The method according to claim 1, characterized in that: If the noise sound pressure level SPL at the measuring point satisfies the following inequality, it is considered that the measuring point is affected by the feedback shock wave: SPL-SPL turb ≥ΔSPL (1) Among them, SPL turb is the incoming turbulent boundary layer noise, and ΔSPL is 5dB.

5. The method according to claim 4, characterized in that Get SPL turb is the turbulent boundary layer noise at a distance of 0.2 times the cavity depth from the leading edge.

6. A supersonic cavity self-sustaining oscillation loop feedback strength calculation system, characterized in that: include: A noise sound pressure level calculation module is used to calculate the noise sound pressure level of each measuring point according to the measured pulsating pressure data; An affected measuring point judgment module is used to calculate the incoming flow turbulent boundary layer noise at a preset position according to the noise sound pressure level of each measuring point by using linear interpolation, and judge the measuring point affected by the feedback shock wave by comparing the incoming flow turbulent boundary layer noise with a preset threshold; The shock wave intensity change calculation module is used to count the number of measuring points affected by the feedback shock wave and compare the noise sound pressure levels of all measuring points affected by the feedback shock wave to calculate the change in the feedback shock wave intensity.

7. The system according to claim 6, characterized in that Before the noise sound pressure level calculation module, it also includes: a sensor arrangement module, which is used to: On the central axis of the leading edge of the supersonic cavity, a number of pulsating pressure sensors are arranged without interval, and the coverage range of the sensors exceeds 0.2 times the cavity depth.

8. The system according to claim 6, characterized in that The pulsating pressure sensor is used to detect feedback shock wave signals and incoming flow turbulent boundary layer noise.

9. The system according to claim 6, characterized in that If the noise sound pressure level SPL at the measuring point satisfies the following inequality, it is considered that the measuring point is affected by the feedback shock wave: SPL-SPL turb ≥ΔSPL (1) Among them, SPL turb is the incoming turbulent boundary layer noise, and ΔSPL is 5dB.

10. The system according to claim 9, characterized in that Get SPL turb is the turbulent boundary layer noise at a distance of 0.2 times the cavity depth from the leading edge.

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