Coherent output power acquisition method based on PSP measurement system and medium

Abstract

The invention relates to a coherent output power acquisition method based on a PSP measurement system and a medium, and relates to the technical field of aircraft aerodynamic noise research. For a noise source positioning object, in the same preset time period, measuring pressure fluctuation based on a PSP measurement system in a near field and acquiring a pulsating pressure image, and synchronously acquiring a sound pressure signal based on an acoustic sensor in a far field; respectively calculating self-spectrum estimated values of the sound pressure signal and the pulsating pressure image, and calculating cross-spectrum estimated values of the sound pressure signal and the pulsating pressure image based on discrete Fourier transform components of the sound pressure signal and the three-dimensional pulsating pressure image data at a preset frequency f; and calculating the coherence degree of the sound pressure signal and the pulsating pressure image so as to calculate the coherent output power of the sound pressure signal and the pulsating pressure image. The spatial distribution and intensity of the noise source with high spatial complexity can be extracted more accurately, and the method is more suitable for accurate positioning of the sound source required in aircraft aerodynamic noise research.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft aerodynamic noise research, and in particular to a coherent output power acquisition method and medium based on a PSP measurement system. Background Art

[0002] In the field of aerospace, the study of aerodynamic noise has become an important research direction. With the continuous advancement of aircraft design, the control of aerodynamic noise has gradually become an important issue to improve aircraft performance and reduce environmental impact. Aerodynamic noise not only affects the flight performance of aircraft, but may also have an adverse effect on the safety and comfort of pilots and ground personnel. Advanced flow field and acoustic field testing technology is of great significance for obtaining the unsteady flow field information of the research object, the distribution of noise sources, and the noise propagation characteristics, understanding the noise generation mechanism, and optimizing the noise control strategy.

[0003] In the study of aerodynamic noise, commonly used testing technologies mainly include particle image velocimetry (PIV) technology, sensor array technology and pressure sensitive coating (PSP) technology. PIV technology is mainly used for flow field measurement and can provide non-contact flow field information, but it has limitations in noise source location and acoustic spectrum analysis. Microphone array technology collects sound pressure data through multiple microphone arrays, which can accurately locate far-field noise sources and analyze sound source intensity, but it cannot analyze the noise generation mechanism. PSP technology can monitor surface pressure in real time through pressure sensitive coatings, and obtain high-precision pressure pulsation fields through corresponding image processing technology. After analyzing these pulsation field information, the spatial distribution, amplitude and phase field of pressure pulsations of different frequencies and modes can be obtained, but it is still impossible to accurately locate the specific location of the sound source of aerodynamic noise.

[0004] In the study of aerodynamic noise, high-intensity pulsating pressure is the direct cause of noise. The pressure pulsation in the near field will radiate outward to form far-field noise. Therefore, it is particularly important to have a deep understanding of the relationship between the pressure pulsation in the near field and the far-field noise. Therefore, how to accurately locate the specific location of the sound source of aerodynamic noise has become an urgent problem to be solved. Summary of the invention

[0005] The technical problem to be solved by the present application is to provide a method and medium for obtaining coherent output power based on a PSP measurement system, which can be applied to aerodynamic noise research and can obtain more accurate coherent output power based on the PSP measurement system, thereby helping to accurately locate the specific position of the sound source of aerodynamic noise.

[0006] In a first aspect, an embodiment provides a method for obtaining coherent output power based on a PSP measurement system, including: For the noise source location object, in the same preset time period, the pressure fluctuation is measured in the near field based on the PSP measurement system to collect the pulsating pressure image, and the sound pressure signal is synchronously collected in the far field based on the acoustic sensor; Calculate the autospectral estimation values ​​of the acoustic pressure signal and the pulsating pressure image respectively; Calculate a cross-spectrum estimation value of the sound pressure signal and the pulsating pressure image based on a discrete Fourier transform component of the sound pressure signal at a preset frequency f and a Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f; Calculating the coherence of the sound pressure signal and the pulsation pressure image based on the autospectral estimation value and the cross-spectral estimation value of the sound pressure signal and the pulsation pressure image; Based on the autospectral estimation value of the pulsation pressure image and the coherence degree, the coherent output power of the sound pressure signal and the pulsation pressure image is calculated.

[0007] In one embodiment, the method for calculating the autospectral estimation value of the sound pressure signal includes: Calculate the discrete Fourier transform component of the sound pressure signal at a preset frequency f; Based on the discrete Fourier transform component of the sound pressure signal at a preset frequency f, an autospectral estimation value of the sound pressure signal is calculated.

[0008] In one embodiment, the step of calculating the discrete Fourier transform component of the sound pressure signal at a preset frequency f includes: , in, represents the sound pressure signal, n represents the index of the sound pressure signal, N represents the number of sound pressure signals, 1≤n≤N, Indicates the sound pressure signal The discrete Fourier transform component at a preset frequency f, i represents an imaginary number, and e represents a natural number exponent; The method of calculating the autospectral estimation value of the sound pressure signal based on the discrete Fourier transform component of the sound pressure signal at a preset frequency f includes: , in, represents the autospectral estimate of the sound pressure signal, express The complex conjugate of Represents the average in the frequency domain.

[0009] In one embodiment, the method for calculating the autospectral estimation value of the pulsating pressure image includes: Acquiring collected three-dimensional pulsating pressure image data; Perform Fourier transform on the three-dimensional pulsating pressure image data and calculate the value of each frequency point in the frequency domain; Based on the value of each frequency point calculated in the frequency domain, a Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f is obtained; Based on the Fourier transform components of the three-dimensional pulsating pressure image data at a preset frequency f, an autospectral estimation value of the pulsating pressure image is calculated.

[0010] In one embodiment, the step of acquiring the collected three-dimensional pulsating pressure image data includes: , Where Q represents the three-dimensional pulsating pressure image data, represents a single image data, m represents the index of the image data, M represents the number of image data, 1≤m≤M, and the pixel size of each image data is , Indicates the width of the image. Indicates the length of the image; The method of performing Fourier transform on the three-dimensional pulsating pressure image data and calculating the value of each frequency point in the frequency domain includes: , in, Represents the value of each frequency point calculated in the frequency domain, Represents the value of the corresponding position of the three-dimensional pulsating pressure image data in the time domain; , and Represents the index of the 3D time domain image data in the 3D pulsating pressure image, Represents the index of the row in the 3D time domain image data, 1≤ ≤ , Represents the index of the column in the 3D time domain image data, 1≤ ≤ , Represents the index of the image in the 3D time domain image data, 1≤ ≤M; , and Represents the index of the three-dimensional frequency domain image data in the three-dimensional pulsating pressure image, Represents the index of the row in the 3D frequency domain image data, 1≤ ≤ , Represents the index of the column in the 3D frequency domain image data, 1≤ ≤ , Indicates the frequency index, 1≤ ≤M; represents the corresponding complex exponential factor, i represents an imaginary number, , and Respectively represent the frequency components of different dimensions; The method of calculating the autospectral estimation value of the pulsating pressure image data based on the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f includes: , in, represents the autospectral estimate of the pulsating pressure image data, represents the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f, express The complex conjugate of Represents the average in the frequency domain.

[0011] In one embodiment, before calculating the autospectral estimation value of the sound pressure signal, the method further includes: Perform low-pass filtering on the collected sound pressure signal to filter out frequency components higher than the sampling frequency of the pulsating pressure image; The low-pass filtered sound pressure signal is interpolated using the weighted average of adjacent samples in the collected original sound pressure signal; Resampling the interpolated sound pressure signal according to the pulsating pressure image sampling frequency; The calculating of the discrete Fourier transform component of the sound pressure signal at the preset frequency f comprises: calculating the discrete Fourier transform component of the sound pressure signal at the preset frequency f based on the resampled sound pressure signal.

[0012] In one embodiment, the method of calculating the cross-spectral estimation value of the sound pressure signal and the pulsating pressure image based on the discrete Fourier transform component of the sound pressure signal at the preset frequency f and the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f includes: , in, represents the cross-spectral estimation value of the acoustic pressure signal and the pulsating pressure image, represents the discrete Fourier transform component of the sound pressure signal at the preset frequency f, Represents the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f The complex conjugate of .

[0013] In one embodiment, the calculating the coherence of the sound pressure signal and the pulsation pressure image based on the autospectral estimation value and the cross-spectral estimation value of the sound pressure signal and the pulsation pressure image includes: , in, Indicates the coherence between the acoustic pressure signal and the pulsating pressure image, with a value range between 0 and 1, where 0 indicates complete irrelevance and 1 indicates complete correlation; represents the cross-spectral estimation value of the acoustic pressure signal and the pulsating pressure image, represents the autospectral estimate of the sound pressure signal, Represents the autospectral estimate of the pulsating pressure image data.

[0014] In one embodiment, the calculation of the coherent output power of the sound pressure signal and the pulsating pressure image based on the autospectral estimation value of the pulsating pressure image and the coherence degree includes: , , in, represents the coherent output power of the acoustic pressure signal and the pulsating pressure image, Represents the coherence between the acoustic pressure signal and the pulsating pressure image, represents the RMS power of the pulsating pressure image at the preset frequency f, represents the autospectral estimate of the pulsating pressure image data, express The complex conjugate of .

[0015] In a second aspect, an embodiment provides a computer-readable storage medium, wherein the medium stores a program, and the program can be loaded by a processor to execute the coherent output power acquisition method described in any one of the above embodiments.

[0016] The beneficial effects of the present invention are: Since the pulsating pressure image is collected based on the PSP measurement system to measure pressure fluctuations, a three-dimensional pulsating pressure image can be obtained. Since the changes in different positions can be measured through the optical properties of the pressure-sensitive layer, each pixel in the PSP image is equivalent to a pulse pressure sensor. Therefore, two-dimensional pressure distribution data with high spatial resolution can be obtained. Combined with the acoustic sensor data for coherent output power analysis, the spatial distribution and intensity of noise sources with strong spatial complexity can be more accurately extracted. It has important application value in multi-source noise and complex environments, and is more suitable for the precise positioning of sound sources required in aircraft aerodynamic noise research. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic flow chart of a method for obtaining coherent output power based on a PSP measurement system according to an embodiment of the present application; Figure 2 It is a flowchart of a method for calculating an autospectral estimation value of a sound pressure signal according to an embodiment of the present application; Figure 3It is a schematic flow chart of a method for calculating an autospectral estimation value of a pulsating pressure image according to an embodiment of the present application; Figure 4 is a spectrum of a sound pressure signal obtained in one embodiment of the present application; Figure 5 This application is this application Figure 4 The corresponding embodiment obtains a pulsating pressure image; Figure 6 This application Figure 4 The root mean square power image obtained in the corresponding embodiment; Figure 7 This application Figure 4 A coherence image obtained in the corresponding embodiment; Figure 8 This application Figure 4 The coherent output power image obtained in the corresponding embodiment. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0019] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0020] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0021] To facilitate the description of the inventive concept of the present application, the noise source localization technology is briefly described below.

[0022] In the current noise source location, the coherent output power (COP) method can analyze the coherence between the pulsating pressure signal and the noise signal at different frequencies. High coherence indicates that the near-field pressure pulsation at this frequency has a strong relationship with the far-field noise, thus helping to locate the sound source. In the current coherent output power method, a single or multiple pulse pressure sensor arrays are used to measure the pulsating pressure signal, and then based on the coherent output power analysis of the pulse pressure sensor and acoustic sensor data, the noise source can be preliminarily located more easily, with a wide frequency analysis range and high resolution.

[0023] However, the applicant discovered during the research that since the coherent output power method is based on two one-dimensional signals, the result is the signal coherence at a single point position. Even if the pulse pressure sensor array is arranged densely, its spatial resolution ability for locating the sound source is limited. Therefore, when locating the noise source, the spatial resolution obtained is low, and it is difficult to accurately locate the specific position of the sound source, which makes it difficult to apply to the precise positioning of the sound source required in the study of aircraft aerodynamic noise.

[0024] In view of this, a method and medium for obtaining coherent output power based on a PSP measurement system are provided in an embodiment of the present application. In the scheme, a pulsating pressure image is collected by measuring pressure fluctuations based on the PSP measurement system, so that a three-dimensional pulsating pressure image can be obtained. Since the changes in different positions can be measured through the optical properties of the pressure-sensitive layer, each pixel in the PSP image is equivalent to a pulse pressure sensor. Therefore, two-dimensional pressure distribution data with high spatial resolution can be obtained. Combined with the acoustic sensor data for coherent output power analysis, the spatial distribution and intensity of noise sources with strong spatial complexity can be more accurately extracted. It has important application value in multi-source noise and complex environments, and is more suitable for the precise positioning of sound sources required in aircraft aerodynamic noise research.

[0025] A method for obtaining coherent output power based on a PSP measurement system provided in the embodiment of the present application is provided in Figure 1 ,include: Step S10, for the noise source positioning object, in the same preset time period, in the near field, based on the PSP measurement system, the pressure fluctuation is measured to collect the pulsating pressure image, and in the far field, based on the acoustic sensor, the sound pressure signal is synchronously collected.

[0026] In the embodiments of the present application, the jet impacting a flat plate of an aircraft takeoff research model is used as an example for explanation.

[0027] The jet impacting a flat plate in the research model of aircraft takeoff is used as the noise source positioning object. A fast-response PSP measurement system is used in the near field to collect the pressure fluctuation on the surface of the flat plate to obtain a pulse pressure image. In the far field, the sound pressure signal is synchronously collected based on an acoustic sensor. The collection of the two signals is synchronous.

[0028] In one embodiment, the pulsating pressure image and the sound pressure signal of 1 s may be collected synchronously.

[0029] Step S20, calculating the autospectral estimation values ​​of the sound pressure signal and the pulsation pressure image respectively.

[0030] In one embodiment, please refer to Figure 2 , the calculation method of the autospectral estimation value of the sound pressure signal includes: Step S2011, calculating the discrete Fourier transform component of the sound pressure signal at a preset frequency f.

[0031] In one embodiment, assuming that the length of the sound pressure signal with a sampling time of 1 s is N, that is, the number of sound pressure signals is N, step S201 can be expressed as: , in, represents the sound pressure signal, n represents the index of the sound pressure signal, 1≤n≤N, Indicates the sound pressure signal The discrete Fourier transform component at the preset frequency f, i represents an imaginary number, and e represents a natural number exponent.

[0032] In one embodiment, the preset frequency f may be a significant peak frequency in the spectrum, so that a significant grayscale feature can be obtained and a more accurate noise source location can be obtained.

[0033] Step S2012: Calculate the autospectral estimation value of the sound pressure signal based on the discrete Fourier transform component of the sound pressure signal at the preset frequency f.

[0034] In one embodiment, step S202 can be expressed as: , in, represents the autospectral estimate of the sound pressure signal, express The complex conjugate of Represents the average in the frequency domain.

[0035] In one embodiment, please refer to Figure 3 , the calculation method of the autospectral estimation value of the pulsating pressure image includes: Step S2021, acquiring the collected three-dimensional pulsating pressure image data.

[0036] Assuming that the number of pulsating pressure images with a sampling time of 1 s is M, the acquired three-dimensional pulsating pressure image data can be expressed as: , Where Q represents the three-dimensional pulsating pressure image data, represents a single image data, m represents the index of the image data, M represents the number of image data, 1≤m≤M, and the pixel size of each image data is , Indicates the width of the image. Indicates the length of the image.

[0037] Step S2022, performing Fourier transform on the three-dimensional pulsating pressure image data, and calculating the value of each frequency point in the frequency domain.

[0038] For a multidimensional array, discrete Fourier transform is achieved by performing a one-dimensional Fourier transform on each dimension, so that the multidimensional array can be converted from the time domain to the frequency domain. Therefore, the third dimension can be Fourier transformed first, and then the second and first dimensions can be Fourier transformed. Then step S2022 can be expressed as: , in, Represents the value of each frequency point calculated in the frequency domain, Represents the value of the corresponding position of the three-dimensional pulsating pressure image data in the time domain; , and Represents the index of the 3D time domain image data in the 3D pulsating pressure image, Represents the index of the row in the 3D time domain image data, 1≤ ≤ , Represents the index of the column in the 3D time domain image data, 1≤ ≤ , Represents the index of the image in the 3D time domain image data, 1≤ ≤M; , and Represents the index of the three-dimensional frequency domain image data in the three-dimensional pulsating pressure image, Represents the index of the row in the 3D frequency domain image data, 1≤ ≤ , Represents the index of the column in the 3D frequency domain image data, 1≤ ≤ , Indicates the frequency index, 1≤ ≤M; represents the corresponding complex exponential factor, i represents an imaginary number, , and They represent frequency components of different dimensions respectively.

[0039] Step S2023, based on the value of each frequency point calculated in the frequency domain, obtain the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f.

[0040] Based on the value of each frequency point calculated in the frequency domain , the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f can be obtained .

[0041] Those skilled in the art can understand that, when the value of each frequency point calculated in the frequency domain is obtained, the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f can be obtained, which will not be described in detail here.

[0042] Step S2024: Calculate the autospectral estimation value of the pulsating pressure image based on the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f.

[0043] In one embodiment, step S2023 can be expressed as: , in, represents the autospectral estimate of the pulsating pressure image data, represents the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f, express The complex conjugate of Represents the average in the frequency domain.

[0044] Step S30, calculating a cross-spectrum estimation value of the sound pressure signal and the pulsating pressure image based on a discrete Fourier transform component of the sound pressure signal at a preset frequency f and a Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f.

[0045] The cross-spectrum estimation value represents the correlation between the two data in the frequency domain, reflects the phase relationship and amplitude relationship between the two data in the frequency domain, and can be given based on the discrete Fourier transform component of the sound pressure signal at the preset frequency f and the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f.

[0046] In one embodiment, step S30 can be expressed as: , in, represents the cross-spectral estimation value of the acoustic pressure signal and the pulsating pressure image, represents the discrete Fourier transform component of the sound pressure signal at the preset frequency f, Represents the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f The complex conjugate of .

[0047] The applicant also found in the study that, due to the performance limitations of the PSP system, the sampling frequency of the PSP image is generally lower than the sampling frequency of the acoustic sensor. Due to the inconsistency of the sampling frequencies, when calculating the cross-spectrum estimation value of the two signals, the calculation results may be inaccurate or distorted.

[0048] In view of this, in one embodiment of the present application, before calculating the autospectral estimation value of the sound pressure signal, the following step is further included: Step S100: low-pass filter the collected sound pressure signal to filter out frequency components higher than the sampling frequency of the pulsating pressure image.

[0049] Through step S100, the frequency aliasing phenomenon that occurs during the downsampling process can be prevented.

[0050] Step S200: performing interpolation processing on the low-pass filtered sound pressure signal using the weighted average value of adjacent samples in the collected original sound pressure signal.

[0051] Through interpolation processing, the sound pressure signal can be smoothed and its original characteristics can be maintained.

[0052] Step S300: resample the sound pressure signal after the interpolation processing according to the pulsation pressure image sampling frequency.

[0053] Then calculating the discrete Fourier transform component of the sound pressure signal at the preset frequency f includes: calculating the discrete Fourier transform component of the sound pressure signal at the preset frequency f based on the resampled sound pressure signal.

[0054] The resampled sound pressure signal can ensure the consistency of the frequencies of the sound pressure signal and the pulsating pressure signal, so that the quantities of the two signals are consistent, making the obtained cross-spectrum estimation value more accurate.

[0055] Step S40: Calculate the coherence of the sound pressure signal and the pulsation pressure image based on the autospectral estimation value and the cross-spectral estimation value of the sound pressure signal and the pulsation pressure image.

[0056] The coherence measures the coherence of two signals and can be calculated by the ratio of the autospectral estimation value and the cross-spectral estimation value of the two signals, which represents the coherence of the two signals at a preset frequency f.

[0057] In one embodiment, step S40 can be expressed as: , in, Indicates the coherence between the acoustic pressure signal and the pulsating pressure image, with a value range between 0 and 1, where 0 indicates complete irrelevance and 1 indicates complete correlation; represents the cross-spectral estimation value of the acoustic pressure signal and the pulsating pressure image, represents the autospectral estimate of the sound pressure signal, Represents the autospectral estimate of the pulsating pressure image data.

[0058] Step S50, calculating the coherent output power of the sound pressure signal and the pulsation pressure image based on the autospectral estimation value and the coherence of the pulsation pressure image.

[0059] The coherent output power describes the power intensity of the coherent signal output. In one embodiment, step S50 can be expressed as: , , in, represents the coherent output power of the acoustic pressure signal and the pulsating pressure image, Represents the coherence between the acoustic pressure signal and the pulsating pressure image, represents the RMS power of the pulsating pressure image at the preset frequency f, represents the autospectral estimate of the pulsating pressure image data; express The conjugate complex number of reflects the intensity and energy distribution of the image at different frequencies.

[0060] In practical applications, the coherence between different signals can be evaluated by calculating the correlation output power between the sound pressure signal and the pulsating pressure image. High coherence indicates that the coherence between the two signals is strong, indicating that they share a common physical source (such as a sound source or a vibration source). Specifically, when the coherent output power images of the sound pressure signal and the pulsating pressure image at a preset frequency f show coherence in a certain area, it indicates that the noise of this frequency is generated by the pulsating pressure in this area, that is, the noise source is located in this area, so that the noise source can be located.

[0061] Based on the coherent output power acquisition method based on the PSP measurement system in any of the above embodiments, since the pulsating pressure image is collected based on the PSP measurement system to measure pressure fluctuations, a three-dimensional pulsating pressure image can be obtained. Since the changes in different positions can be measured through the optical properties of the pressure-sensitive layer, each pixel in the PSP image is equivalent to a pulse pressure sensor. Therefore, two-dimensional pressure distribution data with high spatial resolution can be obtained. Combined with the acoustic sensor data for coherent output power analysis, the spatial distribution and intensity of noise sources with strong spatial complexity can be more accurately extracted. It has important application value in multi-source noise and complex environments, and is more suitable for the precise positioning of sound sources required in aircraft aerodynamic noise research.

[0062] Based on the coherent output power acquisition method based on the PSP measurement system in the above embodiment, the experimental effect verification is carried out as follows, wherein: Figures 4 to 8All of them are obtained by using the methods of the embodiments of the present application.

[0063] Please refer to Figure 4 , is the sound pressure level spectrum of the far-field microphone (acoustic sensor). The horizontal axis is the dimensionless frequency St. There is an obvious peak at St=0.31. The data can be analyzed at this frequency later. The vertical axis is the sound pressure level (SPL) in decibels (dB). Figure 5 This is a pulsating pressure image. The pressure fluctuation is most significant in the jet impact area and the interference area, about -12kPa~12kPa. Figure 6 The root mean square power of the pulsating pressure image at position St = 0.31 , Figure 7 This is a coherence image (where 0.5 and 0.8 in the color chart refer to the coherence). The areas with strong coherence of near-field pressure fluctuations and far-field noise are mainly concentrated in the core of the jet impact area of ​​the double jets, the wall jet area where the double ring structure is located, and near the jet interference area. Figure 8 In the coherent output power image, the larger the grayscale value, the stronger the coherence of the area, which can be defined as the noise source. Therefore, it can be concluded that at the position of St = 0.31, the noise source is mainly composed of three parts: (1) jet core sound source (circular area); (2) wall jet sound source (fan-shaped area); (3) interference sound source (rectangular area). The jet core sound source is located in the core of the jet impact and has the highest average intensity; the wall jet sound source is located in the double ring area and occupies the largest area; the interference sound source is located in the intersection area of ​​the double ring structure, occupies a small area and has a lower intensity. Figures 5 to 8 In the figure, x represents the horizontal coordinate of the image, y represents the vertical coordinate of the image, D represents the nozzle diameter of the jet in the study of jet impacting the flat plate, and x / D and y / D use the nozzle diameter as a reference to represent the physical location of the data distribution.

[0064] It can be seen that the coherent output power acquisition method based on the PSP measurement system of the present application links the pulsating pressure image with the far-field sound pressure signal, accurately identifies the three noise sources at the corresponding frequencies in the pulsating pressure, and provides new ideas for the research on noise suppression and control technology.

[0065] In one embodiment of the present application, a computer-readable storage medium is provided, on which a program is stored. The stored program includes a method that can be loaded by a processor and process any of the above embodiments.

[0066] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0067] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A method for obtaining coherent output power based on a PSP measurement system, characterized in that: include: For the noise source location object, in the same preset time period, the pressure fluctuation is measured in the near field based on the PSP measurement system to collect the pulsating pressure image, and the sound pressure signal is synchronously collected in the far field based on the acoustic sensor; Calculate the autospectral estimation values ​​of the acoustic pressure signal and the pulsating pressure image respectively; Calculate a cross-spectrum estimation value of the sound pressure signal and the pulsating pressure image based on a discrete Fourier transform component of the sound pressure signal at a preset frequency f and a Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f; Calculating the coherence of the sound pressure signal and the pulsation pressure image based on the autospectral estimation value and the cross-spectral estimation value of the sound pressure signal and the pulsation pressure image; Based on the autospectral estimation value of the pulsation pressure image and the coherence degree, the coherent output power of the sound pressure signal and the pulsation pressure image is calculated.

2. The coherent output power acquisition method according to claim 1, characterized in that: The method for calculating the autospectral estimation value of the sound pressure signal comprises: Calculate the discrete Fourier transform component of the sound pressure signal at a preset frequency f; Based on the discrete Fourier transform component of the sound pressure signal at a preset frequency f, an autospectral estimation value of the sound pressure signal is calculated.

3. The coherent output power acquisition method according to claim 2, characterized in that: The method of calculating the discrete Fourier transform component of the sound pressure signal at a preset frequency f includes: ， in, represents the sound pressure signal, n represents the index of the sound pressure signal, N represents the number of sound pressure signals, 1≤n≤N, Indicates the sound pressure signal The discrete Fourier transform component at a preset frequency f, i represents an imaginary number, and e represents a natural number exponent; The method of calculating the autospectral estimation value of the sound pressure signal based on the discrete Fourier transform component of the sound pressure signal at a preset frequency f includes: ， in, represents the autospectral estimate of the sound pressure signal, express The complex conjugate of Represents the average in the frequency domain.

4. The coherent output power acquisition method according to claim 1, characterized in that: The method for calculating the autospectral estimation value of the pulsating pressure image comprises: Acquiring collected three-dimensional pulsating pressure image data; Perform Fourier transform on the three-dimensional pulsating pressure image data and calculate the value of each frequency point in the frequency domain; Based on the value of each frequency point calculated in the frequency domain, a Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f is obtained; Based on the Fourier transform components of the three-dimensional pulsating pressure image data at a preset frequency f, an autospectral estimation value of the pulsating pressure image is calculated.

5. The method for obtaining coherent output power according to claim 4, characterized in that: The acquisition of the collected three-dimensional pulsating pressure image data includes: ， Where Q represents the three-dimensional pulsating pressure image data, represents a single image data, m represents the index of the image data, M represents the number of image data, 1≤m≤M, and the pixel size of each image data is , Indicates the width of the image. Indicates the length of the image; The method of performing Fourier transform on the three-dimensional pulsating pressure image data and calculating the value of each frequency point in the frequency domain includes: ， in, Represents the value of each frequency point calculated in the frequency domain, Represents the value of the corresponding position of the three-dimensional pulsating pressure image data in the time domain; , and Represents the index of the 3D time domain image data in the 3D pulsating pressure image, Represents the index of the row in the 3D time domain image data, 1≤ ≤ , Represents the index of the column in the 3D time domain image data, 1≤ ≤ , Represents the index of the image in the 3D time domain image data, 1≤ ≤M; , and Represents the index of the three-dimensional frequency domain image data in the three-dimensional pulsating pressure image, Represents the index of the row in the 3D frequency domain image data, 1≤ ≤ , Represents the index of the column in the 3D frequency domain image data, 1≤ ≤ , Indicates the frequency index, 1≤ ≤M; represents the corresponding complex exponential factor, i represents an imaginary number, , and Respectively represent the frequency components of different dimensions; The method of calculating the autospectral estimation value of the pulsating pressure image data based on the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f includes: ， in, represents the autospectral estimate of the pulsating pressure image data, represents the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f, express The complex conjugate of Represents the average in the frequency domain.

6. The method for obtaining coherent output power according to claim 2, characterized in that: Before calculating the autospectral estimate of the sound pressure signal, it also includes: Perform low-pass filtering on the collected sound pressure signal to filter out frequency components higher than the sampling frequency of the pulsating pressure image; The low-pass filtered sound pressure signal is interpolated using the weighted average of adjacent samples in the collected original sound pressure signal; Resampling the interpolated sound pressure signal according to the pulsating pressure image sampling frequency; The calculating of the discrete Fourier transform component of the sound pressure signal at the preset frequency f comprises: calculating the discrete Fourier transform component of the sound pressure signal at the preset frequency f based on the resampled sound pressure signal.

7. The method for obtaining coherent output power according to claim 6, characterized in that: The method of calculating the cross-spectrum estimation value of the sound pressure signal and the pulsating pressure image based on the discrete Fourier transform component of the sound pressure signal at the preset frequency f and the Fourier transform component of the three-dimensional pulsating pressure image data at the preset frequency f includes: ， in, represents the cross-spectral estimation value of the acoustic pressure signal and the pulsating pressure image, represents the discrete Fourier transform component of the sound pressure signal at the preset frequency f, Represents the Fourier transform component of the three-dimensional pulsating pressure image data at a preset frequency f The complex conjugate of .

8. The method for obtaining coherent output power according to claim 1, wherein: The calculating the coherence of the sound pressure signal and the pulsation pressure image based on the autospectral estimation value and the cross-spectral estimation value of the sound pressure signal and the pulsation pressure image comprises: ， in, Indicates the coherence between the acoustic pressure signal and the pulsating pressure image, with a value range between 0 and 1, where 0 indicates complete irrelevance and 1 indicates complete correlation; represents the cross-spectral estimation value of the acoustic pressure signal and the pulsating pressure image, represents the autospectral estimate of the sound pressure signal, Represents the autospectral estimate of the pulsating pressure image data.

9. The method for obtaining coherent output power according to claim 1, wherein: The method of calculating the coherent output power of the sound pressure signal and the pulsating pressure image based on the autospectral estimation value of the pulsating pressure image and the coherence degree comprises: ， ， in, represents the coherent output power of the acoustic pressure signal and the pulsating pressure image, Represents the coherence between the acoustic pressure signal and the pulsating pressure image, represents the RMS power of the pulsating pressure image at the preset frequency f, represents the autospectral estimate of the pulsating pressure image data, express The complex conjugate of .

10. A computer-readable storage medium, characterized in that: The medium stores a program, which can be loaded by a processor and execute the coherent output power acquisition method as described in any one of claims 1 to 9.

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