Method and system for accurately identifying vibration frequency of model in wind tunnel test

Abstract

A method for accurately identifying the vibration frequency of a model in a wind tunnel test comprises the following steps: acquiring a two-dimensional data matrix of physical quantity distribution on the surface of a wind tunnel test model in a wind tunnel flow field; performing singular value decomposition on the two-dimensional data matrix of the surface physical quantity distribution of the wind tunnel test model to obtain a corresponding vibration frequency mode of the wind tunnel test model in a wind tunnel flow field; the vibration frequency modes of the wind tunnel test model in the wind tunnel flow field are sequenced according to the energy ratio, the frequency corresponding to the vibration frequency mode with the maximum energy ratio is the frequency leading the vibration of the wind tunnel test model, and the growth rate corresponding to the frequency leading the vibration of the wind tunnel test model is obtained. The method provided by the invention is convenient and rapid, the vibration frequency and growth rate of the model can be accurately obtained, the influence of model vibration on the optical measurement precision can be eliminated through modal decomposition, and a new method is provided for wind tunnel test data processing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wind tunnel test measurement, and particularly relates to a method and system for accurately obtaining model vibration frequency during test. BACKGROUND

[0002] During hypersonic wind tunnel test, the motion or vibration phenomenon of the test model can be captured by high-speed camera with ultra-high frame rate, and the change of the physical quantity on the model surface can be obtained. Such technology is generally referred to as optical measurement technology (non-contact surface measurement technology).

[0003] For example:

[0004] Infrared thermal imaging technology (the real-time temperature change on the model surface can be photographed by high-speed thermal imager);

[0005] High-frequency pressure surface measurement technology (by spraying pressure-sensitive paint on the model surface, when the pressure on the model surface changes, the light intensity reflected by the pressure-sensitive paint under ultraviolet light changes with temperature, and the light intensity distribution on the model surface is recorded by high-speed camera to solve the pressure distribution on the model surface);

[0006] High-frequency heat flow surface measurement technology (by spraying temperature-sensitive paint on the model surface, when the temperature on the model surface changes, the light intensity reflected by the temperature-sensitive paint under ultraviolet light changes with temperature, and the light intensity distribution on the model surface is recorded by high-speed camera to solve the pressure distribution on the model surface);

[0007] Friction value surface measurement technology (by spraying shear-sensitive material on the model surface, when the friction on the model surface changes, the color of the shear-sensitive paint changes with temperature, and the color distribution on the model surface is recorded by high-speed camera to solve the friction distribution on the model surface).

[0008] The test model in the flow field will inevitably be disturbed by some disturbance sources, resulting in certain vibration of the model during wind tunnel test. When performing optical surface measurement, the vibration of the model will affect the acquisition of the physical quantity on the model surface. Because the data at different times is needed for difference or comparison when observing the change of the physical quantity on the model surface, the vibration of the model will cause problems and errors when the data is differentiated. In order to accurately obtain the change of the physical quantity on the model surface, the vibration information must be removed.

[0009] The vibration of the test model in the flow field can be caused by many factors. If the causes of the vibration are to be explored, the model vibration information must be converted into vibration data first, and the spatial vibration information must be decomposed into different single frequency spatial distribution information. SUMMARY

[0010] The technical problem solved by the present application is that the present application provides a method and system for accurately identifying the vibration frequency of a model in a wind tunnel test based on F-POD (Single-Frequency Proper Orthogonal Decomposition), so as to accurately obtain the vibration information of the test model in the flow field and decompose it into single-frequency information, and also can obtain the change of the surface physical quantity when the model is stable, remove the influence of vibration on the model, and improve the measurement accuracy of optical measurement technology in a hypersonic wind tunnel.

[0011] To achieve the above technical purpose, the present application adopts the following technical scheme: a method for accurately identifying the vibration frequency of a model in a wind tunnel test, comprising:

[0012] In the wind tunnel flow field, a two-dimensional data matrix of the surface physical quantity distribution of the wind tunnel test model is collected and obtained;

[0013] The two-dimensional data matrix of the surface physical quantity distribution of the wind tunnel test model is singular value decomposed to obtain the vibration frequency mode of the wind tunnel test model in the wind tunnel flow field;

[0014] The vibration frequency mode of the wind tunnel test model in the wind tunnel flow field is sorted according to the energy ratio, and the frequency corresponding to the vibration frequency mode with the largest energy ratio is the frequency of the dominant wind tunnel test model vibration, and the growth rate corresponding to the frequency of the dominant wind tunnel test model vibration is obtained.

[0015] Further, the surface physical quantity of the wind tunnel test model includes density, temperature, pressure and frictional resistance.

[0016] Further, the collection and acquisition of the two-dimensional data matrix of the surface physical quantity distribution of the wind tunnel test model comprises:

[0017] In the wind tunnel test, a high-speed camera is used to shoot the surface of the wind tunnel test model, and data of the surface physical quantity of the wind tunnel test model changing with time is obtained to form a two-dimensional data matrix of MxN corresponding to each surface physical quantity The element in the two-dimensional matrix X represents the jth transient wind tunnel test model surface physical quantity collected by the high-speed camera at the ith time; M represents the number of instantaneous pressure data of the wind tunnel test model collected by the high-speed camera; and N is a positive integer.

[0018] Further, the F-POD method is used to obtain the vibration frequency mode of the wind tunnel test model in the wind tunnel flow field.

[0019] Further, the method for accurately identifying model vibration frequency during wind tunnel test further comprises: analyzing other vibration frequency modes except the vibration frequency mode with the largest energy proportion, and analyzing the influence of the other vibration frequency modes on the vibration of the wind tunnel test model according to the energy proportion.

[0020] Further, the method for accurately identifying model vibration frequency during wind tunnel test further comprises: analyzing the vibration frequency mode with a frequency of 0, and reconstructing to obtain the surface physical quantity distribution of the wind tunnel test model when the wind tunnel test model is static.

[0021] Further, the wind tunnel is a low-speed wind tunnel, a sub-transonic and supersonic wind tunnel, a hypersonic wind tunnel or a low-density wind tunnel.

[0022] A system for accurately identifying model vibration frequency during wind tunnel test based on the above method, comprising:

[0023] A first module is configured to collect a two-dimensional data matrix of the surface physical quantity distribution of the wind tunnel test model in the wind tunnel flow field;

[0024] A second module is configured to perform singular value decomposition on the two-dimensional data matrix of the surface physical quantity distribution of the wind tunnel test model to obtain the vibration frequency mode of the wind tunnel test model in the wind tunnel flow field;

[0025] A third module is configured to sort the vibration frequency mode of the wind tunnel test model in the wind tunnel flow field according to the energy proportion, the vibration frequency mode with the largest energy proportion corresponds to the frequency of the dominant wind tunnel test model vibration, and the growth rate corresponding to the frequency of the dominant wind tunnel test model vibration is obtained.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] (1) The method for accurately obtaining the model vibration frequency and growth rate during the test based on the single frequency mode decomposition can eliminate the influence of model vibration on optical measurement accuracy through mode decomposition.

[0028] (2) The method for accurately obtaining the model vibration frequency and growth rate during the test based on the single frequency mode decomposition can more accurately obtain the frequency and growth rate information of the model vibration compared with the traditional mode decomposition method, so that the source causing the model vibration can be further analyzed. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.

[0030] Figure 1 The flowchart of the method for accurately obtaining the model vibration frequency during the test provided by the embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to better understand the above technical solutions, the following will be described in detail by the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solutions of the present application, and are not limitations of the technical solutions of the present application. In the case of no conflict, the technical features in the embodiments and the embodiments can be combined with each other.

[0032] The method for accurately identifying the vibration frequency of the model in the wind tunnel test provided by the embodiments of the present application is further described in detail below in combination with the accompanying drawings of the specification.

[0033] The method for accurately obtaining the vibration frequency and growth rate of the model in the test provided by the embodiments of the present application based on single-frequency modal decomposition, as shown in Figure 1 includes the following steps:

[0034] 1) The two-dimensional data matrix of the physical quantity (density, temperature, pressure, friction) distribution of the wind tunnel test model surface acquired by the high-speed camera: taking pressure as an example, define representing the transient pressure field at the i-th moment, is the j-th transient pressure value of the model surface collected by the high-speed camera at the i-th moment; wherein j=1, 2, 3, …, M; M represents the number of transient pressure data of the model surface collected by the high-speed camera (usually the pressure data of the model surface acquired by the camera is a two-dimensional matrix, which needs to be changed into a one-dimensional matrix in the order of small to large, y' first and x' second, where M represents the number of elements of the matrix, x' represents the horizontal coordinate of the pressure of the model surface acquired by the camera, and y' represents the vertical coordinate of the pressure of the model surface acquired by the camera). Select the transient pressure field of the database at N moments i=1, 2, 3, …, N, to form a two-dimensional data matrix of MxN N is a positive integer.

[0035] The wind tunnel in the physical quantity of the model surface acquired by the high-speed camera in step 1) can be a low-speed wind tunnel, a subsonic transonic supersonic wind tunnel, a hypersonic wind tunnel, a low-density wind tunnel, etc.

[0036] 2) The vibration frequency mode of the model in the wind tunnel flow field obtained by single-frequency modal decomposition. Compared with other modal decomposition methods, the single-frequency modal decomposition method can more accurately capture the change of the vibration amplitude of the model in the wind tunnel flow field. Using the single-frequency modal decomposition method to perform single-frequency modal decomposition on the two-dimensional data matrix of the physical quantity (density, temperature, pressure, friction) distribution of the model surface acquired by the high-speed camera in the wind tunnel test, different vibration modes can be obtained, and each mode corresponds to a separate frequency.

[0037] 3), the modal is sorted according to the energy ratio, and the frequency corresponding to the largest energy ratio is the frequency of the dominant model vibration, and the corresponding growth rate information can also be accurately obtained.

[0038] 4), other frequencies of model vibration correspond to the remaining modes, and the influence of the model vibration can be analyzed according to the energy ratio; for the mode with frequency of 0, the physical quantity distribution of the model at rest can be obtained after reconstruction.

[0039] A system for accurately identifying model vibration frequency during wind tunnel test based on the above method, comprising:

[0040] The first module is used for collecting and acquiring the two-dimensional data matrix of the physical quantity distribution of the wind tunnel test model surface in the wind tunnel flow field;

[0041] The second module is used for singular value decomposition of the two-dimensional data matrix of the physical quantity distribution of the wind tunnel test model surface, to obtain the corresponding vibration frequency mode of the wind tunnel test model in the wind tunnel flow field;

[0042] The third module is used for sorting the vibration frequency mode of the wind tunnel test model in the wind tunnel flow field according to the energy ratio, and the frequency corresponding to the largest energy ratio is the frequency of the dominant wind tunnel test model vibration, and the growth rate corresponding to the frequency of the dominant wind tunnel test model vibration is obtained.

[0043] Embodiment:

[0044] Dynamic pressure test of a certain aircraft model surface in a hypersonic wind tunnel:

[0045] A certain model is tested in a hypersonic wind tunnel, the model surface is sprayed with pressure sensitive paint, and the temperature change of the model surface can be obtained by using a high-speed camera to take pictures.

[0046] (1) First, select 201 pressure distribution maps taken by the camera during the test as the original data matrix, that is, the transient pressure field The 201x10000 two-dimensional data matrix is composed, where 10000 is the number of pixel points of the camera picture at a single time.

[0047] (2) Then, the vibration frequency mode of the model in the wind tunnel flow field obtained by single frequency modal decomposition (single frequency modal decomposition method itself is a method of adding inverse Fourier transform and field modal superposition on the basis of POD method, so single frequency modal decomposition needs to be carried out first POD decomposition)

[0048] (3) Singular value decomposition is performed on the matrix Pt to obtain Pt'=USV HWhere An=US is the time variable, corresponding to the amplitude of the mode changing with time, which can be used for time series analysis, phiU=V H The mode is POD.

[0049] (4) The eigenvalue of each POD mode is obtained by taking the square of the diagonal element of the matrix S and dividing 201, that is, the energy corresponding to each mode. The main POD mode can be extracted by sorting the energy ratio.

[0050] (5) Then, the frequency information of the time variable corresponding to each mode is obtained by performing fast Fourier transform on the eigenvalue An of each mode. (Note: Unlike the DMD method, the time information corresponding to the mode obtained by POD decomposition has multiple coupled frequencies)

[0051] (6) There are multiple dominant frequencies in the pressure field of the model surface. The dominant frequency in the mode and the frequency in its field (the frequency between two dominant frequencies) are inversely Fourier transformed to obtain time variable information containing only the dominant frequency.

[0052] (7) The time variable containing the same dominant frequency in different modes is multiplied by the corresponding mode to obtain the pressure field under the action of a single frequency, and the accurate growth rate information is obtained.

[0053] (8) The mode corresponding to the frequency of 0 is the surface pressure distribution of the model without vibration.

[0054] (9) The frequency corresponding to the mode with high energy ratio is the main vibration frequency of the mode, which provides certain data support for suppressing model vibration when the wind tunnel blows.

[0055] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

[0056] The contents not described in detail in the specification of the present application are the known technologies of those skilled in the art.

Claims

1. A method for accurately identifying the vibration frequency of a model during a wind tunnel test, characterized in that: include: In the wind tunnel flow field, the two-dimensional data matrix of the distribution of physical quantities on the surface of the wind tunnel test model is collected; Perform singular value decomposition on the two-dimensional data matrix of the physical quantity distribution on the wind tunnel test model surface to obtain the corresponding vibration frequency mode of the wind tunnel test model in the wind tunnel flow field; The vibration frequency modes of the wind tunnel test model in the wind tunnel flow field are sorted according to their energy proportion. The frequency corresponding to the vibration frequency mode with the largest energy proportion is the frequency that dominates the vibration of the wind tunnel test model, and the corresponding growth rate of the frequency that dominates the vibration of the wind tunnel test model is obtained.

2. The method for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 1, characterized in that: The surface physical quantities of the wind tunnel test model include density, temperature, pressure and friction resistance.

3. The method for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 2, characterized in that: The acquisition of a two-dimensional data matrix of the distribution of physical quantities on the surface of the wind tunnel test model includes: During the wind tunnel test, a high-speed camera is used to shoot the surface of the wind tunnel test model to obtain data on the changes in physical quantities on the wind tunnel test model over time, and to form an M×N two-dimensional data matrix corresponding to each surface physical quantity. is an element in the two-dimensional matrix X and represents the physical quantity of the j-th transient wind tunnel test model surface collected by the high-speed camera at the i-th moment; M represents the number of instantaneous pressure data on the wind tunnel test model surface collected by the high-speed camera; N is a positive integer.

4. The method for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 3, characterized in that: The F-POD method is used to obtain the vibration frequency modes of the wind tunnel test model in the wind tunnel flow field.

5. The method for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 4, characterized in that: Also includes: Analyze the vibration frequency modes other than the vibration frequency mode with the largest energy proportion, and analyze the influence of other vibration frequency modes on the vibration of the wind tunnel test model based on the energy proportion.

6. The method for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 5, characterized in that: Also includes: The vibration frequency mode with a frequency of 0 is analyzed and reconstructed to obtain the surface physical quantity distribution of the wind tunnel test model when it is stationary.

7. The method for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 6, characterized in that: The wind tunnel is a low-speed wind tunnel, a subsonic wind tunnel, a hypersonic wind tunnel or a low-density wind tunnel.

8. A system for accurately identifying the vibration frequency of a model during a wind tunnel test, characterized in that: include: The first module is used to collect and obtain the two-dimensional data matrix of the distribution of physical quantities on the surface of the wind tunnel test model in the wind tunnel flow field; The second module is used to perform singular value decomposition on the two-dimensional data matrix of the physical quantity distribution on the surface of the wind tunnel test model to obtain the vibration frequency mode of the corresponding wind tunnel test model in the wind tunnel flow field; The third module is used to sort the vibration frequency modes of the wind tunnel test model in the wind tunnel flow field according to their energy proportion. The frequency corresponding to the vibration frequency mode with the largest energy proportion is the frequency of the dominant wind tunnel test model vibration, and the corresponding growth rate of the frequency of the dominant wind tunnel test model vibration is obtained.

9. The system for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 8, characterized in that: The surface physical quantities of the wind tunnel test model include density, temperature, pressure and friction resistance.

10. The system for accurately identifying the vibration frequency of a model during a wind tunnel test according to claim 9, characterized in that: The acquisition of a two-dimensional data matrix of the distribution of physical quantities on the surface of the wind tunnel test model includes: During the wind tunnel test, a high-speed camera is used to shoot the surface of the wind tunnel test model to obtain data on the changes in physical quantities on the wind tunnel test model over time, and to form an M×N two-dimensional data matrix corresponding to each surface physical quantity. is an element in the two-dimensional matrix X and represents the physical quantity of the j-th transient wind tunnel test model surface collected by the high-speed camera at the i-th moment; M represents the number of instantaneous pressure data on the wind tunnel test model surface collected by the high-speed camera; N is a positive integer.

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