CN110455490A - Method and device for calculating supersonic velocity and hypersonic velocity wind tunnel flow field turbulence - Google Patents
Method and device for calculating supersonic velocity and hypersonic velocity wind tunnel flow field turbulence Download PDFInfo
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Abstract
The embodiment of the invention discloses a method and a device for calculating the turbulence degree of a supersonic velocity and hypersonic velocity wind tunnel flow field, which are used for acquiring original total pressure data after a wind tunnel flow field shock wave, and decomposing the original total pressure data at each moment into wave-rear total pressure data without pulsation and actual wave-rear total pressure pulsation data; respectively calculating actual wavefront static pressure pulsation data corresponding to each actual wave-rear total pressure pulsation data according to a pressure pulsation conversion coefficient corresponding to a wind tunnel flow field obtained in advance and each actual wave-rear total pressure pulsation data at each moment; dividing each actual total pressure pulsation datum after wave generation into a plurality of data segments according to characteristic time; and calculating the average value of the wave front static pressure of the wind tunnel flow field in a preset time period according to the average value of the wave rear total pressure data without pulsation and a first preset formula, and calculating the turbulence degree corresponding to each data segment according to the average value of the wave front static pressure and each actual wave front static pressure pulsation data and a second preset formula. The invention can improve the calculation precision of the turbulence degree.
Description
Technical Field
The invention relates to the technical field of wind tunnel flow fields, in particular to a method and a device for calculating the turbulence degree of a supersonic speed and hypersonic speed wind tunnel flow field.
Background
The wind tunnel is the main equipment for the simulation experiment of the unfolding bottom surfaces of aircrafts and the like, and the aerodynamic data of the aircraft model obtained in the wind tunnel is the basis and foundation for the design of the aircrafts and the unfolding flight test in the future. The wind tunnel turbulence is a standard for measuring the pulsation degree of the air flow velocity of the wind tunnel experiment section. In a supersonic or hypersonic wind tunnel, hot wire measurements are relatively difficult and the measurement result is a pulsation in the flow, resulting in an inaccurate assessment of the turbulence level. In recent years, in the development of hypersonic aircrafts, it is found that a plurality of flight tests fail due to the fact that flight tests are carried out according to ground supersonic/hypersonic wind tunnel test results. The reason for this is that the turbulence of the supersonic/hypersonic wind tunnel flow field is usually 1-2 orders of magnitude higher than the incoming flow turbulence in the flight environment of the aircraft in real flight, which causes a large difference between the ground wind tunnel experiment and the real flight experiment. Therefore, accurately evaluating the turbulence of the flow field of the existing wind tunnel and researching the influence of the turbulence on a ground experiment are a problem concerned in the current supersonic/hypersonic flight research.
Disclosure of Invention
The invention aims to provide a method and a device for calculating the turbulence degree of a supersonic speed and hypersonic speed wind tunnel flow field aiming at the defects in the prior art.
In one embodiment, the invention provides a method for calculating the turbulence degree of a supersonic and hypersonic wind tunnel flow field, which comprises the following steps:
acquiring original total pressure data after a shock wave in a preset time period of a wind tunnel flow field, and decomposing the original total pressure data at each moment into wave-rear total pressure data without the shock wave and actual wave-rear total pressure shock data;
respectively calculating actual wavefront static pressure pulsation data corresponding to each actual wave-rear total pressure pulsation data according to a pressure pulsation conversion coefficient corresponding to a wind tunnel flow field obtained in advance and each actual wave-rear total pressure pulsation data at each moment;
dividing each actual total pressure pulsation data after wave into a plurality of data segments according to pre-selected characteristic time;
and calculating the average value of the corresponding wave front static pressure of the wind tunnel flow field in a preset time period according to the average value of the wave rear total pressure data without pulsation and a first preset formula, and calculating the turbulence degree corresponding to each data segment according to the average value of the wave front static pressure and each actual wave front static pressure pulsation data and a second preset formula.
In a specific embodiment, the characteristic time is obtained based on the following steps:
the pre-selected characteristic time is obtained based on the following steps:
acquiring the physical characteristic length of a designated target object in a wind tunnel flow field and the uniform incoming flow speed of a wind tunnel experiment section of the wind tunnel flow field;
and taking the ratio of the physical characteristic length to the uniform incoming flow speed as the characteristic time.
In a specific embodiment, the second predetermined formula is:
wherein I represents the turbulence level corresponding to each data segment,representing the average value of the corresponding wavefront static pressure in a preset time period; p'1Representing actual wavefront static pressure pulsation data.
In a specific embodiment, the first predetermined formula is:
wherein,representing an average value of the wavefront static pressure within a preset time period; ma1Representing the Mach number of the wind tunnel flow field; gamma represents a gas specific heat ratio;represents the average of the post-wave total pressure data each without pulsation.
In a specific embodiment, the pre-obtained pressure pulsation conversion coefficient corresponding to the wind tunnel flow field is obtained based on the following steps:
obtaining predicted post-wave total pressure pulsation data through numerical simulation of the wind tunnel flow field according to the obtained incoming flow Mach number, shock wave front total pressure, wind tunnel flow field total temperature and preset wave front static pressure pulsation data of the wind tunnel flow field under the current working condition;
and taking the ratio of the preset wave front static pressure pulsation data to the predicted wave rear total pressure pulsation data as a pressure pulsation conversion coefficient.
In a specific embodiment, the method further comprises the following steps:
and carrying out Fourier transform according to the time interval and the turbulence degree corresponding to each data segment to obtain the frequency spectrum and the power spectrum of the turbulence degree of the wind tunnel flow field in a preset time segment.
In a specific embodiment, acquiring original total pressure data after a wave in a preset time period of a wind tunnel flow field, and decomposing the original total pressure data at each moment into wave-rear total pressure data without pulsation and actual wave-rear total pressure pulsation data includes:
preprocessing the original total pressure data to obtain post-wave total pressure data without pulsation;
subtracting the post-wave total pressure data without pulsations from the original total pressure data to obtain actual post-wave total pressure pulsation data.
In a particular embodiment, the pre-treatment comprises any one of the following pre-treatments: polynomial fitting, wavelet decomposition, and empirical mode decomposition.
On the other hand, the embodiment of the invention also provides a device for calculating the turbulence degree of the supersonic speed and hypersonic speed wind tunnel flow field, which comprises:
the data acquisition processing module is used for acquiring the original total pressure data after the wave-excited wave in a preset time period of a wind tunnel flow field and decomposing the original total pressure data at each moment into wave-back total pressure data without the pulse and actual wave-back total pressure pulse data;
the pulse value conversion module is used for respectively calculating actual wavefront static pressure pulse data corresponding to each actual post-wave total pressure pulse data according to a pre-acquired pressure pulse conversion coefficient corresponding to the wind tunnel flow field and each actual post-wave total pressure pulse data at each moment;
the segmentation module is used for dividing each actual total pressure pulsation datum after wave generation into a plurality of data segments according to the pre-selected characteristic time;
and the turbulence degree calculation module is used for calculating the average value of the corresponding wave front static pressure of the wind tunnel flow field in a preset time period according to the first preset formula and the average value of each wave rear total pressure data without pulsation, and calculating the turbulence degree corresponding to each data segment according to the second preset formula and the average value of the wave front static pressure and each actual wave front static pressure pulsation data.
On the other hand, the embodiment of the invention also provides computer equipment, which comprises a memory and a processor, wherein the memory stores a computer program, and the processor realizes the steps of the calculation method of the turbulence degree of the flow field of the supersonic speed and hypersonic speed wind tunnel when executing the computer program.
One of the above technical solutions has the following advantages and beneficial effects:
according to the method and the device for calculating the turbulence degree of the supersonic velocity and hypersonic velocity wind tunnel flow field, the post-wave total pressure data without pulsation and the actual post-wave total pressure pulsation data are decomposed by preprocessing the original total pressure data after the shock wave in the preset time period, and the influence of non-stationary signals on the calculation of the turbulence degree can be eliminated. Furthermore, the actual wavefront static pressure pulsation data corresponding to the actual post-wave total pressure pulsation data at each moment is obtained through conversion, so that the problem of low and inaccurate precision in direct measurement of the wind tunnel wavefront static pressure can be avoided. Furthermore, the actual total pressure pulsation data after wave at each moment is segmented according to the characteristic time, so that the turbulence degree of the wind tunnel flow field and the rule of the change of the turbulence degree along with time can be calculated and analyzed. The embodiments of the invention can enable the calculation result of the turbulence degree of the wind tunnel flow field to be closer to the real situation, improve the calculation precision and provide more detailed data support for analyzing the influence of the turbulence degree on the wind tunnel experiment result.
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In order to more clearly illustrate the technical solution of the present invention, the drawings required to be used in the embodiments will be briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope of the present invention. Like components are numbered similarly in the various figures.
FIG. 1 is a flow chart diagram illustrating a method for calculating the turbulence of the flow field of a supersonic and hypersonic wind tunnel according to an embodiment of the present invention;
FIG. 2 is a graph illustrating the raw total pressure data after a laser in an embodiment of the invention;
FIG. 3 illustrates a graphical representation of post-wave total pressure data without pulsations in an embodiment of the present disclosure;
FIG. 4 illustrates a graphical representation of actual post-wave total pressure pulsation data in accordance with the present invention;
fig. 5 shows a schematic structural diagram of a calculating device for supersonic and hypersonic wind tunnel flow field turbulence according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
Hereinafter, the terms "including", "having", and their derivatives, which may be used in various embodiments of the present invention, are only intended to indicate specific features, numbers, steps, operations, elements, components, or combinations of the foregoing, and should not be construed as first excluding the existence of, or adding to, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.
The wind tunnels are generally classified by Mach number Ma, the supersonic speed wind tunnel is used when Ma is more than 1.4 and less than 5, and the hypersonic speed wind tunnel is used when Ma is more than or equal to 5. In the traditional technology, in the measurement of the turbulence of the flow field of the supersonic and hypersonic wind tunnel, pressure pulsation is often adopted to measure the turbulence of the wind tunnel, and the turbulence of the flow field of the wind tunnel is one of important parameters for measuring the quality of the flow field of the wind tunnel and the reliability of experimental data of the wind tunnel. The method for evaluating the turbulence degree of the wind tunnel flow field by using the pressure measurement data is an important link for calculating the turbulence degree of the wind tunnel based on the original pressure data besides adopting a more accurate method for measuring the pressure pulsation in the wind tunnel flow field (for example, adopting a sensor with higher sensitivity and faster frequency response). In the conventional art, the turbulence level is calculated based on the following formula:
where I is the wind tunnel flow field turbulence, p02Is the total pressure after the shock wave (i.e. the pressure data measured by the sensor) at a certain moment in a certain period of time, p0′2Is the pulsation value of the total pressure after the shock wave,is the average value of the total pressure after the shock wave in the period of time. However, this calculation method can only be used for smooth pressure signals (i.e. the pressure of the flow field during the operation of the wind tunnel, without taking the pulse into account)Substantially constant in the case of motion). However, most wind tunnels actually operate in a manner that the pressure of the flow field may change up and down, such as a gradual pressure rise, or a gradual pressure drop, or a periodic pressure rise and drop. If the flow field pressure is uniformly increased in the wind tunnel operation process, even if the flow field pressure does not have pulsation change (the turbulence degree is considered to be zero), a nonzero turbulence degree result can be obtained by calculation according to the formula, and the result is not consistent with the real situation.
On the other hand, the calculation of the turbulence degree is to calculate the whole measured signal to obtain the average turbulence degree in the whole measuring process, and the parameter can be used as the standard for evaluating the quality of the wind tunnel flow field. Different wind tunnel experiments with the same turbulence value may result, and the measured results thereof differ. Although frequency characteristics in a wind tunnel turbulence power spectrum are considered in research, besides the influence of frequency domain characteristics, the influence of wind tunnel turbulence time domain characteristics (the change of turbulence with time) on experimental results is not negligible. Even if the frequency domain characteristics of the turbulence degree are consistent, the difference of the real-time turbulence degree of the wind tunnel along with the change of time can also cause the difference of the experimental results.
Referring to fig. 1 to 4, the abscissa X in fig. 2 to 4 represents the rank number of the sampled data points, indicating the several sampled data, and the ordinate kPa represents the pressure. In one embodiment, the invention provides a method for calculating the turbulence degree of a supersonic and hypersonic wind tunnel flow field, which comprises the following steps:
step S110: the method comprises the steps of obtaining original total pressure data after shock waves in a preset time period of a wind tunnel flow field, and decomposing the original total pressure data at each moment into wave-rear total pressure data without the shock waves and actual wave-rear total pressure shock data.
Fig. 2 is a schematic graph of laser-wave original total pressure data acquired within a preset time period, where each sampled data point represents one original total pressure data. In order to eliminate the non-stationary characteristic of a flow field pressure signal in a wind tunnel flow field as much as possible, therefore, the original total pressure data after the shock wave at each moment is preprocessed and decomposed into wave-following total pressure data without pulsation and actual wave-following total pressure pulsation data. Fig. 3 shows time-varying post-pulse-wave-free total pressure data decomposed from the post-shock raw total pressure data of fig. 2, with each sampled data point representing a post-pulse-wave-free total pressure data. Fig. 4 illustrates actual post-wave total pressure ripple data decomposed from the post-shock raw total pressure data of fig. 2, with each sampled data point representing an actual post-wave total pressure ripple data.
The embodiment of the invention can eliminate the influence of non-stationary change in the original total pressure data after the shock wave on the calculation of the turbulence degree, and is beneficial to optimizing the calculation and precision of the turbulence degree.
In a specific embodiment, acquiring original total pressure data after a wave in a preset time period of a wind tunnel flow field, and decomposing the original total pressure data at each moment into wave-rear total pressure data without pulsation and actual wave-rear total pressure pulsation data includes:
step S2: and preprocessing the original total pressure data to obtain post-wave total pressure data without pulsation.
In a particular embodiment, the pre-treatment comprises any one of the following pre-treatments: polynomial fitting, wavelet decomposition, and empirical mode decomposition.
For example, polynomial fitting is performed on the original total pressure data after the laser, and data on a fitting curve is used as post-wave total pressure data without pulsation (such as polynomial fitting of 5 th order, polynomial fitting of 7 th order, and the like); or performing wavelet decomposition on the original total pressure data after the shock wave, and decomposing the signal into a low-frequency signal and a high-frequency signal of different layers, wherein the low-frequency signal is used as the total pressure data after the shock wave without pulsation; or performing adaptive filtering on the original total pressure data after the wave excitation according to empirical mode decomposition, and taking the obtained data as wave-borne total pressure data without pulsation.
The polynomial fitting mode is suitable for processing the original total pressure data after the shock waves which gradually rise or gradually fall, and the wavelet decomposition and the empirical mode decomposition are suitable for processing the original total pressure data after the shock waves which periodically change.
Step S4: subtracting the post-wave total pressure data without pulsations from the original total pressure data to obtain actual post-wave total pressure pulsation data.
The embodiment of the invention can preprocess the original total pressure data after the shock waves with different variation trends in various modes, and is beneficial to improving the precision of data processing.
Step S120: and respectively calculating actual wavefront static pressure pulsation data corresponding to each actual post-wave total pressure pulsation data according to a pre-obtained pressure pulsation conversion coefficient corresponding to the wind tunnel flow field and each actual post-wave total pressure pulsation data at each moment.
The wind tunnel flow field corresponds to a pressure pulsation conversion coefficient under each working condition and represents the proportional relation between wave-rear total pressure pulsation data and wave-front static pressure pulsation data. In the analysis of the numerical simulation of the flow field on the process of passing through the shock wave by the acoustic wave disturbance with the attack angle, a proportional relation between actual wavefront static pressure pulsation data and actual total pressure pulsation data after wave is provided, and the actual wavefront static pressure pulsation data corresponding to each actual total pressure pulsation data after wave can be obtained based on the following relation as follows:
wherein, P'1Representing actual wavefront static pressure pulsation data, P'2Representing actual post-wave total pressure ripple data,the coefficient is obtained through a transfer function of pressure pulsation before and after shock waves, namely a pressure pulsation conversion coefficient, is a determined numerical value under a certain determined working condition of a wind tunnel flow field, and is used for converting actual wavefront static pressure pulsation data corresponding to actual post-wave total pressure pulsation data.
Step S130: and dividing each actual total pressure pulsation datum after wave into a plurality of data segments according to the pre-selected characteristic time.
The characteristic time is a time length, the selection of the characteristic time is related to the wind tunnel experiment model and the flow field characteristics, and each data segment after segmentation comprises data in 1 or more characteristic times. Dividing each actual post-wave total pressure pulsation data into a plurality of data segments according to pre-selected characteristic time, and segmenting in the following way: if the characteristic time is taken as a unit, equally dividing each actual total pressure pulsation datum after wave into a plurality of data segments; or the time length corresponding to each segment of data can be a multiple of the characteristic time, so that each segment of data is correspondingly divided into multiple segments, and if the characteristic time is 1T, the time corresponding to each segment of data is 1T, 5T, 10T, 0.1T, 0.5T, and the like. Therefore, the embodiment of the invention is beneficial to analyzing the influence of the time change on the turbulence degree and improving the analysis precision.
According to the embodiment of the invention, each actual total wave-rear pressure pulsation data is segmented according to the selected characteristic time, so that the turbulence degree changing along with time and the change rule of the turbulence degree can be obtained, and the analysis precision of the wind tunnel experiment result based on the turbulence degree is improved.
Some specific frequencies have great influence on the flow field of the wind tunnel, such as boundary layer transition, and the occurrence time of some specific frequencies is different, so that the generated effects are also different. For example, if a certain specific frequency appears first, the wind tunnel flow field is affected, which causes the experimental result to change, and even if the specific frequency disappears later, the influence of the wind tunnel flow field does not disappear immediately, or even remains. Therefore, the flow field changes may not be the same due to the occurrence of the specific frequency in time sequence, and the influence on the experimental result is different. Most of the analysis methods in the traditional technology only have a time-averaged turbulence degree result and the corresponding frequency spectrum distribution condition of the turbulence degree in the whole data segment time, but neglect the influence of the time-varying characteristics, and are not beneficial to the analysis of the experimental result based on the turbulence degree.
In a specific embodiment, the pre-selected feature time is obtained based on the following steps:
step S6: and acquiring the physical characteristic length of a specified target object in the wind tunnel flow field and the uniform incoming flow speed of the wind tunnel experiment section of the wind tunnel flow field.
The wind tunnel experiment section is an area for placing a model for experiment. The selection of the characteristic time is related to the wind tunnel experiment model and the flow field characteristics. For example, U is used for characterizing the speed by the uniform incoming flow speed of the wind tunnel experiment sectionfIndicating that L is a characteristic length of a certain physical dimensionfAnd (4) showing. The physical characteristic length can be selected according to actual requirements, the length or the width of a certain aircraft profile can be selected as the characteristic length, if a certain flow structure is concerned, the physical length dimension of the structure is taken as the physical characteristic length, for example, boundary layer flow which is relatively concerned by a hypersonic aircraft, and the boundary layer thickness can be selected as the physical characteristic length.
Step S8: and taking the ratio of the physical characteristic length to the uniform incoming flow speed as the characteristic time.
The embodiment of the invention determines the characteristic time through the specified physical characteristic length of the target object and the uniform incoming flow velocity of the wind tunnel experiment segment, is beneficial to improving the accuracy of calculating the turbulence degree, and can provide more detailed data support for analyzing the influence of the turbulence degree on the wind tunnel experiment result. Further, in the comparison with the results of the similar experiment (i.e. the experiment same as the target object), in order to facilitate the rule of extracting the experiment results, the same physical parameters as the similar experiment can be selected, such as the characteristic length of the target object and the uniform inflow velocity of the wind tunnel experiment segment as characteristic parameters, which is helpful for analyzing the experiment results and comparing the experiment results with the results of the similar experiment.
Step S140: and calculating the average value of the wave front static pressure of the wind tunnel flow field in a preset time period according to the average value of the wave rear total pressure data without pulsation and a first preset formula, and calculating the turbulence degree corresponding to each data segment according to the average value of the wave front static pressure and each actual wave front static pressure pulsation data and a second preset formula.
In a specific embodiment, the first predetermined formula is:
wherein,representing the average value of the corresponding wavefront static pressure in a preset time period; ma1Representing the Mach number of the wind tunnel flow field; gamma represents a gas specific heat ratio;represents the average of the post-wave total pressure data each without pulsation.
The method is implemented based on the first preset formula to obtain the average value of the wave front static pressure of the wind tunnel flow field in the preset time period, the calculation process is simple, and the redundancy of the program can be reduced.
In a specific embodiment, the second predetermined formula is:
wherein I represents the turbulence level corresponding to each data segment,representing the average value of the corresponding wavefront static pressure in a preset time period; p'1Representing actual wavefront static pressure pulsation data. Further, Σ (P'1) And 2 is the sum of squares of corresponding actual wavefront static pressure pulsation data in each data segment.
The turbulence degree in different periods can be obtained based on the second preset formula, the sum of squares of actual wave front static pressure pulsation data corresponding to each data segment and the average value of wave front static pressure corresponding to the wind tunnel flow field in the preset time period, the calculation is simple, and the calculation precision of the turbulence degree can be improved. Meanwhile, the method is beneficial to obtaining the change rule of the turbulence degree along with time according to the turbulence degree result of each section of data, and provides more detailed data for analyzing the influence of the turbulence degree on the wind tunnel experiment result.
According to the method for calculating the turbulence degree of the supersonic velocity wind tunnel flow field and the hypersonic velocity wind tunnel flow field, the original total pressure data after the shock wave in the preset time period are preprocessed to decompose the wave-rear total pressure data without pulsation and the actual wave-rear total pressure pulsation data, and the influence of non-stationary signals on the calculation of the turbulence degree can be eliminated. Furthermore, the actual wavefront static pressure pulsation data corresponding to the actual post-wave total pressure pulsation data at each moment is obtained through conversion, so that the problem of low and inaccurate precision in direct measurement of the wind tunnel wavefront flow field static pressure can be avoided. Furthermore, the actual total pressure pulsation data after wave at each moment is segmented according to the characteristic time, so that the turbulence degree of the wind tunnel flow field and the rule of the change of the turbulence degree along with time can be calculated and analyzed. The embodiment of the invention can enable the calculation result of the turbulence of the wind tunnel flow field to be closer to the real situation, improve the calculation precision and provide more detailed data support for analyzing the influence of the turbulence on the wind tunnel experiment result.
In a specific embodiment, the method further comprises the following steps:
and carrying out Fourier transform according to the time interval and the turbulence degree corresponding to each data segment to obtain the frequency spectrum and the power spectrum of the turbulence degree of the wind tunnel flow field in a preset time segment.
Each data segment is segmented according to the pre-selected characteristic time, and therefore, the time interval, i.e., the time length, corresponding to each data segment may be one characteristic time or a multiple of the characteristic time. Specifically, the turbulence degree corresponding to each data segment is used as a sample parameter, a sampling interval is used according to a time interval corresponding to each data segment and is converted into a sampling frequency, and a common function in Matlab, such as a Fourier function, is used for Fourier transform, so that the frequency spectrum and the power spectrum of the turbulence degree of the wind tunnel flow field in a preset time period are calculated.
The method for calculating the turbulence of the supersonic and hypersonic wind tunnel flow field in the embodiment of the invention obtains the frequency spectrum and the power spectrum through Fourier change based on the turbulence changing along with time, thereby further obtaining the rule of the turbulence changing along with time, namely frequency spectrum distribution and power spectrum distribution, and providing more accurate basis for analyzing the influence of the turbulence of the wind tunnel flow field on the experimental result.
In a specific embodiment, the pre-obtained pressure pulsation conversion coefficient corresponding to the wind tunnel flow field is obtained based on the following steps:
step S10: according to the obtained incoming flow Mach number, the shock front total pressure, the wind tunnel flow field total temperature and the preset wave front static pressure pulsation data of the wind tunnel flow field under the current working condition, the predicted wave rear total pressure pulsation data is obtained through numerical simulation of the wind tunnel flow field.
According to the working condition of the wind tunnel flow field determined by the wind tunnel experiment, in order to obtain a more accurate pressure pulsation conversion coefficient of the wind tunnel flow field under the current working condition, the calculation can be carried out in advance through a numerical simulation experiment of the wind tunnel flow field. The preset wave front static pressure pulsation data can be set for people and is used for simulating wave front static pressure pulsation of a wind tunnel flow field. Specifically, parameters of the wind tunnel flow field under the current working condition, including incoming flow mach number, total pressure of the shock wave front, total temperature of the wind tunnel flow field and preset wave front static pressure pulsation data, of the wind tunnel flow field are input at the inlet boundary of numerical simulation, so that total pressure pulsation data after prediction wave is simulated.
Step S12: and taking the ratio of the preset wave front static pressure pulsation data to the predicted wave rear total pressure pulsation data as a pressure pulsation conversion coefficient.
According to the proportional relation among the wavefront static pressure pulsation, the post-wave total pressure pulsation and the front-back transfer function of the shock wave, namely the relation formula of the embodiment:substituting preset wavefront static pressure pulsation data with P'1Replacing P 'with predicted post-total pressure pulsation data simulated by numerical simulation'2Therefore, the ratio of the preset wave front static pressure pulsation data to the predicted wave rear total pressure pulsation data is used as a pressure pulsation conversion coefficient, namely, the corresponding pressure pulsation conversion coefficient under the current working condition of the wind tunnel flow field is determined
The method for calculating the turbulence degree of the supersonic speed and hypersonic speed wind tunnel flow field can obtain the pressure pulsation conversion coefficient with higher precision according to the specific current working condition of the wind tunnel flow field and the proportional relation between the static pressure pulsation data and the post-wave total pressure pulsation data. Therefore, actual wavefront static pressure pulsation data can be obtained according to actual total wave-rear pressure pulsation data conversion based on the pressure pulsation conversion coefficient, so that turbulence is calculated by using the actual wavefront static pressure pulsation data and the average value of wavefront static pressure, and the calculation result of the turbulence of the wind tunnel flow field is closer to the real situation.
According to the definition of the turbulence degree, the turbulence degree is calculated by pressure data, wherein the pressure data refers to static pressure data of a wind tunnel flow field, but supersonic and ultra-sonic speed wind tunnels generally adopt pitot tube measured total pressure data after a laser. Therefore, the turbulence calculated using the total pressure data after the shock wave is different from the turbulence calculated using the static pressure, and the calculation using the static pressure and the static pressure pulsation data is more consistent with the definition of the turbulence.
Referring to fig. 5, in one embodiment, the present invention further provides a device for calculating the turbulence of supersonic and hypersonic wind tunnel flow field, comprising:
the data obtaining and processing module 510 is configured to obtain original total pressure data after a shock wave in a preset time period of a wind tunnel flow field, and decompose the original total pressure data at each time into wave-rear total pressure data without a pulse and actual wave-rear total pressure pulse data.
And a pulse value conversion module 520, configured to calculate actual wavefront static pressure pulse data corresponding to each actual post-wave total pressure pulse data according to a pre-obtained pressure pulse conversion coefficient corresponding to the wind tunnel flow field and each actual post-wave total pressure pulse data at each time.
A segmenting module 530, configured to segment each actual post-total pressure ripple data into a plurality of data segments according to a pre-selected characteristic time.
And the turbulence degree calculating module 540 is configured to calculate an average value of the wavefront static pressure of the wind tunnel flow field in a preset time period according to a first preset formula and an average value of each post-wave total pressure data without pulsation, and calculate the turbulence degree corresponding to each data segment according to a second preset formula and each actual wavefront static pressure pulsation data and the average value of the wavefront static pressure.
According to the device for calculating the turbulence degree of the supersonic velocity and hypersonic velocity wind tunnel flow field, disclosed by the embodiment of the invention, the post-wave total pressure data without pulsation and the actual post-wave total pressure pulsation data are decomposed by preprocessing the original total pressure data after the shock wave in the preset time period, so that the influence of a non-stationary signal on the calculation of the turbulence degree can be eliminated. Furthermore, the actual wavefront static pressure pulsation data corresponding to the actual post-wave total pressure pulsation data at each moment is obtained through conversion, so that the problem of low and inaccurate precision in direct measurement of the wind tunnel wavefront static pressure can be avoided. Furthermore, the actual total pressure pulsation data after wave at each moment is segmented according to the characteristic time, so that the turbulence degree of the wind tunnel flow field and the rule of the change of the turbulence degree along with time can be calculated and analyzed. The embodiment of the invention can enable the calculation result of the turbulence of the wind tunnel flow field to be closer to the real situation, improve the calculation precision and provide more detailed data support for analyzing the influence of the turbulence on the wind tunnel experiment result.
In a specific embodiment, the method further comprises the following steps:
the characteristic acquisition module is used for acquiring the physical characteristic length of a specified target object in the wind tunnel flow field and the uniform incoming flow speed of the wind tunnel experiment section of the wind tunnel flow field.
And the characteristic time calculation module is used for taking the ratio of the physical characteristic length to the uniform incoming flow speed as the characteristic time.
In a specific embodiment, the method further comprises the following steps:
and the numerical simulation module is used for obtaining the total pressure pulsation data after the prediction wave through numerical simulation of the wind tunnel flow field according to the obtained incoming flow Mach number, the total pressure in the shock wave front, the total temperature of the wind tunnel flow field and the preset static pressure pulsation data of the wave front of the wind tunnel flow field under the current working condition.
And the conversion coefficient calculation module is used for taking the ratio of the preset wavefront static pressure pulsation data to the predicted post-wave total pressure pulsation data as a pressure pulsation conversion coefficient.
In a specific embodiment, the method further comprises the following steps:
and the transformation module is used for carrying out Fourier transformation according to the time interval and the turbulence degree corresponding to each data segment to obtain the frequency spectrum and the power spectrum of the turbulence degree of the wind tunnel flow field in a preset time period.
In a specific embodiment, the data acquisition processing module includes:
the first preprocessing unit is used for preprocessing the original total pressure data to obtain post-wave total pressure data without pulsation.
And the second preprocessing unit is used for subtracting the post-wave total pressure data without pulsation from the original total pressure data to obtain actual post-wave total pressure pulsation data.
The specific limitations of the calculating device for the supersonic velocity and hypersonic velocity wind tunnel flow field turbulence can be referred to the limitations of the calculating method for the supersonic velocity and hypersonic velocity wind tunnel flow field turbulence, and are not described herein again. All modules in the calculating device for the supersonic and hypersonic wind tunnel flow field turbulence can be completely or partially realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.
In one embodiment, the present invention further provides a computer device, including a memory and a processor, where the memory stores a computer program, and the processor implements the steps of the method for calculating the turbulence of the flow field of the supersonic and hypersonic wind tunnels when executing the computer program.
The computer device may be a terminal comprising a processor, a memory, a network interface, a display screen and an input means connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to realize a calculation method of the turbulence degree of the flow field of the supersonic and hypersonic wind tunnel. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.
In one implementation, a computer device is provided that includes a memory having a computer program stored therein and a processor that, when executed by the processor, implements a method of calculating a supersonic and a hypersonic wind tunnel flow field turbulence.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method can be implemented in other ways. The apparatus embodiments described above are merely illustrative and, for example, the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, each functional module or unit in each embodiment of the present invention may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention or a part of the technical solution that contributes to the prior art in essence can be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a smart phone, a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention.
Claims (10)
1. A method for calculating the turbulence degree of a supersonic velocity wind tunnel flow field and a hypersonic velocity wind tunnel flow field is characterized by comprising the following steps:
acquiring original total pressure data after a shock wave in a preset time period of a wind tunnel flow field, and decomposing the original total pressure data at each moment into wave-rear total pressure data without the shock wave and actual wave-rear total pressure shock data;
respectively calculating actual wavefront static pressure pulsation data corresponding to each actual post-wave total pressure pulsation data according to a pre-obtained pressure pulsation conversion coefficient corresponding to the wind tunnel flow field and each actual post-wave total pressure pulsation data at each moment;
dividing each actual post-wave total pressure pulsation data into a plurality of data segments according to pre-selected characteristic time;
and calculating the average value of the corresponding wave front static pressure of the wind tunnel flow field in the preset time period according to the average value of the wave rear total pressure data without pulsation and a first preset formula, and calculating the turbulence degree corresponding to each data segment according to the average value of the wave front static pressure and each actual wave front static pressure pulsation data and a second preset formula.
2. The method of claim 1, wherein the pre-selected characteristic time is obtained based on the following steps:
acquiring the physical characteristic length of a designated target object in the wind tunnel flow field and the uniform incoming flow speed of a wind tunnel experiment section of the wind tunnel flow field;
and taking the ratio of the physical characteristic length to the uniform incoming flow speed as the characteristic time.
3. The method for calculating the turbulence of the flow field of a supersonic and hypersonic wind tunnel according to claim 1, wherein the second predetermined formula is:
wherein I represents the turbulence level corresponding to each data segment,representing the average value of the corresponding wave front static pressure in the preset time period; p'1Representing the actual wavefront static pressure pulsation data.
4. The method for calculating the turbulence of the flow field of a supersonic and hypersonic wind tunnel according to claim 1, wherein the first predetermined formula is:
wherein,representing the average value of the corresponding wave front static pressure in the preset time period; ma1Representing the Mach number of the wind tunnel flow field; gamma represents a gas specific heat ratio;represents the average of the post-wave total pressure data each without pulsation.
5. The method for calculating the turbulence of the flow field of the supersonic and hypersonic wind tunnel according to claim 1, wherein the pre-obtained pressure pulsation conversion coefficient corresponding to the flow field of the wind tunnel is obtained based on the following steps:
obtaining total pressure pulsation data after prediction waves through numerical simulation of the wind tunnel flow field according to the obtained incoming flow Mach number, the shock front total pressure, the wind tunnel flow field total temperature and preset wave front static pressure pulsation data of the wind tunnel flow field under the current working condition;
and taking the ratio of the preset wavefront static pressure pulsation data to the predicted post-wave total pressure pulsation data as the pressure pulsation conversion coefficient.
6. The method for calculating the turbulence of the flow field of a supersonic and hypersonic wind tunnel according to claim 1, further comprising:
and carrying out Fourier transform according to the time interval corresponding to each data segment and the turbulence degree to obtain the frequency spectrum and the power spectrum of the turbulence degree of the wind tunnel flow field in the preset time segment.
7. The method for calculating the turbulence degree of the flow field of the supersonic and hypersonic wind tunnel according to any one of claims 1 to 6, wherein the method comprises the steps of obtaining original total pressure data after a shock wave in a preset time period of the wind tunnel flow field, and decomposing the original total pressure data at each moment into wave-following total pressure data without the shock wave and actual wave-following total pressure and shock wave data, and comprises the following steps:
preprocessing the original total pressure data to obtain post-wave total pressure data without pulsation;
and subtracting the post-wave total pressure data without pulsation from the original total pressure data to obtain the actual post-wave total pressure pulsation data.
8. The method for calculating the turbulence of the flow field of supersonic and hypersonic wind tunnels according to claim 7, wherein the preprocessing comprises any one of the following preprocessing: polynomial fitting, wavelet decomposition, and empirical mode decomposition.
9. A device for calculating the turbulence degree of a supersonic speed wind tunnel flow field and a hypersonic speed wind tunnel flow field is characterized by comprising:
the data acquisition processing module is used for acquiring original total pressure data after a wave in a preset time period of a wind tunnel flow field and decomposing the original total pressure data at each moment into wave-rear total pressure data without pulse and actual wave-rear total pressure pulse data;
the pulse value conversion module is used for respectively calculating actual wavefront static pressure pulse data corresponding to each actual post-wave total pressure pulse data according to a pre-acquired pressure pulse conversion coefficient corresponding to the wind tunnel flow field and each actual post-wave total pressure pulse data at each moment;
the segmentation module is used for dividing each actual total pressure pulsation datum after wave transmission into a plurality of data segments according to pre-selected characteristic time;
and the turbulence degree calculation module is used for calculating the average value of the wave front static pressure of the wind tunnel flow field in the preset time period according to the average value of the wave rear total pressure data without pulsation and a first preset formula, and calculating the turbulence degree corresponding to each data segment according to the average value of the wave front static pressure and each actual wave front static pressure pulsation data and a second preset formula.
10. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor when executing the computer program performs the method of calculating the turbulence of supersonic and hypersonic wind tunnel flow fields according to any one of claims 1 to 8.
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