Real-time monitoring system for three-dimensional flow field in wind tunnel based on laser Doppler velocimetry

Abstract

This invention discloses a real-time monitoring system for three-dimensional flow fields in wind tunnels based on laser Doppler velocimetry, belonging to the field of measurement technology. It includes: a region classification module; a pre-monitoring module; a gradient formation module, which forms a preliminary gradient distribution map of monitoring points based on monitored values; a monitoring formation module, which divides the control area into a conventional control area and a special control area; a model building module, which forms a velocity direction prediction model in the special control area; and a monitoring and control module. By setting up the region classification module, gradient formation module, monitoring formation module, model building module, and monitoring and control module, the adjusted target monitoring points can meet the accuracy requirements of monitoring. Simultaneously, the results from different target monitoring points differ, resulting in low data homogeneity and reducing the amount of data processing. Furthermore, it also determines the velocity direction.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, specifically to a real-time monitoring system for three-dimensional flow fields in wind tunnels based on laser Doppler velocimetry. Background Technology

[0002] Methods for measuring airflow parameters and model aerodynamic characteristics in a wind tunnel. To obtain data on the aerodynamic characteristics of an aircraft through wind tunnel experiments, it is necessary to accurately measure both the aerodynamic characteristics of the model and the airflow parameters in the wind tunnel. The aerodynamic characteristics of the model to be measured typically include forces and moments, pressure distribution, and heat flux distribution. The airflow parameters to be measured typically include pressure, temperature, density, and velocity. Among these, the measurement of velocity is the most important because changes in pressure, temperature, and density have a certain proportional relationship with velocity. Therefore, apart from the different instruments used, the setting of the monitoring points is similar.

[0003] When conducting measurements, it is necessary to ensure accuracy. However, due to the different shapes of the objects being measured, the monitoring points are different for each measurement. Increasing the number of monitoring points can improve accuracy, but it will also generate too much homogeneous data during the wind tunnel experiment, which will slow down the data processing speed. In addition, when measuring velocity, it is necessary not only to determine its value, but also its direction. Due to the different shapes of the objects being measured, it is difficult to determine the velocity direction. Summary of the Invention

[0004] To address the aforementioned technical problems, a real-time monitoring system for three-dimensional flow fields in wind tunnels based on laser Doppler velocimetry is provided. This technical solution solves the problems mentioned in the background section.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A real-time monitoring system for three-dimensional flow fields in wind tunnels based on laser Doppler velocimetry includes:

[0007] The region classification module acquires a three-dimensional model of the object being tested in the wind tunnel, and based on the three-dimensional model, analyzes and obtains at least one regular region and at least one irregular region.

[0008] A preliminary monitoring module is provided, which acquires the maximum target wind speed of the object being measured, forms at least one preliminary monitoring point in a regular area and an irregular area, and acquires the monitoring value of the preliminary monitoring point under the condition of the maximum target wind speed.

[0009] A gradient forming module, which generates a preliminary gradient distribution map of the monitoring points based on the monitored values;

[0010] The monitoring formation module acquires the allowable monitoring error of the three-dimensional flow field in the wind tunnel, forms at least one control region based on the allowable monitoring error and gradient distribution map, adjusts the preliminary monitoring points in the control region, takes the adjusted preliminary monitoring points as target monitoring points, and divides the control region into a conventional control region and a special control region.

[0011] A model building module, which forms a velocity direction prediction model in a specific control region;

[0012] The monitoring and control module sets up a laser Doppler velocimeter at the target monitoring point, uses the laser Doppler velocimeter to measure velocity, and uses a velocity direction prediction model to form the monitoring results of the target monitoring point.

[0013] Preferably, the step of analyzing and obtaining at least one regular region and at least one irregular region based on the three-dimensional model includes the following steps:

[0014] To obtain the wind speed direction during wind tunnel testing, at least one closed contour line is obtained by intersecting the surface of the 3D model with at least one equally spaced vertical plane along the wind speed direction.

[0015] Obtain the tangents of points on the closed contour line, and use the points on the closed contour line whose tangent direction is perpendicular to the direction as feature points. Use the feature points to segment the closed contour line into sampling contour lines.

[0016] At least one equally spaced feature surface perpendicular to the wind speed direction is intersected with the sampling contour line to obtain at least one sampling point. The sampling points on the sampling contour line are numbered from small to large according to the wind speed direction. The tangent plane of the 3D model at the sampling point is obtained, and the normal vector of the tangent plane at the corresponding sampling point is obtained.

[0017] When two adjacent sampling points are located on the same sampling contour line and have the same normal vector direction, the two adjacent sampling points are of the same type.

[0018] When two adjacent sampling points are located on the same feature surface and have the same normal vector direction, the two adjacent sampling points are of the same type.

[0019] By summing up adjacent sampling points that have the same relationship, we obtain a set of sampling points;

[0020] The surface area of ​​the 3D model covered by the sampling points in the sampling point set is taken as the regular area;

[0021] At least one connected portion of the surface of the 3D model other than the regular regions is considered as an irregular region.

[0022] Preferably, forming at least one preliminary monitoring point in the regular and irregular areas includes the following steps:

[0023] The sampling points with the largest and smallest numbers that are located on the same sampling contour line within the regular area are used as the initial monitoring points.

[0024] Sampling points whose tangent planes are parallel to the direction of wind speed movement within the irregular region are used as initial monitoring points.

[0025] Preferably, the step of forming a preliminary gradient distribution map of monitoring points based on monitoring values ​​includes the following steps:

[0026] Connect adjacent preliminary monitoring points located on the same sampling contour line in sequence to form at least one gradient vertical line;

[0027] Connect adjacent preliminary monitoring points located on the same feature surface in sequence to form at least one gradient horizontal line;

[0028] The difference between the monitoring values ​​of the initial monitoring points at the endpoints of the gradient vertical line is used to form the measurement gradient. The difference between the monitoring values ​​of the initial monitoring points at the endpoints of the gradient horizontal line is also used to form the measurement gradient. The measurement gradient is then assigned to the corresponding gradient vertical line or gradient horizontal line to form a gradient distribution map.

[0029] Preferably, forming at least one control region based on allowable monitoring error and gradient distribution map includes the following steps:

[0030] In regular or irregular regions, gradient vertical lines located on the same sampling contour line are merged into a gradient composite vertical line;

[0031] The maximum absolute value of the measured gradient of the horizontal gradient line connecting adjacent gradient composite vertical lines is used as the identification value.

[0032] In regular or irregular regions, obtain all possible combinations of gradient synthesis vertical lines, and use the gradient synthesis vertical lines in the possible combinations to divide the regular or irregular regions into at least one preparatory region.

[0033] The identification values ​​of adjacent gradient composite vertical lines in the preparatory region are accumulated to obtain the screening value of the preparatory region;

[0034] The error coefficient of the possible combination of cases is obtained by subtracting the screening value of the preparatory area corresponding to the possible combination of cases from the allowable monitoring error and taking the mean value.

[0035] The preparatory region corresponding to the possible combination with the smallest error coefficient is taken as the control region.

[0036] Preferably, adjusting the initial monitoring points in the control area includes the following steps:

[0037] Delete the initial monitoring points of the gradient horizontal lines and their endpoints that do not touch the edge of the control area. When the initial monitoring points at both ends of the gradient vertical lines are deleted, delete the gradient vertical lines.

[0038] When the absolute value of the measured gradient of the gradient vertical line in the control area is greater than the allowable monitoring error, the absolute value of the measured gradient and the allowable monitoring error are rounded to obtain the target value.

[0039] At least one identification point is uniformly selected on the gradient vertical line where the measured gradient exceeds the allowable monitoring error. The number of identification points is equal to the target value. The identification points are used as additional locations for the initial monitoring points.

[0040] When the absolute value of the measured gradient of the gradient line in the control area does not exceed the allowable monitoring error, only one of the initial monitoring points at both ends of the gradient line is retained.

[0041] Preferably, dividing the control area into a conventional control area and a special control area includes the following steps:

[0042] The control area generated by the irregular region and facing the direction of wind speed movement is regarded as the special control area;

[0043] The irregular area that is generated and is in the opposite direction of wind speed movement is taken as the regular control area;

[0044] The control region generated by the rule region is used as the regular control region.

[0045] Preferably, forming a velocity direction prediction model in the specific control region includes the following steps:

[0046] Within a specific control area, at least one sample point is taken, and the tangent plane of the 3D model at the sample point is obtained as the sample plane.

[0047] The angle between the sample plane and the direction of wind speed movement is obtained as the feature angle. The average value of the feature angles corresponding to the sample points in the special control area is taken to obtain the sample angle.

[0048] Use twice the sample angle as the direction prediction angle.

[0049] Preferably, the speed measurement using a laser Doppler velocimeter includes the following steps:

[0050] During wind speed testing, scattering particles are added to the air fluid, and the concentration of the scattering particles is controlled to ensure that when the wind speed remains constant, the change in the measured value of the laser Doppler velocimeter is less than the allowable monitoring error.

[0051] Preferably, the process of using a velocity direction prediction model to generate monitoring results for the target monitoring point includes the following steps:

[0052] Obtain the measured velocity value of the target monitoring point in the special control area. When the target monitoring point is in the regular control area, the direction of the measured velocity value is along the direction of wind speed movement.

[0053] When the target monitoring point is in a special control area, the angle between the direction of the measured velocity value and the direction of wind movement is the direction prediction angle.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0055] By setting up modules for region classification, gradient formation, monitoring formation, model building, and monitoring control, different monitoring points can be set according to the 3D model of the object being measured. More monitoring points can be set in areas with large velocity changes, and fewer monitoring points can be set in areas with small velocity changes. Through analysis of the preliminary monitoring results, the preliminary monitoring points can be adjusted so that the adjusted target monitoring points can meet the monitoring accuracy requirements. At the same time, the results of the target monitoring points are different from each other, and the data homogeneity is small, resulting in high data quality and reducing the amount of data processing. In addition, the direction of velocity can be determined based on physical knowledge and different monitoring areas, thereby improving the completeness of monitoring data. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the real-time monitoring system for three-dimensional flow field in a wind tunnel based on laser Doppler velocimetry, according to the present invention.

[0057] Figure 2 This is a schematic diagram of the process of obtaining at least one regular region and at least one irregular region based on a three-dimensional model according to the present invention.

[0058] Figure 3 This is a schematic diagram of the process of forming at least one preliminary monitoring point in a regular area and an irregular area according to the present invention;

[0059] Figure 4 This is a schematic diagram of the process of generating a gradient distribution map of preliminary monitoring points based on monitoring values ​​according to the present invention;

[0060] Figure 5 This is a schematic diagram of the process of forming at least one control region based on the allowable monitoring error and gradient distribution map of the present invention;

[0061] Figure 6 This is a schematic diagram illustrating the process of adjusting the initial monitoring points in the control area according to the present invention;

[0062] Figure 7This is a flowchart illustrating how the control area is divided into a conventional control area and a special control area according to the present invention.

[0063] Figure 8 This is a schematic diagram of the process of forming a velocity direction prediction model in a special control region according to the present invention;

[0064] Figure 9 This is a schematic diagram illustrating the process of using the velocity direction prediction model of the present invention to generate monitoring results for target monitoring points. Detailed Implementation

[0065] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0066] Reference Figure 1 As shown, the wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry includes:

[0067] The region classification module acquires a three-dimensional model of the object being tested in the wind tunnel, and based on the three-dimensional model, analyzes and obtains at least one regular region and at least one irregular region.

[0068] A preliminary monitoring module is provided, which acquires the maximum target wind speed of the object being measured, forms at least one preliminary monitoring point in a regular area and an irregular area, and acquires the monitoring value of the preliminary monitoring point under the condition of the maximum target wind speed.

[0069] A gradient forming module, which generates a preliminary gradient distribution map of the monitoring points based on the monitored values;

[0070] The monitoring formation module acquires the allowable monitoring error of the three-dimensional flow field in the wind tunnel, forms at least one control region based on the allowable monitoring error and gradient distribution map, adjusts the preliminary monitoring points in the control region, takes the adjusted preliminary monitoring points as target monitoring points, and divides the control region into a conventional control region and a special control region.

[0071] A model building module, which forms a velocity direction prediction model in a specific control region;

[0072] The monitoring and control module sets up a laser Doppler velocimeter at the target monitoring point, uses the laser Doppler velocimeter to measure velocity, and uses a velocity direction prediction model to form the monitoring results of the target monitoring point.

[0073] When measuring different objects, their structures vary. Typically, some parts are flat, while others are irregular. In flat areas, wind speed changes are small, so fewer monitoring points are needed; otherwise, the data would be highly homogenized. The specific number of monitoring points needs to be determined based on the measurement results. For irregular areas, due to the large speed variations, more monitoring points are required. In this scheme, corresponding steps are set up to systematically set up monitoring points for different objects, ensuring that the number of points is sufficiently small while maintaining the required measurement accuracy. A small number of monitoring points will significantly impact wind tunnel experiments because measurements are taken under different wind speed conditions, generating many sets of data. When each set of data contains a large amount of homogenous data, the amount of data that needs to be processed will increase significantly.

[0074] Reference Figure 2 As shown, based on the 3D model, the analysis to obtain at least one regular region and at least one irregular region includes the following steps:

[0075] To obtain the wind speed direction during wind tunnel testing, at least one closed contour line is obtained by intersecting the surface of the 3D model with at least one equally spaced vertical plane along the wind speed direction.

[0076] Obtain the tangents of points on the closed contour line, and use the points on the closed contour line whose tangent direction is perpendicular to the direction as feature points. Use the feature points to segment the closed contour line into sampling contour lines.

[0077] At least one equally spaced feature surface perpendicular to the wind speed direction is intersected with the sampling contour line to obtain at least one sampling point. The sampling points on the sampling contour line are numbered from small to large according to the wind speed direction. The tangent plane of the 3D model at the sampling point is obtained, and the normal vector of the tangent plane at the corresponding sampling point is obtained.

[0078] When two adjacent sampling points are located on the same sampling contour line and have the same normal vector direction, the two adjacent sampling points are of the same type.

[0079] When two adjacent sampling points are located on the same feature surface and have the same normal vector direction, the two adjacent sampling points are of the same type.

[0080] By summing up adjacent sampling points that have the same relationship, we obtain a set of sampling points;

[0081] The surface area of ​​the 3D model covered by the sampling points in the sampling point set is taken as the regular area;

[0082] At least one connected portion of the surface of the 3D model other than the regular regions is considered as an irregular region.

[0083] The distinction between regular and irregular regions is mainly based on the direction of their normal vectors. To understand the above method, consider two cases as examples. The first is a horizontal cylinder whose side is parallel to the wind direction. Using the above method, the sampling points on the side of the cylinder are all of the same type, so it is identified as a regular region, and fewer initial monitoring points can be set. The second is a sphere, where the sampling points are not of the same type, so it is identified as an irregular region.

[0084] Reference Figure 3 As shown, forming at least one preliminary monitoring point in both regular and irregular areas includes the following steps:

[0085] The sampling points with the largest and smallest numbers that are located on the same sampling contour line within the regular area are used as the initial monitoring points.

[0086] Sampling points whose tangent planes are parallel to the direction of wind speed movement within the irregular region are used as initial monitoring points.

[0087] The changes in the regular area are regular. Therefore, the sampling points with the largest and smallest numbers that are located on the same sampling contour line within the regular area are taken as the initial monitoring points. Here, two edge points along the wind speed movement direction in the regular area are selected because the data of the initial monitoring points on the same sampling contour line change linearly. Based on the condition of the maximum target wind speed, the monitoring values ​​of the initial monitoring points are obtained, and the initial monitoring points can be added through the linear relationship.

[0088] The changes in irregular areas are irregular. Sampling points in irregular areas with tangent planes parallel to the wind speed direction are used as initial monitoring points. The reason for this is that, due to the way the initial monitoring points are set, the irregular area between two adjacent initial monitoring points must face the wind speed direction or face away from the wind speed direction. There will not be a situation where both situations occur simultaneously. When an area contains both faces facing the wind speed direction and faces away from the wind speed direction, there will inevitably be points with tangent planes parallel to the wind speed direction during the change process. Therefore, the situation between adjacent initial monitoring points can also be regarded as approximately linear, and subsequent additions of initial monitoring points can be made based on the linear relationship.

[0089] Reference Figure 4 As shown, the process of creating a preliminary gradient distribution map of monitoring points based on the monitored values ​​includes the following steps:

[0090] Connect adjacent preliminary monitoring points located on the same sampling contour line in sequence to form at least one gradient vertical line;

[0091] Connect adjacent preliminary monitoring points located on the same feature surface in sequence to form at least one gradient horizontal line;

[0092] The difference between the monitoring values ​​of the initial monitoring points at the endpoints of the gradient vertical line is used to form the measurement gradient. The difference between the monitoring values ​​of the initial monitoring points at the endpoints of the gradient horizontal line is also used to form the measurement gradient. The measurement gradient is then assigned to the corresponding gradient vertical line or gradient horizontal line to form a gradient distribution map.

[0093] The measurement gradient is the difference between the monitoring data of two adjacent preliminary monitoring points. It can be used to determine the difference between the monitoring data of two preliminary monitoring points. When the difference is very small, one of them can be deleted.

[0094] Reference Figure 5 As shown, forming at least one control region based on the allowable monitoring error and gradient distribution map includes the following steps:

[0095] In regular or irregular regions, gradient vertical lines located on the same sampling contour line are merged into a gradient composite vertical line;

[0096] The maximum absolute value of the measured gradient of the horizontal gradient line connecting adjacent gradient composite vertical lines is used as the identification value.

[0097] In regular or irregular regions, obtain all possible combinations of gradient synthesis vertical lines, and use the gradient synthesis vertical lines in the possible combinations to divide the regular or irregular regions into at least one preparatory region.

[0098] The identification values ​​of adjacent gradient composite vertical lines in the preparatory region are accumulated to obtain the screening value of the preparatory region;

[0099] The error coefficient of the possible combination of cases is obtained by subtracting the screening value of the preparatory area corresponding to the possible combination of cases from the allowable monitoring error and taking the mean value.

[0100] The preparatory region corresponding to the possible combination with the smallest error coefficient is taken as the control region.

[0101] The sampling outline and sampling points are set relatively densely because, in order to obtain the required monitoring points, an excessive number of sampling points need to be set initially to form preliminary monitoring points. Since the monitoring value of the preliminary monitoring point only occurs once under the condition of maximum target wind speed, even if more monitoring points are set, it will not have a significant impact. However, the target monitoring points obtained based on this condition analysis can meet all measurement conditions because the remaining wind speeds are smaller, and the error of the target monitoring points is smaller.

[0102] The sampling contour lines are set relatively densely, and the preliminary monitoring points connected by gradient horizontal lines in adjacent sampling contour lines can be merged. Therefore, the control area is divided as described above.

[0103] Reference Figure 6As shown, adjusting the initial monitoring points in the control area includes the following steps:

[0104] Delete the initial monitoring points of the gradient horizontal lines and their endpoints that do not touch the edge of the control area. When the initial monitoring points at both ends of the gradient vertical lines are deleted, delete the gradient vertical lines.

[0105] When the absolute value of the measured gradient of the gradient vertical line in the control area is greater than the allowable monitoring error, the absolute value of the measured gradient and the allowable monitoring error are rounded to obtain the target value.

[0106] At least one identification point is uniformly selected on the gradient vertical line where the measured gradient exceeds the allowable monitoring error. The number of identification points is equal to the target value. The identification points are used as additional locations for the initial monitoring points.

[0107] When the absolute value of the measured gradient of the gradient line in the control area does not exceed the allowable monitoring error, only one of the initial monitoring points at both ends of the gradient line is retained.

[0108] The distance between the initial monitoring points set along the wind speed direction may be large, and therefore the difference may be significant. Thus, it is necessary to analyze the acquired monitoring results to determine whether additional monitoring points need to be added. When adding additional monitoring points, the linear relationship should be considered. This ensures that the difference between the monitoring results of adjacent initial monitoring points along the wind speed direction after the addition is small. Therefore, the monitoring results of all initial monitoring points can be used to characterize the overall situation of the area, and the error is very small.

[0109] Reference Figure 7 As shown, dividing the control area into a regular control area and a special control area includes the following steps:

[0110] The control area generated by the irregular region and facing the direction of wind speed movement is regarded as the special control area;

[0111] The irregular area that is generated and is in the opposite direction of wind speed movement is taken as the regular control area;

[0112] The control region generated by the rule region is used as the regular control region.

[0113] The special control area faces the direction of wind movement. The wind direction will change due to an impact. Therefore, the wind direction of the special control area needs to be determined separately. The other areas do not have the impact and therefore maintain the direction of wind movement.

[0114] Reference Figure 8 As shown, in the specific control region, forming a velocity direction prediction model includes the following steps:

[0115] Within a specific control area, at least one sample point is taken, and the tangent plane of the 3D model at the sample point is obtained as the sample plane.

[0116] The angle between the sample plane and the direction of wind speed movement is obtained as the feature angle. The average value of the feature angles corresponding to the sample points in the special control area is taken to obtain the sample angle.

[0117] Use twice the sample angle as the direction prediction angle.

[0118] Based on the relationship that the incident angle and the reflection angle of the impact are equal, it is easy to know through geometric construction that the direction prediction angle is the angle between the velocity after the impact and the direction of wind speed.

[0119] The steps involved in measuring speed using a laser Doppler velocimeter are as follows:

[0120] During wind speed testing, scattering particles are added to the air fluid, and the concentration of the scattering particles is controlled to ensure that when the wind speed remains constant, the change in the measured value of the laser Doppler velocimeter is less than the allowable monitoring error.

[0121] Laser Doppler velocimeters cannot directly identify airflow. They need to mix scattered particles into the air of a wind tunnel experiment and identify the velocity of the scattered particles to determine the velocity at various points on the object being measured.

[0122] Reference Figure 9 As shown, the process of generating monitoring results for target monitoring points using a velocity direction prediction model includes the following steps:

[0123] Obtain the measured velocity value of the target monitoring point in the special control area. When the target monitoring point is in the regular control area, the direction of the measured velocity value is along the direction of wind speed movement.

[0124] When the target monitoring point is in a special control area, the angle between the direction of the measured velocity value and the direction of wind movement is the direction prediction angle.

[0125] Furthermore, this solution also proposes a storage medium on which a computer-readable program is stored. When the computer-readable program is invoked, it executes the aforementioned real-time monitoring system for three-dimensional flow fields in a wind tunnel based on laser Doppler velocimetry.

[0126] It is understandable that the storage medium can be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; an optical medium, such as a DVD; or a semiconductor medium, such as a solid-state drive (SSD).

[0127] In summary, the advantages of this invention are as follows: by setting up a region classification module, a gradient formation module, a monitoring formation module, a model building module, and a monitoring control module, different monitoring points can be set according to the three-dimensional model of the object being measured. More monitoring points can be set in areas with large velocity changes, and fewer monitoring points can be set in areas with small velocity changes. Through the analysis of the preliminary monitoring results, the preliminary monitoring points can be adjusted so that the adjusted target monitoring points can meet the monitoring accuracy requirements. At the same time, there are differences between the results of the target monitoring points, and the data homogeneity is small, resulting in high data quality and reducing the amount of data processing. In addition, the direction of velocity can be determined based on physical knowledge and different monitoring areas, thereby improving the completeness of monitoring data.

[0128] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A real-time monitoring system for three-dimensional flow field in a wind tunnel based on laser Doppler velocimetry, characterized in that, include: The region classification module acquires a three-dimensional model of the object being tested in the wind tunnel, and based on the three-dimensional model, analyzes and obtains at least one regular region and at least one irregular region. A preliminary monitoring module is provided, which acquires the maximum target wind speed of the object being measured, forms at least one preliminary monitoring point in a regular area and an irregular area, and acquires the monitoring value of the preliminary monitoring point under the condition of the maximum target wind speed. A gradient forming module, which generates a preliminary gradient distribution map of the monitoring points based on the monitored values; The monitoring formation module acquires the allowable monitoring error of the three-dimensional flow field in the wind tunnel, forms at least one control region based on the allowable monitoring error and gradient distribution map, adjusts the preliminary monitoring points in the control region, takes the adjusted preliminary monitoring points as target monitoring points, and divides the control region into a conventional control region and a special control region. A model building module, which forms a velocity direction prediction model in a specific control region; The monitoring and control module sets up a laser Doppler velocimeter at the target monitoring point, uses the laser Doppler velocimeter to measure velocity, and uses a velocity direction prediction model to form the monitoring results of the target monitoring point; The process of analyzing and obtaining at least one regular region and at least one irregular region based on a three-dimensional model includes the following steps: To obtain the wind speed direction during wind tunnel testing, at least one closed contour line is obtained by intersecting the surface of the 3D model with at least one equally spaced vertical plane along the wind speed direction. Obtain the tangents of points on the closed contour line, and use the points on the closed contour line whose tangent direction is perpendicular to the direction as feature points. Use the feature points to segment the closed contour line into sampling contour lines. At least one equally spaced feature surface perpendicular to the wind speed direction is intersected with the sampling contour line to obtain at least one sampling point. The sampling points on the sampling contour line are numbered from small to large according to the wind speed direction. The tangent plane of the 3D model at the sampling point is obtained, and the normal vector of the tangent plane at the corresponding sampling point is obtained. When two adjacent sampling points are located on the same sampling contour line and have the same normal vector direction, the two adjacent sampling points are of the same type. When two adjacent sampling points are located on the same feature surface and have the same normal vector direction, the two adjacent sampling points are of the same type. By summing up adjacent sampling points that have the same relationship, we obtain a set of sampling points; The surface area of ​​the 3D model covered by the sampling points in the sampling point set is taken as the regular area; At least one connected portion of the surface of the 3D model other than the regular regions is considered an irregular region. The process of dividing the control area into a conventional control area and a special control area includes the following steps: The control area generated by the irregular region and facing the direction of wind speed movement is regarded as the special control area; The irregular area that is generated and is in the opposite direction of wind speed movement is taken as the regular control area; The control region generated by the rule region is used as the regular control region.

2. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 1, characterized in that, The process of establishing at least one preliminary monitoring point in both regular and irregular areas includes the following steps: The sampling points with the largest and smallest numbers that are located on the same sampling contour line within the regular area are used as the initial monitoring points. Sampling points whose tangent planes are parallel to the direction of wind speed movement within the irregular region are used as initial monitoring points.

3. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 2, characterized in that, The process of generating a preliminary gradient distribution map of monitoring points based on monitoring values ​​includes the following steps: Connect adjacent preliminary monitoring points located on the same sampling contour line in sequence to form at least one gradient vertical line; Connect adjacent preliminary monitoring points located on the same feature surface in sequence to form at least one gradient horizontal line; The difference between the monitoring values ​​of the initial monitoring points at the endpoints of the gradient vertical line is used to form the measurement gradient. The difference between the monitoring values ​​of the initial monitoring points at the endpoints of the gradient horizontal line is also used to form the measurement gradient. The measurement gradient is then assigned to the corresponding gradient vertical line or gradient horizontal line to form a gradient distribution map.

4. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 3, characterized in that, The process of forming at least one control region based on allowable monitoring error and gradient distribution map includes the following steps: In regular or irregular regions, gradient vertical lines located on the same sampling contour line are merged into a gradient composite vertical line; The maximum absolute value of the measured gradient of the horizontal gradient line connecting adjacent gradient composite vertical lines is used as the identification value. In regular or irregular regions, obtain all possible combinations of gradient synthesis vertical lines, and use the gradient synthesis vertical lines in the possible combinations to divide the regular or irregular regions into at least one preparatory region. The identification values ​​of adjacent gradient composite vertical lines in the preparatory region are accumulated to obtain the screening value of the preparatory region; The error coefficient of the possible combination of cases is obtained by subtracting the screening value of the preparatory area corresponding to the possible combination of cases from the allowable monitoring error and taking the mean value. The preparatory region corresponding to the possible combination with the smallest error coefficient is taken as the control region.

5. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 4, characterized in that, The adjustment of the initial monitoring points in the control area includes the following steps: Delete the initial monitoring points of the gradient horizontal lines and their endpoints that do not touch the edge of the control area. When the initial monitoring points at both ends of the gradient vertical lines are deleted, delete the gradient vertical lines. When the absolute value of the measured gradient of the gradient vertical line in the control area is greater than the allowable monitoring error, the absolute value of the measured gradient and the allowable monitoring error are rounded to obtain the target value. At least one identification point is uniformly selected on the gradient vertical line where the measured gradient exceeds the allowable monitoring error. The number of identification points is equal to the target value. The identification points are used as additional locations for the initial monitoring points. When the absolute value of the measured gradient of the gradient line in the control area does not exceed the allowable monitoring error, only one of the initial monitoring points at both ends of the gradient line is retained.

6. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 5, characterized in that, The process of forming a velocity direction prediction model in the specific control region includes the following steps: Within a specific control area, at least one sample point is taken, and the tangent plane of the 3D model at the sample point is obtained as the sample plane. The angle between the sample plane and the direction of wind speed movement is obtained as the feature angle. The average value of the feature angles corresponding to the sample points in the special control area is taken to obtain the sample angle. Use twice the sample angle as the direction prediction angle.

7. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 6, characterized in that, The speed measurement using a laser Doppler velocimeter includes the following steps: During wind speed testing, scattering particles are added to the air fluid, and the concentration of the scattering particles is controlled to ensure that when the wind speed remains constant, the change in the measured value of the laser Doppler velocimeter is less than the allowable monitoring error.

8. The wind tunnel three-dimensional flow field real-time monitoring system based on laser Doppler velocimetry according to claim 7, characterized in that, The process of using a velocity direction prediction model to generate monitoring results for target monitoring points includes the following steps: Obtain the measured velocity value of the target monitoring point in the special control area. When the target monitoring point is in the regular control area, the direction of the measured velocity value is along the direction of wind speed movement. When the target monitoring point is in a special control area, the angle between the direction of the measured velocity value and the direction of wind movement is the direction prediction angle.

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