Flow field velocity and temperature synchronous measurement method, device and storage medium

Abstract

The present application provides a method, device and storage medium for synchronously measuring flow field velocity and temperature. The method includes: determining the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; determining the velocity of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; determining the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; determining the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship; determining the velocity and temperature of the flow field to be measured according to the velocity of the target temperature-sensitive phosphorescent particle and the temperature of the target temperature-sensitive phosphorescent particle. The method of the present application avoids interference with the flow field and improves measurement accuracy.

Description

Technical Field

[0001] The present application relates to the field of measurement technology, and in particular to a method, device and storage medium for synchronously measuring flow field velocity and temperature. Background Art

[0002] In the fields of aerospace, electrical and electronics, energy production, and other engineering fields, there are various complex scenarios where heat transfer and flow are coupled, such as film cooling of engine blades, near-wall heat flow of hypersonic vehicles, and microfluidic cooling of electronic devices. These flow processes involve the interaction of multiple parameters such as temperature and velocity. Synchronous measurement of the velocity and temperature of the flow field helps to deepen the understanding of the coupling mechanism between heat transfer and flow.

[0003] At present, separate flow field velocity measurement methods and temperature measurement methods have become relatively mature. In the existing technology, the velocity of a single point in the fluid flow is generally measured based on devices such as hot wire or laser Doppler velocimeters, and the temperature of each point in the fluid flow is measured using methods such as thermocouples or laser induced fluorescence.

[0004] However, the technology for synchronous measurement of flow field velocity and temperature is still in the development stage. The existing methods for synchronous measurement of flow field velocity and temperature have technical problems such as limited measurement range and large errors in velocity and temperature measurement. Summary of the invention

[0005] The present application provides a method, device and storage medium for synchronously measuring flow field velocity and temperature, so as to solve the technical problem of large errors in velocity and temperature measurement existing in the prior art.

[0006] In a first aspect, the present application provides a method for synchronously measuring flow field velocity and temperature, comprising:

[0007] Determine the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, where the particle time-series frame image is an image obtained by continuously sampling multiple frames of the phosphorescence attenuation process of the target temperature-sensitive phosphorescent particle in the flow field to be measured;

[0008] Determine the speed of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image;

[0009] According to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, the attenuation slope constant of the target temperature-sensitive phosphorescent particle is determined;

[0010] Determining the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship, wherein the corresponding relationship represents the corresponding relationship between the attenuation slope constant of the temperature-sensitive phosphorescent particle and the temperature;

[0011] The velocity and temperature of the flow field to be measured are determined according to the velocity of the target temperature-sensitive phosphorescent particles and the temperature of the target temperature-sensitive phosphorescent particles.

[0012] In a possible design of the first aspect, determining the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image includes:

[0013] Performing enhancement processing on the initial particle time-series frame image to obtain a first initial particle time-series frame image;

[0014] Performing expansion processing on the first initial particle time-series frame image to obtain a second initial particle time-series frame image;

[0015] Comparing the first initial particle time-series frame image with the second initial particle time-series frame image, determining the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle;

[0016] According to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle, the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle are determined.

[0017] In a possible design of the first aspect, determining the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle according to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle includes:

[0018] Screening the initial temperature-sensitive phosphorescent particles according to the grayscale of the initial temperature-sensitive phosphorescent particles and a preset grayscale threshold to obtain initial target temperature-sensitive phosphorescent particles, wherein the preset grayscale threshold is determined according to the type of the initial temperature-sensitive phosphorescent particles;

[0019] According to the two-dimensional Gaussian template, the initial coordinates and grayscale of the initial target temperature-sensitive phosphorescent particles are fitted to obtain the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles;

[0020] Determine the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle;

[0021] According to the grayscale of the initial target temperature-sensitive phosphorescent particle, the grayscale change of the target temperature-sensitive phosphorescent particle is determined.

[0022] In a possible design of the first aspect, determining the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle includes:

[0023] Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image, wherein the first initial target time-sequential frame image to the fourth initial target time-sequential frame image are four frames of images that are adjacent in time sequence;

[0024] Determining an initial motion trajectory of the initial target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image;

[0025] Determining the speed of the initial target temperature-sensitive phosphorescent particle according to the initial motion trajectory of the initial target temperature-sensitive phosphorescent particle;

[0026] According to the speed of the initial target temperature-sensitive phosphorescent particles, the initial target temperature-sensitive phosphorescent particles are screened to determine the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles;

[0027] Determining the acceleration of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image;

[0028] According to the speed and acceleration of the target temperature-sensitive phosphorescent particle, the motion trajectory of the target temperature-sensitive phosphorescent particle is obtained.

[0029] In a possible design of the first aspect, determining the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image includes:

[0030] Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-series frame image, the corresponding neighbor particles, and the first coordinate position of the neighbor particles, wherein the neighbor particles represent particles within a preset distance from the initial target temperature-sensitive phosphorescent particle;

[0031] According to the initial target temperature-sensitive phosphorescent particle and the neighbor particle, determining a second coordinate position of the neighbor particle in a second initial target time-series frame image;

[0032] Determine the target displacement according to the first coordinate position and the second coordinate position;

[0033] The sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image and the target displacement are determined in the third initial target time-sequential frame image to the fourth initial target time-sequential frame image.

[0034] In a possible design of the first aspect, the initial target temperature-sensitive phosphorescent particles are screened according to the speed of the initial target temperature-sensitive phosphorescent particles to determine the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles, including:

[0035] Determine the velocity of neighbor particles of the initial target temperature-sensitive phosphorescent particle;

[0036] According to the speed of neighbor particles, determine the speed range of neighbor particles and the median of the speed range;

[0037] According to the velocity of the neighbor particle and the median of the velocity range, the velocity residual range and the median of the velocity residual range of the neighbor particle are determined;

[0038] Determine the velocity residual of the initial target temperature-sensitive phosphorescent particle according to the velocity of the neighboring particles, the median of the velocity range, and the median of the velocity residual range;

[0039] The initial target temperature-sensitive phosphorescent particles are screened according to the velocity residual of the initial target temperature-sensitive phosphorescent particles and a preset velocity residual threshold, and the target temperature-sensitive phosphorescent particles in the initial target temperature-sensitive phosphorescent particles and the velocity of the target temperature-sensitive phosphorescent particles are determined.

[0040] In a possible design of the first aspect, determining the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image includes:

[0041] Determine the grayscale of the target temperature-sensitive phosphorescent particle in the target particle time-series frame image;

[0042] According to the relationship between the luminescence intensity and time of the target temperature-sensitive phosphorescent particle, as well as the grayscale in the target particle time-series frame image and the corresponding target time, the luminescence lifetime and attenuation slope constant of the target temperature-sensitive phosphorescent particle are determined.

[0043] In a possible design of the first aspect, determining the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship includes:

[0044] Determine the fitting relationship between the flow field temperature under standard conditions and the corresponding attenuation slope constant;

[0045] The temperature of the target temperature-sensitive phosphorescent particle is determined according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and the fitting relationship between the standard flow field temperature and the corresponding attenuation slope constant.

[0046] In a second aspect, the present application provides a flow field velocity and temperature synchronous measurement device, comprising:

[0047] The first determination module is used to determine the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, where the particle time-series frame image is an image obtained by continuously sampling multiple frames of the phosphorescence attenuation process of the target temperature-sensitive phosphorescent particle in the flow field to be measured;

[0048] A second determination module is used to determine the speed of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image;

[0049] A third determination module is used to determine the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image;

[0050] A fourth determination module is used to determine the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship, wherein the corresponding relationship represents the corresponding relationship between the attenuation slope constant of the temperature-sensitive phosphorescent particle and the temperature;

[0051] The fifth determination module is used to determine the speed and temperature of the flow field to be measured according to the speed of the target temperature-sensitive phosphorescent particles and the temperature of the target temperature-sensitive phosphorescent particles.

[0052] In a third aspect, the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the above first aspect and / or various possible implementations of the first aspect.

[0053] The present application provides a method, device and storage medium for synchronously measuring flow field velocity and temperature, which perform continuous multi-frame sampling of the phosphorescence emitted by thermosensitive phosphorescent particles in the flow field, obtain the particle velocity by tracing the motion trajectory of the thermosensitive phosphorescent particles in the particle time-series frame image, and accurately obtain the particle grayscale and its grayscale attenuation process during the motion process, calculate the attenuation slope constant of the thermosensitive phosphorescent particles according to the grayscale change of the particles, and then obtain the temperature of the thermosensitive phosphorescent particles according to the corresponding relationship between the attenuation slope constant and the temperature of the thermosensitive phosphorescent particles. Since the thermosensitive phosphorescent particles have good velocity following and temperature following properties, the velocity and temperature of the phosphorescent particles can be used to represent the velocity and temperature of the particle position in the flow field at that moment, thereby realizing synchronous measurement of the flow field velocity and temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0055] Figure 1 A schematic diagram of an application scenario of the method for synchronously measuring flow field velocity and temperature provided in an embodiment of the present application;

[0056] Figure 2 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 1 ;

[0057] Figure 3 A temperature-attenuation slope constant calibration curve diagram provided for an embodiment of the present application;

[0058] Figure 4The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 2 ;

[0059] Figure 5 A timing diagram of synchronous measurement of flow field velocity and temperature provided in an embodiment of the present application;

[0060] Figure 6 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 3 ;

[0061] Figure 7 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 4 ;

[0062] Figure 8 A diagram showing the synchronous measurement results of the velocity field and temperature field of the cold jet provided in the embodiment of the present application;

[0063] Fig. 9 A schematic diagram of the structure of a device for synchronously measuring flow field velocity and temperature provided in an embodiment of the present application.

[0064] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0065] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0066] First, the terms involved in this application are explained:

[0067] Thermosensitive phosphorescent particles: refers to a type of phosphorescent particle with temperature response characteristics. It is composed of solid crystal materials doped with rare earth or transition metal ions. It can emit phosphorescence after being acted upon by excitation light of a specific wavelength. Its phosphorescence signal characteristics such as luminescence lifetime, luminescence wavelength, and luminescence intensity will change with changes in temperature.

[0068] Flow field: refers to the flow state and distribution of liquid or gas in space.

[0069] At present, the individual flow field velocity measurement methods and temperature measurement methods are relatively mature, but the technology for synchronous measurement of flow field velocity and temperature is still in the development stage. In the existing technology, the velocity distribution of a single point in the fluid flow is generally measured based on equipment such as hot wires or laser Doppler velocimeters, and the temperature of each point in the fluid flow is measured using methods such as thermocouples or laser induced fluorescence, but these velocity and temperature measurement methods cannot be simply combined to achieve synchronous measurement of flow field velocity and temperature. In the existing synchronous measurement technology, the two-dimensional probe method is an invasive measurement method that can only measure a limited number of discrete points and is prone to interfere with the flow field. The cross-correlation technology used in the three-dimensional flow field velocity and temperature measurement method based on the light field camera will result in a low spatial resolution of the velocity measurement, and the particle tailing problem caused by the long-term exposure of the image will result in a small velocity measurement range and large velocity and temperature measurement errors.

[0070] The method for synchronously measuring flow field velocity and temperature provided in the present application realizes synchronous measurement of flow field velocity and temperature by using phosphorescent particles whose decay lifetime decreases as temperature increases as tracer particles to be sown into the flow field, and combining particle tracking velocity measurement technology and thermal imaging temperature measurement technology based on phosphorescent lifetime decay method of multi-frame particle images. The method is non-contact, has no interference with the flow field, and can realize instantaneous surface measurement of velocity field and temperature field. At the same time, the particle tracking velocity measurement method is used to measure the velocity field, and the flow field velocity is obtained by tracking the motion trajectory of a single particle in a multi-frame image, which can achieve a sub-pixel spatial resolution of measurement and improve the measurement resolution. Due to continuous multi-frame sampling, the phosphorescent decay process of each particle can be tracked, so that the decay lifetime of the phosphorescent particles can be calculated using multi-frame particle images. The image exposure time is short, which avoids the influence of particle tailing, and the number of fitting points is more, which can effectively reduce the influence of noise, so it has a larger velocity measurement range and higher measurement accuracy.

[0071] Figure 1 Schematic diagram of the application scenario of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application. Figure 1 As shown, the application scenario of the solution provided in this application includes a high-speed camera 101, an ultraviolet laser 102, and a control host 103.

[0072] The control host 103 can send control signals to the high-speed camera 101 and the ultraviolet laser 102 at the same time. After receiving the control signal, the ultraviolet laser 102 sends out a laser pulse, which can instantly illuminate the flow field area A to be measured. The phosphorescent particles in the flow field area A to be measured emit phosphorescence after being excited. The high-speed camera 101 focuses on the area A to be measured. After receiving the control signal from the control host 103, the high-speed camera 101 starts to collect the luminescence process of the phosphorescent particles. A bandpass filter is installed on the camera lens to filter stray light of other wavelengths. After the acquisition is completed, the high-speed camera 101 transmits the image to the control host 103, and the control host 103 completes the subsequent image processing.

[0073] although Figure 1 Only one high-speed camera 101 , laser 102 , and control host 103 are shown in the figure, but it should be understood that there may be two or more high-speed cameras 101 , laser 102 , and control host 103 .

[0074] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0075] Figure 2 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 1 .

[0076] like Figure 2 As shown, the method may include:

[0077] S201, determining the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, where the particle time-series frame image is an image obtained by continuously sampling multiple frames of the phosphorescence attenuation process of the target temperature-sensitive phosphorescent particle in the flow field to be measured.

[0078] Among them, the target thermosensitive phosphorescent particles can refer to the thermosensitive phosphorescent particles whose grayscale and speed meet the threshold requirements after the particles are screened and imaged by a high-speed camera. The phosphorescent particles with temperature-sensitive effect spread in a certain concentration uniformly in the flow field to be tested are the initial temperature-sensitive phosphorescent particles.

[0079] The particle time-series frame image may include an initial particle time-series frame image, an initial target time-series frame image, and a target particle time-series frame image. In the particle time-series frame image, each frame image represents the position and state of the particle at a certain moment. Through a continuous image sequence, the particle's motion trajectory, velocity, and grayscale distribution and other information can be observed. Among them, the initial particle time-series frame image is a sequence of images at different time points in the particle luminescence process captured by a high-speed camera, the initial target time-series frame image is a sequence of particle images obtained by screening the particles in the initial particle time-series frame image according to the grayscale threshold, and the target particle time-series frame image is a sequence of particle images obtained by screening the particles in the initial target time-series frame image according to the velocity. Since the high-speed camera has a high frame rate and can shoot videos or continuous images at a speed of hundreds or even thousands of frames per second, in the embodiment of the present application, by using a high-speed camera to collect a cycle of temperature-sensitive phosphorescent particle images corresponding to a flow field at a moment, and then processing the particle image by the life decay method and tracking speed measurement technology, the velocity field and temperature field at the same moment can be obtained.

[0080] The motion trajectory may refer to the path or trajectory described by an object during the motion process, and describes the law of the position of an object in space changing over time. The motion trajectory of the particle can be obtained by a particle matching algorithm, including a nearest neighbor matching algorithm, a regression multi-frame algorithm, a relaxation algorithm, a Thiessen polygon matching algorithm, a neural network algorithm, etc., by matching particles or targets in two or more image sequences with a computer algorithm, tracking the position, speed, trajectory and other information of the particles between different frames, so as to realize the analysis and monitoring of the particle motion. In the embodiment of the present application, since the temperature-sensitive phosphorescent particles have good speed following and temperature following properties, after being excited by the laser to emit phosphorescence, a high-speed camera can be used to continuously sample the phosphorescence decay process of the phosphorescent particles in multiple frames, and the motion trajectory and grayscale changes of each phosphorescent particle in the multi-frame image are tracked to obtain the speed and temperature of the particle, so that the speed and temperature of the phosphorescent particle are used to represent the speed and temperature of the particle position in the flow field at that moment.

[0081] Grayscale changes can refer to changes in the grayscale values ​​displayed by phosphorescent particles in multiple frames of images taken by a high-speed camera. The grayscale values ​​of phosphorescent particles are usually related to the intensity of phosphorescence emitted by them. Brighter phosphorescent particles present higher grayscale values ​​in imaging, while darker phosphorescent particles present lower grayscale values. By analyzing and processing the grayscale of phosphorescent particles, the number and distribution of phosphorescent particles in the sample can be quantitatively evaluated. The grayscale distribution of particles can be obtained through particle recognition algorithms, including threshold segmentation algorithms, edge detection algorithms, morphological processing algorithms, feature extraction algorithms, and machine learning algorithms. According to specific application requirements and image features, particles or target objects in images or videos are automatically detected and identified to achieve accurate identification, quantitative analysis, statistics, tracking and other applications of particles. In the embodiment of the present application, the phosphorescent thermal imaging temperature measurement technology based on the lifetime decay method is used to obtain the grayscale changes of particles by taking multiple frames of images with a high-speed camera, fit the phosphorescence decay process, and calculate the phosphorescence decay lifetime.

[0082] Among them, in the embodiment of the present application, the method of determining the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image may include:

[0083] Performing enhancement processing on the initial particle time-series frame image to obtain a first initial particle time-series frame image;

[0084] Performing expansion processing on the first initial particle time-series frame image to obtain a second initial particle time-series frame image;

[0085] Comparing the first initial particle time-series frame image with the second initial particle time-series frame image, determining the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle;

[0086] According to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle, the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle are determined.

[0087] The initial particle time-series frame image may refer to the original time-series frame image taken by a high-speed camera. The target particle time-series frame image is obtained by processing the image and screening it according to the particle grayscale and speed. The target particle time-series frame image is a standard time-series frame image.

[0088] Enhancement processing may refer to processing the image through a Gaussian Laplacian filter, smoothing the image on the basis of reducing the influence of noise, enhancing the contours and edges of the particles in the image, and facilitating improving the accuracy of particle center coordinate identification and sub-pixel coordinate fitting. In an embodiment of the present application, the grayscale value of the image may be processed through a Gaussian Laplacian filter to highlight the contours of the particles in the image, and obtain a first initial particle time series frame image.

[0089] The details of the Gaussian Laplace filtering process are as follows:

[0090] (1) First, generate a two-dimensional square grid centered at 0. The size of the grid is usually the smallest odd number greater than twice the particle size. The particle size is affected by the actual shooting conditions and can vary from one to more than ten pixels. The phosphorescent particles used in this experiment are relatively small, and the particle size is usually 3. Assuming the particle size is 3, the size of the grid matrix is ​​7×7, that is, the values ​​of m and n in the grid coordinates (m,n) of the two-dimensional grid are -3, -2, -1, 0, 1, 2, 3.

[0091] (2) Substitute the coordinates (m, n) of the two-dimensional square grid into the Gaussian Laplacian operator generation formula to obtain a Gaussian Laplacian operator with the same size as the grid. The calculation formula of the Gaussian Laplacian operator H is:

[0092]

[0093] Where σ is the standard deviation of the Gaussian distribution, and its value is taken as the particle size; m and n are grid coordinates.

[0094] (3) Use the Gaussian Laplacian operator to filter the particle image. The specific method is: for the pixel with coordinates (cx, cy) in the image, substitute its gray value I(cx, cy) into the following filtering formula for calculation:

[0095]

[0096] Then use the calculated I * Replace the original gray value I of the pixel. This process is repeated for all pixels on the image, and the Gaussian Laplace filter operation on the entire image is completed, that is, the gray value processing of each pixel on the image is completed.

[0097] Dilation processing may refer to dilation processing of a binary image or a grayscale image through an imdilate function, using a structural element (also called a dilation kernel or a dilation template) to slide along each pixel position of the image. If the structural element overlaps with the target area in the image, the pixel position is marked as the target area, and the target area or object in the image is enhanced to obtain an image with an enlarged target area. In an embodiment of the present application, the pixel with the largest grayscale can be expanded to the surrounding pixels through dilation processing to obtain a second initial particle time-series frame image.

[0098] The specific details of the expansion are as follows:

[0099] (1) First, generate a square structure element whose size is the smallest odd number greater than twice the particle size. Assuming the particle size is 3 pixels, the size of the structure element is 7×7, and the grayscale image is dilated using the structure element.

[0100] (2) Slide the structural element along each pixel position of the particle image. When the center of the structural element is located at the pixel with coordinates (cx, cy) in the image, for the remaining pixels within the structural element range, if their grayscale value is less than the grayscale value I(cx, cy) of the center of the structural element, then the grayscale value of the pixel is replaced by I(cx, cy); if their grayscale value is greater than the grayscale value I(cx, cy) of the center of the structural element, then the grayscale value of the pixel is not replaced. When each pixel in the image completes the above process, the entire image is expanded. The expansion process can expand the pixel with the largest grayscale on the particle to the surrounding pixels, avoiding the identification of a single particle as multiple particles when comparing images later.

[0101] The initial coordinates of the initial temperature-sensitive phosphorescent particles can refer to the standard pixel coordinates, where the image is divided into discrete pixel units, each pixel unit has an integer coordinate value to represent its position, and the images before and after the expansion process are compared, and the same grayscale is the position of the pixel with the largest local grayscale, that is, the initial coordinates of the particle center, which are integer coordinates. The grayscale corresponding to the integer coordinates (the grayscale value of the pixel with the largest particle grayscale) can be the grayscale mean of the local area (such as a 3×3 pixel area) centered on the integer coordinates, or it can be the peak grayscale obtained by Gaussian fitting of the local area (required to be greater than or equal to a 3×3 pixel area).

[0102] Among them, in the embodiment of the present application, the method of determining the movement trajectory and grayscale change of the target temperature-sensitive phosphorescent particle according to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle may include:

[0103] Screening the initial temperature-sensitive phosphorescent particles according to the grayscale of the initial temperature-sensitive phosphorescent particles and a preset grayscale threshold to obtain initial target temperature-sensitive phosphorescent particles, wherein the preset grayscale threshold is determined according to the type of the initial temperature-sensitive phosphorescent particles;

[0104] According to the two-dimensional Gaussian template, the initial coordinates and grayscale of the initial target temperature-sensitive phosphorescent particles are fitted to obtain the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles;

[0105] Determine the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle;

[0106] According to the grayscale of the initial target temperature-sensitive phosphorescent particle, the grayscale change of the target temperature-sensitive phosphorescent particle is determined.

[0107] Among them, the preset grayscale threshold may refer to that in phosphorescent imaging, phosphorescent particles usually have a higher grayscale value than the surrounding background. Therefore, a grayscale threshold can be set to extract the signal of the phosphorescent particles, remove background noise, and distinguish the phosphorescent particles from the background. Common grayscale threshold processing methods include global threshold method, adaptive threshold method, and threshold method based on statistical methods. In an embodiment of the present application, the image is segmented by setting a fixed grayscale value, and the identified particles are screened and filtered, and only particles with grayscale above the threshold are retained, that is, the initial target temperature-sensitive phosphorescent particles.

[0108] The two-dimensional Gaussian template may refer to a particle grayscale distribution in a captured particle time-series frame image that is Gaussian, high in the middle and low at the edge. In order to determine the center position, a template with a similar shape may be nested, and the template is the two-dimensional Gaussian template.

[0109] The fitting process may refer to moving the template position on the plane. When the correlation between the grayscale distribution of the template and the particle is the largest, the two are considered to be fitted, and the center position of the highest point of the template is considered to be the center position of the particle. Through the fitting process, the integer coordinates of the particles obtained in the above steps, that is, the initial coordinates of the center of the particles, can be refined into sub-pixel coordinates. Sub-pixel coordinates are usually expressed in floating point form and may contain decimals to represent finer positions between pixels. Thus, by fitting all particle images, the specific coordinate positions and corresponding grayscales of the particles on all graphics can be obtained.

[0110] Among them, in the embodiment of the present application, the method of determining the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle may include:

[0111] Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image, wherein the first initial target time-sequential frame image to the fourth initial target time-sequential frame image are four frames of images that are adjacent in time sequence;

[0112] Determining an initial motion trajectory of the initial target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image;

[0113] Determining the speed of the initial target temperature-sensitive phosphorescent particle according to the initial motion trajectory of the initial target temperature-sensitive phosphorescent particle;

[0114] According to the speed of the initial target temperature-sensitive phosphorescent particles, the initial target temperature-sensitive phosphorescent particles are screened to determine the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles;

[0115] Determining the acceleration of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image;

[0116] According to the speed and acceleration of the target temperature-sensitive phosphorescent particle, the motion trajectory of the target temperature-sensitive phosphorescent particle is obtained.

[0117] Among them, the first initial target time sequence frame image to the fourth initial target time sequence frame image can refer to four continuous and adjacent frame images in the initial target time sequence frame image, such as the first frame image to the fourth frame image, the second frame image to the fifth frame image, and so on.

[0118] The initial motion trajectory of the initial target thermosensitive phosphorescent particle can refer to the determination of the correspondence between the two consecutive frames by comparing and analyzing the spatial distribution of the feature points between the two consecutive frames of images through double-frame matching, so as to obtain the motion trajectory of the thermosensitive phosphorescent particle that meets the grayscale threshold requirement. The double-frame method can perform particle matching on images with a large particle concentration. In the embodiment of the present application, it is applicable to the first four frames of images collected during the phosphorescence attenuation process. The grayscale of these four frames is large, and the number of particles identified is large. The sub-pixel coordinates and grayscale (x i1 ,y i1 ,I i1 ) in the second initial target time frame image and grayscale (x i2 ,y i2 ,I i2 ), until the sub-pixel coordinates and grayscale (x i4 ,y i4 ,I i4 ), and determine the initial motion trajectory of the particle based on the sub-pixel coordinate changes of the particle.

[0119] The velocity of the initial target temperature-sensitive phosphorescent particle can be determined by dividing the difference between the positions of the temperature-sensitive phosphorescent particle in the previous and next frames in the initial target time-series frame image by the cross-frame time to preliminarily calculate the particle velocity.

[0120] Screening can refer to identifying and analyzing data points or observations in a data set that are significantly different from the rest of the data through outlier detection. Outliers can be identified through statistical methods, distance or density-based screening, and machine learning algorithms. In the embodiment of the present application, the particles in the image are screened by using a local velocity detection pseudo vector to check whether the velocity vector is an outlier.

[0121] The target temperature-sensitive phosphorescent particle may refer to a temperature-sensitive phosphorescent particle that has passed an outlier detection on the basis that its grayscale meets a grayscale threshold requirement.

[0122] The motion trajectory of the target temperature-sensitive phosphorescent particle can be obtained by extrapolating the initial motion trajectory through a four-frame matching algorithm. Since the sub-pixel coordinates of the particle in the first initial target time-series frame image to the fourth initial target time-series frame image have been obtained in the previous steps, the speed and acceleration of the particle movement are calculated through the collected four consecutive frames of images, and the sub-pixel coordinates of the particle in the fifth initial target time-series frame image are predicted. Then, the sub-pixel coordinates of the particle in the sixth initial target time-series frame image are predicted through the second to fifth initial target time-series frame images. By analogy, the matching of the particle in multiple frames is obtained to obtain the motion trajectory of the particle. The four-frame matching algorithm makes full use of the particle information in the first four frames of images to perform trajectory extrapolation, and can still achieve efficient and accurate matching when the particle grayscale in the particle time-series frame decreases with phosphorescence attenuation.

[0123] Among them, in the embodiment of the present application, the method of determining the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time sequence frame image to the fourth initial target time sequence frame image may include:

[0124] Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-series frame image, the corresponding neighbor particles, and the first coordinate position of the neighbor particles, wherein the neighbor particles represent particles within a preset distance from the initial target temperature-sensitive phosphorescent particle;

[0125] Determine a second coordinate position of the neighbor particle in a second initial target time-series frame image according to the initial target temperature-sensitive phosphorescent particle and the neighbor particle;

[0126] Determine the target displacement according to the first coordinate position and the second coordinate position;

[0127] The sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image and the target displacement are determined in the third initial target time-sequential frame image to the fourth initial target time-sequential frame image.

[0128] Among them, the preset distance can be adjusted according to the concentration of the temperature-sensitive phosphorescent particles sown in the experiment, the number of neighbor particles is generally 10 to 25, and the search range is generally 25 pixels.

[0129] Determining the second coordinate position of the neighbor particle in the second initial target time-series frame image may refer to finding N neighbor particles Ni of the initial target temperature-sensitive phosphorescent particle P in the first initial target time-series frame image A, and then traversing each initial target temperature-sensitive phosphorescent particle P and the neighbor particle Ni according to a preset search range. If there is a corresponding particle Mi in the search range in the second initial target time-series frame image B, the distances Δx and Δy between the first coordinate position of the neighbor particle Ni and the second coordinate position of the particle Mi are calculated, and the search steps are repeated to traverse the initial target temperature-sensitive phosphorescent particle P and all its neighbor particles Ni, and a number of distances Δx and Δy are obtained. The distances are used to draw a histogram, and the peak value Δx obtained in the figure is max and Δy max is the most likely particle displacement, i.e., the target displacement.

[0130] Determining the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the second initial target time-series frame image may refer to the initial target temperature-sensitive phosphorescent particle P in the first initial target time-series frame image A, the position is (x, y), and the moving target displacement Δx max and Δy max After reaching the predicted position (x+Δx) in the second initial target time sequence frame image B max ,y+Δy max ), then the particle closest to the predicted position in the second initial target time-series frame image B is the successfully matched particle.

[0131] Among them, in the embodiment of the present application, according to the speed of the initial target temperature-sensitive phosphorescent particles, the initial target temperature-sensitive phosphorescent particles are screened, and the method of determining the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles may include:

[0132] Determine the velocity of neighbor particles of the initial target temperature-sensitive phosphorescent particle;

[0133] According to the speed of neighbor particles, determine the speed range of neighbor particles and the median of the speed range;

[0134] According to the velocity of the neighbor particle and the median of the velocity range, the velocity residual range and the median of the velocity residual range of the neighbor particle are determined;

[0135] Determine the velocity residual of the initial target temperature-sensitive phosphorescent particle according to the velocity of the neighboring particles, the median of the velocity range, and the median of the velocity residual range;

[0136] The initial target temperature-sensitive phosphorescent particles are screened according to the velocity residual of the initial target temperature-sensitive phosphorescent particles and a preset velocity residual threshold, and the target temperature-sensitive phosphorescent particles in the initial target temperature-sensitive phosphorescent particles and the velocity of the target temperature-sensitive phosphorescent particles are determined.

[0137] Among them, the velocity residual range of the neighboring particles can refer to the velocity of the initial target temperature-sensitive phosphorescent particle with a velocity of U0 in the time series frame image, and the velocity of its neighboring particle k is U k , first calculate the median velocity U of multiple neighbor particles m , and then calculate the velocity residual r corresponding to each neighbor particle k =|U k -U m |, thus obtaining the velocity residual range of neighboring particles, where the median velocity residual is r m .

[0138] Determining the velocity residual of the initial target temperature-sensitive phosphorescent particle may refer to calculating the normalized velocity residual by the following formula 1 based on the velocity, velocity range median, and velocity residual range median of the neighboring particle:

[0139] Formula 1:

[0140] Where r′ is the velocity residual of the initial target temperature-sensitive phosphorescent particle; ε is a small amount used to avoid the denominator being zero; U k is the velocity of neighbor particle k; U m is the median value of the velocity range of neighbor particle k; r m is the median value in the range of velocity residuals of neighbor particle k.

[0141] The screening process may refer to screening the initial target temperature-sensitive phosphorescent particles with a speed of U0 in the time-series frame image according to a preset speed residual threshold. In the embodiment of the present application, the preset speed residual threshold is 2. When the speed residual obtained by the above calculation is less than 2, it indicates that the detected vector is a normal value. For example, when the speed U0 of the initial target temperature-sensitive phosphorescent particle is 2, the speed of its neighbor particle U k are 1, 1, 1, 2, 2, 3, 3, 3 respectively, then the median velocity range of the neighboring particles is U m is 2, and the velocity residual r of the neighboring particle is calculated k is 1, 1, 1, 0, 0, 1, 1, 1, then the median value of the velocity residual range of the neighboring particles is r m is 1, and the velocity residual r′ of the initial target temperature-sensitive phosphorescent particle calculated by the above formula is 0, which is less than the velocity residual threshold 2. Then the initial target temperature-sensitive phosphorescent particle passes the outlier detection and is the target temperature-sensitive phosphorescent particle.

[0142] S202, determining the speed of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image.

[0143] The speed of the target temperature-sensitive phosphorescent particle can be determined based on the positions of the particle i in the adjacent first frame and second frame images, respectively (x i1,y i1 ) and (x i2 ,y i2 ), according to the speed calculation formula and Get the moving speed of phosphorescent particle i (v ix ,v iy ).

[0144] S203, determining the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image.

[0145] Among them, the decay slope constant can refer to the reciprocal of the decay lifetime τ of the thermosensitive phosphorescent particle, that is, the rate of change of the logarithm of the phosphorescent luminescence intensity ratio. In phosphorescent materials, electrons in an excited state will transition from a high energy level to a low energy level, releasing photons to form phosphorescence. As time goes by, the electrons in the excited state gradually return to the ground state, and the intensity of the released phosphorescence will gradually weaken over time. This phenomenon is called phosphorescence decay. The luminescence lifetime and decay slope constant of the phosphorescent particle can be calculated by substituting the grayscale of the particle in multiple consecutive frames of images into the following formula:

[0146] Formula 2: I=I0e -t / τ ,

[0147] Wherein, I is the luminescence intensity of the thermosensitive phosphorescent particles. In the embodiment of the present application, the decay process of the particles is captured by a high-speed camera, and the luminescence intensity of the thermosensitive phosphorescent particles in the camera image is expressed as grayscale changes; I0 is the luminescence intensity after the thermosensitive phosphorescent particles are fully excited; τ is the phosphorescence decay lifetime related to temperature, and the higher the temperature, the shorter the phosphorescence decay lifetime; t is time.

[0148] Formula 3:

[0149] Among them, I i1 is the luminescence intensity of phosphorescent particle i in the first frame of image collected after the laser is turned off; I ij is the luminous intensity of phosphorescent particle i in the jth frame image; λ is the attenuation slope constant of the temperature-sensitive phosphorescent particle.

[0150] Among them, in the embodiment of the present application, according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, the method of determining the attenuation slope constant of the target temperature-sensitive phosphorescent particle may include:

[0151] Determine the grayscale of the target temperature-sensitive phosphorescent particle in the target particle time-series frame image;

[0152] According to the relationship between the luminescence intensity and time of the target temperature-sensitive phosphorescent particle, as well as the grayscale in the target particle time-series frame image and the corresponding target time, the luminescence lifetime and attenuation slope constant of the target temperature-sensitive phosphorescent particle are determined.

[0153] The target moment may refer to the moment of each frame of image collected after the target temperature-sensitive phosphorescent particle is excited by the laser and starts to emit light according to the actual situation of the experiment.

[0154] S204, determining the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship, wherein the corresponding relationship represents the corresponding relationship between the attenuation slope constant of the temperature-sensitive phosphorescent particle and the temperature.

[0155] The preset corresponding relationship may refer to: measuring the temperature field under constant temperature conditions where the temperature is known, calculating the corresponding attenuation slope constant, fitting a set of data points into a curve or function through multiple experimental calibration data points, and obtaining a temperature-attenuation slope constant schematic diagram, such as Figure 3 As shown, the temperature-decay slope constant calibration curve diagram provided in the embodiment of the present application is shown, and the decay slope constant increases with increasing temperature. Therefore, after determining the decay slope constant of the temperature-sensitive phosphorescent particle, it can be brought into the temperature-decay slope constant calibration curve diagram to obtain the temperature of the temperature-sensitive phosphorescent particle.

[0156] In the embodiment of the present application, according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and the preset corresponding relationship, the method for determining the temperature of the target temperature-sensitive phosphorescent particle may include:

[0157] Determine the fitting relationship between the flow field temperature under standard conditions and the corresponding attenuation slope constant;

[0158] The temperature of the target temperature-sensitive phosphorescent particle is determined according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and the fitting relationship between the standard flow field temperature and the corresponding attenuation slope constant.

[0159] S205 , determining the velocity and temperature of the flow field to be measured according to the velocity of the target temperature-sensitive phosphorescent particles and the temperature of the target temperature-sensitive phosphorescent particles.

[0160] Among them, according to the above steps, the speed of the thermosensitive phosphorescent particles can be obtained, and the speed distribution of the entire measurement area can be obtained by traversing all the particles that are successfully matched on the entire image. At the same time, the temperature of the thermosensitive phosphorescent particles in the flow field at the same time is obtained. Based on the speed following and temperature following properties of the thermosensitive phosphorescent particles, the speed and temperature of the phosphorescent particles can be used to represent the speed and temperature of the particle position in the flow field at that moment, thereby synchronously determining the flow field speed and temperature.

[0161] The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application Figure 1 , the particle velocity can be obtained by continuously sampling the phosphorescence emitted by the thermosensitive phosphorescent particles in the flow field by multiple frames, by tracing the motion trajectory of the thermosensitive phosphorescent particles in the particle time-series frame image, and at the same time accurately obtaining the particle grayscale and grayscale attenuation process during the motion process, and calculating the attenuation slope constant of the thermosensitive phosphorescent particles according to the grayscale change of the particles, and then obtaining the temperature of the thermosensitive phosphorescent particles according to the corresponding relationship between the attenuation slope constant of the thermosensitive phosphorescent particles and the temperature. Since the thermosensitive phosphorescent particles have good speed following and temperature following properties, the speed and temperature of the phosphorescent particles can be used to represent the speed and temperature of the particle position in the flow field at that moment, thereby realizing the synchronous measurement of the flow field speed and temperature.

[0162] Figure 4 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 2 .

[0163] like Figure 4 As shown, the method may include:

[0164] S401, collecting particle images containing flow field velocity and temperature information.

[0165] Among them, particle image can refer to the phosphorescent particles with temperature-sensitive effect being uniformly spread in the flow field to be measured at a certain concentration, and the control host simultaneously sends control signals to the high-speed camera and ultraviolet laser, so that the laser emits laser pulses, and the phosphorescent particles in the flow field area to be measured are excited to emit phosphorescence, and at the same time, the high-speed camera is focused on the area to be measured, and the luminescence process of the phosphorescent particles is collected to obtain the particle image, wherein the pulse duration is about 8 to 9ns, in the form of a sheet of light with a thickness of 1mm, which can instantly illuminate the flow field area to be measured. Figure 5 As shown, it is a timing diagram of the synchronous measurement of flow field velocity and temperature provided in an embodiment of the present application. The laser emits a laser pulse, the phosphorescent particles are excited to emit phosphorescence, and the high-speed camera continuously captures multiple frames of images (10 frames in the figure). When the laser emits the next pulse, the camera will again continuously capture multiple frames of images.

[0166] S402, identifying the position and grayscale information of the phosphorescent particles from the particle image.

[0167] S403, matching particles in adjacent frames to find the motion trajectory of the same particle in multiple consecutive frames of time-series images, obtaining the velocity field from the successfully matched particles, and accurately obtaining the grayscale of the particles during the motion process.

[0168] S404, fitting the grayscale variation pattern of the phosphorescent particles in the multi-frame images, thereby calculating the decay lifetime.

[0169] S405, bringing the calculated phosphorescent particle decay lifetime into the decay lifetime-temperature calibration curve to obtain the particle temperature, that is, the flow field temperature.

[0170] The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application Figure 2 , the non-contact optical measurement method can be used to avoid interference with the flow field, and the flow field velocity and temperature can be measured instantaneously and on a surface basis. In addition, the sub-pixel fitting method is used to improve the particle recognition accuracy, and the histogram matching and four-frame matching algorithms are used to realize the trajectory tracking of particles between multiple frames of images, thereby improving the spatial resolution of velocity measurement. At the same time, the trajectory tracking of particles can obtain the particle grayscale and its decay process during the motion process, thereby accurately fitting the decay life of phosphorescent particles and reducing the influence of noise such as environmental noise and camera background noise. At the same time, the shorter exposure time avoids the particle tailing problem, increases the velocity measurement range, and improves the velocity and temperature measurement accuracy.

[0171] Figure 6 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 3 .

[0172] like Figure 6 As shown, the method may include:

[0173] S601, performing Laplacian Gaussian filtering on the original particle image.

[0174] S602: Perform dilation processing on the image.

[0175] S603, identifying the center position of the particle, and obtaining the integer coordinates of the pixel where the center position of the particle is located and its corresponding grayscale by comparing the images before and after the expansion.

[0176] S604: Filter the identified particles using a given grayscale threshold, and only retain particles with grayscales above the threshold.

[0177] S605 , for particles with integer pixel coordinates, a two-dimensional Gaussian template is used to perform sub-pixel fitting of the particle coordinate position to obtain the sub-pixel coordinates of the phosphorescent particles.

[0178] The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application Figure 3 , the image processing technology of Gaussian Laplace filtering and dilation processing can be combined, and then the sub-pixel fitting method can be used to realize the particle identification process and obtain accurate particle coordinates, thereby improving the accuracy of establishing particle motion trajectories and the accuracy of speed and temperature measurement.

[0179] Figure 7 The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application is as follows Figure 4 .

[0180] like Figure 7 As shown, the method may include:

[0181] S701, double-frame matching is performed on the first frame particle image and the second frame particle image. For particles that are successfully matched, double-frame matching is performed in the second frame and the third frame, and in the third frame and the fourth frame, respectively, to find the corresponding particles, until matching is completed in the first four frames, thereby establishing the initial trajectory of the particles.

[0182] S702, preliminarily calculating the particle velocity by dividing the difference between the positions of the particle in the previous and next frames by the cross-frame time, and then using outlier detection to check whether the velocity vector is an outlier, thereby checking whether the matching is successful or not.

[0183] S703, the particles detected by the outlier further use the four-frame matching algorithm to extrapolate the trajectory, extending it to the fifth frame, the sixth frame, and finally the last frame of the calculation, thereby completing the matching of the particles in the multi-frame images and obtaining the movement trajectory of the particles.

[0184] The process of the method for synchronously measuring flow field velocity and temperature provided in the embodiment of the present application Figure 4 , particle matching can be performed through double-frame matching and four-frame matching algorithms, realizing particle trajectory tracking between multi-frame images with gradually decaying particle grayscale and increasing signal-to-noise ratio, and accurately obtaining the particle grayscale and its grayscale decay process during the motion process.

[0185] Figure 8 This is a diagram of the synchronous measurement results of the velocity field and temperature field of the cold jet provided in the embodiment of the present application. When the velocity field and temperature field of the jet flow field section are synchronously measured in a 100×100×100mm transparent quartz cylinder, the temperature in the cylinder is 156°C, the jet temperature is 31°C, the jet velocity is about 0.1m / s, the jet nozzle diameter D is 4mm, and Mg4FGeO6:Mn phosphorescent particles are used as experimental particles. They can be excited by ultraviolet light to emit red phosphorescence, and the peak wavelength of the light is about 655nm. The exposure time of each frame of the camera is 0.5 milliseconds, and 10 frames are taken each time. The measurement results are as follows: Figure 8 As shown, Figure 8 (a) is the velocity vector diagram, Figure 8 (b) is the particle diagram of temperature field.

[0186] As can be seen from the figure, the velocity of the jet area is relatively high and the temperature is relatively low, while the velocity of the remaining areas is relatively low and the temperature is relatively high. The measurement results prove that the present invention has good speed and temperature synchronous measurement capabilities.

[0187] Fig. 9 This is a schematic diagram of the structure of the flow field velocity and temperature synchronous measurement device provided in the embodiment of the present application. Fig. 9 As shown, the flow field velocity and temperature synchronous measurement device 90 includes: a first determination module 901 , a second determination module 902 , a third determination module 903 , a fourth determination module 904 , and a fifth determination module 905 .

[0188] in:

[0189] The first determination module 901 is used to determine the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, where the particle time-series frame image is an image obtained by continuously sampling multiple frames of the phosphorescence attenuation process of the target temperature-sensitive phosphorescent particle in the flow field to be measured;

[0190] A second determination module 902 is used to determine the speed of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image;

[0191] The third determination module 903 is used to determine the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image;

[0192] The fourth determination module 904 is used to determine the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship, wherein the corresponding relationship represents the corresponding relationship between the attenuation slope constant of the temperature-sensitive phosphorescent particle and the temperature;

[0193] The fifth determination module 905 is used to determine the velocity and temperature of the flow field to be measured according to the velocity of the target temperature-sensitive phosphorescent particle and the temperature of the target temperature-sensitive phosphorescent particle.

[0194] In the embodiment of the present application, the first determining module 901 may also be specifically used for:

[0195] Performing enhancement processing on the initial particle time-series frame image to obtain a first initial particle time-series frame image;

[0196] Performing expansion processing on the first initial particle time-series frame image to obtain a second initial particle time-series frame image;

[0197] Comparing the first initial particle time-series frame image with the second initial particle time-series frame image, determining the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle;

[0198] According to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle, the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle are determined.

[0199] In the embodiment of the present application, the first determining module 901 may also be specifically used for:

[0200] Screening the initial temperature-sensitive phosphorescent particles according to the grayscale of the initial temperature-sensitive phosphorescent particles and a preset grayscale threshold to obtain initial target temperature-sensitive phosphorescent particles, wherein the preset grayscale threshold is determined according to the type of the initial temperature-sensitive phosphorescent particles;

[0201] According to the two-dimensional Gaussian template, the initial coordinates and grayscale of the initial target temperature-sensitive phosphorescent particles are fitted to obtain the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles;

[0202] Determining the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle;

[0203] According to the grayscale of the initial target temperature-sensitive phosphorescent particle, the grayscale change of the target temperature-sensitive phosphorescent particle is determined.

[0204] In the embodiment of the present application, the first determining module 901 may also be specifically used for:

[0205] Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image, wherein the first initial target time-sequential frame image to the fourth initial target time-sequential frame image are four frames of images that are adjacent in time sequence;

[0206] Determining an initial motion trajectory of the initial target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image;

[0207] Determining the speed of the initial target temperature-sensitive phosphorescent particle according to the initial motion trajectory of the initial target temperature-sensitive phosphorescent particle;

[0208] According to the speed of the initial target temperature-sensitive phosphorescent particles, the initial target temperature-sensitive phosphorescent particles are screened to determine the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles;

[0209] Determining the acceleration of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image;

[0210] According to the speed and acceleration of the target temperature-sensitive phosphorescent particle, the motion trajectory of the target temperature-sensitive phosphorescent particle is obtained.

[0211] In the embodiment of the present application, the first determining module 901 may also be specifically used for:

[0212] Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-series frame image, the corresponding neighbor particles, and the first coordinate position of the neighbor particles, wherein the neighbor particles represent particles within a preset distance from the initial target temperature-sensitive phosphorescent particle;

[0213] Determine a second coordinate position of the neighbor particle in a second initial target time-series frame image according to the initial target temperature-sensitive phosphorescent particle and the neighbor particle;

[0214] Determine the target displacement according to the first coordinate position and the second coordinate position;

[0215] The sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image and the target displacement are determined in the third initial target time-sequential frame image to the fourth initial target time-sequential frame image.

[0216] In the embodiment of the present application, the first determining module 901 may also be specifically used for:

[0217] Determine the velocity of neighbor particles of the initial target temperature-sensitive phosphorescent particle;

[0218] According to the speed of neighbor particles, determine the speed range of neighbor particles and the median of the speed range;

[0219] According to the velocity of the neighbor particle and the median of the velocity range, the velocity residual range and the median of the velocity residual range of the neighbor particle are determined;

[0220] Determine the velocity residual of the initial target temperature-sensitive phosphorescent particle according to the velocity of the neighboring particles, the median of the velocity range, and the median of the velocity residual range;

[0221] The initial target temperature-sensitive phosphorescent particles are screened according to the velocity residual of the initial target temperature-sensitive phosphorescent particles and a preset velocity residual threshold, and the target temperature-sensitive phosphorescent particles in the initial target temperature-sensitive phosphorescent particles and the velocity of the target temperature-sensitive phosphorescent particles are determined.

[0222] In the embodiment of the present application, the third determining module 903 may also be specifically used for:

[0223] Determine the grayscale of the target temperature-sensitive phosphorescent particle in the target particle time-series frame image;

[0224] According to the relationship between the luminescence intensity and time of the target temperature-sensitive phosphorescent particle, as well as the grayscale in the target particle time-series frame image and the corresponding target time, the luminescence lifetime and attenuation slope constant of the target temperature-sensitive phosphorescent particle are determined.

[0225] In the embodiment of the present application, the fourth determining module 904 may also be specifically configured to:

[0226] Determine the fitting relationship between the flow field temperature under standard conditions and the corresponding attenuation slope constant;

[0227] The temperature of the target temperature-sensitive phosphorescent particle is determined according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and the fitting relationship between the standard flow field temperature and the corresponding attenuation slope constant.

[0228] The flow field velocity and temperature synchronous measurement device 90 provided in the embodiment of the present application can execute the above method embodiment. Its specific implementation principle and technical effects can be found in the above method embodiment, and this embodiment will not be repeated here.

[0229] A person of ordinary skill in the art will appreciate that all or part of the steps in the various methods of the above embodiments may be completed by instructions, or by controlling related hardware through instructions. The instructions may be stored in a computer-readable storage medium and loaded and executed by a processor.

[0230] To this end, an embodiment of the present application provides a computer-readable storage medium, which stores multiple instructions, and the instructions can be loaded by a processor to execute the steps in any one of the flow field velocity and temperature synchronous measurement methods provided in the embodiments of the present application.

[0231] The storage medium may include: a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0232] According to one aspect of the present application, a computer program product or a computer program is provided. The computer program product or the computer program comprises computer-executable instructions stored in a computer-readable storage medium.

[0233] Since the instructions stored in the storage medium can execute the steps in any one of the flow field velocity and temperature synchronous measurement methods provided in the embodiments of the present application, the beneficial effects that can be achieved by any one of the flow field velocity and temperature synchronous measurement methods provided in the embodiments of the present application can be achieved. Please see the previous embodiments for details and will not be repeated here.

[0234] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0235] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for synchronously measuring flow field velocity and temperature, characterized in that: include: Determine the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, wherein the particle time-series frame image is an image obtained by continuously sampling multiple frames of the phosphorescence attenuation process of the target temperature-sensitive phosphorescent particle in the flow field to be measured; the target temperature-sensitive phosphorescent particle is a temperature-sensitive phosphorescent particle whose grayscale and speed both meet the threshold requirements; Determining the speed of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; Determining the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; Determining the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship, wherein the corresponding relationship represents the corresponding relationship between the attenuation slope constant of the temperature-sensitive phosphorescent particle and the temperature; Determining the velocity and temperature of the flow field to be measured according to the velocity of the target temperature-sensitive phosphorescent particle and the temperature of the target temperature-sensitive phosphorescent particle; The step of determining the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image includes: Performing enhancement processing on the initial particle time-series frame image to obtain a first initial particle time-series frame image; Performing expansion processing on the first initial particle time-series frame image to obtain a second initial particle time-series frame image; Comparing the first initial particle time-series frame image with the second initial particle time-series frame image to determine the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle; Determining the movement trajectory and grayscale change of the target temperature-sensitive phosphorescent particle according to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle; The step of determining the movement trajectory and grayscale change of the target temperature-sensitive phosphorescent particle according to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle comprises: According to the grayscale of the initial temperature-sensitive phosphorescent particles and a preset grayscale threshold, the initial temperature-sensitive phosphorescent particles are screened to obtain initial target temperature-sensitive phosphorescent particles, wherein the preset grayscale threshold is determined according to the type of the initial temperature-sensitive phosphorescent particles; According to the two-dimensional Gaussian template, the initial coordinates and grayscale of the initial target temperature-sensitive phosphorescent particles are fitted to obtain the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles; Determining the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle; According to the grayscale of the initial target temperature-sensitive phosphorescent particle, a grayscale change of the target temperature-sensitive phosphorescent particle is determined.

2. The method according to claim 1, characterized in that The step of determining the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle comprises: Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image, wherein the first initial target time-sequential frame image to the fourth initial target time-sequential frame image are four frames of images that are adjacent in time sequence; Determining an initial motion trajectory of the initial target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image; Determining the speed of the initial target temperature-sensitive phosphorescent particle according to the initial motion trajectory of the initial target temperature-sensitive phosphorescent particle; According to the speed of the initial target temperature-sensitive phosphorescent particles, the initial target temperature-sensitive phosphorescent particles are screened to determine the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles; determining the acceleration of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the target temperature-sensitive phosphorescent particle in the first initial target time-sequential frame image to the fourth initial target time-sequential frame image; The motion trajectory of the target temperature-sensitive phosphorescent particle is obtained according to the speed and acceleration of the target temperature-sensitive phosphorescent particle.

3. The method according to claim 2, characterized in that The determining of the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time sequence frame image to the fourth initial target time sequence frame image comprises: Determine the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle in the first initial target time-series frame image, the corresponding neighbor particles, and the first coordinate position of the neighbor particles, wherein the neighbor particles represent particles within a preset distance from the initial target temperature-sensitive phosphorescent particle; Determining a second coordinate position of the neighbor particle in a second initial target time-series frame image according to the initial target temperature-sensitive phosphorescent particle and the neighbor particle; Determining a target displacement according to the first coordinate position and the second coordinate position; The sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles in the first initial target time-sequential frame image and the target displacement are determined in the third initial target time-sequential frame image to the fourth initial target time-sequential frame image.

4. The method according to claim 2, characterized in that: The screening process of the initial target temperature-sensitive phosphorescent particles according to the speed of the initial target temperature-sensitive phosphorescent particles to determine the target temperature-sensitive phosphorescent particles and the speed of the target temperature-sensitive phosphorescent particles includes: Determining the velocity of neighbor particles of the initial target temperature-sensitive phosphorescent particle; Determine a speed range of the neighbor particle and a median of the speed range according to the speed of the neighbor particle; Determine a velocity residual range and a velocity residual range median of the neighbor particle according to the velocity of the neighbor particle and the velocity range median; Determining the velocity residual of the initial target temperature-sensitive phosphorescent particle according to the velocity of the neighbor particle, the median of the velocity range, and the median of the velocity residual range; The initial target temperature-sensitive phosphorescent particles are screened according to the velocity residual of the initial target temperature-sensitive phosphorescent particles and a preset velocity residual threshold, and the target temperature-sensitive phosphorescent particles in the initial target temperature-sensitive phosphorescent particles and the velocity of the target temperature-sensitive phosphorescent particles are determined.

5. The method according to claim 1, characterized in that The step of determining the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image comprises: Determining the grayscale of the target temperature-sensitive phosphorescent particle in the target particle time-series frame image; The luminescence lifetime and attenuation slope constant of the target temperature-sensitive phosphorescent particle are determined according to the relationship between the luminescence intensity of the target temperature-sensitive phosphorescent particle and time, as well as the grayscale in the target particle time-series frame image and the corresponding target time.

6. The method according to claim 1, characterized in that The step of determining the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship includes: Determine the fitting relationship between the flow field temperature under standard conditions and the corresponding attenuation slope constant; The temperature of the target temperature-sensitive phosphorescent particle is determined according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a fitting relationship between the standard flow field temperature and the corresponding attenuation slope constant.

7. A flow field velocity and temperature synchronous measurement device, characterized in that: include: The first determination module is used to determine the motion trajectory and grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image, wherein the particle time-series frame image is a time-series frame image of the target temperature-sensitive phosphorescent particle emitting light in the flow field to be measured; the target temperature-sensitive phosphorescent particle is a temperature-sensitive phosphorescent particle whose grayscale and speed both meet the threshold requirements; A second determination module is used to determine the speed of the target temperature-sensitive phosphorescent particle according to the motion trajectory of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; A third determination module is used to determine the attenuation slope constant of the target temperature-sensitive phosphorescent particle according to the grayscale change of the target temperature-sensitive phosphorescent particle in the particle time-series frame image; a fourth determination module, configured to determine the temperature of the target temperature-sensitive phosphorescent particle according to the attenuation slope constant of the target temperature-sensitive phosphorescent particle and a preset corresponding relationship, wherein the corresponding relationship represents the corresponding relationship between the attenuation slope constant of the temperature-sensitive phosphorescent particle and the temperature; a fifth determination module, configured to determine the velocity and temperature of the flow field to be measured according to the velocity of the target temperature-sensitive phosphorescent particle and the temperature of the target temperature-sensitive phosphorescent particle; The first determining module is further specifically configured to: Performing enhancement processing on the initial particle time-series frame image to obtain a first initial particle time-series frame image; Performing expansion processing on the first initial particle time-series frame image to obtain a second initial particle time-series frame image; Comparing the first initial particle time-series frame image with the second initial particle time-series frame image to determine the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle; Determining the movement trajectory and grayscale change of the target temperature-sensitive phosphorescent particle according to the initial coordinates and grayscale of the initial temperature-sensitive phosphorescent particle; The first determining module is further specifically configured to: According to the grayscale of the initial temperature-sensitive phosphorescent particles and a preset grayscale threshold, the initial temperature-sensitive phosphorescent particles are screened to obtain initial target temperature-sensitive phosphorescent particles, wherein the preset grayscale threshold is determined according to the type of the initial temperature-sensitive phosphorescent particles; According to the two-dimensional Gaussian template, the initial coordinates and grayscale of the initial target temperature-sensitive phosphorescent particles are fitted to obtain the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particles; Determining the motion trajectory of the target temperature-sensitive phosphorescent particle according to the sub-pixel coordinates of the initial target temperature-sensitive phosphorescent particle; According to the grayscale of the initial target temperature-sensitive phosphorescent particle, a grayscale change of the target temperature-sensitive phosphorescent particle is determined.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 6 when executed by a processor.

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