A mobile vortex structure automatic tracking circulation calculation method

Abstract

The application discloses a kind of mobile vortex structure automatic tracking circulation calculation method, the present application relates to vortex structure circulation meter technical field, present and propose the following scheme, including following partial process: define two coordinate matrices to unify global position information, i.e. the physical position of each point that is discrete to two-dimensional matrix space, i.e. X and Y matrix of n rows m columns.The application compared with the cumbersome process of artificial determination target vortex structure position and boundary then carry out circulation calculation, reduce to minimum degree with artificial intervention;And using the automatic tracking identification method based on the vortex core area vortex distribution characteristics design, discard the needs of complex edge detection algorithm, image feature extraction and image tracking algorithm, instead, it focuses on the vortex core area vortex distribution, as key features, to greatly simplify the calculation process, simultaneously no longer rely on cumbersome image processing and tracking technology, thus greatly reduce the demand for computing resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vortex structure circulation calculation, and particularly relates to a mobile vortex structure automatic tracking circulation calculation method. BACKGROUND

[0002] In the process of researching and applying low-speed aircraft or underwater submersible vehicle power propulsion, especially in the bionic technology of imitating the way of bird flapping wings, fish swinging, jellyfish jet, etc. to design aircraft or underwater submersible vehicle, the circulation of key vortex structure in the wake can be analyzed to indirectly calculate the thrust and propulsion efficiency of the propeller and other key characteristics, so as to solve the problem that the flow field near the flexible variable propeller is difficult to measure, and the thrust generated by the mobile propeller is difficult to directly measure. The circulation of vortex structure is the area integral of the vorticity corresponding to the region of vortex structure in the vorticity field. However, when calculating the circulation of key vortex structure in the wake, it is necessary to face the complex factors that the vortex structure moves continuously with the development of the flow field, is deformed by the shear force of the flow field, and other vortex structures exist around.

[0003] Therefore, when dealing with the wake of dynamically evolving vortex structure, it is necessary to sample the vorticity field frame by frame to manually determine the position and boundary of the target vortex structure, which leads to a large consumption of manpower and material resources, and also reduces the frequency of test sampling. The dynamic evolution of vortex structure is a challenging problem because the movement of vortex in the flow field is constantly changing, and the surrounding fluid environment is also constantly changing. Therefore, when dealing with vortex structure, it is necessary to develop an automatic data processing method to reduce the need for human intervention, identify and track the target vortex structure in the collected vorticity field image, and combine the vortex boundary criterion to calculate the circulation of the vortex structure corresponding to the region of the vortex structure in the vorticity field.

[0004] The existing mobile vortex structure automatic tracking calculation technology of circulation mainly based on computer vision technology combined with classic tracking algorithm, has higher technical complexity and higher requirement for post-processing power, its typical technical process is as follows: ①Convert the vortex distribution of the target two-dimensional plane into a vortex cloud picture and output the corresponding picture at each sampling frame, and based on image recognition, the mobile vortex core area is automatically identified and tracked for the continuous frame picture, and the circulation changing with time is calculated. ②Edge detection, using Sobel operator, Canny algorithm and other algorithms to identify the boundary of the image, aiming to identify the boundary or the area with large changes in the image, which may correspond to the boundary of the vortex structure. Then determine the possible vortex structure area through connected region analysis, that is, the area composed of adjacent pixels with similar properties (such as color, gray value, etc.). In the determination process of the connected region, manual intervention is needed to determine the area corresponding to the vortex structure of interest. ③Feature extraction, including shape, texture, color, gray scale and other features of the region are extracted and described. Common feature extraction methods include Haar feature, histogram of oriented gradients (HOG), local binary pattern (LBP), etc. ④Finally, use tracking algorithms such as Kalman filter, mean shift, etc. to track the motion and change of vortex structure in continuous frame images. SUMMARY

[0005] In view of the defects in the above background art, the present application provides a technical solution of a mobile vortex structure automatic tracking circulation calculation method, including the following circulation calculation process:

[0006] S1: Define two coordinate matrices to unify the global position information, that is, the physical position of each point discretized to a two-dimensional matrix space, that is, the X and Y matrices of n rows and m columns:

[0007]

[0008] S2: According to the X and Y matrices, the vortex distribution of the two-dimensional plane is interpolated into the V matrix of n rows and m columns; using the unified X and Y matrices to interpolate the V matrix and the Q matrix will make the same index of the above four matrices correspond to the same physical space position, and associate the elements in each matrix;

[0009] S3: Considering the continuous calculation of the method, input the X and Y matrices, and the V matrix and the Q matrix sampled N times in succession, respectively V1, V2, …, VN-1, VN matrix, Q1, Q2, …, QN-1, QN matrix;

[0010] S4: Calculate the first frame of sampling that needs manual intervention; first, identify the vortex structure, binarize the Q matrix, that is, mark the area greater than the threshold value as 1 and mark the part less than the threshold value as 0, so as to obtain the region with a value of 1 that may exist several block distributions; number each region starting from 1 and assign the number to the corresponding block distribution region with a value of 1 to obtain a label matrix L; input the manual intervention into the number LN of the vortex core region that needs to be identified and tracked, and combine the label matrix, the method will obtain the index sequence INDEX of the vortex core region containing discrete points in the matrix when the first frame of sampling needs to be identified and tracked, and under the condition of uniform X and Y position matrix interpolation, that is, through INDEX, the vortex condition of the corresponding vortex core region in the vortex matrix is obtained, the index sequence is stored in the form of a matrix, the first row element is the row index of the vortex core region containing discrete points in the matrix, and the second row element is the column index of the vortex core region containing discrete points in the matrix:

[0011]

[0012] Thus, the circulation corresponding to the vortex core is calculated by discrete area integration, that is, the sum of all elements corresponding to the index sequence INDEX in the vortex matrix V is calculated, multiplied by the physical space area dA corresponding to a single element, and then saved as Γ1:

[0013] Γ = sum (V (INDEX)) * dA

[0014] At the same time, the index corresponding to the highest point of the vortex amplitude in the vortex core region is saved, the row index I and the column index J;

[0015] S5: In the automatic tracking and circulation calculation process of the moving vortex structure from the second frame to the Nth frame, the index of the highest point of the vortex amplitude in the vortex core region obtained from the last frame is used to determine the number LN of the vortex core region that needs to be identified and tracked in the label matrix L, so as to realize the automatic tracking of the moving vortex structure.

[0016] In the technical scheme of the above-mentioned automatic tracking and circulation calculation method of the moving vortex structure, preferably, in the process of interpolating the vortex distribution of the two-dimensional plane into the V matrix of n rows and m columns in step S2, but not limited to, the Q criterion vortex core region identification method is introduced, the definition of Q value is the second invariant of velocity gradient tensor, combined with the setting of threshold value, it is considered that the region with Q value greater than the threshold value is the vortex core region, and Q value is also interpolated to form a Q matrix of n rows and m columns.

[0017] In the above-mentioned technical solution of the automatic tracking and circulation calculation method for a moving vortex structure, preferably, the automatic tracking and circulation calculation process in step S5 is mainly based on the near-Gaussian distribution of vortex distribution in the vortex core region. The highest point of vortex amplitude in the vortex core region is generally located in the middle of the vortex core region. This point is not affected by complex factors such as the continuous movement of the vortex structure with the development of the flow field, deformation due to the shear force of the flow field, or the presence of other vortex structures in the surrounding area. Moreover, within a short sampling time interval, the displacement change of the highest point of vortex amplitude in the vortex core region is limited and much smaller than the characteristic size of the vortex core region.

[0018] In the above-mentioned technical solution of the automatic tracking and circulation calculation method for a moving vortex structure, preferably, the automatic tracking and circulation calculation process of the moving vortex structure from the 2nd frame to the Nth frame in step S5 specifically includes:

[0019] Step 1: Input the X and Y matrices, V1, V2, ..., VN-1, VN matrices, and Q1, Q2, ..., QN-1, QN matrices;

[0020] Step 2: Convert the criteria Q1, Q2, ..., QN-1, QN into the label matrix L1, L2, ..., LN-1, LN;

[0021] Step 3: If the first frame calculation uses manual initial intervention, input the number LN of the target vortex core region in the label matrix L1 to obtain the index sequence INDEX corresponding to LN in the label matrix of the current calculation frame;

[0022] Step 4: Extract part V of the index sequence INDEX corresponding to the vortex matrix of the current calculation frame, and sum V to obtain the circulation of the current frame, and save the index of the highest point of vortex amplitude in the core region of the record in row I and column J.

[0023] Step 5: If it is not the first frame to be calculated, automatically track the number LN in the I row and J column of the current frame label matrix, obtain the index sequence INDEX corresponding to LN in the current frame label matrix, and proceed to step 4.

[0024] Step 6: After obtaining the information in the index of the highest point of the vortex amplitude in the current frame circulation and the index of the I-th row and J-th column, determine whether it is the Nth frame for calculation. If the result is negative, return the I and J values ​​to the automatic tracking step; if the result is positive, output the time series of circulation: Γ1, Γ2, ..., ΓN-1, ΓN.

[0025] In the above-mentioned technical solution of the automatic tracking circulation calculation method for a moving vortex structure, preferably, in step S5, after obtaining the number LN of the vortex core region to be identified and tracked, the circulation calculation process will be the same as the calculation process of the first frame, and the circulation Γ2, ..., ΓN-1, ΓN of the second to Nth frames will be calculated.

[0026] As can be seen from the above technical solution, the present invention provides an automatic tracking circulation calculation method for moving vortex structures. Compared with the prior art, the present invention has the following beneficial effects:

[0027] ① Compared to the tedious process of manually determining the location and boundary of the target vortex structure and then calculating the circulation, this method minimizes manual intervention. Operators only need to specify the vortex structure of interest in the first sampling frame and then wait for the output of the time-varying process data of the vortex structure circulation.

[0028] ② Compared to existing automatic tracking and calculation techniques for the circulation of moving vortices, the new method employs an automatic tracking and identification method based on the vortex distribution characteristics within the vortex core region. This innovative method eliminates the need for complex edge detection algorithms, image feature extraction, and image tracking algorithms. Instead, it focuses on the vortex distribution within the vortex core region as the key feature, thereby greatly simplifying the calculation process.

[0029] ③ The new method no longer relies on cumbersome image processing and tracking techniques, thus significantly reducing the demand for computing resources. This optimization makes the calculation of circulation in vortex structures during transient evolution more efficient. By reducing the demand for computing power, the circulation calculation process is accelerated, making the tracking and analysis of vortex structure evolution faster and more accurate.

[0030] ④ The approach of processing based on two-dimensional matrices, rather than using a single image recognition calculation, makes it feasible to introduce more advanced vortex core region identification methods, such as the Q criterion, in addition to vorticity.

[0031] ⑤ The method for automatically tracking and identifying vortex structures and calculating circulation in the core region of a two-dimensional plane based on a two-dimensional matrix can be extended to automatically tracking and identifying the position and shape of three-dimensional vortex structures by converting the representation from a two-dimensional matrix to a three-dimensional matrix. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments of the present invention or the prior art will be briefly introduced and explained below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of the automatic tracking circulation calculation method for a moving vortex structure;

[0034] Figure 2 This is a schematic diagram illustrating the index association between the physical space and the parameter space;

[0035] Figure 3 A schematic diagram of the matrix-based vortex region labeling process;

[0036] Figure 4 This is a schematic diagram of vortex distribution within a typical vortex core region. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] To provide a clearer explanation and description of the technical solution and implementation of the present invention, several preferred specific embodiments for implementing the technical solution of the present invention are described below.

[0039] Example:

[0040] A preferred scheme for the automatic tracking circulation calculation method of moving vortex structures:

[0041] This embodiment includes:

[0042] Automatic tracking and circulation calculation of moving vortex structures based on two-dimensional matrices are performed. Therefore, two coordinate matrices are first defined to unify the global position information, that is, to represent the physical position of each point discretized into the two-dimensional matrix space, namely the X and Y matrices with n rows and m columns.

[0043]

[0044] Based on the X and Y matrices, the vorticity distribution in the two-dimensional plane is interpolated into an n x m matrix (V matrix). If advanced vortex core region identification methods, such as the Q criterion, are to be introduced, the Q values ​​are similarly interpolated to form an n x m matrix (Q matrix). Using a unified X and Y matrix interpolation to form the V and Q matrices ensures that the same indices in the four matrices correspond to the same physical spatial location, thus associating the elements in each matrix.

[0045] Based on the above preparations, considering the continuous calculation of the method, the input X and Y matrices, as well as the V and Q matrices sampled N times consecutively, numbered V1, V2, ..., VN-1, VN and Q1, Q2, ..., QN-1, QN respectively, will be used to calculate the first frame of sampling requiring manual intervention. First, the vortex structure is identified by binarizing the Q matrix, marking regions with values ​​greater than a threshold as 1 and those less than the threshold as 0. This yields several potentially blocky regions with values ​​of 1. Each region is numbered starting from 1 and assigned its number to the corresponding blocky region with a value of 1, resulting in the labeling matrix L. Subsequently, the manual intervention input is the number LN of the vortex core region to be identified and tracked. Combined with the labeling matrix, the method obtains the index sequence INDEX of the discrete points in the matrix for the vortex core region to be identified and tracked during the first frame sampling. Under the condition of unified X and Y position matrix interpolation, the vortex quantity of the corresponding vortex core region in the vortex quantity matrix is ​​obtained through INDEX. The index sequence is stored in matrix form. The first row of elements is the row index of the discrete points contained in the vortex core region in the matrix, and the second row of elements is the column index of the discrete points contained in the vortex core region in the matrix.

[0046]

[0047] Therefore, the circulation corresponding to the vortex core can be calculated using discrete surface integrals. This involves summing all elements of the index sequence INDEX in the vortex V matrix, multiplying it by the physical space area dA corresponding to a single element, and then storing it as Γ1.

[0048] I = sum(V(INDEX)) * CdA

[0049] Simultaneously, the index corresponding to the highest point of vortex amplitude within the vortex core region is saved: row index I and column index J. Subsequently, automatic tracking and circulation calculation of the moving vortex structure will begin from frame 2 to frame N. This is primarily based on the near-Gaussian distribution of vortex amplitude within the vortex core region. The highest point of vortex amplitude within the vortex core region is generally located in the middle of the vortex core region, unaffected by complex factors such as the continuous movement of the vortex structure with the development of the flow field, deformation due to flow field shear forces, or the presence of other vortex structures in the surrounding area. Furthermore, within a short sampling time interval, the displacement change of the highest point of vortex amplitude within the vortex core region is limited, much smaller than the characteristic size of the vortex core region. Therefore, during the automatic tracking and circulation calculation of the moving vortex structure from frame 2 to frame N, the index of the highest point of vortex amplitude within the vortex core region obtained in the previous frame will be used to determine the number LN of the vortex core region to be identified and tracked in the marking matrix L, thereby achieving automatic tracking of the moving vortex structure. Once the number LN of the vortex core region that needs to be identified and tracked is obtained, the circulation calculation process will be the same as that of the first frame, and the circulation Γ2, ..., ΓN-1, ΓN of the second to Nth frames will be calculated.

[0050] The automatic tracking and circulation calculation process of the moving vortex structure from frame 2 to frame N specifically includes:

[0051] Input X and Y matrices, V1, V2, ..., VN-1, VN matrices, Q1, Q2, ..., QN-1, QN matrices; convert the criteria Q1, Q2, ..., QN-1, QN into label matrices L1, L2, ..., LN-1, LN; if the first frame calculation uses manual initial intervention, input the number LN of the target vortex core region in the label matrix L1 to obtain the index sequence INDEX corresponding to LN in the label matrix of the current calculation frame;

[0052] Extract a portion V of the index sequence INDEX corresponding to the vortex matrix of the current calculation frame, and sum V to obtain the circulation of the current frame. Also, save the index of the highest point of vortex amplitude in the core region of the vortex, in row I and column J. If it is not the first frame, automatically track the number LN of the current calculation frame marker matrix in row I and column J, and obtain the index sequence INDEX corresponding to LN in the current calculation frame marker matrix. Then, extract a portion V of the index sequence INDEX corresponding to the vortex matrix of the current calculation frame, and sum V to obtain the circulation of the current frame. Also, save the index of the highest point of vortex amplitude in the core region of the vortex, in row I and column J.

[0053] After obtaining the information in the index of the I-th row and J-th column corresponding to the highest point of the vortex amplitude in the current frame circulation and the vortex core region, it is determined whether it is the Nth frame for calculation. If the result is negative, the I and J values ​​are returned to the automatic tracking step; if the result is positive, the time series of circulation is output: Γ1, Γ2, ..., ΓN-1, ΓN.

[0054] Finally, it should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0055] This invention is not limited to the above-described preferred embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

Claims

1. A method for automatically tracking and calculating the circulation of a moving vortex structure, characterized in that, The circulation calculation process includes the following: S1: Define two coordinate matrices to unify global position information, representing the physical position of each point discretized into a two-dimensional matrix space, i.e., an n x m matrix X and a Y matrix: S2: Based on the X and Y matrices, the vorticity distribution of the two-dimensional plane is interpolated into an n-row m-column V matrix; by using the unified X and Y matrix interpolation to form the V matrix and Q matrix, the same index of the above four matrices will correspond to the same physical spatial location, and the elements in each matrix will be associated. S3: Considering the continuous calculation of the method, the input X and Y matrices, as well as the V and Q matrices sampled N times, are numbered as V1, V2, ..., VN-1, VN matrices and Q1, Q2, ..., QN-1, QN matrices, respectively. S4: Calculate the first frame of the sampled data requiring manual intervention. First, identify the vortex structure and binarize the Q matrix, marking regions with values ​​greater than a threshold as 1 and regions with values ​​less than the threshold as 0, thus obtaining regions with values ​​of 1 that may exist in several blocky distributions. Number each region starting from 1 and assign its number to the corresponding blocky distribution region with a value of 1, obtaining the labeling matrix L. Input the manual intervention into the number LN of the vortex core region to be identified and tracked. Combined with the labeling matrix, the method obtains the index sequence INDEX of the discrete points in the matrix of the vortex core region to be identified and tracked in the first frame of sampling. Under the condition of unified X and Y position matrix interpolation, the vortex situation of the corresponding vortex core region in the vortex matrix is ​​obtained through INDEX. The index sequence is stored in matrix form, with the first row element being the row index of the discrete points in the vortex core region in the matrix and the second row element being the column index of the discrete points in the vortex core region in the matrix. Therefore, the circulation corresponding to the vortex core is obtained by discrete surface integral calculation, which involves summing all elements of the index sequence INDEX in the vortex V matrix, multiplying it by the physical space area dA corresponding to a single element, and then storing it as Γ1: Γ = sum(V(INDEX)) * dA At the same time, save the index corresponding to the highest point of vortex amplitude in the core region of the vortex, row index I, column index J; S5: During the automatic tracking and circulation calculation of the moving vortex structure from frame 2 to frame N, the index of the highest point of vortex amplitude in the vortex core region obtained in the previous frame will be used to determine the number LN of the vortex core region that needs to be identified and tracked in the marker matrix L, thereby realizing the automatic tracking of the moving vortex structure.

2. The method for automatically tracking circulation calculation of a moving vortex structure according to claim 1, characterized in that, In step S2, the process of interpolating the vortex distribution of the two-dimensional plane into an n-row m-column V matrix also includes, but is not limited to, introducing the Q-criterion vortex core region identification method. The Q value is defined as the second invariant of the velocity gradient tensor. Combined with the setting of a threshold, the region where the Q value is greater than the threshold is considered to be the vortex core region. Similarly, the Q value is interpolated to form an n-row m-column Q matrix.

3. The method for automatically tracking circulation calculation of a moving vortex structure according to claim 1, characterized in that, In the automatic tracking and circulation calculation process of step S5, it is mainly based on the near-Gaussian distribution of vorticity distribution in the vortex core region. The highest point of vorticity amplitude in the vortex core region is generally located in the middle of the vortex core region. This point is not affected by complex factors such as the continuous movement of the vortex structure with the development of the flow field, deformation due to the shear force of the flow field, and the presence of other vortex structures in the surrounding area. Moreover, within a short sampling time interval, the displacement change of the highest point of vorticity amplitude in the vortex core region is limited and much smaller than the characteristic size of the vortex core region.

4. The method for automatically tracking circulation calculation of a moving vortex structure according to claim 1, characterized in that, The automatic tracking and circulation calculation process of the moving vortex structure from frame 2 to frame N in step S5 specifically includes: Step 1: Input the X and Y matrices, V1, V2, ..., VN-1, VN matrices, and Q1, Q2, ..., QN-1, QN matrices; Step 2: Convert the criteria Q1, Q2, ..., QN-1, QN into the label matrix L1, L2, ..., LN-1, LN; Step 3: If the first frame calculation uses manual initial intervention, input the number LN of the target vortex core region in the label matrix L1 to obtain the index sequence INDEX corresponding to LN in the label matrix of the current calculation frame; Step 4: Extract part V of the index sequence INDEX corresponding to the vortex matrix of the current calculation frame, and sum V to obtain the circulation of the current frame, and save the index of the highest point of vortex amplitude in the core region of the record in row I and column J. Step 5: If it is not the first frame to be calculated, automatically track the number LN in the I row and J column of the current frame label matrix, obtain the index sequence INDEX corresponding to LN in the current frame label matrix, and proceed to step 4. Step 6: After obtaining the information in the index of the highest point of the vortex amplitude in the current frame circulation and the index of the I-th row and J-th column, determine whether it is the Nth frame for calculation. If the result is negative, return the I and J values ​​to the automatic tracking step; if the result is positive, output the time series of circulation: Γ1, Γ2, ..., ΓN-1, ΓN.

5. The method for automatically tracking circulation calculation of a moving vortex structure according to claim 1, characterized in that, In step S5, after obtaining the number LN of the vortex core region that needs to be identified and tracked, the circulation calculation process will be the same as the calculation process of the first frame, and the circulation Γ2, ..., ΓN-1, ΓN of the second to Nth frames will be calculated.

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