A method for tracking vortex structures in a planar flow field

Abstract

This application provides a method for tracking vortex structures in a planar flow field, belonging to the technical field of vortex motion research. Specifically, it determines the vortex structure in a planar flow field based on traditional vortex identification methods, integrates parameters such as the geometric center or extreme point of the vortex structure, its velocity, and its geometric region, and achieves automatic trajectory tracking of a large number of multi-scale vortex structures based on minimum distance and the direction of vortex structure motion. At the same time, based on the overlap of vortex structure regions and the change in area at different time points, it establishes the correspondence between vortex structures in the merging and breaking processes. That is, while automatically tracking the trajectories of a large number of multi-scale vortex structures, it matches the source of newly generated vortex structures and the destination of disappearing vortex structures. This is of great significance for accurately elucidating the generation, development, and interaction laws of turbulent structures.

Description

Technical Field

[0001] This application relates to the field of vortex motion research, and in particular to a method for tracking vortex structures in a planar flow field. Background Technology

[0002] Vortexes are a widespread phenomenon in natural environments and engineering systems. Examples include visible natural phenomena like tornadoes and hurricanes, and the airflow generated when a cigarette is burned; in engineering, they are observed in flow around aircraft surfaces, flow around cylinders, and flow separation on the surface of aero-engine blades. As a core component of fluid motion, vortex morphology exhibits typical multi-scale characteristics, with representative vortex structures displaying significantly different forms at different scales. From microscopic cellular motion to planetary-scale meteorological systems, their formation principles and physical implications vary considerably. Furthermore, these vortices play a crucial role in the generation and evolution of turbulence.

[0003] Currently, methods for vortex identification can be mainly divided into two categories: the first is the Eulerian method, derived from Eulerian quantities such as velocity gradient; the second is the Lagrangian method, derived from Lagrangian quantities such as particle trajectory. Among these, the local regional methods within the Eulerian method are the most commonly used, such as the frequently used Q-criteria. Methods and These methods, among others, can not only respond instantly to constantly changing unsteady flow fields by calculating point-by-point, but are also conceptually easy to understand—vortices exist where certain thresholds are met. Although these methods may differ in identifying three-dimensional vortex structures, these criteria all yield similar results in planar flow fields. While extensive research has been conducted on how to acquire or identify complex vortex structures, relatively little attention has been paid to characterizing or tracking the temporal evolution of vortex structures. Summary of the Invention

[0004] In view of this, this application provides a method for tracking planar flow field vortex structures, which solves the problems in the prior art and realizes automatic trajectory tracking of a large number of multi-scale vortex structures based on the minimum distance and the motion direction of the vortex structure.

[0005] The method for tracking planar flow field vortex structures provided in this application adopts the following technical solution:

[0006] A method for tracking vortex structures in a planar flow field includes:

[0007] Step 1: Determine the vortex structure based on the planar flow field vortex structure identification method, and determine the current time according to the preset first threshold α. The boundaries and distribution areas of all vortex structures are defined, and the vortex positions are marked by extreme points or the center of the distribution area, denoted as vortex centers.

[0008] Step 2, at the current moment Select one vortex structure from all vortex structures as the selected vortex structure;

[0009] Step 3, calculate the current time. The distance between the vortex center of the selected vortex structure and the vortex centers of all other vortex structures is determined. The nearest vortex structure corresponding to the vortex center of the selected vortex structure that is closest to its own vortex center is identified, and the minimum distance between the vortex center of the selected vortex structure and the vortex center of the nearest vortex structure is recorded. ;

[0010] Step 4: Calculate the selected vortex structure at the current moment based on the flow field data. The direction of motion is denoted as the first direction of motion;

[0011] Step 5: Based on the preset second threshold β, determine the selected vortex structure at the current time. The vortex center is the center of the circle, β× For radius, Find the next moment within the sector formed by the central angle. The vortex structures that were not selected by the label, The angle is equal to 90°, and one radial radius side of the sector lies on the straight line containing the first direction of motion.

[0012] Step 6, if the next moment If an unmarked vortex structure exists within the sector, then the selected vortex structure is determined at the next moment. The location of the vortex core, and determine the position at the previous moment. Does the selected vortex structure exist among all vortex structures? If it does, search for the selected vortex structure in the record matrix / vector at the previous time step. The recording position is determined, and the selected vortex structure is matched and recorded at the corresponding position in the next moment. If the vortex structure information does not exist, the selected vortex structure is recorded at the current moment using a new recording matrix / vector. With the next moment vortex structure information;

[0013] Step 7, if the next moment If no unmarked vortex structure exists within the sector, the recording of the selected vortex structure is terminated.

[0014] Step 8, at the current moment From all vortex structures, select a new vortex structure as the chosen vortex structure, and repeat steps 3 to 7 until the current time is traversed. For all vortex structures, obtain the time trajectory of each vortex structure.

[0015] Optionally, in step 6, the selected vortex structure is determined at the next moment. The specific steps for determining the location of the vortex core include:

[0016] If the next moment If an unmarked vortex structure exists within the sector, then the next moment is determined. The area of ​​the vortex structure within the fan-shaped region and the current moment Vortex structures with area ratios within a preset range are selected as candidate vortex structures; the position of the vortex center of the candidate vortex structure closest to the vortex center of the selected vortex structure is taken as the selected vortex structure at the next moment. The location of the vortex core.

[0017] Optionally, step 9 is also included, which determines the cause of the newly generated vortex structure and the cause of the disappearance of the vortex structure based on the merging and breaking behavior of the vortex structure.

[0018] Optionally, determining the cause of the newly generated vortex structure in step 9 specifically includes:

[0019] Step 91: Select one vortex structure from all the vortex structures as the first vortex structure to be judged;

[0020] Step 92: Locate the starting time of the first vortex structure. The vortex structure is used as the initial vortex structure;

[0021] Step 93, set the start time of the initial vortex structure. The previous moment is taken as the moment before the start. The moment before the start The existence of a first overlapping vortex structure that coincides with the initial vortex structure distribution region is taken as the first condition. This first overlapping vortex structure is then considered from the moment preceding the initial value. To the start time The second condition is that the area of ​​the vortex structure decreases over time. If both the first and second conditions are met, the initial vortex structure of the first judgment vortex structure is generated after the first overlapping vortex structure breaks down. If the first and second conditions cannot be met simultaneously, the initial vortex structure of the first judgment vortex structure is generated at the initial time. produce;

[0022] Step 94: Select a new vortex structure from all the vortex structures as the first vortex structure to be judged, and repeat steps 92 and 93 until all vortex structures have been traversed.

[0023] Optionally, in step 9, the specific steps for determining the cause of the disappearance of the vortex structure include:

[0024] Step 95: Select one vortex structure from all the vortex structures as the second judgment vortex structure;

[0025] Step 96: Locate the trajectory termination time of the second judgment vortex structure. The vortex structure serves as the terminating vortex structure.

[0026] Step 97: Determine the termination time of the vortex structure. The next moment as the moment after termination The next moment will end The existence of a second overlapping vortex structure that coincides with the distribution region of the terminating vortex structure is taken as a third condition. This second overlapping vortex structure is considered to occur at a moment after termination. Compared to the end time The increase in the vortex structure area is taken as the fourth condition. If both the third and fourth conditions are met simultaneously, the terminating vortex structure of the second judgment vortex structure will merge and disappear; if the third and fourth conditions cannot be met simultaneously, the vortex structure of the second judgment vortex structure will terminate at the time of termination. Dissipation and disappearance;

[0027] Step 98: Select a new vortex structure from all the vortex structures as the second vortex structure, and repeat steps 96 and 97 until all vortex structures have been traversed.

[0028] Optionally, in step 1, based on The method identifies multi-scale vortex structures in planar flow fields, with a first threshold α of 0.52. This represents the region where the vortex structure exists, where... It is a dimensionless scalar used to measure the rotational intensity of a fluid.

[0029] Optionally, the vortex structure information includes the vortex center location and vortex area.

[0030] In summary, this application includes the following beneficial technical effects:

[0031] This system achieves automatic trajectory tracking of numerous multi-scale vortex structures using methods such as minimum distance and vortex structure motion direction. Simultaneously, based on the overlap of vortex structure regions and changes in area between consecutive time points, it establishes a correspondence between vortex structures during merging and breaking processes. This means that while automatically tracking the trajectories of numerous multi-scale vortex structures, it matches the source of newly generated vortex structures and the destination of vanishing vortex structures, solving the problem of mismatched vortex structures at adjacent time points caused by breaking and merging processes during the evolution of vortex structures of different scales in a planar flow field. This helps analyze the temporal correlation between vortex structures that break and merge during long-term vortex evolution, and explores the temporal evolution and motion characteristics of multi-scale vortex structures. Attached Figure Description

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

[0033] Figure 1 This is a flowchart illustrating the tracking method for vortex structures in a planar flow field. Detailed Implementation

[0034] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0035] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0037] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0039] This application provides a method for tracking planar flow field vortex structures.

[0040] like Figure 1 As shown, a method for tracking vortex structures in a planar flow field includes:

[0041] Step 1, Identify all vortex structures: Determine planar vortex structures based on the planar flow field vortex structure identification method, and determine the current time according to the preset first threshold α. The boundaries and distribution areas of all vortex structures are defined, and the vortex positions are marked by extreme points or the center of the distribution area, denoted as vortex centers.

[0042] Step 2, at the current moment Select one vortex structure from all vortex structures as the selected vortex structure;

[0043] Step 3, calculate the current time. The distance between the vortex center of the selected vortex structure and the vortex centers of all other vortex structures is determined. The nearest vortex structure corresponding to the vortex center of the selected vortex structure that is closest to its own vortex center is identified, and the minimum distance between the vortex center of the selected vortex structure and the vortex center of the nearest vortex structure is recorded. ;

[0044] Step 4: Calculate the selected vortex structure at the current moment based on the flow field data. The direction of motion is denoted as the first direction of motion;

[0045] Step 5: Find the next moment within a specific range Unselected vortex structures: Based on a preset second threshold β, the selected vortex structures at the current time... The vortex center is the center of the circle, β× For radius, Find the next moment within the sector formed by the central angle. The vortex structures that were not selected by the label, The angle is equal to 90°, and one radial radius side of the sector lies on the straight line containing the first direction of motion.

[0046] Step 6, if the next moment If an unmarked vortex structure exists within the sector, then the selected vortex structure is determined at the next moment. The location of the vortex core, and determine the position at the previous moment. Does the selected vortex structure exist among all vortex structures? (Based on the current...) Is the selected vortex structure at time step affected by the previous time step? Matching records to determine the previous moment Does the selected vortex structure exist among all vortex structures? If it does, search for the selected vortex structure in the record matrix / vector at the previous time step. The recording position is determined, and the selected vortex structure is matched and recorded at the corresponding position in the next moment. If the vortex structure information is not found, it means that the current time... If the selected vortex structure is a newly generated vortex structure, then the selected vortex structure at the current moment is recorded using a new recording matrix / vector. With the next moment The vortex structure information includes the vortex center location and vortex area.

[0047] Step 7, if the next moment The absence of unmarked vortex structures within the sector indicates that the selected vortex structure will not be present in the next time step. If it disappears, the recording of the selected vortex structure will be terminated;

[0048] Step 8, at the current moment From all vortex structures, select a new vortex structure as the chosen vortex structure, and repeat steps 3 to 7 until the current time is traversed. All vortex structures;

[0049] For each vortex structure at each time point, execute steps 1 to 8, traverse the tracking of all vortex structures at each time point, and obtain the time trajectory of each vortex structure.

[0050] Step 9: Based on the merging and breaking behavior of vortex structures, determine the causes of the formation of newly generated vortex structures and the causes of the disappearance of vortex structures.

[0051] This application utilizes traditional vortex identification methods to determine the vortex structure in a planar flow field. It integrates parameters such as the geometric center or extreme point of the vortex structure, its velocity, and its geometric region. Based on methods such as minimum distance and the direction of motion of the vortex structure, it achieves automatic trajectory tracking of a large number of multi-scale vortex structures. At the same time, it establishes the correspondence between vortex structures in the merging and breaking processes. That is, while automatically tracking the trajectories of a large number of multi-scale vortex structures, it matches the source of newly generated vortex structures and the destination of disappearing vortex structures. This is of great significance for accurately elucidating the generation, development, and interaction laws of turbulent structures.

[0052] Specifically:

[0053] In step 1, based on The method identifies multi-scale vortex structures in planar flow fields, with a first threshold α of 0.52. This represents the region where the vortex structure exists, where... It is a dimensionless scalar used to measure the rotational intensity of a fluid.

[0054] In step 6, the selected vortex structure is determined at the next moment. The specific steps for determining the location of the vortex core include:

[0055] If the next moment If an unmarked vortex structure exists within the sector, then the next moment is determined. The area of ​​the vortex structure within the fan-shaped region and the current moment Vortex structures with area ratios within a preset range are selected as candidate vortex structures; the position of the vortex center of the candidate vortex structure closest to the vortex center of the selected vortex structure is taken as the selected vortex structure at the next moment. The location of the vortex core; if no candidate vortex structure exists, the selected vortex structure is considered to be at the next moment. Disappears, terminating the recording of the selected vortex structure.

[0056] The specific reasons for determining the generation of the newly generated vortex structure in step 9 include:

[0057] Step 91: Select one vortex structure from all the vortex structures as the first vortex structure to be judged;

[0058] Step 92: Locate the starting time of the first vortex structure. The vortex structure is used as the initial vortex structure at the initial time. The moment when the first vortex structure is determined;

[0059] Step 93, set the start time of the initial vortex structure. The previous moment is taken as the moment before the start. The moment before the start The existence of a first overlapping vortex structure that coincides with the initial vortex structure distribution region is taken as the first condition. This first overlapping vortex structure is then considered from the moment preceding the initial value. To the start time The second condition is that the area of ​​the vortex structure decreases over time. If both the first and second conditions are met, the initial vortex structure of the first judgment vortex structure is generated after the first overlapping vortex structure breaks down. If the first and second conditions cannot be met simultaneously, the initial vortex structure of the first judgment vortex structure is generated at the initial time. produce;

[0060] Step 94: Select a new vortex structure from all the vortex structures as the first vortex structure to be judged, and repeat steps 92 and 93 until all vortex structures have been traversed.

[0061] In step 9, the specific steps for determining the cause of the disappearance of the vortex structure include:

[0062] Step 95: Select one vortex structure from all the vortex structures as the second judgment vortex structure;

[0063] Step 96: Locate the trajectory termination time of the second judgment vortex structure. The vortex structure serves as the terminating vortex structure.

[0064] Step 97: Determine the termination time of the vortex structure. The next moment as the moment after termination The next moment will end The existence of a second overlapping vortex structure that coincides with the distribution region of the terminating vortex structure is taken as a third condition. This second overlapping vortex structure is considered to occur at a moment after termination. Compared to the end time The increase in the vortex structure area is taken as the fourth condition. If both the third and fourth conditions are met simultaneously, the terminating vortex structure of the second judgment vortex structure will merge and disappear; if the third and fourth conditions cannot be met simultaneously, the vortex structure of the second judgment vortex structure will terminate at the time of termination. Dissipation and disappearance;

[0065] Step 98: Select a new vortex structure from all the vortex structures as the second vortex structure, and repeat steps 96 and 97 until all vortex structures have been traversed.

[0066] Based on the overlap of vortex structure regions and the changes in their area at different time points, this application establishes the correspondence between vortex structures during the merging and breaking processes.

[0067] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for tracking vortex structures in a planar flow field, characterized in that, include: Step 1: Determine the vortex structure based on the planar flow field vortex structure identification method, and determine the current time according to the preset first threshold α. The boundaries and distribution areas of all vortex structures are defined, and the vortex positions are marked by extreme points or the center of the distribution area, denoted as vortex centers. Step 2, at the current moment Select one vortex structure from all vortex structures as the selected vortex structure; Step 3, calculate the current time. The distance between the vortex center of the selected vortex structure and the vortex centers of all other vortex structures is determined. The nearest vortex structure corresponding to the vortex center of the selected vortex structure that is closest to its own vortex center is identified, and the minimum distance between the vortex center of the selected vortex structure and the vortex center of the nearest vortex structure is recorded. ; Step 4: Calculate the selected vortex structure at the current moment based on the flow field data. The direction of motion is denoted as the first direction of motion; Step 5: Based on the preset second threshold β, determine the selected vortex structure at the current time. The vortex center is the center of the circle, β× For radius, Find the next moment within the sector formed by the central angle. The vortex structures that were not selected by the label, The angle is equal to 90°, and one radial radius side of the sector lies on the straight line containing the first direction of motion. Step 6, if the next moment If an unmarked vortex structure exists within the sector, then the selected vortex structure is determined at the next moment. The location of the vortex core, and determine the position at the previous moment. Does the selected vortex structure exist among all vortex structures? If it does, search for the selected vortex structure in the record matrix / vector at the previous time step. The recording position is determined, and the selected vortex structure is matched and recorded at the corresponding position in the next moment. If the vortex structure information does not exist, the selected vortex structure is recorded at the current moment using a new recording matrix / vector. With the next moment vortex structure information; Step 7, if the next moment If no unmarked vortex structure exists within the sector, the recording of the selected vortex structure is terminated. Step 8, at the current moment From all vortex structures, select a new vortex structure as the chosen vortex structure, and repeat steps 3 to 7 until the current time is traversed. For all vortex structures, obtain the time trajectory of each vortex structure.

2. The method for tracking planar flow field vortex structures according to claim 1, characterized in that, In step 6, the selected vortex structure is determined at the next moment. The specific steps for determining the location of the vortex core include: If the next moment If an unmarked vortex structure exists within the sector, then the next moment is determined. The area of ​​the vortex structure within the fan-shaped region and the current moment Vortex structures with area ratios within a preset range are selected as candidate vortex structures; the position of the vortex center of the candidate vortex structure closest to the vortex center of the selected vortex structure is taken as the selected vortex structure at the next moment. The location of the vortex core.

3. The method for tracking planar flow field vortex structures according to claim 1, characterized in that, It also includes step 9, which determines the cause of the newly generated vortex structure and the cause of the disappearance of the vortex structure based on the merging and breaking behavior of the vortex structure.

4. The method for tracking planar flow field vortex structures according to claim 3, characterized in that, The specific reasons for determining the generation of the newly generated vortex structure in step 9 include: Step 91: Select one vortex structure from all the vortex structures as the first vortex structure to be judged; Step 92: Locate the starting time of the first vortex structure. The vortex structure is used as the initial vortex structure; Step 93, set the start time of the initial vortex structure. The previous moment is taken as the moment before the start. The moment before the start The existence of a first overlapping vortex structure that coincides with the initial vortex structure distribution region is taken as the first condition. This first overlapping vortex structure is then considered from the moment preceding the initial value. To the start time The second condition is that the area of ​​the vortex structure decreases over time. If both the first and second conditions are met, the initial vortex structure of the first judgment vortex structure is generated by the rupture of the first overlapping vortex structure. If the first and second conditions cannot be met simultaneously, the initial vortex structure of the first judgment vortex structure is generated at the initial time. Spontaneously generated; Step 94: Select a new vortex structure from all the vortex structures as the first vortex structure to be judged, and repeat steps 92 and 93 until all vortex structures have been traversed.

5. The method for tracking planar flow field vortex structures according to claim 3, characterized in that, In step 9, the specific steps for determining the cause of the disappearance of the vortex structure include: Step 95: Select one vortex structure from all the vortex structures as the second judgment vortex structure; Step 96: Locate the trajectory termination time of the second judgment vortex structure. The vortex structure serves as the terminating vortex structure. Step 97: Determine the termination time of the vortex structure. The next moment as the moment after termination The next moment will end The existence of a second overlapping vortex structure that coincides with the distribution region of the terminating vortex structure is taken as a third condition. This second overlapping vortex structure is considered to occur at a moment after termination. Compared to the end time The increase in the vortex structure area is taken as the fourth condition. If both the third and fourth conditions are met simultaneously, the terminating vortex structure of the second judgment vortex structure will merge and disappear; if the third and fourth conditions cannot be met simultaneously, the vortex structure of the second judgment vortex structure will terminate at the time of termination. Dissipation and disappearance; Step 98: Select a new vortex structure from all the vortex structures as the second vortex structure, and repeat steps 96 and 97 until all vortex structures have been traversed.

6. The method for tracking planar flow field vortex structures according to claim 1, characterized in that, In step 1, based on The method identifies multi-scale vortex structures in planar flow fields, with a first threshold α of 0.

52. This represents the region where the vortex structure exists, where... It is a dimensionless scalar used to measure the rotational intensity of a fluid.

7. The method for tracking planar flow field vortex structures according to claim 1, characterized in that, The vortex structure information includes the location of the vortex center and the vortex area.

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