A method for quantitatively analyzing local vortex structure for optimizing performance of biomimetic submersible

Abstract

The application discloses a kind of local vortex structure quantitative analysis methods for optimizing the performance of biomimetic submersible, belong to underwater biomimetic robot technical field.The method of the present application comprises, first based on the numerical calculation of flow field is carried out based on the immersed boundary method, obtains overall flow field data;Then according to the geometric characteristics and function of biomimetic body Preset division local analysis area;Finally, the contribution of each area to overall hydrodynamic force is calculated using quantitative formula based on vortex dynamics.The method solves the problem that the existing technology has space dimension reduction, grid is not suitable for large deformation motion and cannot complete time-varying analysis, quantifies the contribution of local vortex structure of key parts to water power at each moment, establishes the quantitative space-time mapping relationship between local vortex structure and stress, realizes the quantitative connection from flow field micro mechanism to engineering optimization design, provides accurate and reliable quantitative analysis tool and decision basis for deep understanding of biological propulsion mechanism and implementation of targeted performance optimization of biomimetic submersible.

Description

Technical Field

[0001] This invention belongs to the field of underwater biomimetic robot technology, specifically relating to a quantitative analysis method for local vortex structures used to optimize the performance of biomimetic submersibles. Background Technology

[0002] The demand for underwater environmental monitoring and resource exploration is growing. Biomimetic submersibles, with their efficient propulsion and good biocompatibility, have become an ideal platform for performing such tasks. The key to accurately optimizing the propulsion performance of biomimetic submersibles lies in the quantitative analysis of the local vortex structure in their flow field. Numerical simulations based on computational fluid dynamics can effectively obtain overall performance parameters and flow field information, while further quantitative analysis of the local vortex structure and establishment of a quantitative correlation between the vortex structure and local forces can reveal its underlying physical mechanisms. This is crucial for a deep understanding of the principles of efficient biological propulsion and for targeted optimization of the local configuration of biomimetic submersibles to improve overall performance.

[0003] Fish in nature achieve efficient propulsion through the flapping of flexible fins, and the exploration of their propulsion mechanism relies on the quantitative correlation between vortex structure and local hydrodynamics. Similarly, the targeted optimization design of fish-inspired submersibles requires precise local hydrodynamic analysis. However, traditional analysis methods typically only obtain the overall hydrodynamic performance of biomimetic submersibles. Existing local vortex structure analysis methods mainly focus on two-dimensional fixed airfoils and steady flow, which have significant limitations: First, two-dimensional airfoils are a simplified reduction of the actual three-dimensional biomimetic submersible and cannot fully reflect the complex vortex structure evolution and interactions caused by the motion of three-dimensional objects. Second, body-fitted meshes for fixed airfoils struggle to handle mesh distortion caused by large deformations in three-dimensional objects. Third, steady simulations of fixed airfoils cannot demonstrate the time-varying characteristics of unsteady problems, failing to capture the dynamic evolution of vortex structures at different times and attitudes during the flapping motion of the biomimetic submersible, making it difficult to achieve correlation analysis between time-varying local vortex structures and forces. These limitations restrict further improvements in the performance of biomimetic submersibles.

[0004] In summary, existing technologies suffer from a critical "analytical divide": on one hand, there are numerical methods that can efficiently calculate overall performance but cannot pinpoint local contributions; on the other hand, there are analytical methods that can deeply analyze flow mechanisms but are difficult to directly apply to engineering optimization and have stringent requirements for the continuity of input data. Therefore, there is an urgent need for a method specifically designed for biomimetic submersibles, capable of seamlessly integrating efficient numerical computation with refined flow field analysis, and able to quantitatively map the analysis results to the local vortex structure of specific physical components, thus bridging the gap between "flow mechanism understanding" and "performance optimization design." Summary of the Invention

[0005] The technical problem to be solved: To overcome the shortcomings of existing technologies, this invention provides a quantitative analysis method for local vortex structures to optimize the performance of biomimetic submersibles. This method, through numerical calculation and quantitative vortex structure analysis, aims to achieve two main objectives: first, by calculating the local vortex structure in the transient flow field, it establishes a quantitative mapping between the vortex structure and the local forces acting on the submersible in the spatiotemporal distribution; second, based on the hydrodynamic contribution of each local region, it quantitatively assesses the impact on overall propulsion performance, thereby clarifying the optimization objectives and basis, and ultimately establishing a complete quantitative relationship chain between "vortex structure evolution—local forces—overall performance optimization." This solves the problems of spatial dimension reduction, mesh inapplicability to large deformation motions, and inability to perform time-varying analysis in existing vortex structure analysis techniques.

[0006] The technical solution of this invention is: a quantitative analysis method for local vortex structure for optimizing the performance of biomimetic submersibles, comprising the following steps: Step 1. Numerical calculation and flow field acquisition: Based on the submerged boundary method, unsteady flow field numerical calculation is performed on the biomimetic submersible model to be analyzed to obtain the overall time-domain flow field data including the velocity field and pressure field, as well as the overall hydrodynamic parameters of the biomimetic submersible. Step 2. Local Region Division: Based on the geometry and optimization objectives of the biomimetic submersible, at least one local analysis region associated with key physiological structures or expected vortex structure generation sites is predefined in its flow field; Step 3. Quantitative analysis of local vortex structure: For each local analysis region defined in Step 2, extract the corresponding local flow field data from the overall time-domain flow field data obtained in Step 1; use a quantitative analysis method based on vortex dynamics theory to process the local flow field data and independently calculate the contribution of each local analysis region to the total hydrodynamic force of the biomimetic submersible at each time step. In particular, through steps 1 to 3, a quantitative mapping relationship is established between the evolution of local vortex structures, the forces in local areas and the overall hydrodynamic performance in the flow field of the biomimetic submersible, which is used to guide its targeted performance optimization.

[0007] A further technical solution of the present invention is: in step 1, the numerical calculation based on the immersion boundary method includes: Prediction step: Solve the Navier-Stokes equations without submerged boundary force source terms to obtain the predicted velocity field at time step t+1; Correction step: Combining the constructed linear equations including the contribution of the submerged boundary force source, the predicted velocity field is corrected to obtain the corrected velocity field at time step t+1; the expression of the linear equations is:

[0008] In the formula, For the density of the fluid, u For speed,p For pressure, The coefficient of dynamic viscosity, f The additional force term representing the boundary effect, I Unit tensor; Final velocity field: The predicted velocity field is combined with the corrected velocity field to obtain the final velocity field at time step t+1.

[0009] A further technical solution of the present invention is that the division of the local analysis region follows the geometry-function mapping principle, specifically including: The surface of the pectoral or caudal fin and the near-field flow field of the biomimetic submersible are divided into at least two sub-regions corresponding to the leading edge vortex generation region, the trailing edge vortex generation region, and the fin tip vortex generation region, respectively.

[0010] A further technical solution of the present invention is: the kinematic control equations of the biomimetic submersible model include: For the left wing, its form is as follows:

[0011] The right wing is symmetrical in form; In the formula, A l , A r The amplitude is measured on the left and right sides; t For time; ( x 0, y 0, z 0) represents the initial position coordinates of the manta ray model; x , y , z )for t Position coordinates at that moment; W l , W r For the wave numbers on the left and right sides; f l , f r The frequency of left and right movements; , These are the control parameters for left and right chordal oscillations; , This represents the maximum value of the left and right bending angles; u l , u r To control the parameters of the upward offset of the left and right wings, d l , d r Parameters for controlling the downward offset of the left and right wings; , To adjust the phase of movement of the left and right pectoral fins; ML The body length is designed to resemble that of a manta ray submersible model. MW The model is a manta ray-inspired submersible with a half-length span.

[0012] A further technical solution of the present invention is: in step 3, the calculation strategy of the quantitative analysis method for vortex structures includes the following steps: Step 3.1: Data import and preprocessing; import the flow field data of the current time step obtained in Step 1, and extract only the velocity field and pressure field data belonging to this local analysis region to remove irrelevant information; Step 3.2: Calculation of intermediate variables; According to the formula for quantitative analysis of local vortex structures:

[0013] in, Fl Represents the entire fluid domain. S For the boundary of the region, M The boundary of the object's surface; d The position vector from each grid point to the centroid of the manta ray model; ω It is vorticity; u t represents velocity; t represents time. V Let be the integration variable, representing the integration over the volume; F This refers to the forces acting on this local area. This represents the result of integration over the interior region of an object; For the surface integration results; Calculate intermediate variables from the preprocessed velocity field data; ω It is vorticity, calculated from the velocity field. curl We obtain that in a three-dimensional rectangular coordinate system ( x,y,z In ), the velocity component is (u,v,w ), can vorticity ω The three-dimensional components are written as:

[0014] The three-dimensional components of the vorticity field can be discretized and calculated using the central difference method; ρ is the fluid density, which can be directly obtained in this calculation method; μ is the viscosity, which can be directly obtained in this calculation method; n is the unit normal vector of the domain boundary. Since the regions divided in this quantitative analysis method are all hexahedral square domains, the unit normal vector n of the domain boundary can be directly obtained. To complete The calculation will be saved after the calculation in the previous time step. As a result, by taking the current time step The result is forward-differenced from the result of the previous time step, thereby realizing the calculation of the intermediate parameter; Step 3.3: Integral calculation; Using different local regions as different integration regions, complete the calculations of each item in the formula of the quantitative analysis method for local vortex structure, and obtain the hydrodynamic parameters of each local region; Step 3.4: Output Results; Save the hydrodynamic parameters obtained at each time step for different regions, and process and display the data after all time steps have been calculated. A further technical solution of the present invention is: in step 2, an overall verification strategy is also included: The entire structure of the biomimetic submersible is defined as a whole local analysis region; After performing step 3, the calculated overall regional hydrodynamic contribution is compared with the overall hydrodynamic parameters directly obtained in step 1 to verify the accuracy of the quantitative analysis method.

[0015] A further technical solution of the present invention is: step 2 further includes a local hydrodynamic parameter analysis strategy. After verification, based on the optimization design requirements, the bionic submersible is divided into multiple local analysis regions, and the contribution of each region is calculated to quantify the impact of each component on the overall performance.

[0016] A further technical solution of the present invention is: the method for generating the Euler background mesh in step 1 includes: A three-dimensional, uniformly meshed area is set around the biomimetic submersible model; Outside the encrypted area, a non-uniform grid with progressively increasing grid size is used; Two virtual meshes are added to the outermost layer of the computational domain to handle boundary conditions. A further technical solution of the present invention is that the method further includes: Step 4. Optimization Design and Feedback: Analyze the contribution time history curves of each local analysis region output in Step 3 to identify the key regions that have a gain or drag effect on propulsion performance and their phases of action; Based on this, the geometric configuration, kinematic parameters, or control strategy of the corresponding region of the bionic submersible are adjusted, and steps 1 to 3 are repeated for iterative optimization.

[0017] A quantitative analysis system for local vortex structures used to optimize the performance of biomimetic submersibles includes: The flow field calculation module is used to perform unsteady flow field numerical calculations on the biomimetic submersible model based on the submerged boundary method, generating overall time-domain flow field data including velocity and pressure fields. The region definition module is used to pre-define at least one local analysis subdomain associated with the key vortex structure generation location in the flow field space, based on the geometric characteristics and performance optimization objectives of the biomimetic submersible. The quantitative analysis module is used to extract the local flow field data corresponding to each local analysis subdomain from the overall time-domain flow field data, and calculate the real-time contribution of each subdomain to the overall hydrodynamics of the biomimetic submersible based on eddy dynamics theory. The optimization decision module is used to generate optimization suggestions for specific structural or motion parameters of the biomimetic submersible based on the time history data of the contribution of each subdomain. The system establishes a mapping relationship between flow field subdomains and physical components through the region definition module, and forms a closed-loop analysis process from quantitative analysis of local vortex structures to targeted performance optimization through the quantitative analysis module and the optimization decision module. Beneficial effects The beneficial effects of this invention are as follows: This invention proposes a quantitative analysis method for local vortex structures to optimize the performance of biomimetic submersibles. Based on obtaining the unsteady hydrodynamic parameters during the overall motion of the three-dimensional biomimetic submersible, it can quantify the contribution of key local regions to propulsion performance and establish a quantitative mapping relationship between the evolution of local vortex structures and instantaneous forces during unsteady time-varying processes. Specific effects are analyzed as follows: 1. The method of this invention uses the overall flow field information obtained through numerical calculation as input. By dividing the object into local regions, it quantitatively analyzes the flow field data of the corresponding regions, thereby obtaining the specific impact of each local region on hydrodynamic performance. This method can accurately locate the key flow field regions affecting performance, quantify the hydrodynamic contribution of vortex structures within them, and establish a quantitative mapping relationship between "local vortex-force," providing a reliable quantitative basis for in-depth understanding of biological propulsion mechanisms and the implementation of targeted optimization design for biomimetic submersibles. 2. To address the disconnect between existing vortex analysis methods and specific design components, this invention proposes a "regional partitioning strategy based on geometric and functional pre-defined parameters." This strategy addresses the issue of unsteady hydrodynamic parameters of local vortex structures during the motion of a three-dimensional biomimetic submersible, which cannot be quantified and leads to a disconnect between vortex analysis methods and specific design components. Before analysis, this method actively binds the analysis domain to specific geometric regions of the submersible (such as the leading edge of the pectoral fin and the fin tip) based on biological propulsion mechanisms. This allows all quantitative analysis results to be directly and clearly attributed to specific physical components. Designers no longer obtain abstract flow field diagrams, but rather intuitive and actionable conclusions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall calculation process of the quantitative analysis method in an embodiment of the present invention.

[0019] Figure 2This is a schematic diagram of the manta ray-inspired submersible model used in the quantitative analysis method of this invention.

[0020] Figure 3 This diagram illustrates the subdomain partitioning using the quantitative analysis method of this invention.

[0021] Figure 4 This is a schematic diagram of the calculation process of the quantitative analysis method in an embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the hydrodynamic parameters obtained using the quantitative analysis method of this invention in a single region.

[0023] Figure 6 This is a schematic diagram of the hydrodynamic parameters obtained using the quantitative analysis method of this invention in three regions.

[0024] Figure 7 This is a schematic diagram of the three-region vortex structure results obtained using the quantitative analysis method of this invention. Detailed Implementation

[0025] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0026] In existing technologies, Chinese patent CN 119397942 B provides a quantitative analysis method for the local vortex structure of a two-dimensional airfoil under steady flow, addressing the "quantitative analysis method for complex flow dynamic mechanisms in body-fitted CFD calculations." This method is based on a two-dimensional body-fitted mesh and is applicable to steady-state conditions without motion, effectively decomposing the vortex-induced aerodynamic loads on the surface of the two-dimensional airfoil. However, for three-dimensional biomimetic submersibles undergoing unsteady motion, their complex shapes and large deformations make body-fitted meshes difficult to apply. Furthermore, steady-state analysis cannot reflect the time-varying vortex structure characteristics during motion and cannot quantitatively link the time-varying vortex structure with time-varying mechanical properties. Currently, the analysis of local vortex structures has limitations in terms of spatial dimension, mesh adaptability, and time-varying analysis capabilities. Although analysis results can be obtained, they have not yet been used in the simulation calculation of three-dimensional moving biomimetic submersibles.

[0027] Based on the problems existing in the prior art, this invention proposes a quantitative analysis method for local vortex structure to optimize the performance of biomimetic submersibles, comprising the following steps: Step 1. Numerical calculation and flow field acquisition: Based on the submerged boundary method, unsteady flow field numerical calculation is performed on the biomimetic submersible model to be analyzed to obtain the overall time-domain flow field data including the velocity field and pressure field, as well as the overall hydrodynamic parameters of the biomimetic submersible. Step 2. Local Region Division: Based on the geometry and optimization objectives of the biomimetic submersible, at least one local analysis region associated with key physiological structures or expected vortex structure generation sites is predefined in its flow field; Step 3. Quantitative analysis of local vortex structure: For each local analysis region defined in Step 2, extract the corresponding local flow field data from the overall time-domain flow field data obtained in Step 1; use a quantitative analysis method based on vortex dynamics theory to process the local flow field data and independently calculate the contribution of each local analysis region to the total hydrodynamic force of the biomimetic submersible at each time step. In particular, through steps 1 to 3, a quantitative mapping relationship is established between the evolution of local vortex structures, the forces in local areas and the overall hydrodynamic performance in the flow field of the biomimetic submersible, which is used to guide its targeted performance optimization.

[0028] This invention also proposes a quantitative analysis system for local vortex structures to optimize the performance of biomimetic submersibles, comprising: The flow field calculation module is used to perform unsteady flow field numerical calculations on the biomimetic submersible model based on the submerged boundary method, generating overall time-domain flow field data including velocity and pressure fields. The region definition module is used to pre-define at least one local analysis subdomain associated with the key vortex structure generation location in the flow field space, based on the geometric characteristics and performance optimization objectives of the biomimetic submersible. The quantitative analysis module is used to extract the local flow field data corresponding to each local analysis subdomain from the overall time-domain flow field data, and calculate the real-time contribution of each subdomain to the overall hydrodynamics of the biomimetic submersible based on eddy dynamics theory. The optimization decision module is used to generate optimization suggestions for specific structural or motion parameters of the biomimetic submersible based on the time history data of the contribution of each subdomain. The system establishes a mapping relationship between flow field subdomains and physical components through the region definition module, and forms a closed-loop analysis process from quantitative analysis of local vortex structures to targeted performance optimization through the quantitative analysis module and the optimization decision module.

[0029] The above technical solution will be further analyzed below with reference to the accompanying drawings and examples: In one embodiment, taking the performance analysis of a manta ray-inspired submersible as an example, the specific implementation steps of the present invention are described in detail, such as... Figure 1 As shown.

[0030] This embodiment presents a quantitative analysis method for local vortex structures used to optimize the performance of biomimetic submersibles, comprising the following steps: Step 1: Refer to Figure 2As shown, a simulation computational physics model is established and a triangular surface mesh is generated. In this embodiment, a manta ray-inspired submersible model is used as an example, with the body length represented by... ML Indicates body width using MW It means that among them ML =1.85m, MW =1.45m. The model was imported into ICEM software to generate a triangular surface mesh, and the Lagrange point data was output as the initial values ​​for the physical model and input into the numerical calculation method.

[0031] Step 2: Initialize simulation settings. Set the input speed according to... CFL =0.5 sets the duration of a single time step; sets the total number of iterations to be greater than 5 flapping cycles to ensure that the mechanical performance has stabilized; sets the boundary conditions for the inlet, outlet, and four far-field walls.

[0032] Step 3: Generate the flow field mesh, determine the flow field region, and simulate the flow field environment surrounding the physical model. The fluid domain mesh is generated using a mesh generation method. In this application, the surrounding flow field range is determined based on the model size, with a total flow field size of 16.2. ML ×16.2 ML ×16.2 ML The uniformly encrypted area size is 1.62. ML ×1.95 ML ×1.62 ML The mesh size of the uniformly encrypted zone is 0.01. ML .

[0033] Step 4: Calculation of overall flow field information. Set up the Lagrange nodal motion equations, complete the search for the corresponding Eulerian nodes for each Lagrange node, and save the data; construct a system of linear equations and complete the iterative solution; calculate the overall hydrodynamic parameters of the biomimetic submersible, and obtain the velocity field and pressure field parameters.

[0034] A motion equation was established to control the flapping motion of the manta ray-inspired submersible model. The movement of a manta ray can be viewed as a coupling of spanwise and chordal deformation. Based on the motion pattern of a real organism with a constant body length, the motion equation is as follows: Left wing:

[0035] The equation of motion for the right wing is:

[0036] In the formula, A For amplitude, t For time; ( x 0, y 0, z 0) represents the initial position coordinates of the manta ray model; x ,y , z )for t Position coordinates at that moment; W It is a dimensionless wavenumber; f The frequency of the pectoral fin flapping; For chordal wave control parameters; This represents the maximum bending angle. u , d To adjust the parameters of the vertical offset of the motion. In this embodiment, the following is selected: f =1Hz, W =0.4, A =0.35 ML , u =0, d =1.

[0037] Step 5: Detailed iterative calculation process. The effect of the boundary on the flow field is expressed through a force source. f The form is reflected in the Navier-Stokes equations:

[0038] In the formula, For the density of the fluid, u For speed, p For pressure, The coefficient of dynamic viscosity, f The additional force term representing the boundary effect, I It is a unit tensor.

[0039] Based on the conventional Navier-Stokes equations:

[0040]

[0041] The prediction-correction method is used to solve the problem. The prediction step solves the conventional Navier-Stokes equations to obtain the solution. t+ Density of 1 time step and prediction speed :

[0042] The correction speed is obtained by calculating the correction step using the following formula. ,

[0043] Based on the predicted speed and correction speed Get t+ The velocity field at time step 1 is :

[0044] The data interaction between Lagrange nodes and Euler nodes is as follows:

[0045]

[0046] Step 6: The force applied to the object can be... x , y , z The thrust is obtained by decomposing the material in three directions. T Lift L Dimensionless thrust coefficient C T and lift coefficient C L as follows:

[0047]

[0048] in, For density, U This refers to the inlet velocity.

[0049] Step 7: Refer to Figure 3 As shown, the quantitative analysis method divides the region to solve for local hydrodynamic parameters. Since the region division can be defined according to requirements, this embodiment uses two different region division strategies: First, the entire manta ray model is divided into one region. In this case, the quantitative analysis method can obtain the hydrodynamic performance parameters of all structures in the manta ray model. The correctness of the analysis method can be determined by comparing the quantitative analysis results with the numerical calculation results. Second, the pectoral fin of the manta ray model is divided into three regions, corresponding to the anterior edge of the pectoral fin (…). Z 1) The caudal margin of the pectoral fin ( Z 2) Pectoral fin tips ( Z 3) In the three regions, Z Region 1 is used to calculate the leading-edge vortex (LEV) generated by the leading edge of the pectoral fin. Z Region 2 is used to calculate the trailing edge vortex (TEV) generated by the caudal margin of the pectoral fin. Z Region 3 is used to calculate the tip vortex TV generated by the pectoral fin tip.

[0050] Step 8: Refer to Figure 4 The flowchart illustrates the quantitative analysis method. The flow field information obtained in step 4 is imported into the analysis module via an interface, and the imported velocity field is then processed. The following processing is performed. For the three-dimensional fluid domain Z... f , around solid M External control surface S Boundary:

[0051] in, Z f It consists of two parts: the boundary of the region. S and object surface boundary M In this embodiment, M Its deformation is controlled by the Lagrange point coordinates and motion equations on the surface of the manta ray model; d It is the position vector of each grid point from the centroid of the manta ray model; ω It is vorticity, calculated from the velocity field. curl We obtain that in a three-dimensional rectangular coordinate system ( x , y , z In ), the velocity component is ( u , v , w ), can vorticity ω The three-dimensional components are written as:

[0052] The three-dimensional components of the vorticity field can be discretized and calculated using the central difference method; ρ It is the fluid density, which can be directly obtained in this calculation method; μ It is viscosity, which can be directly obtained in this calculation method; n This is the unit normal vector of the domain boundary. Since the regions divided in this quantitative analysis method are all hexahedral square domains, the unit normal vector of the domain boundary can be obtained directly. n .

[0053] To complete The calculation will be saved after the calculation in the previous time step. As a result, by taking the current time step The intermediate parameter is calculated by forward difference between the result and the result of the previous time step.

[0054] The expression is:

[0055] In this invention, the numerical calculation method used is the submerged boundary method, and the object boundary... M Both sides n They cancel each other out. Therefore, the original formula for quantitative analysis of vortex structures can be simplified in the submerged boundary method as follows:

[0056] In the formula, Fl Represents the entire fluid domain. and for:

[0057]

[0058] To facilitate visualization, an output module is set up at the end of this quantitative analysis method to output the dimensionless hydrodynamic parameters in different subdomains to the corresponding files.

[0059] In one embodiment, the flow field mesh generation method includes the following steps: Step 1: Settings x , y , z The computational domain lengths in the three directions are set. x , y , z The coordinates of the center point of the uniformly encrypted region in three directions and the length of the uniformly encrypted region, as well as the length of the computational domain and the length of the uniformly encrypted region, can be adjusted according to the CFD calculation requirements. Step 2: Settings x , y , z The number of grid cells in the uniformly encrypted region in three directions is set. x , y , z The grid numbers located at the center point of the uniformly dense region in three directions; the number of grids in the uniformly dense region can be adjusted according to the object's feature size. Step 3: Obtain the uniformly encrypted region. Each Euler node is in... x , y , z Coordinates in three directions; to ensure a continuous transition between the uniformly encrypted and unencrypted mesh regions, the coordinates of each Euler node in the unencrypted region are set via a function. x , y , z Coordinates in three directions; Step 4: Add two more ghost meshes outside the outer mesh, with the length of each mesh determined by the size of its adjacent internal meshes; Step 5, calculate the value of each grid cell. x , y , z The coordinates of the center point in three directions, the interpolation relationship with the two grids before and after it, and the generated grid output.

[0060] In one embodiment, the vortex structure quantitative analysis method, the region division strategy includes the following steps: Strategy 1: Overall Validation Strategy. The model is divided into a single region. In this case, the quantitative analysis method can obtain the hydrodynamic performance parameters of all structures within the model, which are the overall hydrodynamic parameters of the model. Comparing the quantitative analysis results with the numerical calculation results can determine the correctness of the analysis method. Strategy 2: Local hydrodynamic parameter analysis strategy. Based on successful validation, a local hydrodynamic parameter analysis strategy can be adopted. This involves dividing the target model into characteristic regions based on its shape, and then calculating the hydrodynamic performance of these local regions.

[0061] Effect verification: To ensure the accuracy of the quantitative analysis method of this invention, Figure 5 This paper compares the overall hydrodynamic coefficients of the manta ray-inspired submersible obtained using the quantitative analysis method of this invention with those obtained through numerical calculation. During the five-cycle calculation process, the quantitative analysis method provided by this invention showed a high degree of agreement with the numerical calculation results in terms of trend and magnitude when calculating the overall hydrodynamic parameters in a single region. The peak values, trough values, and their occurrence times of the numerical calculation results and the quantitative analysis results of the vortex structure essentially correspond completely, proving that this quantitative analysis method can accurately capture the magnitude, frequency, and phase of unsteady forces caused by the motion of an object, and can accurately calculate the hydrodynamic parameters of the manta ray-inspired submersible.

[0062] To apply this quantitative analysis method to the analysis and design process of a manta ray-inspired submersible, Figure 6 These are the local hydrodynamic parameters of the manta ray in three regions obtained using the quantitative analysis method of this invention. Figure 7 This is a schematic diagram of the three-region vortex structure obtained using the quantitative analysis method of this invention. From... Figure 6 It can be seen that within one cycle, Z The average thrust coefficient generated by the LEV (Leading Vortex) at the leading edge of the pectoral fin in region 1 is -0.45. Z The average thrust coefficient generated by the TEV (transverse vortex) at the pectoral fin caudal rim in region 2 is -0.55. Z The average thrust coefficient generated by the pectoral fin tip vortex (TV) in region 3 is 1.34. Figure 7 This shows the specific locations of the leading-edge vortex (LEV), fin-tip vortex (TEV), and trailing-edge vortex (TV) of the manta ray-inspired submersible, proving the rationality of the three-region division. The results obtained from quantitative analysis clearly show that the main part of the thrust is related to... Z The contribution of the three regions is related, and Z 1 and Z The contribution of region 2 is mainly unfavorable; that is, the main part of the thrust is contributed by TV, while LEV and TEV generate more drag. ZRegion 1 represents the primary contributor to lift. The quantitative analysis method visually demonstrates which local forces contribute to the overall thrust and lift, and when they contribute, thus establishing a quantitative correlation between vortex structure evolution and local forces. These results provide specific guidance for optimizing the performance of biomimetic submersibles, namely, suppressing drag at the leading and trailing edges and enhancing gain at the fin tips.

[0063] In summary, this invention proposes a quantitative analysis method for local vortex structures to optimize the performance of biomimetic submersibles. Based on the overall stress and flow field parameter calculations, it can calculate the local stress conditions of the object using flow field information, thus quantitatively correlating the time-varying vortex structure generated by motion with the object's local time-varying hydrodynamic parameters. This provides quantitative guidance for a deeper understanding of biological propulsion mechanisms and the targeted optimization design of biomimetic submersibles.

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A quantitative analysis method for local vortex structures used to optimize the performance of biomimetic submersibles, characterized in that, Includes the following steps: Step 1. Numerical calculation and flow field acquisition: Based on the submerged boundary method, unsteady flow field numerical calculation is performed on the biomimetic submersible model to be analyzed to obtain the overall time-domain flow field data including the velocity field and pressure field, as well as the overall hydrodynamic parameters of the biomimetic submersible. Step 2. Local Region Division: Based on the geometry and optimization objectives of the biomimetic submersible, at least one local analysis region associated with key physiological structures or expected vortex structure generation sites is predefined in its flow field; Step 3. Quantitative analysis of local vortex structure: For each local analysis region defined in Step 2, extract the corresponding local flow field data from the overall time-domain flow field data obtained in Step 1; use a quantitative analysis method based on vortex dynamics theory to process the local flow field data and independently calculate the contribution of each local analysis region to the total hydrodynamic force of the biomimetic submersible at each time step. In particular, through steps 1 to 3, a quantitative mapping relationship is established between the evolution of local vortex structures, the forces in local areas and the overall hydrodynamic performance in the flow field of the biomimetic submersible, which is used to guide its targeted performance optimization.

2. The method for quantitative analysis of local vortex structure for optimizing the performance of a biomimetic submersible according to claim 1, characterized in that: In step 1, the numerical calculation based on the submerged boundary method includes: Prediction step: Solve the Navier-Stokes equations without submerged boundary force source terms to obtain the predicted velocity field at time step t+1; Correction step: Combining the constructed linear equations including the contribution of the submerged boundary force source, the predicted velocity field is corrected to obtain the corrected velocity field at time step t+1; the expression of the linear equations is: In the formula, For the density of the fluid, u For speed, p For pressure, The coefficient of dynamic viscosity, f The additional force term representing the boundary effect, I Unit tensor; Final velocity field: The predicted velocity field is combined with the corrected velocity field to obtain the final velocity field at time step t+1.

3. The method for quantitative analysis of local vortex structure for optimizing the performance of a biomimetic submersible according to claim 1, characterized in that: The division of the local analysis region follows the geometry-function mapping principle, specifically including: The surface of the pectoral or caudal fin and the near-field flow field of the biomimetic submersible are divided into at least two sub-regions corresponding to the leading edge vortex generation region, the trailing edge vortex generation region, and the fin tip vortex generation region, respectively.

4. The method for quantitative analysis of local vortex structures for optimizing the performance of biomimetic submersibles according to claim 1, characterized in that: The kinematic control equations of the biomimetic submersible model include: For the left wing, its form is as follows: The right wing is symmetrical in form; In the formula, A l , A r The amplitude is measured on the left and right sides; t For time; ( x 0, y 0, z 0) represents the initial position coordinates of the manta ray model; x , y , z )for t Position coordinates at that moment; W l , W r For the wave numbers on the left and right sides; f l , f r The frequency of left and right movements; , These are the control parameters for left and right chordal oscillations; , This represents the maximum value of the left and right bending angles; u l , u r To control the parameters of the upward offset of the left and right wings, d l , d r Parameters for controlling the downward offset of the left and right wings; , To adjust the phase of movement of the left and right pectoral fins; ML The body length is designed to resemble that of a manta ray submersible model. MW The model is a manta ray-inspired submersible with a half-length span.

5. The method for quantitative analysis of local vortex structure for optimizing the performance of a biomimetic submersible according to claim 1, characterized in that: In step 3, the calculation strategy of the quantitative analysis method for vortex structures includes the following steps: Step 3.1: Data import and preprocessing; import the flow field data of the current time step obtained in Step 1, and extract only the velocity field and pressure field data belonging to this local analysis region to remove irrelevant information; Step 3.2: Calculation of intermediate variables; According to the formula for quantitative analysis of local vortex structures: in, Fl Represents the entire fluid domain. S For the boundary of the region, M The boundary of the object's surface; d The position vector from each grid point to the centroid of the manta ray model; ω It is vorticity; u t represents velocity; t represents time. V Let be the integration variable, representing the integration over the volume; F This refers to the forces acting on this local area. This represents the result of integration over the interior region of an object; For the surface integration results; Calculate intermediate variables from the preprocessed velocity field data; ω It is vorticity, calculated from the velocity field. curl We obtain that in a three-dimensional rectangular coordinate system ( x,y,z In ), the velocity component is (u,v,w ), can vorticity ω The three-dimensional components are written as: The three-dimensional components of the vorticity field can be discretized and calculated using the central difference method; ρ is the fluid density, which can be directly obtained in this calculation method; μ is the viscosity, which can be directly obtained in this calculation method; n is the unit normal vector of the domain boundary. Since the regions divided in this quantitative analysis method are all hexahedral square domains, the unit normal vector n of the domain boundary can be directly obtained. To complete The calculation will be saved after the calculation in the previous time step. As a result, by using the current time step The result is forward-differenced from the result of the previous time step, thereby realizing the calculation of the intermediate parameter; Step 3.3: Integral calculation; Using different local regions as different integration regions, complete the calculations of each item in the formula of the quantitative analysis method for local vortex structure, and obtain the hydrodynamic parameters of each local region; Step 3.4: Output Results; Save the hydrodynamic parameters obtained at each time step for different regions, and process and display the data after all time steps have been calculated.

6. The method for quantitative analysis of local vortex structures for optimizing the performance of biomimetic submersibles according to claim 1, characterized in that: Step 2 also includes an overall verification strategy: The entire structure of the biomimetic submersible is defined as a whole local analysis region; After performing step 3, the calculated overall regional hydrodynamic contribution is compared with the overall hydrodynamic parameters directly obtained in step 1 to verify the accuracy of the quantitative analysis method.

7. The method for quantitative analysis of local vortex structures for optimizing the performance of biomimetic submersibles according to claim 1, characterized in that: Step 2 also includes a strategy for analyzing local hydrodynamic parameters: After verification, based on the optimization design requirements, the bionic submersible is divided into multiple local analysis regions, and the contribution of each region is calculated to quantify the impact of each component on the overall performance.

8. The method for quantitative analysis of local vortex structures for optimizing the performance of biomimetic submersibles according to claim 1, characterized in that: In step 1, the method for generating the Euler background mesh includes: A three-dimensional, uniformly meshed area is set around the biomimetic submersible model; Outside the encrypted area, a non-uniform grid with progressively increasing grid size is used; Two virtual meshes are added to the outermost layer of the computational domain to handle boundary conditions.

9. The method for quantitative analysis of local vortex structures for optimizing the performance of biomimetic submersibles according to claim 1, characterized in that: The method further includes: Step 4. Optimization Design and Feedback: Analyze the contribution time history curves of each local analysis region output in Step 3 to identify the key regions that have a gain or drag effect on propulsion performance and their phases of action; Based on this, the geometric configuration, kinematic parameters, or control strategy of the corresponding region of the bionic submersible are adjusted, and steps 1 to 3 are repeated for iterative optimization.

10. A quantitative analysis system for local vortex structures used to optimize the performance of biomimetic submersibles, characterized in that, include: The flow field calculation module is used to perform unsteady flow field numerical calculations on the biomimetic submersible model based on the submerged boundary method, generating overall time-domain flow field data including velocity and pressure fields. The region definition module is used to pre-define at least one local analysis subdomain associated with the key vortex structure generation location in the flow field space, based on the geometric characteristics and performance optimization objectives of the biomimetic submersible. The quantitative analysis module is used to extract the local flow field data corresponding to each local analysis subdomain from the overall time-domain flow field data, and calculate the real-time contribution of each subdomain to the overall hydrodynamics of the biomimetic submersible based on eddy dynamics theory. The optimization decision module is used to generate optimization suggestions for specific structural or motion parameters of the biomimetic submersible based on the time history data of the contribution of each subdomain. The system establishes a mapping relationship between flow field subdomains and physical components through the region definition module, and forms a closed-loop analysis process from quantitative analysis of local vortex structures to targeted performance optimization through the quantitative analysis module and the optimization decision module.

Images