Numerical simulation method for autonomous swimming behavior of aquatic organisms

Abstract

The invention discloses a numerical simulation method for autonomous swimming behaviors of aquatic organisms. The method comprises the following steps: 1) obtaining motion videos and images of swimming of the aquatic organisms; 2) processing the acquired image, and acquiring the body trunk center line position information of the aquatic organism in the swimming process; 3) analyzing the motion characteristics of the aquatic organisms based on the trunk line position change process of the organism body; 4) according to the motion characteristics, establishing an autonomous deformation motion description of the organism, and obtaining a muscle contraction pre-strain tensor equation of the organism based on the autonomous deformation motion description of the organism; 5) constructing an autonomous propulsion motion calculation model of the aquatic organisms in various flow field environments; and 6) analyzing in the autonomous propulsion motion calculation model of the aquatic creatures to obtain motion characteristics and mechanical characteristics of autonomous swimming behaviors of the aquatic creatures. The invention provides a method for directly simulating a living body to realize various swimming exercises through the action of muscle contraction and a surrounding water body.

Description

Technical Field

[0001] The present invention relates to bionic engineering technology, and in particular to a numerical simulation method for autonomous swimming behavior of aquatic organisms. Background Art

[0002] Fish and other aquatic organisms in nature exhibit a wide variety of swimming patterns, often characterized by high maneuverability, low energy consumption, and high efficiency. In-depth research into the kinematic characteristics and mechanical mechanisms of aquatic swimming behavior in various flow environments is of great significance for biomimetic applications and ecological conservation.

[0003] The random nature of biological motion, the sensitivity of the surrounding flow field to disturbances, and the limitations of methods for measuring biological mechanical parameters limit the information that can be obtained through experimental observation. Numerical simulation is an effective means of studying the swimming behavior of aquatic organisms. Due to the complexity of aquatic organisms' anatomy and the diversity of flow fields, analyzing the swimming patterns and mechanical mechanisms of various aquatic organisms requires knowledge from multiple disciplines, including fluid mechanics and biology. Therefore, designing and implementing effective numerical simulation algorithms for aquatic swimming behavior is a key area of ​​research that researchers are constantly striving to address. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a numerical simulation method for the autonomous swimming behavior of aquatic organisms in response to the defects in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a numerical simulation method for the autonomous swimming behavior of aquatic organisms, comprising the following steps:

[0006] 1) Obtain motion videos and images of aquatic organisms swimming;

[0007] 2) Processing the acquired images to obtain the centerline position information of the body of the aquatic organism during swimming;

[0008] 3) Analyzing the movement characteristics of aquatic organisms based on the change in the position of the organism's trunk line; the movement characteristics include: the speed of the aquatic organism's center of mass movement, the body deflection angle, and the autonomous muscle deformation morphology;

[0009] 4) Establishing a description of the organism's autonomous deformation motion based on the motion characteristics, and obtaining the organism's muscle contraction pre-strain tensor equation based on the organism's autonomous deformation motion description;

[0010] 5) Construct computational models of autonomous propulsion motion of aquatic organisms in various flow environments;

[0011] 6) Use the prestrain tensor of the muscle contraction prestrain tensor equation to control the autonomous deformation movement of the organism model, analyze and obtain the motion characteristics and mechanical characteristics of the autonomous swimming behavior of aquatic organisms in the calculation model of the autonomous propulsion movement of aquatic organisms, and complete the simulation of the swimming behavior of aquatic organisms through autonomous muscle deformation in various water flow environments.

[0012] According to the above scheme, in step 4), the muscle contraction pre-strain tensor equation of the organism is obtained, which is as follows:

[0013] 4.1) Using image processing software, extract the position coordinates (X, Y) of each point along the organism's trunk line in the flow field at each moment and calculate its swimming speed U and direction of travel α;

[0014] The position coordinates of each point on the body trunk of the organism in the flow field are converted into the position (x, y) of the body trunk in the body coordinate system;

[0015] 4.2) Treating aquatic organisms as elastically deformable bodies, the observed swimming behavior of aquatic organisms is decomposed through motion analysis to obtain the active deformation component controlled by the organisms;

[0016] 4.3) Represent the organism's lateral displacement y as a function of the organism's body position coordinate x and time t to obtain the equation describing the aquatic organism's motion;

[0017] 4.4) Based on the displacement y3 representing the autonomous deformation of the organism, calculate the organism's muscle contraction pre-strain tensor E0 according to the following formula:

[0018]

[0019] Among them, E0(x, y, t) is the prestrain of the organism's body at the position (x, y) due to muscle contraction at time t.

[0020] According to the above scheme, in step 4.2), the lateral displacement y of the organism is decomposed into three parts: the floating displacement y1 of the body along the center of mass, the displacement y2 around the center of mass, and the self-deformation displacement y3. According to the main line of the organism at each moment, the center of mass position and head rotation angle of the organism are extracted, and the displacement y3 caused by the organism's self-deformation is calculated.

[0021] For the main line of the organism at each moment, the center of mass position and head rotation angle of the organism are extracted, and then the displacement y1 caused by the floating of the center of mass and the displacement y2 caused by the rotation of the head are calculated. The displacement y3 caused by the deformation of the organism itself is obtained by deducting these two parts from the total displacement.

[0022] According to the above scheme, in step 4.3), the motion description equation of the organism is:

[0023] y(x,t)=y1(x,t)+y2(x,t)+y3(x,t)

[0024] y1(x,t)=y 10 sin(2πft+φ1),y2(x,t)=xθ0sin(2πft+φ2)

[0025] A(x)=|a0+a1x+a2x 2 +a3x 3 |

[0026] Among them, f is the frequency of the organism's movement; λ is the wavelength of the organism's fluctuation; y 10 is the amplitude of the sinking and floating motion of the organism's center of mass; θ0 is the maximum angle of the organism's head swing; A(x) represents the variation of the amplitude of the organism's autonomous deformation along the body position, and its expression depends on the specific swimming motion pattern; φ1, φ2, and φ3 are the initial phases of the three displacement components y1, y2, and y3, respectively. The specific values ​​are related to the choice of the initial moment, but the difference between the three is determined by the motion pattern and does not change with the choice of the initial moment.

[0027] Based on the above equations, the numerical values ​​of various parameters can be obtained through multi-parameter fitting using the position data of the body trunk at each moment obtained in the experiment.

[0028] According to the above scheme, in step 5), a computational model of autonomous propulsion motion of aquatic organisms in various flow field environments is constructed in Comsol Multiphysics software.

[0029] According to the above scheme, in step 5), the calculation model of the autonomous propulsion motion of aquatic organisms is a fluid-solid coupling model, wherein the fluid calculation domain is the area enclosed by the flow field structure boundary and the outer contour of the aquatic organism, and the material is set to liquid water; the solid calculation domain is the entire aquatic organism, and the material is set to an elastomer; the fluid-solid coupling boundary is the outer contour of the entire aquatic organism.

[0030] According to the above scheme, in step 6), the motion characteristics and mechanical characteristics of the autonomous swimming behavior of the aquatic organism are analyzed and obtained in the calculation model of the autonomous propulsion motion of the aquatic organism, and the steps are as follows:

[0031] 6.1) Grid division of the numerical calculation area;

[0032] 6.2) Set calculation parameters, solution parameters, boundary conditions and initial conditions for the calculation model;

[0033] 6.3) Controlling the autonomous deformation motion of a biological model based on pre-strain tensors;

[0034] 6.4) The k-ω turbulence model in the computational fluid dynamics module is used to calculate the flow field and fluid forces. The structural mechanics module is used to calculate the displacement and velocity of the organism. Through fluid-structure interaction calculations, the process of aquatic organisms swimming under the combined action of their own muscle contraction and the surrounding water flow is obtained. The motion and mechanical characteristics of their autonomous swimming behavior are then analyzed.

[0035] According to the above scheme, in step 6.2), the calculation parameters, solution parameters, boundary conditions and initial conditions are set as follows:

[0036] The calculation parameters include: incoming flow velocity, biological muscle contraction pre-strain tensor; wherein, the biological muscle contraction pre-strain tensor uses the pre-strain tensor of the muscle contraction pre-strain tensor equation;

[0037] The solution parameter settings include: turbulence model, solution algorithm, discrete format, solution accuracy and time step;

[0038] The boundary conditions of the fluid computational domain are set as follows: the right boundary is set as the velocity inlet boundary condition; the left boundary is set as the pressure outlet boundary condition; the upper and lower boundary conditions are moving wall boundary conditions, and the moving velocity is equal to the incoming flow velocity; the obstacles in the flow field and the outer contour of the organism are set as no-slip wall conditions;

[0039] The initial conditions are set as follows: the velocity of the entire fluid domain is equal to the incoming flow velocity and the organism is stationary.

[0040] The beneficial effects produced by the present invention are:

[0041] 1. Based on the biological motion information obtained by high-speed photography technology, the present invention establishes the pre-strain tensor of the organism and realizes the numerical simulation of the process of the organism controlling its own muscle contraction and swimming autonomously in water.

[0042] 2. The present invention regards aquatic organisms as elastically deformable bodies. Through motion analysis, the experimentally observed swimming motion of aquatic organisms is decomposed into two parts: "overall motion under the action of hydrodynamic forces" and "active deformation controlled by the organism". The active deformation is used as input and attached to the elastic body in the form of a pre-strain tensor. Based on fluid-solid coupling calculation, simulation analysis of autonomous swimming behavior is realized.

[0043] 3. The present invention provides a method for directly simulating the various swimming movements achieved by organisms through muscle contraction and the interaction with the surrounding water. It can be used to study the fluid-solid coupling process of various aquatic organisms swimming in various modes in different flow field environments, explore their motion and mechanical characteristics, analyze the response mechanism of aquatic organisms to the water flow environment and the mechanical mechanisms contained therein, and provide guidance for bionic applications and ecological protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0045] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0046] Figure 2 1 is a typical image and extracted body trunk line of a fish swimming experiment according to an embodiment of the present invention;

[0047] Figure 3 Schematic diagram of the decomposition of the motion of the fish body trunk line in an embodiment of the present invention;

[0048] Figure 4 1 is a diagram showing the fitting results of the fish trunk line displacement description equation according to an embodiment of the present invention;

[0049] Figure 5 is a calculation model and a grid division diagram in an embodiment of the present invention;

[0050] Figure 6 Schematic diagram of typical moment pre-strain distribution representing muscle contraction strength of fish body according to an embodiment of the present invention;

[0051] Figure 7 1 is a schematic diagram of the fluid-solid coupling process and flow field information of a fish moving in a Karman vortex flow field calculated in an embodiment of the present invention;

[0052] Figure 8 3 is a schematic diagram of the motion and mechanical parameter curves of a fish moving in a Karman vortex flow field, obtained by calculation in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0054] like Figure 1 As shown, a numerical simulation method for autonomous swimming behavior of aquatic organisms includes the following steps:

[0055] 1) Use high-speed photography to obtain motion videos and images of aquatic organisms swimming;

[0056] 2) Processing the acquired images to obtain the centerline position information of the body of the aquatic organism during swimming;

[0057] 3) Analyzing the movement characteristics of aquatic organisms based on the change in the position of the organism's trunk line; the movement characteristics include: the speed of the aquatic organism's center of mass movement, the body deflection angle, and the autonomous muscle deformation morphology;

[0058] 4) Establishing a description of the organism's autonomous deformation motion based on the motion characteristics, and obtaining the organism's muscle contraction pre-strain tensor equation based on the organism's autonomous deformation motion description;

[0059] 4.1) Using image processing software, extract the position coordinates (X, Y) of each point along the organism's trunk line in the flow field at each moment, and calculate the organism's swimming speed U and direction of travel α;

[0060] The position coordinates of each point on the body trunk of the organism in the flow field are obtained by coordinate translation and rotation of the body trunk in the body coordinate system (x, y);

[0061] 4.2) Treating aquatic organisms as elastically deformable bodies, the observed swimming behavior of aquatic organisms is decomposed through motion analysis to obtain the active deformation component controlled by the organisms;

[0062] The lateral displacement y of the organism is decomposed into three parts: the floating displacement y1 of the body along the center of mass, the displacement y2 around the center of mass, and the self-deformation displacement y3. According to the main line of the organism at each moment, the center of mass position and head rotation angle of the organism are extracted, and the displacement y3 caused by the organism's self-deformation is calculated.

[0063] For the main line of the organism at each moment, the center of mass position and head rotation angle of the organism are extracted, and then the displacement y1 caused by the floating of the center of mass and the displacement y2 caused by the rotation of the head are calculated. The displacement y3 caused by the deformation of the organism itself is obtained by deducting these two parts from the total displacement.

[0064] 4.3) Represent the organism's lateral displacement y as a function of the organism's body position coordinate x and time t to obtain the equation describing the aquatic organism's motion;

[0065] The equation describing the motion of an organism is:

[0066] y(x,t)=y1(x,t)+y2(x,t)+y3(x,t)

[0067] y1(x,t)=y 10 sin(2πft+φ1),y2(x,t)=xθ0sin(2πft+φ2)

[0068] A(x)=|a0+a1x+a2x 2 +a3x 3 |

[0069] Among them, f is the frequency of the organism's movement; λ is the wavelength of the organism's fluctuation; y 10is the amplitude of the sinking and floating motion of the organism's center of mass; θ0 is the maximum angle of the organism's head swing; A(x) represents the variation of the amplitude of the organism's autonomous deformation along the body position, and its expression depends on the specific swimming motion pattern; φ1, φ2, and φ3 are the initial phases of the three displacement components y1, y2, and y3, respectively. The specific values ​​are related to the choice of the initial moment, but the difference between the three is determined by the motion pattern and does not change with the choice of the initial moment.

[0070] Based on the above equation, the parameters of the equation can be obtained through multi-parameter fitting using the position data of the body trunk line at each moment obtained in the collected image.

[0071] 4.4) Based on the displacement y3 representing the autonomous deformation of the organism, calculate the organism's muscle contraction pre-strain tensor E0 according to the following formula for use in subsequent numerical simulations;

[0072]

[0073] Among them, E0(x, y, t) is the prestrain generated by muscle contraction at the (x, y) position of the organism's body at time t.

[0074] 5) Construct computational models of autonomous propulsion motion of aquatic organisms in various flow environments;

[0075] A computational model for the autonomous propulsion of aquatic organisms in various flow field environments was constructed using Comsol Multiphysics software. This model is a fluid-solid coupling model, where the fluid computational domain is the area bounded by the flow field structure boundary and the outer contour of the aquatic organism, and the material is set to liquid water; the solid computational domain is the entire aquatic organism, and the material is set to an elastic body, with material parameters given according to actual conditions; and the fluid-solid coupling boundary is the outer contour of the entire aquatic organism.

[0076] 6) Use the prestrain tensor of the muscle contraction prestrain tensor equation to control the autonomous deformation movement of the organism model, analyze and obtain the motion characteristics and mechanical characteristics of the autonomous swimming behavior of aquatic organisms in the calculation model of the autonomous propulsion movement of aquatic organisms, and complete the simulation of the swimming behavior of aquatic organisms through autonomous muscle deformation in various water flow environments.

[0077] 6.1) Grid division of the numerical calculation area;

[0078] The numerical calculation area is meshed, the mesh sizes of different areas are determined and the meshes are divided into different areas. The area around the aquatic organism is set as a moving area, and the dynamic mesh technology is used to realize the mesh following the movement of the aquatic organism as well as the update and reconstruction of the mesh.

[0079] 6.2) Set calculation parameters, solution parameters, boundary conditions and initial conditions for the calculation model;

[0080] The calculation parameters include: incoming flow velocity, biological muscle contraction pre-strain tensor; wherein, the biological muscle contraction pre-strain tensor uses the pre-strain tensor of the muscle contraction pre-strain tensor equation;

[0081] The solution parameter settings include: turbulence model, solution algorithm, discrete format, solution accuracy and time step;

[0082] The boundary conditions of the fluid computational domain are set as follows: the right boundary is set as the velocity inlet boundary condition; the left boundary is set as the pressure outlet boundary condition; the upper and lower boundary conditions are moving wall boundary conditions, and the moving velocity is equal to the incoming flow velocity; the obstacles in the flow field and the outer contour of the organism are set as no-slip wall conditions;

[0083] The initial conditions are set as follows: the velocity of the entire fluid domain is equal to the incoming flow velocity and the organism is stationary.

[0084] 6.3) Controlling the autonomous deformation motion of a biological model based on pre-strain tensors;

[0085] 6.4) The k-ω turbulence model in the Computational Fluid Dynamics Module is used to calculate the flow field and fluid forces, and the Structural Mechanics Module is used to calculate the displacement and velocity of the organism. Through fluid-structure interaction calculations, the process of swimming achieved by the aquatic organism under the combined action of its own muscle contraction and the surrounding water flow is analyzed. The kinematic and mechanical characteristics of its autonomous swimming behavior are then analyzed. Specific embodiment:

[0087] This embodiment takes the simulation of a crucian carp swimming in a Karman vortex flow field formed by a cylindrical flow as an example to illustrate the specific implementation method of the present invention, including the following steps:

[0088] 1) Conduct a crucian carp swimming experiment downstream of a cylinder and obtain a series of high-speed photographs of the crucian carp swimming process;

[0089] 2) If Figures 2 to 4 , extract the body trunk information of the fish at each moment, decompose the body trunk displacement y at each moment into three parts y1, y2, y3 caused by center of mass floating, head rotation and autonomous deformation, and fit the crucian carp motion description equation based on the experimental data as follows:

[0090] y(x,t)=y1(x,t)+y2(x,t)+y3(x,t)

[0091] y1(x,t)=0.076sin(2.45t+2.99)

[0092] y2(x,t)=0.21xsin(2.45t+0.78)

[0093] y3(x,t)=(0.11x-1.65x 2 +0.26x 3 )sin(2.45t+6.28x+2.52).

[0094] The fish muscle contraction pre-strain tensor equation is calculated based on the fitting equation of the fish deformation displacement y3:

[0095] E0(x,y,t)=(3.3-0.56x-20.72x 2 +4.90x 3 )ysin(2.45t+6.28x)

[0096] -(0.80-27.32x-2.56x 2 )ycos(2.45t+6.28x)

[0097] 3) Establish Figure 5 The calculation model shown. This embodiment uses the NACA0020 airfoil as the basic outline of the crucian carp. Based on experimental data, the fish body length is selected to be 200 mm, and a tail fin with a length of 30 mm is added to the end of the airfoil, transitioning to the fish body at a distance of 198 mm from the snout. The cylinder diameter is 110 mm. The fluid calculation domain is 3300 mm long and 1320 mm wide. The center of mass of the fish body is 330 mm from the center of the cylinder.

[0098] The fluid in this model is set to liquid water, and the density is 1000 kg / m 3 , the dynamic viscosity is 0.01Pa·s; the fish body is set as an isotropic linear elastic body with a density of 1050kg / m 3 , the elastic modulus is 0.2MPa and the Poisson's ratio is 0.3.

[0099] 4) Divide the numerical calculation area into grids. Figure 5 The cylinder and the fish are meshed using a boundary layer mesh with eight layers. The maximum boundary layer cell size is 0.008 m. The flow field is meshed using a triangular mesh with a maximum cell size of 0.02 m and a cell growth rate of 1.04. The total number of meshes is 104,580, including 104,580 triangular cells and 6,340 quadrilateral cells. The area surrounding the fish is designated as a moving region, and dynamic meshing techniques are used to ensure that the mesh follows the fish's motion, allowing for mesh updates and reconstruction.

[0100] (5) Set the calculation parameters, boundary conditions and initial conditions for the flow field. The right boundary of the fluid calculation domain is set as the velocity-inlet boundary condition, and the velocity is set to 0.2m / s; the left boundary is set as the pressure-out boundary condition, and the pressure is 0; the upper and lower boundary conditions are moving wall boundary conditions, and the moving velocity is equal to the incoming flow velocity; the cylinder and the fish body are set as no-slip wall conditions. Figure 6 The prestrain tensor generated by the fish muscle contraction is shown. The maximum time step is set to 0.05s. The initial conditions are that the velocity of the entire fluid domain is equal to 0.2m / s, the turbulent kinetic energy fish is stationary, the turbulence intensity is 0.05, the turbulence length is 0.0077m, and the specific dissipation rate is 2.66s. -1 , initialize the calculation model.

[0101] (6) The k-ω turbulence model in the Computational Fluid Dynamics Module is used to calculate the flow field and fluid forces, and the Structural Mechanics Module is used to calculate the displacement and velocity of the organism. Through fluid-solid coupling calculations, the process of aquatic organisms swimming under the combined action of their own muscle contraction and the surrounding water flow is obtained, such as Figure 7 ; Then analyze the motion and mechanical characteristics of its autonomous swimming, such as Figure 8 .

[0102] The calculation results in this example show that, driven by the combined effects of fish muscle contraction and the surrounding water flow, the fish accelerates through the vortices to a certain position, then moves in a stable Kármán gait for three cycles. During this Kármán gait, the displacement of the fish's tail is approximately π / 4 out of phase with the displacement of its head and center of mass. Subsequently, the fish's body movement fails to keep pace with the vortices in the oncoming flow and is swept away from the vortex street. This swimming process is consistent with the experimental results.

[0103] The present invention, based on the commercial software COMSOL Multiphysics and biological motion information acquired from experiments using high-speed photography, establishes a pre-strain tensor for the organism, enabling numerical simulation of the process of an organism controlling its own muscle contractions while autonomously swimming in water. Using this method, the applicant successfully simulated and analyzed the diverse swimming behaviors of fish and tadpoles in various aquatic environments, including cruising and turning in uniform flow fields, navigating a Kármán gait in a Kármán vortex flow field, and swimming upstream in a sudden expansion flow field. These simulations were then compared with experimental results.

[0104] The embodiments fully illustrate that the present invention provides an effective method for directly simulating the various swimming movements of organisms through muscle contraction and the interaction with the surrounding water. It can be used to study the fluid-solid coupling process of various aquatic organisms swimming in various modes in different flow field environments, explore their motion and mechanical characteristics, analyze the response mechanism of aquatic organisms to the water flow environment and the mechanical mechanism contained therein, and provide guidance for bionic applications and ecological protection.

[0105] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A numerical simulation method for autonomous swimming behavior of aquatic organisms, characterized in that: The following steps are involved: 1) Obtain motion videos and images of aquatic organisms swimming; 2) Processing the acquired images to obtain the body centerline position information of the aquatic organism during swimming; 3) Analyzing the movement characteristics of aquatic organisms based on the change process of the position of the body trunk; the movement characteristics include: the speed of the center of mass of the aquatic organisms, the body deflection angle and the autonomous muscle deformation morphology; 4) According to the motion characteristics, the autonomous deformation motion description of the organism is established, and the muscle contraction pre-strain tensor equation of the organism is obtained based on the autonomous deformation motion description of the organism; 5) Construct computational models of autonomous propulsion motion of aquatic organisms in various flow field environments; 6) Use the pre-strain tensor of the muscle contraction pre-strain tensor equation to control the autonomous deformation movement of the organism model, analyze and obtain the motion characteristics and mechanical characteristics of the autonomous swimming behavior of aquatic organisms in the calculation model of the autonomous propulsion movement of aquatic organisms, and complete the simulation of the swimming behavior of aquatic organisms through autonomous muscle deformation in various water flow environments.

2. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 1, characterized in that: In the step 4), the muscle contraction pre-strain tensor equation of the organism is obtained, which is as follows: 4.1) The position coordinates (X, Y) of each point on the organism's body trunk in the flow field at each moment are extracted through image processing software, and its swimming speed U and travel direction α are calculated; The position coordinates of each point on the body trunk of the organism in the flow field are converted to obtain the position (x, y) of the body trunk of the organism in the body coordinate system; 4.2) Considering aquatic organisms as elastic deformable bodies, the observed swimming behavior of aquatic organisms is decomposed through motion analysis to obtain the active deformation part controlled by the organisms; 4.3) Represent the lateral displacement y of the organism as a function of the body position coordinate x and time t of the organism, and obtain the motion description equation of the aquatic organism; 4.4) Based on y3 representing the autonomous deformation displacement of the organism, the organism's muscle contraction pre-strain tensor E0 is calculated according to the following formula; Among them, E0(x, y, t) is the pre-strain generated by muscle contraction at the (x, y) position of the organism's body at time t.

3. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 2, characterized in that: In step 4.2), the lateral displacement y of the organism is decomposed into three parts: the floating displacement y1 of the body with the center of mass, the rotation displacement y2 around the center of mass, and the self-deformation displacement y3. According to the main line of the organism at each moment, the center of mass position and the head rotation angle of the organism are extracted, and the displacement y3 caused by the organism's self-deformation is calculated.

4. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 2, characterized in that: In step 4.3), the motion description equation of the organism is: y(x,t)=y1(x,t)+y2(x,t)+y3(x,t) y1(x,t)=y 10 sin(2πft+φ1),y2(x,t)=xθ0sin(2πft+φ2) Among them, f is the movement frequency of the organism; λ is the wavelength of the organism's fluctuation; y 10 is the amplitude of the sinking and floating motion of the center of mass of the organism; θ0 is the maximum angle of the organism's head swing; A(x) represents the variation of the amplitude of the organism's autonomous deformation along the body position, and its expression depends on the organism's swimming motion pattern; φ1, φ2 and φ3 are the initial phases of the three displacement components y1, y2 and y3 respectively.

5. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 1, characterized in that: In the step 5), a computational model of autonomous propulsion motion of aquatic organisms in various flow field environments is constructed in Comsol Multiphysics software.

6. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 1, characterized in that: In the step 5), the calculation model of the autonomous propulsion motion of aquatic organisms is a fluid-solid coupling model, wherein the fluid calculation domain is the area enclosed by the flow field structure boundary and the outer contour of the aquatic organism, and the material is set to liquid water; the solid calculation domain is the entire aquatic organism, and the material is set to an elastomer; and the fluid-solid coupling boundary is the outer contour of the entire aquatic organism.

7. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 1, characterized in that: In step 6), the motion characteristics and mechanical characteristics of the autonomous swimming behavior of the aquatic organisms are analyzed and obtained in the aquatic organism autonomous propulsion motion calculation model, and the steps are as follows: 6.1) Grid the numerical calculation area; 6.2) Setting calculation parameters, solution parameters, boundary conditions and initial conditions for the calculation model; 6.3) Control the autonomous deformation motion of the biological model based on the pre-strain tensor; 6.4) The turbulence model is used to calculate the flow field and fluid force, and the structural mechanics module is selected to calculate the displacement and velocity of the organism. The process of swimming of the aquatic organism under the combined action of its own muscle contraction and the surrounding water flow is obtained through fluid-solid coupling calculation, and then the motion and mechanical characteristics of its autonomous swimming behavior are analyzed.

8. The numerical simulation method for autonomous swimming behavior of aquatic organisms according to claim 7, characterized in that: In step 6.2), the calculation parameters, solution parameters, boundary conditions and initial conditions are set as follows: The calculation parameters are set up including: incoming flow velocity, biological muscle contraction pre-strain tensor; wherein, the biological muscle contraction pre-strain tensor uses the pre-strain tensor of the muscle contraction pre-strain tensor equation; The solution parameter settings include: turbulence model, solution algorithm, discrete format, solution accuracy and time step; The boundary conditions of the fluid calculation domain are set as follows: the right boundary is set as the velocity inlet boundary condition; the left boundary is set as the pressure outlet boundary condition; the upper and lower boundary conditions are moving wall boundary conditions, and the moving speed is equal to the incoming flow speed; the obstacles in the flow field and the outer contour of the organism are no-slip wall conditions; The initial conditions are set as follows: the velocity of the entire fluid domain is equal to the incoming flow velocity and the organism is stationary.

9. An electronic device, characterized in that: include: one or more processors; as well as a storage device for storing one or more programs, When the one or more programs are executed by the one or more processors, the one or more processors execute the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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