Simulation method and system for immersed boundary method of finite element Lagrange grid discretization

Abstract

The invention discloses a finite element Lagrange grid discrete immersion boundary method simulation method and system, and the method comprises the steps: obtaining an N-S equation for viscous incompressible liquid under the condition of not considering the temperature; based on an N-S equation, a fluid-structure interaction equation is constructed; the N-S equation is a continuous equation, and spatial discretization is carried out on a continuous fluid domain; the fluid-solid coupling equation is a continuous equation, and spatial discretization is carried out on a continuous fluid-solid coupling boundary; discretizing the processed N-S equation and the fluid-structure interaction equation by adopting a difference operator to obtain an algebraic equation set of the N-S equation and the fluid-structure interaction equation; and solving the algebraic equation set obtained by discretization to obtain the velocity field and pressure field information of the flow field under the fluid-solid coupling effect. The system comprises an equation construction module, an equation processing module, an algebraic equation set construction module and a solving module. According to the invention, fluid-solid coupling problem simulation of a complex structure or a dynamic boundary in the thermal power field is realized.

Description

Technical Field

[0001] The invention belongs to the field of fluid-solid coupling simulation, and in particular relates to a simulation method and system of a finite element Lagrangian grid discrete immersed boundary method. Background Art

[0002] Fluid-solid coupling is a common phenomenon in nature. The field of thermal power often involves fluid-solid coupling problems, such as fluid-solid coupling problems in pipelines and fluid-solid coupling problems in rotor blades. In engineering practice, engineers generally use a combination of experimental and numerical methods to perform fluid-solid coupling analysis. Fluid-solid coupling numerical methods mainly include the arbitrary Lagrangian-Euler method and the immersed boundary method. The arbitrary Lagrangian-Euler method is also called the traditional method. Currently, almost all commercial CFD software uses this method for numerical simulation. The characteristic of the arbitrary Lagrangian-Euler method is that the fluid grid needs to fit the fluid-solid coupling interface, which is the so-called body-fitting grid. When faced with fluid-solid coupling problems with complex structures, large deformations or moving boundaries, mesh division has problems such as difficulty, cumbersomeness, time-consuming, and updating. Summary of the invention

[0003] The purpose of the present invention is to propose a simulation method and system of the immersed boundary method of finite element Lagrangian grid discretization to realize the simulation of fluid-solid coupling problems of complex structures or dynamic boundaries in the field of thermal power.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: The simulation method of the immersed boundary method for finite element Lagrangian grid discretization includes: Step 1: For viscous incompressible liquid, without considering the temperature, obtain the NS equation; Step 2: Based on the NS equation, construct the fluid-solid coupling equation; Step 3: The NS equations in step 1 are continuous equations. The continuous fluid domain is spatially discretized. The mesh used in the fluid domain of the immersed boundary method is a uniform Euler mesh, which is constructed using the finite difference method and the computational domain is divided using the same grid. Step 4: The fluid-solid coupling equations in step 2 are continuous equations. The continuous fluid-solid coupling boundary is spatially discretized. The finite element software is used to perform Lagrangian discretization on the fluid-solid coupling boundary. The boundary between the solid and the fluid is a curve. The modeling function in the finite element software can construct any fluid-solid coupling boundary, and the constructed fluid-solid coupling boundary is meshed to obtain the curve coordinates of each Lagrangian discrete point. Step 5, discretizing the NS equation and fluid-solid coupling equation processed in step 3 and step 4 by using a differential operator to obtain an algebraic equation system of the NS equation and the fluid-solid coupling equation; Step 6: Solve the algebraic equations obtained by discretization in step 5 to obtain the velocity field and pressure field information of the flow field under the action of fluid-solid coupling.

[0005] A further improvement of the present invention is that the NS equation is as follows: (1) (2) Where: is the density of the fluid; for The fluid velocity at time, for Speed ​​in direction, for Speed ​​in direction; is a Hamiltonian operator; for Fluid pressure at the moment; is the dynamic viscosity coefficient of the fluid; for The coupled boundary of the fluid at the moment exerts an Euler-style fluid-solid coupling force on the nearby fluid, which characterizes the effect of the boundary on the fluid; is the Laplace operator.

[0006] A further improvement of the present invention is that, based on the NS equation, a fluid-solid coupling equation is constructed, including: In the immersed boundary method, the information transfer between the Euler variables and the Lagrangian variables is achieved by including the regularization The information transmission between Euler variables and Lagrangian variables includes two aspects. On the one hand, the fluid-solid coupling force on the fluid generated by the boundary after being acted upon by the fluid is regularized. The function diffuses to nearby Euler mesh nodes, namely: (3) Where: It is the fluid-solid coupling force in Euler form; The fluid-solid interaction force generated by the boundary; are the curvilinear coordinates of the coupled boundary Lagrangian nodes; Indicates the time Time-Origin Particle Position in Cartesian coordinates; Represents a two-dimensional regularization function; On the other hand, the fluid velocity is regularized by The function is interpolated to the nearby Lagrange points; since the fluid is viscous and the velocity is continuous near the interface, the no-slip condition of the interface is obtained: (4) Where: for At the moment The velocity of the particle.

[0007] A further improvement of the present invention is that the NS equation and the fluid-solid coupling equation processed in step 3 and step 4 are discretized using a differential operator to obtain an algebraic equation group of the NS equation and the fluid-solid coupling equation, including: Discretize the NS equations in step 1 and the fluid-solid coupling equations in step 2; transform the continuous equations into a set of algebraic equations; and define several discrete difference operators: (5) (6) (7) Where: is the central difference operator; is the Laplace difference operator; is the antisymmetric difference operator; is the Euler grid size, is a set of orthogonal bases in two-dimensional space, here we use Direction and The orthogonal basis of directions, that is , ;definition The weight is The vector central difference operator composed of ; According to the discrete difference operator defined above, the continuous equations in step 1 and step 2 are spatially discretized as follows: (8) (9) (10) (11).

[0008] A further improvement of the present invention is that the algebraic equations obtained by discretization in step 5 are solved by using a second-order accurate Runge-Ku method based on the midpoint rule.

[0009] The simulation system of the immersed boundary method with finite element Lagrangian mesh discretization includes: The first equation building module, for viscous incompressible liquids, obtains the NS equations without considering the temperature; The second equation building module builds the fluid-solid coupling equation based on the NS equation; The first equation processing module, the NS equation in the first equation construction module is a continuous equation, which performs spatial discretization on the continuous fluid domain. The mesh used in the fluid domain of the immersed boundary method is a uniform Euler mesh, which is constructed using the finite difference method and the computational domain is divided using the same grid; The second equation processing module: the fluid-solid coupling equation in the second equation construction module is a continuous equation. The continuous fluid-solid coupling boundary is spatially discretized. The finite element software is used to perform Lagrangian discretization on the fluid-solid coupling boundary. The boundary between the solid and the fluid is a curve. The modeling function in the finite element can construct any fluid-solid coupling boundary, and the constructed fluid-solid coupling boundary is meshed to obtain the curve coordinates of each Lagrangian discrete point. an algebraic equation group construction module, which discretizes the NS equation and the fluid-solid coupling equation processed by the first equation processing module and the second equation processing module using a differential operator to obtain an algebraic equation group of the NS equation and the fluid-solid coupling equation; The solving module solves the algebraic equations discretized in the algebraic equations building module to obtain the velocity field and pressure field information of the flow field under the action of fluid-solid coupling.

[0010] A further improvement of the present invention is that in the first equation building module, the NS equation is as follows: (1) (2) Where: is the density of the fluid; for The fluid velocity at time, for Speed ​​in direction, for Speed ​​in direction; is a Hamiltonian operator; for Fluid pressure at the moment; is the dynamic viscosity coefficient of the fluid; for The coupled boundary of the fluid at the moment exerts an Euler-style fluid-solid coupling force on the nearby fluid, which characterizes the effect of the boundary on the fluid; is the Laplace operator.

[0011] A further improvement of the present invention is that in the second equation building module, based on the NS equation, a fluid-solid coupling equation is constructed, including: In the immersed boundary method, the information transfer between the Euler variables and the Lagrangian variables is achieved by including the regularization The information transmission between Euler variables and Lagrangian variables includes two aspects. On the one hand, the fluid-solid coupling force on the fluid generated by the boundary after being acted upon by the fluid is regularized. The function diffuses to nearby Euler mesh nodes, namely: (3) Where: It is the fluid-solid coupling force in Euler form; The fluid-solid interaction force generated by the boundary; are the curvilinear coordinates of the coupled boundary Lagrangian nodes; Indicates the time Time-Origin Particle Position in Cartesian coordinates; Represents a two-dimensional regularization function; On the other hand, the fluid velocity is regularized by The function is interpolated to the nearby Lagrange points; since the fluid is viscous and the velocity is continuous near the interface, the no-slip condition of the interface is obtained: (4) Where: for At the moment The velocity of the particle.

[0012] A further improvement of the present invention is that, in the algebraic equation group construction module, the NS equation and the fluid-solid coupling equation processed by the first equation processing module and the second equation processing module are discretized using a differential operator to obtain an algebraic equation group of the NS equation and the fluid-solid coupling equation, including: Discretize the NS equations in the first equation building module and the fluid-solid coupling equations in the second equation building module; transform the continuous equations into a set of algebraic equations; and define several discrete difference operators: (5) (6) (7) Where: is the central difference operator; is the Laplace difference operator; is the antisymmetric difference operator; is the Euler grid size, is a set of orthogonal bases in two-dimensional space, here we use Direction and The orthogonal basis of directions, that is , ;definition The weight is The vector central difference operator composed of ; According to the discrete difference operator defined above, the continuous equations in the first equation building block and the second equation building block are spatially discretized as follows: (8) (9) (10) (11).

[0013] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a simulation method based on an immersed boundary method of finite element Lagrangian grid discretization.

[0014] Compared with the prior art, the present invention has at least the following beneficial technical effects: The fluid-solid coupling analysis method proposed in the present invention is an immersed boundary method and system for finite element Lagrangian grid discretization. Compared with the traditional method, the immersed boundary method can realize the automatic tracking of the fluid-solid coupling interface, and effectively avoid the problems existing in traditional methods such as independent grid division and grid update. In dealing with fluid-solid coupling problems with complex boundaries, the immersed boundary method has better computational efficiency than traditional methods. This is because the immersed boundary method uses Euler grids to avoid the time spent on body-fitting grid generation. In addition, the Euler grids of the simulated fluid domain have constant mathematical relationships and can be processed by simple mathematical operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the present invention.

[0016] Figure 2 Schematic diagram of mesh division of the immersed boundary method of the present invention.

[0017] Figure 3 Schematic diagram of co-location grid and variable storage.

[0018] Figure 4 It is the flow field pressure distribution cloud map.

[0019] Figure 5 is the vorticity cloud diagram of the fluid velocity.

[0020] Figure 6 It is the streamline diagram of the flow field fluid.

[0021] Figure 7 It is a time history diagram of lift coefficient and drag coefficient.

[0022] Figure 8 It is a structural block diagram of the simulation system of the present invention based on the immersed boundary method of finite element Lagrangian grid discretization. DETAILED DESCRIPTION

[0023] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0024] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0025] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0026] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0027] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] Example 1 The simulation method of the immersed boundary method of finite element Lagrangian grid discretization provided by the present invention comprises: Step 1: For viscous incompressible liquid, without considering the temperature, obtain the NS equation; Step 2: Based on the NS equation, construct the fluid-solid coupling equation; Step 3: The NS equations in step 1 are continuous equations. The continuous fluid domain is spatially discretized. The mesh used in the fluid domain of the immersed boundary method is a uniform Euler mesh, which is constructed using the finite difference method and the computational domain is divided using the same grid. Step 4: The fluid-solid coupling equations in step 2 are continuous equations. The continuous fluid-solid coupling boundary is spatially discretized. The finite element software is used to perform Lagrangian discretization on the fluid-solid coupling boundary. The boundary between the solid and the fluid is a curve. The modeling function in the finite element software can construct any fluid-solid coupling boundary, and the constructed fluid-solid coupling boundary is meshed to obtain the curve coordinates of each Lagrangian discrete point. Step 5, discretizing the NS equation and fluid-solid coupling equation processed in step 3 and step 4 by using a differential operator to obtain an algebraic equation system of the NS equation and the fluid-solid coupling equation; Step 6: Solve the algebraic equations obtained by discretization in step 5 to obtain the velocity field and pressure field information of the flow field under the action of fluid-solid coupling.

[0030] Example 2 refer to Figure 1 , Figure 2 and Figure 3 The simulation method of the finite element Lagrangian grid discretized immersed boundary method provided by the present invention comprises the following steps: Step 1: For viscous incompressible liquid, without considering temperature, taking two dimensions as an example, the NS equation is as follows: (1) (2) Where: is the density of the fluid; for The fluid velocity at time, for Speed ​​in direction, for Speed ​​in direction; is a Hamiltonian operator; for Fluid pressure at the moment; is the dynamic viscosity coefficient of the fluid; for The coupled boundary of the fluid at the moment exerts an Euler-style fluid-solid coupling force on the nearby fluid, which characterizes the effect of the boundary on the fluid; is the Laplace operator.

[0031] Step 2: Construct the fluid-solid coupling equation. Step 1 gives the NS equations of the immersed boundary method, in which the effect of the fluid-solid coupling boundary on the nearby fluid is regarded as an Euler-form fluid-solid coupling force, which is used to represent the coupling effect between the boundary and the fluid. The characteristic of the immersed boundary method is to realize interface crossing calculation, the fluid grid passes through the fluid-solid coupling interface without fitting the interface, and a uniform Euler grid is used to divide the entire fluid calculation domain, and a Lagrangian grid is used to divide the fluid-solid coupling boundary. Figure 2 The figure shows the meshing of the immersed boundary method. The solid circles represent the Lagrangian nodes generated by the Lagrangian meshing of the fluid-solid coupling boundary, and the hollow circles represent the Euler nodes generated by the Euler meshing of the fluid calculation domain. From the figure, it can be seen that the Lagrangian nodes and the Euler nodes are not aligned, and the information transfer between the two nodes cannot be directly realized. How to realize the coupling effect between the fluid and the fluid-solid coupling boundary, that is, how to realize the information transfer between the Euler variables and the Lagrangian variables is the core and key of the immersed boundary method. In the immersed boundary method, the information transfer between the Euler variables and the Lagrangian variables is achieved by containing regularization The information transmission between Euler variables and Lagrangian variables includes two aspects. On the one hand, the fluid-solid coupling force on the fluid generated by the boundary after being acted upon by the fluid is regularized. The function diffuses to nearby Euler mesh nodes, namely: (3) Where: It is the fluid-solid coupling force in Euler form; The fluid-solid coupling force generated by the boundary belongs to the Lagrangian variable. Its form is related to the specific problem. Different problems correspond to different mechanical models. are the curvilinear coordinates of the coupled boundary Lagrangian nodes; Indicates the time Time-Origin Particle Position in Cartesian coordinates; Represents a two-dimensional regularization function.

[0032] On the other hand, the fluid velocity is regularized by The function is interpolated to the nearby Lagrange points. Since the fluid is viscous and the velocity is continuous near the interface, the no-slip condition of the interface can be obtained: (4) Where: for At the moment The velocity of the particle.

[0033] Step 3: The mesh used in the fluid domain in the immersed boundary method is a uniform Euler mesh. The mesh is very simple and is relatively simple to construct using the finite difference method. The computational domain is divided using a co-located mesh. The so-called co-located mesh means that all variables are stored on the same mesh node, such as Figure 3 As shown, the fluid Direction speed, Both directional velocity and pressure are stored at the same spatial location.

[0034] Step 4: Use finite element software to perform Lagrangian discretization on the fluid-solid coupling boundary. Taking two dimensions as an example, the boundary between the solid and the fluid is a curve. The modeling function in the finite element can construct any fluid-solid coupling boundary, and mesh the constructed fluid-solid coupling boundary to obtain the curve coordinates of each Lagrangian discrete point.

[0035] Step 5: Discretize the continuity equations to obtain a set of algebraic equations. The NS equations of the immersed boundary method in step 1 and the fluid-solid coupling equations in step 2 are both continuity equations. Most of them do not have analytical solutions, so the above equations need to be discretized. Convert the continuity equations into a set of algebraic equations. Here we define several discrete difference operators: (5) (6) (7) Where: is the central difference operator; is the Laplace difference operator; is the antisymmetric difference operator; is the Euler grid size, is a set of orthogonal bases in two-dimensional space, here we use Direction and The orthogonal basis of directions, that is , .definition The weight is The vector central difference operator composed of .

[0036] According to the discrete difference operator defined above, the continuous equations in step 1 and step 2 are spatially discretized as follows: (8) (9) (10) (11) Step 6: Solve the algebraic equations discretized in step 5 to obtain the velocity field and pressure field of the flow field under fluid-solid coupling, and use the Runge-Kutta2 method with second-order accuracy based on the midpoint rule to solve it.

[0037] Example 3 The numerical simulation of the static flow around a single cylinder is carried out, and the computational domain size is ,in is the diameter of the cylinder, set , the center of the cylinder is located at , the boundary conditions around the computational domain are set to periodic boundary conditions, and the grid size is The uniform Euler grid is divided into , initial velocity at a distance , the fluid-structure interaction boundary is Lagrangian meshed using finite elements. The dimensionless time range is set to , the dimensionless time step is set to , Reynolds number . Figure 4 The pressure distribution cloud diagram of the flow field at a certain moment obtained by this method; Figure 5 for The vorticity cloud diagram of the fluid velocity at a certain instant in the flow field obtained by this method clearly shows that the vortices are alternately shed from the tail of the cylinder; Figure 6 is the streamline diagram of the flow field fluid obtained by using this method; Figure 7 The Reynolds number obtained by this method is The time history diagram of the lift coefficient and the drag coefficient of the flow around the cylinder at this time shows that the drag coefficient and the lift coefficient show periodic changes, indicating that the fluid flow at this time is an unsteady periodic flow. The fluid-solid coupling analysis method is an immersed boundary method of finite element Lagrangian mesh discretization. Compared with the traditional method, the method of the present invention can easily realize the Lagrangian mesh division of the fluid-solid coupling boundary with the help of finite element software, especially for complex coupling boundaries, which can greatly reduce the difficulty of meshing the fluid-solid coupling boundary. The fluid domain adopts uniform Euler meshing to avoid the difficulty of generating body-fitting meshes and greatly save the time spent on meshing.

[0038] Example 4 refer to Figure 8 The simulation system of the finite element Lagrangian grid discretized immersed boundary method provided by the present invention comprises: The first equation building module, for viscous incompressible liquids, obtains the NS equations without considering the temperature; The second equation building module builds the fluid-solid coupling equation based on the NS equation; The first equation processing module, the NS equation in the first equation construction module is a continuous equation, which performs spatial discretization on the continuous fluid domain. The mesh used in the fluid domain of the immersed boundary method is a uniform Euler mesh, which is constructed using the finite difference method and the computational domain is divided using the same grid; The second equation processing module: the fluid-solid coupling equation in the second equation construction module is a continuous equation. The continuous fluid-solid coupling boundary is spatially discretized. The finite element software is used to perform Lagrangian discretization on the fluid-solid coupling boundary. The boundary between the solid and the fluid is a curve. The modeling function in the finite element software can construct any fluid-solid coupling boundary, and the constructed fluid-solid coupling boundary is meshed to obtain the curve coordinates of each Lagrangian discrete point. an algebraic equation group construction module, which discretizes the NS equation and the fluid-solid coupling equation processed by the first equation processing module and the second equation processing module using a differential operator to obtain an algebraic equation group of the NS equation and the fluid-solid coupling equation; The solving module solves the algebraic equations discretized in the algebraic equations building module to obtain the velocity field and pressure field information of the flow field under the action of fluid-solid coupling.

[0039] Example 5 The present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the simulation method based on the immersed boundary method of finite element Lagrangian grid discretization are implemented.

[0040] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0041] The present application is described with reference to the flowcharts and / or block diagrams of the methods, systems and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A system that specifies the functions of a box or boxes.

[0042] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0043] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0044] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0045] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. The simulation method of the immersed boundary method of finite element Lagrangian grid discretization is characterized by: include: Step 1: For viscous incompressible liquid, without considering the temperature, obtain the NS equation; Step 2: Based on the NS equation, construct the fluid-solid coupling equation; Step 3: The NS equations in step 1 are continuous equations. The continuous fluid domain is spatially discretized. The mesh used in the fluid domain of the immersed boundary method is a uniform Euler mesh, which is constructed using the finite difference method and the computational domain is divided using the same grid. Step 4: The fluid-solid coupling equations in step 2 are continuous equations. The continuous fluid-solid coupling boundary is spatially discretized. The finite element software is used to perform Lagrangian discretization on the fluid-solid coupling boundary. The boundary between the solid and the fluid is a curve. The modeling function in the finite element software can construct any fluid-solid coupling boundary, and the constructed fluid-solid coupling boundary is meshed to obtain the curve coordinates of each Lagrangian discrete point. Step 5, discretizing the NS equation and fluid-solid coupling equation processed in step 3 and step 4 by using a differential operator to obtain an algebraic equation system of the NS equation and the fluid-solid coupling equation; Step 6: Solve the algebraic equations obtained by discretization in step 5 to obtain the velocity field and pressure field information of the flow field under the action of fluid-solid coupling.

2. The simulation method according to claim 1, characterized in that: The NS equation is as follows: （1） （2） Where: is the density of the fluid; for The fluid velocity at time, for Speed ​​in direction, for Speed ​​in direction; is a Hamiltonian operator; for Fluid pressure at the moment; is the dynamic viscosity coefficient of the fluid; for The coupled boundary of the fluid at the moment exerts an Euler-style fluid-solid coupling force on the nearby fluid, which characterizes the effect of the boundary on the fluid; is the Laplace operator.

3. The simulation method of the immersed boundary method of finite element Lagrangian grid discretization according to claim 1 is characterized in that: Based on the NS equation, the fluid-solid coupling equation is constructed, including: In the immersed boundary method, the information transfer between the Euler variables and the Lagrangian variables is achieved by including the regularization The information transmission between Euler variables and Lagrangian variables includes two aspects. On the one hand, the fluid-solid coupling force on the fluid generated by the boundary after being acted upon by the fluid is regularized. The function diffuses to nearby Euler mesh nodes, namely: （3） Where: It is the fluid-solid coupling force in Euler form; The fluid-solid interaction force generated by the boundary; are the curvilinear coordinates of the coupled boundary Lagrangian nodes; Indicates the time Time-Origin Particle Position in Cartesian coordinates; Represents a two-dimensional regularization function; On the other hand, the fluid velocity is regularized by The function is interpolated to the nearby Lagrange points; since the fluid is viscous and the velocity is continuous near the interface, the no-slip condition of the interface is obtained: （4） Where: for At the moment The velocity of the particle.

4. The simulation method based on the immersed boundary method of finite element Lagrangian grid discretization according to claim 1 is characterized in that: The NS equations and fluid-solid coupling equations processed in step 3 and step 4 are discretized using a differential operator to obtain a set of algebraic equations of the NS equations and fluid-solid coupling equations, including: Discretize the NS equations in step 1 and the fluid-solid coupling equations in step 2; transform the continuous equations into a set of algebraic equations; and define several discrete difference operators: （5） （6） （7） Where: is the central difference operator; is the Laplace difference operator; is the antisymmetric difference operator; is the Euler grid size, is a set of orthogonal bases in two-dimensional space, here we use Direction and The orthogonal basis of directions, that is , ;definition The weight is The vector central difference operator composed of ; According to the discrete difference operator defined above, the continuous equations in step 1 and step 2 are spatially discretized as follows: （8） （9） （10） （11）。 5. The simulation method based on the immersed boundary method of finite element Lagrangian grid discretization according to claim 1 is characterized in that: The algebraic equations obtained by discretization in step 5 are solved using the Runge-Ku method with second-order accuracy based on the midpoint rule.

6. Finite element Lagrangian grid discretized immersed boundary method simulation system, characterized in that, include: The first equation building module, for viscous incompressible liquids, obtains the NS equations without considering the temperature; The second equation building module builds the fluid-solid coupling equation based on the NS equation; The first equation processing module, the NS equation in the first equation construction module is a continuous equation, which performs spatial discretization on the continuous fluid domain. The mesh used in the fluid domain of the immersed boundary method is a uniform Euler mesh, which is constructed using the finite difference method and the computational domain is divided using the same grid; The second equation processing module: the fluid-solid coupling equation in the second equation construction module is a continuous equation. The continuous fluid-solid coupling boundary is spatially discretized. The finite element software is used to perform Lagrangian discretization on the fluid-solid coupling boundary. The boundary between the solid and the fluid is a curve. The modeling function in the finite element software can construct any fluid-solid coupling boundary, and the constructed fluid-solid coupling boundary is meshed to obtain the curve coordinates of each Lagrangian discrete point. An algebraic equation group construction module discretizes the NS equation and the fluid-solid coupling equation processed by the first equation processing module and the second equation processing module using a differential operator to obtain an algebraic equation group of the NS equation and the fluid-solid coupling equation; The solving module solves the algebraic equations discretized in the algebraic equations building module to obtain the velocity field and pressure field information of the flow field under the action of fluid-solid coupling.

7. The simulation system based on the immersed boundary method of finite element Lagrangian grid discretization according to claim 6, characterized in that: The first equation building block, the NS equation, is as follows: （1） （2） Where: is the density of the fluid; for The fluid velocity at time, for Speed ​​in direction, for Speed ​​in direction; is a Hamiltonian operator; for Fluid pressure at the moment; is the dynamic viscosity coefficient of the fluid; for The coupled boundary of the fluid at the moment exerts an Euler-style fluid-solid coupling force on the nearby fluid, which characterizes the effect of the boundary on the fluid; is the Laplace operator.

8. The simulation system based on the immersed boundary method of finite element Lagrangian grid discretization according to claim 7, characterized in that: In the second equation building module, based on the NS equation, the fluid-solid coupling equation is constructed, including: In the immersed boundary method, the information transfer between the Euler variables and the Lagrangian variables is achieved by including the regularization The information transmission between Euler variables and Lagrangian variables includes two aspects. On the one hand, the fluid-solid coupling force on the fluid generated by the boundary after being acted upon by the fluid is regularized. The function diffuses to nearby Euler mesh nodes, namely: （3） Where: It is the fluid-solid coupling force in Euler form; The fluid-solid interaction force generated by the boundary; are the curvilinear coordinates of the coupled boundary Lagrangian nodes; Indicates the time Time-Origin Particle Position in Cartesian coordinates; Represents a two-dimensional regularization function; On the other hand, the fluid velocity is regularized by The function is interpolated to the nearby Lagrange points; since the fluid is viscous and the velocity is continuous near the interface, the no-slip condition of the interface is obtained: （4） Where: for At the moment The velocity of the particle.

9. The simulation system of the finite element Lagrangian grid discretized immersed boundary method according to claim 8, characterized in that: In the algebraic equation group construction module, the NS equation and the fluid-solid coupling equation processed by the first equation processing module and the second equation processing module are discretized using a differential operator to obtain an algebraic equation group of the NS equation and the fluid-solid coupling equation, including: Discretize the NS equations in the first equation building module and the fluid-solid coupling equations in the second equation building module; transform the continuous equations into a set of algebraic equations; and define several discrete difference operators: （5） （6） （7） Where: is the central difference operator; is the Laplace difference operator; is the antisymmetric difference operator; is the Euler grid size, is a set of orthogonal bases in two-dimensional space, here we use Direction and The orthogonal basis of directions, that is , ;definition The weight is The vector central difference operator composed of ; According to the discrete difference operator defined above, the continuous equations in the first equation building block and the second equation building block are spatially discretized as follows: （8） （9） （10） （11）。 10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the simulation method based on the immersed boundary method of finite element Lagrangian grid discretization according to any one of claims 1 to 5.

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