A method and system for numerical simulation of immersed boundaries based on grid pruning method

Abstract

The present invention provides an immersed boundary numerical simulation method and system based on a grid pruning method, relates to the field of computational fluid dynamics, and solves the problems of grid generation and computational accuracy in numerical simulation of flow fields with complex geometric shapes; the method comprises: setting a computational domain grid, identifying and determining the interface between a fluid and a geometric object; the computational domain grid forms a cut grid under the action of the interface, and the basic parameters of the cut grid are determined by calculation; the control equation of a standard grid that is not cut by the surface of the geometric object in the computational domain grid is established; on the basis of the form of the control equation of the standard grid, the control equation of the interface grid that is cut by the surface of the geometric object in the computational domain grid is determined; based on the control equations of the standard grid and the interface grid, the flow field is numerically simulated in an iterative solution manner; the present invention can effectively reduce the amount of grids and the technical difficulty of numerical simulation, and can use a high-order method to obtain high-order accuracy.

Description

Technical Field

[0001] The present invention relates to the field of computational fluid dynamics, and is applied to numerical simulation and transition prediction of complex geometric shapes and moving boundary problems, and specifically to an immersed boundary numerical simulation method and system based on a grid pruning method. Background Art

[0002] In the field of aircraft design, the phenomenon of boundary layer flow transitioning from laminar to turbulent poses a severe challenge to the aerodynamic performance and thermal protection of aircraft. This transition process will cause a significant increase in surface heat flux and friction resistance, usually 3 to 5 times the original. Therefore, controlling the delayed transition of the boundary layer can not only effectively reduce the weight of the aircraft and increase the range, but also has important theoretical significance and engineering value.

[0003] The current methods for boundary layer transition control are mainly divided into two categories: active control methods and passive control methods. Active control methods usually involve introducing energy input methods such as blowing and suction devices or heating devices into the upstream area of ​​the boundary layer; while passive control methods do not require additional energy input and are achieved by using porous walls, corrugated walls or utilizing natural surface deformations formed during the manufacturing process. Passive control methods have been widely favored in practical applications due to their advantages such as simple processing, no need to carry additional equipment and high cost-effectiveness.

[0004] However, for complex geometric shapes such as corrugated walls, when performing high-precision numerical simulations, it is necessary to construct a computational domain mesh that fits the complex wall surface and implement block encryption to ensure calculation accuracy. This process faces the huge challenge of generating high-quality meshes and maintaining good mesh quality. Especially when it comes to deformable geometric objects, it is also necessary to create adaptive meshes or regenerate meshes. As the degree of deformation of the object increases, the mesh quality may deteriorate rapidly and even negative volume unit problems may occur. These problems greatly increase the difficulty of mesh generation and the complexity of calculations.

[0005] In order to solve the above problems, the Immersed Boundary Method (IBM) was proposed as an effective means to deal with complex geometric structures. This method can simplify the mesh generation process to a certain extent, especially for objects with complex shapes or undergoing large deformations. However, IBM also has some inherent defects. For example, the mathematical treatment of wall boundaries is cumbersome and requires additional numerical techniques for accurate description. In addition, the integral operation at the boundary becomes more complicated. If the wall is not accurately described, it may cause the calculation to be difficult to converge, which in turn affects the accuracy of the final solution. The combined effect of these factors makes it difficult to simulate the flow field and predict the transition of objects with complex geometric shapes and deformations.

[0006] In summary, it is particularly important to develop a new method that can effectively improve the boundary layer transition control effect and overcome the limitations of existing technologies. Therefore, it has become a research point of concern for technical personnel in this field. Summary of the invention

[0007] Based on the current status of the background technology, the purpose of the present invention is to solve the problems of grid generation and calculation accuracy in numerical simulation of flow fields with complex geometric shapes, and therefore proposes a method and system for numerical simulation of immersed boundaries based on a grid pruning method. The present invention can effectively reduce the amount of grids and technical difficulty of numerical simulation, and can use high-order methods to obtain high-order accuracy.

[0008] The present invention adopts the following technical solutions to achieve the purpose:

[0009] A method for numerical simulation of immersed boundaries based on a grid pruning method, the method comprising the following steps:

[0010] S1. Set up the computational domain grid, identify and determine the interface between the fluid and the geometric object;

[0011] S2. The computational domain mesh forms a cut mesh under the action of the interface, and the basic parameters of the cut mesh are calculated and determined; the cut mesh includes the standard mesh and the interface mesh;

[0012] S3, establishing the control equations of the standard grid in the computational domain grid that is not clipped by the surface of the geometric object;

[0013] S4. Based on the form of the control equation of the standard grid, determine the control equation of the interface grid in the computational domain grid that is sheared by the surface of the geometric object;

[0014] S5. Based on the respective control equations of the standard grid and the interface grid, the flow field is numerically simulated by an iterative solution method.

[0015] Specifically, in step S1, a signed distance function is used to mark the interface between the fluid and the geometric object; in the set computational domain grid, the surface with a distance function value of zero is the interface, the area with a positive distance function value represents the part of the grid that is not immersed in the geometric object, and the area with a negative distance function value represents the part of the grid that is immersed in the geometric object.

[0016] Specifically, in step S2, when the calculation process is initialized, the volume fraction, porosity and cross-sectional area corresponding to each three-dimensional grid unit in the cut grid are further determined based on the determined interface between the fluid and the geometric object; wherein the volume fraction represents the proportion of the fluid and the geometric object in the three-dimensional grid unit, the porosity represents the area fraction of a certain surface of the corresponding three-dimensional grid unit that is in the fluid part, and the cross-sectional area represents the area of ​​the cross section where the corresponding three-dimensional grid unit intersects with the geometric object, and the cross section is the partial area of ​​the interface.

[0017] Furthermore, in step S3, the control equation of the standard grid is established based on the typical conservation equation, and finally the finite volume discrete form of the conservation equation on the standard Cartesian grid is obtained. In step S4, for the interface grid sheared by the surface of the geometric object, after the mesh pruning method is applied, the effective volume of the interface grid and the area fraction of each surface in the grid are changed. Then, the finite volume discrete form of the conservation equation on the standard Cartesian grid established for the standard grid in step S3 is modified as the basis, and a new conservation equation is obtained by weighting the volume fraction and the porosity as the control equation of the interface grid.

[0018] Specifically, in step S5, after setting the boundary conditions and initial conditions of the computational domain grid, the computational domain grid is divided; the control equations of the standard grid and the interface grid are iteratively solved to perform numerical simulation of the flow field.

[0019] The present invention also provides a computer system, including a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the aforementioned immersed boundary numerical simulation method based on the grid pruning method.

[0020] In summary, due to the adoption of this technical solution, the beneficial effects of the present invention are as follows:

[0021] The present invention uses a signed distance function to accurately mark the position of the object surface, and accordingly effectively trims the grid in the computational domain. This method greatly simplifies the traditionally complex wall boundary processing process, and at the same time provides the corresponding conservation equation form for the trimmed grid area, ensuring the correct transfer and calculation of physical quantities at these special points. Therefore, the present invention not only improves the computational efficiency, but also ensures the accuracy of the simulation results.

[0022] The present invention also demonstrates strong versatility and can well adapt to the needs of numerical simulation of flow fields under various complex shapes and moving boundary problems. Compared with the traditional body-fitting grid method, the number of grids required to be generated by the present invention is significantly reduced, which not only reduces the difficulty in the grid generation process, but also improves the final grid quality. In addition, due to the use of a more flexible grid structure, it can easily cope with situations with large changes in geometric shapes, further enhancing the wide range of its application scenarios.

[0023] Compared with the general immersed boundary method, the present invention is more accurate and reliable in identifying boundary walls, avoiding the convergence difficulties and precision loss problems caused by inaccurate boundary representation. At the same time, the present invention is also easy to implement, and is relatively friendly even to technicians with non-professional backgrounds, which helps to promote research work in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The schematic diagram briefly describes the overall process of the method of the present invention;

[0025] Figure 2 It is a schematic diagram of basic parameters of the cut grid in the method of the present invention;

[0026] Figure 3 Cube grid for the present invention Surface schematic diagram of ;

[0027] Figure 4 A schematic diagram of setting the grid and boundary conditions of an example of the present invention;

[0028] Figure 5 For example, the present invention Figure 3 A partial enlarged view of the grid in the middle corrugated wall area;

[0029] Figure 6 Schematic diagram of the boundary layer velocity profile of the flow field near the corrugated wall according to an example of the present invention;

[0030] Figure 7 It is a schematic diagram of the flow field velocity cloud map and streamline distribution according to the example of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] A numerical simulation method for immersed boundaries based on mesh pruning. Figure 1 The process of the method is briefly described in FIG. 1 , which can be viewed simultaneously. The steps of the method are summarized as follows:

[0035] S1. Set up the computational domain grid, identify and determine the interface between the fluid and the geometric object;

[0036] S2. The computational domain mesh forms a cut mesh under the action of the interface, and the basic parameters of the cut mesh are calculated and determined; the cut mesh includes the standard mesh and the interface mesh;

[0037] S3, establishing the control equations of the standard grid in the computational domain grid that is not clipped by the surface of the geometric object;

[0038] S4. Based on the form of the control equation of the standard grid, determine the control equation of the interface grid in the computational domain grid that is sheared by the surface of the geometric object;

[0039] S5. Based on the respective control equations of the standard grid and the interface grid, the flow field is numerically simulated by an iterative solution method.

[0040] This embodiment will introduce the details of each step in detail according to the above step sequence.

[0041] In step S1 of this embodiment, a signed distance function is used to mark the interface between the fluid and the geometric object; in the set calculation domain grid, the surface with a distance function value of zero is the interface, the area with a positive distance function value represents the part of the grid that is not immersed in the geometric object, and the area with a negative distance function value represents the part of the grid that is immersed in the geometric object.

[0042] In step S2 of this embodiment, you can refer to Figure 2 As shown in the figure, based on the numerical discretization method of the finite volume method, the coordinates of the center point in the cut grid are The three-dimensional grid unit is denoted as grid , correspond direction, correspond direction, correspond direction, thus the grid The volume fraction of the fluid part is recorded as , in the grid When it belongs to the interface grid, ; Then the grid The effective volume is recorded as ,in Representative Grid along The spatial grid size in the direction, Representative Grid along The spatial grid size in the direction, Representative Grid along The spatial grid size in the direction; then the grid The area fraction of any surface in the fluid part is recorded as the porosity , .

[0043] In this embodiment, Figure 3 As shown, when the grid When it is a cube, it has a first surface, a second surface, a third surface, a fourth surface, a fifth surface and a sixth surface; the first surface is opposite to the second surface, the third surface is opposite to the fourth surface, and the fifth surface is opposite to the sixth surface; Figure 3 The second surface, the fourth surface and the sixth surface are indicated from a visible angle, and the corresponding surfaces in invisible areas are the first surface, the third surface and the fifth surface respectively.

[0044] The area of ​​the first surface in the fluid portion is expressed as ,in is the porosity corresponding to the first surface; the area of ​​the second surface in the fluid part is expressed as ,in is the porosity corresponding to the second surface; the area of ​​the third surface in the fluid part is expressed as ,in is the porosity corresponding to the third surface; the area of ​​the fourth surface in the fluid part is expressed as ,in is the porosity corresponding to the fourth surface; the area of ​​the fifth surface in the fluid part is expressed as ,in is the porosity corresponding to the fifth surface; the area of ​​the sixth surface in the fluid part is expressed as ,in is the porosity corresponding to the sixth surface;

[0045] Finally, the grid The area of ​​the cross section where it intersects the geometric object is recorded as ; This completes the initialization of the calculation process. The basic parameters of the cut grid include the volume fraction of each three-dimensional grid unit , porosity and cross-sectional area .

[0046] In step S3 of this embodiment, the control equation of the standard grid is established based on a typical conservation equation; the conservation equation is as follows:

[0047]

[0048] In the formula, Represents a conserved variable Over time The rate of change of is the divergence term, is the divergence operator, Corresponding conserved variables The flux function of ; for the standard grid that is not cut by the surface of the geometric object, the above conservation equation is discretized using the finite volume format to obtain the following formula:

[0049]

[0050] In the formula, Represents the number of time integration steps; further use the forward Euler format for time discretization and rewrite the formula as follows:

[0051]

[0052] In the formula, , that is, the conserved variable In the grid The average value on is a conserved variable In the grid The original value on the effective volume is then converted to Convert the volume fraction to effective area The surface integral of is as follows:

[0053]

[0054] In the formula, represents the time step, Represents the normal vector, symbol Indicates the vertical direction, represents the area; after applying the second-order difference format to this formula, the following formula is obtained:

[0055]

[0056] In the formula, , and Grid The average flux on the six surfaces is the finite volume discretization form of the conservation equation on the standard Cartesian grid, thus completing the process of establishing the control equation of the standard grid.

[0057] In step S4 of this embodiment, for the interface mesh that is sheared by the surface of the geometric object, after the mesh pruning method is applied to perform pruning, the effective volume of the interface mesh and the area fraction of each surface in the mesh are changed. Then, based on the finite volume discretization form of the conservation equation on the standard Cartesian grid established for the standard grid in step S3, the new conservation equation is obtained by weighting the volume fraction and the porosity, as shown in the following formula:

[0058]

[0059] In the formula, for the cube grid , is the porosity corresponding to the first surface, is the flux on the first surface; is the porosity corresponding to the second surface, is the flux on the second surface; is the porosity corresponding to the third surface, is the flux on the third surface; is the porosity corresponding to the fourth surface, is the flux on the fourth surface; is the porosity corresponding to the fifth surface, is the flux on the fifth surface; is the porosity corresponding to the sixth surface, is the flux on the sixth surface;

[0060] In the formula, and They represent additional momentum exchange terms and friction terms, respectively, which are used to consider the effect of immersed boundaries on the fluid; the momentum exchange term Used to satisfy the no-slip condition for the normal component of velocity; friction term Represents the cross-sectional area of ​​the corresponding interface Part of the friction stress is used to satisfy the no-slip condition of the tangential component of the interface velocity.

[0061] Here, according to the physical constraint that there is no fluid inflow or outflow at the immersed boundary, the normal velocity at the interface is determined to be zero; by giving To satisfy this constraint, Representative Grid Momentum exchange term in the vertical direction The velocity component in Representative Grid The velocity component in the vertical direction; the momentum exchange term It is expressed as the following formula:

[0062]

[0063] In the formula, Representative Grid The mean value of the velocity component in the vertical direction; the no-slip condition is also satisfied at the immersed boundary, resulting in shear stress, which is obtained by adding the friction term The friction term As follows:

[0064]

[0065]

[0066] In the formula, Represents the normal vector, symbol Indicates the vertical direction, represents the wall shear stress, represents the velocity component, Represents the viscosity coefficient; symbol Indicates the parallel direction, That is, it represents the mean value of the velocity component in the parallel direction; Represents the normal vector Quantity, Represents the normal vector Quantity, Represents the normal vector Quantity; represents the grid scale;

[0067] The momentum exchange term and friction term After substituting the newly obtained conservation equation in step S4, the discrete form of the conservation equation of the interface mesh is obtained as the control equation of the interface mesh.

[0068] In step S5 of this embodiment, after setting the boundary conditions and initial conditions of the computational domain grid, the computational domain grid is divided; the control equations of the standard grid and the interface grid are iteratively solved to perform numerical simulation of the flow field.

[0069] Example 2

[0070] Based on Example 1, this example uses a corrugated wall example to verify and illustrate the method in Example 1.

[0071] In this embodiment, the outlet boundary condition is a supersonic outlet boundary, the upper boundary adopts a non-reflecting boundary condition based on the Riemann invariant, the wall and the corrugated wall are both isothermal non-slip walls, and the side is set as a periodic boundary. The inlet of the benchmark example and the corrugated wall example are both laminar flow profiles based on the Blasius solution, and the most unstable second mode wave and a pair of second mode oblique waves with smaller amplitudes are applied to study the transition evolution process dominated by the second mode wave. Figure 4 as well as Figure 5 A zoomed-in view of the example mesh and boundary condition settings.

[0072] Based on the application of the method in Example 1, Figure 6 The boundary layer velocity profile of the corrugated wall flow field is given. Figure 7 The boundary layer streamlines of the corrugated wall flow field are given; Figure 6 In represents the incoming flow velocity of the flow field, represents the inlet boundary layer thickness. Figure 6 and Figure 7 , it can be observed that a small recirculation area appears in the corrugated wall cavity, resulting in an inflection point in the boundary layer velocity profile and a shear instability mode. However, this unstable mode is confined to the corrugated wall cavity and does not appear in the downstream area of ​​the corrugated wall. The boundary layer quickly returns to a laminar state. Although the shear instability mode appears in the control area, it does not accelerate the transition process. This result is consistent with conventional cognition and verifies the effectiveness of the immersed boundary numerical simulation method based on the grid trimming method.

[0073] The method in Example 1 can be effectively applied to a computer system, which includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the immersed boundary numerical simulation method based on the grid pruning method.

[0074] In this embodiment, the described computer program / instructions may be stored in a computer-readable memory that can direct 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 a manufactured product including an instruction device that implements the functions specified in one or more steps in its method.

Claims

1. A numerical simulation method for immersed boundary based on mesh pruning method, characterized in that: The method comprises the following steps: S1. Set up the computational domain grid, identify and determine the interface between the fluid and the geometric object; S2. The computational domain mesh forms a cut mesh under the action of the interface, and the basic parameters of the cut mesh are calculated and determined; the cut mesh includes the standard mesh and the interface mesh; S3, establishing the control equations of the standard grid in the computational domain grid that is not clipped by the surface of the geometric object; S4. Based on the form of the control equation of the standard grid, determine the control equation of the interface grid in the computational domain grid that is sheared by the surface of the geometric object; S5. Based on the respective control equations of the standard grid and the interface grid, numerical simulation of the flow field is performed in an iterative solution manner; In step S3, the control equation of the standard grid is established based on a typical conservation equation; the conservation equation is as follows: In the formula, Represents a conserved variable Over time The rate of change of is the divergence term, is the divergence operator, Corresponding conserved variables The flux function of ; for the standard grid that is not cut by the surface of the geometric object, the above conservation equation is discretized using the finite volume format to obtain the following formula: In the formula, Represents the number of time integration steps; further use the forward Euler format for time discretization and rewrite the formula as follows: In the formula, , that is, the conserved variable In the grid The average value on is a conserved variable In the grid The original value on the effective volume is then converted to Convert the volume fraction to effective area The surface integral of is as follows: In the formula, represents the time step, Represents the normal vector, symbol Indicates the vertical direction, represents the area; after applying the second-order difference format to this formula, the following formula is obtained: In the formula, , and Grid The average flux on the six faces is the finite volume discretization form of the conservation equation on the standard Cartesian grid, thus completing the process of establishing the control equation of the standard grid; In step S4, for the interface mesh that is sheared by the surface of the geometric object, after the mesh pruning method is applied for pruning, the effective volume of the interface mesh and the area fraction of each surface in the mesh are changed. Then, the finite volume discretization form of the conservation equation on the standard Cartesian grid established for the standard grid in step S3 is modified as the basis, and a new conservation equation is obtained by weighting the volume fraction and the porosity as the control equation of the interface mesh.

2. The immersed boundary numerical simulation method based on the grid pruning method according to claim 1, characterized in that: In step S1, a signed distance function is used to mark the interface between the fluid and the geometric object; in the set calculation domain grid, the surface with a distance function value of zero is the interface, the area with a positive distance function value represents the part of the grid that is not immersed in the geometric object, and the area with a negative distance function value represents the part of the grid that is immersed in the geometric object.

3. The immersed boundary numerical simulation method based on the grid pruning method according to claim 1, characterized in that: In step S2, when the calculation process is initialized, the volume fraction, porosity and cross-sectional area corresponding to each three-dimensional grid unit in the cut grid are further determined based on the determined interface between the fluid and the geometric object; wherein the volume fraction represents the proportion of the fluid and the geometric object in the three-dimensional grid unit, the porosity represents the area fraction of a certain surface of the corresponding three-dimensional grid unit that is in the fluid part, and the cross-sectional area represents the area of ​​the cross section where the corresponding three-dimensional grid unit intersects with the geometric object, and the cross section is the partial area of ​​the interface.

4. The immersed boundary numerical simulation method based on the grid pruning method according to claim 1, characterized in that: In step S2, based on the numerical discretization method of the finite volume method, the coordinates of the center point in the cut grid are The three-dimensional grid unit is denoted as grid , correspond direction, correspond direction, correspond direction, thus the grid The volume fraction of the fluid part is recorded as , in the grid When it belongs to the interface grid, ; Then the grid The effective volume is recorded as ,in Representative Grid along The spatial grid size in the direction, Representative Grid along The spatial grid size in the direction, Representative Grid along The spatial grid size in the direction; then the grid The area fraction of any surface in the fluid part is recorded as the porosity , ; When the grid When it is a cube, it has a first surface, a second surface, a third surface, a fourth surface, a fifth surface and a sixth surface; the first surface is opposite to the second surface, the third surface is opposite to the fourth surface, and the fifth surface is opposite to the sixth surface; The area of ​​the first surface in the fluid portion is expressed as ,in is the porosity corresponding to the first surface; the area of ​​the second surface in the fluid part is expressed as ,in is the porosity corresponding to the second surface; the area of ​​the third surface in the fluid part is expressed as ,in is the porosity corresponding to the third surface; the area of ​​the fourth surface in the fluid part is expressed as ,in is the porosity corresponding to the fourth surface; the area of ​​the fifth surface in the fluid part is expressed as ,in is the porosity corresponding to the fifth surface; the area of ​​the sixth surface in the fluid part is expressed as ,in is the porosity corresponding to the sixth surface; Finally, the grid The area of ​​the cross section where it intersects the geometric object is recorded as ; This completes the initialization of the calculation process. The basic parameters of the cut grid include the volume fraction of each three-dimensional grid unit , porosity and cross-sectional area .

5. The immersed boundary numerical simulation method based on the grid pruning method according to claim 1, characterized in that: By weighting the volume fraction and porosity, a new conservation equation is obtained as follows: In the formula, for the cube grid , is the porosity corresponding to the first surface, is the flux on the first surface; is the porosity corresponding to the second surface, is the flux on the second surface; is the porosity corresponding to the third surface, is the flux on the third surface; is the porosity corresponding to the fourth surface, is the flux on the fourth surface; is the porosity corresponding to the fifth surface, is the flux on the fifth surface; is the porosity corresponding to the sixth surface, is the flux on the sixth surface; In the formula, and They represent additional momentum exchange terms and friction terms, respectively, which are used to consider the effect of immersed boundaries on the fluid; the momentum exchange term Used to satisfy the no-slip condition for the normal component of velocity; friction term Represents the cross-sectional area of ​​the corresponding interface Part of the friction stress is used to satisfy the no-slip condition of the tangential component of the interface velocity.

6. The immersed boundary numerical simulation method based on the grid pruning method according to claim 5 is characterized in that: According to the physical constraint that there is no fluid inflow or outflow at the immersed boundary, the normal velocity at the interface is determined to be zero; by giving To satisfy the physical constraint that there is no fluid inflow or outflow at the immersed boundary, where Representative Grid Momentum exchange term in the vertical direction The velocity component in Representative Grid The velocity component in the vertical direction; the momentum exchange term It is expressed as the following formula: In the formula, represents the time step, Representative Grid The mean value of the velocity component in the vertical direction; the no-slip condition is also satisfied at the immersed boundary, resulting in shear stress, which is obtained by adding the friction term The friction term As follows: In the formula, Represents the normal vector, symbol Indicates the vertical direction, represents the wall shear stress, represents the velocity component, Represents the viscosity coefficient; symbol Indicates the parallel direction, That is, it represents the mean value of the velocity component in the parallel direction; Represents the normal vector Quantity, Represents the normal vector Quantity, Represents the normal vector Quantity; represents the grid scale; The momentum exchange term and friction term After substituting the newly obtained conservation equation in step S4, the discrete form of the conservation equation of the interface mesh is obtained as the control equation of the interface mesh.

7. The immersed boundary numerical simulation method based on the grid pruning method according to claim 1, characterized in that: In step S5, after setting the boundary conditions and initial conditions of the computational domain grid, the computational domain grid is divided; the control equations of the standard grid and the interface grid are iteratively solved to perform numerical simulation of the flow field.

8. A computer system comprising a memory, a processor, and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the immersed boundary numerical simulation method based on the grid pruning method according to any one of claims 1 to 7.

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