Fluid-solid coupling analysis method and device for slender object based on finite mass point method and SPH

Abstract

The invention discloses a slender beam fluid-solid coupling analysis method and device based on a finite mass point method and SPH. A structure is dispersed into beam mass points, a slender beam is simulated through a two-dimensional beam unit, fluid is simulated through SPH particles, coupling interface pressure transmission is simulated through a transmission unit, and coupling interface displacement coordination is simulated through a coupling unit. A finite mass point method is adopted for dynamic analysis, pure deformation and rigid body displacement of the two-dimensional beam unit are separated through virtual reverse motion, and then the internal force increment of the plane beam unit is calculated; an SPH calculation fluid model is adopted, and a discrete format of a fluid control equation, a tensile stability control method based on a Shepard Filter and a particle displacement correction technology and a leapfrog time integration scheme are given; an FPM-SPH interface coupling scheme is provided, a coupling interface particle arrangement method is given, a physical quantity corresponding relation between beam particles and fluid particles at an interface is established, and a two-dimensional beam fluid-solid coupling analysis framework is established. The method is simple and efficient in calculation, and overcomes the defects of existing research.

Description

Technical Field

[0001] The present application relates to a fluid-solid coupling analysis technology for slender objects, and in particular to a fluid-solid coupling analysis method and device for slender objects based on a finite particle method and SPH. Background Art

[0002] In the field of structural engineering, there are many scenarios involving the interaction between fluid and structure, which is also one of the research hotspots in recent years. For example, the structural response in a dam break scenario, the dynamic response of a large floating structure under complex wave loads, etc. The interaction between fluid and structure is also called fluid-solid coupling, that is, the fluid pressure acts on the structure to cause it to produce large deformation and displacement. At the same time, the structural displacement will also affect the fluid boundary, involving difficulties such as the free surface of the fluid and the strong nonlinear response of the structure. In marine structures, fluid-solid coupling problems are often modeled using numerical simulation methods in order to simulate and interfere with them. The numerical simulation method has a wide range of application scenarios in simulation and calculation fields such as industrial software and structural numerical calculation software.

[0003] There are many applications in the calculation of fluid-structure coupling problems. For example, for slender components such as submarine tunnels, the existing structural calculation methods use more plane solid units for fluid-structure coupling simulation, which is not efficient in structural calculation. Existing fluid calculation methods often use finite element, finite volume and other mesh methods. When the coupling interface involves severe deformation, the mesh-based method requires more complex operations and techniques to capture the interface. At the same time, due to the existence of convection terms, numerical diffusion is difficult to avoid, and the free surface of the liquid is not clear. Therefore, a slender beam fluid-structure coupling analysis method based on SPH and finite particle method is a computational analysis method that needs to be further developed and improved in the current engineering application field. It can effectively reduce the number of units, improve computational efficiency, and provide a good foundation for further expanding the application of slender components in marine structures.

[0004] The current analysis methods for fluid-structure interaction problems of slender beams often have the following defects:

[0005] 1) For complex fluid-solid coupling behaviors, it is often difficult to carry out model tests due to factors such as high test costs, long cycles, and constraints on test conditions.

[0006] 2) For structural simulation, strong fluid action often causes large deformation of the structure. The use of traditional structural numerical analysis methods (such as the finite element method, etc.) often faces problems such as grid distortion, singular overall stiffness matrix, and low efficiency in solving large nonlinear equations. It is difficult to solve large structural deformations and it is difficult to meet the needs of actual engineering structure design calculations.

[0007] 3) For fluid simulation, the evolution of the free liquid surface is very dramatic, and there are strong nonlinear free surface flow problems such as rolling deformation, breakup and fusion of the free liquid surface. The numerical analysis method based on Euler description (such as the finite volume method, etc.) is difficult to avoid numerical diffusion due to the existence of convection terms, and the free surface of the liquid surface is not clear.

[0008] 4) The existing modeling method of slender beams uses plane solid units to simulate panels. However, this type of modeling method leads to a large number of model units, complex calculations, and large amounts of calculations, making it difficult to effectively handle large-scale and large-scale slender beam structural engineering problems.

[0009] 5) Existing fluid-structure coupling analysis methods often focus on fluid-structure coupling calculations between grids and grids or between grids and particles, but there are few studies on particle-particle coupling calculations and analysis. There is a lack of effective calculation methods for the exchange of information on physical quantities such as force and displacement between particles at the coupling interface.

[0010] The existing modeling and analysis methods for fluid-structure coupling problems of slender beams have problems such as lack of modeling and analysis methods, high cost of fluid-structure coupling tests, defects in handling large structural deformation problems, difficulty in tracking the free surface motion of the fluid, and large and complex numerical simulation calculations. Summary of the invention

[0011] The present application provides a fluid-solid coupling analysis method and device for slender objects based on a finite particle method and a smoothed particle hydrodynamics method (SPH) to at least solve the above technical problems existing in the prior art.

[0012] According to a first aspect of the present application, a fluid-solid coupling analysis method for a slender object based on a finite particle method and SPH is provided, wherein a slender object structure model with finite particles and a fluid model based on a smooth particle method SPH are created; based on the slender object structure model and the fluid model, the slender object structure is discretized into particles for representation in combination with the interface coupling mode between the slender object and the liquid; the method comprises:

[0013] The slender object is simulated by two-dimensional slender object unit, the fluid is simulated by SPH fluid model, the pressure transmission of the coupling interface between the slender object and the liquid is simulated by the transmission unit, and the displacement coordination of the coupling interface is simulated by the coupling unit; the discrete particles of the slender object are subjected to force analysis to obtain the virtual reverse motion separation structure deformation and rigid body displacement of the slender object, and the deformation of the slender object in the two-dimensional direction and the internal force it is subjected to are obtained;

[0014] Determine the particle approximate fluid control equations for slender objects based on the transfer unit and SPH fluid model, and the discrete fluid continuity equation and momentum equation;

[0015] Based on the Shepard Filter algorithm and particle correction technology, the approximate fluid control equation is subjected to tensile stability control; the discrete fluid continuity equation is solved by leapfrog time integration to obtain the particle physical quantity of the SPH particle at the next moment; the momentum equation is solved by the central difference method to obtain the particle motion equation of the finite particle method (FPM) of the slender object;

[0016] The coupling interface particle arrangement method is used to evenly distribute multiple layers of virtual particles on the coupling interface, and the simulated physical quantities of the virtual particles at the coupling interface and the corresponding relationship between the physical quantities are determined based on the transfer unit and the coupling unit; the pressure distribution transmission of the coupling interface is obtained by analyzing the transfer unit, and the displacement of the virtual particles is obtained by analyzing the coupling unit, thereby building a two-dimensional fluid-solid coupling analysis framework for slender objects;

[0017] Based on the analysis framework, the fluid-structure coupling of the slender object is analyzed to obtain corresponding analysis results.

[0018] In some executable embodiments, the step of obtaining the virtual inverse motion of the slender object to separate the structural deformation and the rigid body displacement to obtain the deformation of the slender object in two-dimensional directions and the internal force it is subjected to includes:

[0019] By means of virtual inverse motion of the slender object, the rigid body translation and rotation of the inverse motion of the slender object are calculated;

[0020] Deduct the rigid body translation and rotation of the mass point to determine the unit deformation information of the slender object;

[0021] The unit axial force is determined by unit deformation, and the internal forces of the mass points at both ends of the slender object unit are determined based on the force balance relationship.

[0022] In some executable embodiments, simulating fluid by smoothed particle method (SPH) includes:

[0023] Based on the interpolation principle and kernel estimation method, the partial differential equation of the SPH fluid model is transformed into an integral equation. The physical quantities of discrete particles are determined based on the integral equation. The fluid calculation domain is discretized into a series of particles carrying physical information by adding the physical quantities. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area around the particle.

[0024] And the attribute information of the particles at the previous moment is iteratively obtained to obtain the attribute information of the particles at the next moment.

[0025] In some executable embodiments, the method of uniformly distributing multiple layers of virtual particles on the coupling interface by using the coupling interface particle arrangement method includes:

[0026] At the coupling interface, along the axis direction of the elongated object, multiple layers of virtual particles with a distribution density close to that of the fluid particles are arranged with the same particle spacing.

[0027] In some executable embodiments, the coupling interface pressure transmission between the elongated object and the liquid is simulated by a transmission unit, comprising:

[0028] Determine the effect on virtual particle B i The interface pressure on the virtual particle B i The interface pressure on the plane is decomposed into the mass points of the slender object unit. Specifically, it is assumed that the relative position relationship between the plane slender object unit and the corresponding virtual particle always remains unchanged. The virtual particle B i The projection position of the slender object element A0A1 on the coupling boundary is B ip , then the coupling force transmitted to the mass points at both ends of the slender object unit is in The virtual particle coupling force is Along the local coordinate system of the slender object The direction component, d is the distance from the virtual particle projection point to the virtual particle, is the equivalent coupling force acting on the particle at the end of the slender object, N is the shape function matrix, N1=1-3ξ 2 +2ξ 3 ,N2=(ξ-2ξ 2 +ξ 3 )l, N3=3ξ 2 -2ξ 3 ,N4=(-ξ 2 +ξ 3 )l,N′ k N k The derivative of (k=1,2,3,4) with respect to ξ, l is the length of the slender object unit A0A1, A0 to B ip The length of the object is , and A0 and A1 are the two end points of the slender object unit.

[0029] In some executable embodiments, the method further includes: updating the position of the virtual particle at the coupling interface according to the displacement of the coupling unit, that is, the displacement of the slender object particle. Specifically, assuming that the distance from the virtual particle at the coupling interface to the slender object unit remains unchanged during the movement, the angle of the slender object unit rotating counterclockwise at time t+1 relative to time t is θ, and the virtual particle B belonging to the slender object unit is i , the updated position at time t+1 for: d′=R(θ)·d, in, are the positions of the two end mass points of the slender object unit at time t+1, R(θ) is the rotation matrix, and d is the rotation matrix from B at time t. ip Point to B i Vector.

[0030] In some executable embodiments, the step of obtaining the particle motion equation of the finite particle method (FPM) of the slender object includes:

[0031] Assuming that in each time iteration step during the structural motion deformation process, the particles are in a dynamic equilibrium state, and the motion of any particle follows Newton's second law, the equation is: m α is the mass of particle α, and They represent the external force, internal force and damping force of the particle α respectively, μ is the damping coefficient, which is a set constant. Through the central difference algorithm, the displacement of the particle in the path unit is directly obtained, and the position and deformation information of the structure at the next moment are obtained.

[0032] According to a second aspect of the present application, a fluid-solid coupling analysis device for a slender object based on a finite particle method and SPH is provided, comprising:

[0033] Creation unit for creating finite mass slender object structure model and SPH-based fluid model;

[0034] A characterization unit, configured to discretize the structure of the slender object into particles for characterization based on the slender object structure model and the fluid model and in combination with the interface coupling mode between the slender object and the liquid;

[0035] A simulation unit is used to simulate the slender object through a two-dimensional slender object unit, simulate the fluid through an SPH fluid model, simulate the pressure transmission of the coupling interface between the slender object and the liquid through a transmission unit, and simulate the displacement coordination of the coupling interface through a coupling unit;

[0036] A force analysis unit is used to perform force analysis on discrete particles of the slender object, obtain the virtual reverse motion separation structure deformation and rigid body displacement of the slender object, and obtain the deformation of the slender object in two-dimensional directions and the internal force it is subjected to;

[0037] Determine the unit, which is used to determine the particle approximate fluid control equations of the slender object based on the transfer unit and the SPH fluid model, and the discrete fluid continuity equation and momentum equation;

[0038] A processing unit is used to perform tensile stability control on the approximate fluid control equation based on the Shepard Filter algorithm and the particle correction technology; solve the discrete fluid continuity equation by leapfrog time integration to obtain the particle physical quantity of the SPH particle at the next moment; solve the momentum equation by the central difference method to obtain the particle motion equation of the finite particle method FPM of the slender object;

[0039] A construction unit is used to uniformly distribute multiple layers of virtual particles on the coupling interface by using a coupling interface particle arrangement method, and determine the simulated physical quantities of the virtual particles at the coupling interface, as well as the corresponding relationship between the physical quantities based on the transfer unit and the coupling unit; and obtain the pressure distribution transmission of the coupling interface by analyzing the transfer unit, and obtain the displacement of the virtual particles by analyzing the coupling unit, thereby building a two-dimensional fluid-solid coupling analysis framework for slender objects;

[0040] The analysis unit is used to analyze the fluid-solid coupling situation of the slender object based on the analysis framework to obtain corresponding analysis results.

[0041] In some executable embodiments, the force analysis unit is further used for:

[0042] By means of virtual inverse motion of the slender object, the rigid body translation and rotation of the inverse motion of the slender object are calculated;

[0043] Deduct the rigid body translation and rotation of the mass point to determine the unit deformation information of the slender object;

[0044] The unit axial force is determined by unit deformation, and the internal forces of the mass points at both ends of the slender object unit are determined based on the force balance relationship.

[0045] In some executable embodiments, the simulation unit is further used for:

[0046] Based on the interpolation principle and kernel estimation method, the partial differential equation of the SPH fluid model is transformed into an integral equation. The physical quantities of discrete particles are determined based on the integral equation. The fluid calculation domain is discretized into a series of particles carrying physical information by adding the physical quantities. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area around the particle.

[0047] And the attribute information of the particles at the previous moment is iteratively obtained to obtain the attribute information of the particles at the next moment.

[0048] According to a third aspect of the present application, an electronic device is provided, including:

[0049] at least one processor; and

[0050] a memory communicatively connected to the at least one processor; wherein,

[0051] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the steps of the fluid-structure coupling analysis method for slender objects based on the finite particle method and SPH.

[0052] According to the fourth aspect of the present application, a non-temporary computer-readable storage medium is provided. When the instructions in the storage medium are executed by a processor of an electronic device, the electronic device is enabled to perform the steps of the fluid-solid coupling analysis method of slender objects based on the finite particle method and SPH.

[0053] The fluid-solid coupling analysis method and device, electronic device, and storage medium of the slender object based on the finite particle method and SPH of the present application calculate the fluid-solid coupling problem of the slender beam through a numerical method. The simulation cost is low, the cycle is short, and the simulation is good with the test results. The modeling and analysis of the slender beam structure of the present application is based on the finite particle method. The slender beam is simulated by a two-dimensional beam unit. The overall stiffness matrix does not need to be integrated, which avoids the morbid problem of the overall stiffness matrix and can effectively analyze the dynamic response of the slender beam during the movement. At the same time, virtual reverse motion is used to separate the rigid body displacement to obtain the pure deformation of the structure. This method can effectively analyze the dynamic response of the unit internal force and deformation under large deformation when the slender beam structure acts on the fluid, providing an effective analysis method for the calculation of the structure. The fluid analysis of the present application is based on the SPH method and the Lagrangian description. It can simulate complex fluid flow and large deformation, track free surfaces and moving boundaries, improve numerical stability through tensile stability control, and effectively analyze the nonlinear free surface flow of the fluid, providing an effective analysis method for fluid simulation. This application proposes to simulate slender beams with two-dimensional beam units, construct slender beam structures with two-dimensional beam units, obtain unit pure deformation and particle internal force through virtual reverse motion of beam units, avoid deformation and internal force calculation of planar solid units, and greatly reduce the complexity of calculation. This application replaces the planar solid unit with a number of two-dimensional beam units, based on the characteristics of the finite particle method that the particle motions are independent of each other and the unit internal force solutions are independent of each other, and gives full play to the advantages of the high parallelism of the finite particle method. With the help of advanced parallel computing technologies such as Graphics Processing Unit (GPU) and Distributed Parallel Information Passing Interface (MPI), the calculation speed of slender beam structures can be greatly improved, and the fluid-solid coupling problem of large-scale and large-scale slender beams can be solved.

[0054] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become readily understood. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, wherein:

[0056] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0057] Figure 1 A schematic flow chart of a fluid-solid coupling analysis method for a slender object based on a finite particle method and SPH in an embodiment of the present application is shown;

[0058] Figure 2 A schematic diagram of virtual reverse motion of a plane beam unit in an embodiment of the present application is shown;

[0059] Figure 3 A schematic diagram of searching for particles within a smooth radius according to an embodiment of the present application is shown;

[0060] Figure 4 A schematic diagram of particle distribution at the coupling interface of an embodiment of the present application is shown;

[0061] Figure 5 A schematic diagram of pressure transmission at the coupling interface of an embodiment of the present application is shown;

[0062] Figure 6 A schematic diagram of coupling interface displacement coordination in an embodiment of the present application is shown;

[0063] Figure 7 A schematic diagram of the composition structure of a fluid-solid coupling analysis device for a slender object based on the finite particle method and SPH in an embodiment of the present application is shown;

[0064] Figure 8 A schematic diagram of the structure of an electronic device according to an embodiment of the present application is shown.

[0065] Explanation of numbers: 1: beam particle, 2: beam element, 3: virtual particle, 4: fluid particle. DETAILED DESCRIPTION

[0066] In order to make the purpose, features, and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0067] Figure 1FIG. 4 is a flow chart showing a flow chart of a fluid-solid coupling analysis method for a slender object based on a finite particle method and SPH according to an embodiment of the present application. Figure 1 As shown, the fluid-structure coupling analysis method for slender objects based on the finite particle method and SPH in the embodiment of the present application includes the following processing steps:

[0068] Step 101, creating a finite particle slender object structure model and a smoothed particle method (SPH)-based fluid model; based on the slender object structure model and the fluid model, combined with the interface coupling mode between the slender object and the liquid, the slender object structure is discretized to be represented by particles.

[0069] In the embodiment of the present application, before executing the specific steps of the fluid-solid coupling determination method, it is necessary to create relevant simulation models in advance, specifically, at least create a slender object structure model and a fluid model to facilitate the characterization of the structure of the slender object in a particle manner, and mathematical modeling of the fluid to simulate its fluid properties. In the embodiment of the present application, the slender object is mainly a rigid slender object. As an example, the slender object is a slender beam structure. The technical solution of the embodiment of the present application is applicable to scenarios such as structural response in dam break scenarios and dynamic response of large floating structures under complex wave loads.

[0070] Step 102, simulating the slender object through a two-dimensional slender object unit, simulating the fluid through an SPH fluid model, simulating the pressure transmission at the coupling interface between the slender object and the liquid through a transmission unit, and simulating the displacement coordination of the coupling interface through a coupling unit.

[0071] In the embodiment of the present application, the fluid is simulated by the smoothed particle hydrodynamics method (SPH), including:

[0072] Based on the interpolation principle and kernel estimation method, the partial differential equation of the SPH fluid model is converted into an integral equation. The physical quantities of discrete particles are determined based on the integral equation. The fluid calculation domain is discretized into a series of particles carrying physical information by adding the physical quantities. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area around the particle. The attribute information of the particles at the previous moment is iteratively obtained.

[0073] The pressure transmission through the coupled interface between the slender object and the liquid is simulated by the transmission unit, including:

[0074] Determine the effect on virtual particle B i The interface pressure on the virtual particle B iThe interface pressure on the plane is decomposed into the mass points of the slender object unit. Specifically, it is assumed that the relative position relationship between the plane slender object unit and the corresponding virtual particle always remains unchanged. The virtual particle B i The projection position of the slender object element A0A1 on the coupling boundary is B ip , then the coupling force transmitted to the mass points at both ends of the slender object unit is in The virtual particle coupling force is Along the local coordinate system of the slender object The direction component, d is the distance from the virtual particle projection point to the virtual particle, is the equivalent coupling force acting on the particle at the end of the slender object, N is the shape function matrix, N1=1-3ξ 2 +2ξ 3 ,N2=(ξ-2ξ 2 +ξ 3 )l, N3=3ξ 2 -2ξ 3 ,N4=(-ξ 2 +ξ 3 )l,N′ k N k The derivative of (k=1,2,3,4) with respect to ξ, l is the length of the slender object unit A0A1, A0 to B ip The length of the object is , and A0 and A1 are the two end points of the slender object unit.

[0075] Based on the aforementioned models, simulations of the respective objects are performed to determine the analysis object of the fluid-solid coupling between the slender beam and the liquid, so as to analyze the dynamic response of the slender beam under complex wave loads.

[0076] Step 103 , performing force analysis on discrete particles of the slender object, obtaining the virtual reverse motion separation structure deformation and rigid body displacement of the slender object, and obtaining the deformation of the slender object in two-dimensional directions and the internal force it is subjected to.

[0077] Specifically, through virtual inverse motion, the rigid body translation and rotation of the reverse motion are calculated; by deducting the rigid body translation and rotation of the particle, the pure deformation of the beam unit is determined; the unit axial force is determined by the unit deformation, and the internal force of the particles at both ends of the beam unit is obtained from the force balance relationship.

[0078] Step 104 : determining the particle approximate fluid control equations, discrete fluid continuity equations and momentum equations of the slender object based on the transfer unit and the SPH fluid model.

[0079] In the embodiment of the present application, the particle approximation fluid control equation, the discrete fluid continuity equation and the momentum equation can be determined by the existing fluid-related equations and momentum equations, and the details are not repeated here.

[0080] Step 105, based on the Shepard Filter algorithm and particle correction technology, the approximate fluid control equation is subjected to tensile stability control; the discrete fluid continuity equation is solved by leapfrog time integration to obtain the particle physical quantity of the SPH particle at the next moment; the momentum equation is solved by the central difference method to obtain the particle motion equation of the finite particle method FPM of the slender object.

[0081] According to the displacement of the coupling unit, i.e., the displacement of the slender object particle, the position of the virtual particle at the coupling interface is updated. Specifically, assuming that the distance from the virtual particle at the coupling interface to the slender object unit remains unchanged during the motion, the angle of the slender object unit's counterclockwise rotation at time t+1 is θ relative to time t. For the virtual particle B belonging to the slender object unit, i , the updated position at time t+1 for: d′=R(θ)·d, in, are the positions of the two end mass points of the slender object unit at time t+1, R(θ) is the rotation matrix, and d is the rotation matrix from B at time t. ip Point to B i Vector.

[0082] As an example, based on the interpolation principle, the partial differential equation can be converted into an integral form through the kernel estimation formula, and then the integral equation is approximated by the sum of a series of discrete particle physical quantities. SPH discretizes the fluid calculation domain into a series of particles with physical information such as velocity, density, pressure, etc. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area (support domain) around the particle, and then the partial differential equations such as the fluid continuity equation and momentum equation are discretized as:

[0083]

[0084] Using the Lagrangian format, the motion of SPH particles represents the fluid motion.

[0085] Through the leapfrog time integration scheme, the particle properties at the next moment can be iteratively obtained from the particle position, velocity, density and other properties at the existing moment.

[0086] Among them, the particle motion equation of the finite particle method FPM of the slender object is obtained, including:

[0087] Assuming that in each time iteration step during the structural motion deformation process, the particles are in a dynamic equilibrium state, and the motion of any particle follows Newton's second law, the equation is: m α is the mass of particle α, and They represent the external force, internal force and damping force of the particle α respectively, μ is the damping coefficient, which is a set constant. Through the central difference algorithm, the displacement of the particle in the path unit is directly obtained, and the position and deformation information of the structure at the next moment are obtained.

[0088] Step 106, using the coupling interface particle arrangement method to evenly distribute multiple layers of virtual particles on the coupling interface, and determine the simulated physical quantities of the virtual particles at the coupling interface based on the transfer unit and the coupling unit, as well as the corresponding relationship between the physical quantities; and obtain the pressure distribution transmission of the coupling interface by analyzing the transfer unit, and obtain the displacement of the virtual particles by analyzing the coupling unit, thereby building a two-dimensional fluid-solid coupling analysis framework for slender objects.

[0089] In the embodiment of the present application, a two-dimensional fluid-solid coupling analysis framework is obtained through the aforementioned processing equations. Although the fluid-solid coupling analysis framework is obtained by simulation means, the analysis framework can greatly improve the calculation speed of the slender beam structure and solve the large-scale and large-scale fluid-solid coupling problem of slender beams.

[0090] Step 107 : Analyze the fluid-structure coupling of the slender object based on the analysis framework to obtain corresponding analysis results.

[0091] The modeling and analysis of the slender beam structure of the embodiment of the present application is based on the finite particle method. The slender beam is simulated by two-dimensional beam elements. The overall stiffness matrix does not need to be integrated, which avoids the morbid problem of the overall stiffness matrix and can effectively analyze the dynamic response of the slender beam during the movement process; at the same time, the virtual reverse motion is used to separate the rigid body displacement to obtain the pure deformation of the structure. This method can effectively analyze the dynamic response of the unit internal force and deformation under large deformation when the slender beam structure acts on the fluid, and provides an effective analysis method for the calculation of the structure. The fluid analysis of the present application is based on the SPH method, based on the Lagrangian description, and can simulate complex fluid flow and large deformation, can track free surfaces and moving boundaries, improve numerical stability through tensile stability control, can effectively analyze the nonlinear free surface flow of fluids, and provide an effective analysis method for fluid simulation. The present application proposes a two-dimensional beam unit to simulate a slender beam, construct a slender beam structure with a two-dimensional beam unit, and obtain the unit pure deformation and particle internal force through the virtual reverse motion of the beam unit, avoiding the deformation and internal force calculation of the plane solid unit, and greatly reducing the complexity of the calculation. This application replaces the plane solid unit with a number of two-dimensional beam units. Based on the characteristics of the finite particle method that the particle motions are independent of each other and the unit internal force solutions are independent of each other, the advantage of the finite particle method's high parallelism is brought into play. With the help of advanced parallel computing technologies such as graphics processing unit (GPU) and distributed parallel information passing interface (MPI), the calculation speed of slender beam structures can be greatly improved, and the large-scale and large-scale slender beam fluid-solid coupling problem can be solved.

[0092] It should be emphasized that, although the technical solution of the embodiment of the present application is described using a slender beam structure as an example, it is also applicable to application scenarios of other slender objects.

[0093] The essence of the technical solution of the embodiment of the present application is further illustrated by specific examples below.

[0094] The embodiments of the present application propose a beam structure model based on the finite particle method, a fluid model based on SPH, and an interface coupling. First, the beam structure is discretized into beam particles, the slender beam is simulated by a two-dimensional beam unit, the fluid is simulated by an SPH particle, the pressure transmission of the coupling interface is simulated by a transmission unit, and the displacement coordination of the coupling interface is simulated by a coupling unit. The finite particle method is used for dynamic analysis. The deformation of the two-dimensional beam structure and the rigid body displacement are obtained through virtual inverse motion analysis, and the deformation and internal force of the two-dimensional beam unit are obtained. The SPH computational fluid model is used to discretize the fluid continuity equation and momentum equation based on the particle approximate fluid control equation. The tensile stability control is realized based on the ShepardFilter method and particle correction technology. The particle physical quantities at the next moment are solved by the leapfrog time integration scheme from the particle physical quantities at the current moment to meet the requirements of numerical stability, and the minimum time step is solved according to the CFL condition. The coupled interface particle arrangement method uses evenly distributed multi-layer virtual particles to establish the physical quantity correspondence between the virtual particles at the interface and the transfer unit and the coupling unit. The interface pressure on the virtual particles is further transferred to the beam unit particles, and the distribution and transmission of the interface pressure are obtained by analyzing the transfer unit. The virtual particles at the coupling interface update their positions according to the displacement of the beam particles, and the displacement of the virtual particles is obtained by analyzing the coupling unit. Repeat the above analysis steps to complete the analysis of the fluid-solid coupling problem of slender beams and build a two-dimensional beam fluid-solid coupling analysis framework.

[0095] In the FPM-SPH coupling analysis framework of the embodiment of the present application, for each iteration step, the structural field, flow field and fluid-solid coupling interface are calculated respectively. For the structural field, the pure deformation and unit internal force of the plane beam unit are calculated according to the displacement of the beam particles and applied to the particles. For the flow field, the density change rate and velocity change rate are calculated according to the physical quantities such as the position, velocity, density and pressure of the fluid particles, so as to update the physical quantities of the fluid particles through time integration. For the coupling interface, the interface pressure of the fluid particles on the virtual particles is calculated and transmitted to the beam particles; and after the structural field calculates the displacement of the beam particles according to the resultant force of the beam particles, the position of the virtual particles is updated, thereby updating the flow field boundary. The following is a detailed description.

[0096] like Figure 2 As shown, assume that the two ends of the plane beam structure (beam unit) are A and B. a and t b (=t a +Δt), the plane positions of the two end particles are and The rotation angle positions of the two end particles are and Then the particles at both ends are a to b The displacement and rotation angle at the moment are:

[0097]

[0098] The beam element t a ,t b The positions at the two moments are recorded as AB and A′B′ respectively. To calculate the pure deformation of the beam element, the element is moved in reverse according to the linear displacement between the two moments and the rotation angle between the two axes, as shown in Figure 2 As shown. The reverse translation is -Δx A , the reverse rotation amount is -θ ba After the reverse motion, A" coincides with A, and the virtual position A"B" is collinear with AB. Based on the difference between the virtual position A"B" and AB, the pure deformation of the beam element is obtained as:

[0099] Δ e = l b -l a

[0100]

[0101] In the above formula, l is the length of the beam element, Δ e is the expansion and contraction deformation of the beam element along the axial direction of the element, and are the bending deformation of the beam element at points A and B respectively.

[0102] Under the linear elastic constitutive model, the internal force increment generated on the beam unit mass point in the local coordinate system of the AB reference configuration can be obtained based on the pure deformation; after obtaining the internal force increment of the beam unit, it is superimposed on t a Based on the total amount of internal force of the reference configuration at time t, we can get b The total amount of internal force in this configuration at this moment. Then transform it to the global coordinate system, and after the unit is translated forward Δx A and positive rotation θ ba , we get the plane beam element t b The internal force of the unit at time.

[0103] like Figure 3 As shown in Figure 1, SPH approximates the field function (and its derivative) through the kernel function, converting it into the weighted sum of all particles in the support domain Ω (radius is κh, κ is a constant, h is the kernel function radius). The field function f(x) can be approximated by the kernel function W(xx′,h) as:

[0104] <f(x)> =∫ Ω f(x′)W(xx′,h)dx′

[0105] Then the function in X i The function value at <f(x i )> can be approximated by a finite number of particles in a local area:

[0106]

[0107] Where m j , j are the mass and density of the neighborhood particle j, respectively, and N is the number of neighborhood particles around particle i. Through kernel estimation and particle approximation, the continuity equation and momentum equation of the fluid can be discretized as:

[0108]

[0109] In the formula, p i 、v i denote the pressure and velocity of particle i, respectively, v ij is the velocity of particle i relative to particle j, is the kernel function at x i The partial derivative at ij is the artificial viscosity, which can be expressed as:

[0110]

[0111] In order to solve the fluid momentum equation, it is necessary to further calculate the fluid pressure. The artificial state equation is used to characterize the relationship between density change and pressure, so that the calculation time step of the SPH method can be further improved. The artificial state equation is:

[0112] p i =c i 2 (ρ i -ρ0)

[0113] Where c i is the fluid sound velocity, ρ0 is the fluid static density.

[0114] The virtual particle method is used to process the fluid boundary. Multiple layers of virtual particles with similar mass, density and pressure are arranged at the boundary. These virtual particles participate in the calculation of the physical quantities of the fluid particles, thereby alleviating the particle inconsistency. The pressure of the virtual particles at the moving boundary is obtained by interpolating the surrounding fluid particles:

[0115]

[0116] Where p w 、p a are the pressures of virtual particles and fluid particles, respectively, and a w is the acceleration of the virtual particle, and the density of the boundary particles is inversely calculated using the artificial state equation.

[0117] The embodiment of the present application uses Shepard Filter and particle displacement correction technology to achieve tensile stability control. The Shepard Filter method corrects the density once at a certain time step, which has little effect on the SPH calculation framework. The corrected density is expressed as

[0118] in, The density is corrected at intervals of 25 time steps. Secondly, the particle displacement correction technology is used to improve the uneven distribution of particles. The displacement correction amount δx of particle i is i for:

[0119]

[0120] In the formula, the coefficient β ranges from 0.001 to 0.1, v max is the maximum velocity of the particle, Δt is the calculation time step, x ij is the distance between particles i and j, N i is the number of neighboring particles of particle i, e ij is the unit direction vector from particle i to particle j. After obtaining the particle displacement correction, it is necessary to further correct other physical quantities of the fluid particles, such as velocity, pressure, density, etc. The correction amounts are expressed as:

[0121]

[0122] like Figure 4 As shown, the number of beam particles is small and the distance between them is larger than that of fluid particles. Virtual particles with a distribution density similar to that of fluid particles are arranged along the beam axis at the coupling interface. At the same time, multiple layers of virtual particles need to be arranged to provide sufficient boundary pressure, and multiple layers of virtual particles are evenly arranged according to the size of the two-dimensional beam structure.

[0123] like Figure 5 As shown in Figure 2, the interface pressure consists of two parts: fluid particle pressure and coupling interface repulsion. The interface pressure acts on the virtual particles at the coupling interface, and its resultant force is for:

[0124]

[0125] In the formula, is the virtual particle density, m w is the mass of virtual particles; p w is the pressure of the virtual particle, F ij is the coupling interface repulsion. w The pressure of the virtual particle of the moving boundary is obtained by interpolation of the adjacent fluid particles. In the embodiment of the present application, when calculating the resultant force using the above formula, only the contribution from the fluid particles is considered.

[0126] On the basis of considering the fluid particle pressure, the coupling interface repulsion is introduced to further prevent the fluid particles from penetrating the coupling interface. The coupling interface repulsion is expressed as:

[0127]

[0128] In the formula Δd is the initial interval division.

[0129] Acting on virtual particle B i The interface pressure on the beam element is further transferred to the beam element mass point through the transfer unit. Assuming that the relative position relationship between the plane beam element and the corresponding virtual particle always remains unchanged, the virtual particle B i The projection position of beam element A0A1 on the coupling boundary is B ip , the coupling force transmitted to the mass points at both ends of the beam unit is calculated as follows:

[0130]

[0131] in The virtual particle coupling force is Local coordinate system along the beam The direction component, d is the distance from the virtual particle projection point to the virtual particle, is the equivalent coupling force acting on the particle at the end of the beam, N is the shape function matrix, N1=1-3ξ 2 +2ξ 3 ,N2=(ξ-2ξ 2 +ξ 3 )l, N3=3ξ 2 -2ξ 3 ,N4=(-ξ 2 +ξ 3 )l,N′ k N k The derivative of (k=1,2,3,4) with respect to ξ, l is the length of beam element A0A1, A0 to B ip Length.

[0132] like Figure 6 As shown in the figure, the virtual particle at the coupling interface updates its position according to the displacement of the coupling unit (beam particle displacement). By assuming that the distance between the virtual particle at the coupling interface and the beam unit remains unchanged during the motion, the angle of the counterclockwise rotation of the beam unit at time t+1 is θ relative to time t. i , the updated position at time t+1 It can be calculated as follows:

[0133]

[0134] in are the positions of the particles at both ends of the beam at time t+1, R(θ) is the rotation matrix, and d is the rotation matrix from B at time t. ip Point to B i Vector.

[0135] The technical solution of the embodiment of the present application establishes a beam structure model based on the finite particle method and a fluid model based on SPH, which can effectively solve the dynamic response of the slender beam structure and the free surface flow motion; the interface coupling solution for the plane beam and SPH fluid particles of the embodiment of the present application completes the analysis method for the fluid-solid coupling problem of the plane beam. The model and analysis results obtained by using the embodiment of the present application can be directly applied to the design analysis of actual engineering applications related to the fluid-solid coupling of slender beams, can truly simulate the actual situation, and provide an efficient method for the engineering application field, thereby providing a good foundation for further expanding the application of slender components in marine structures.

[0136] Figure 7 FIG. 1 shows a schematic diagram of the composition structure of a fluid-solid coupling analysis device for a slender object based on the finite particle method and SPH according to an embodiment of the present application. Figure 7 As shown, the fluid-solid coupling analysis device for a slender object based on the finite particle method and SPH in the embodiment of the present application includes:

[0137] A creation unit 70, used to create a finite mass elongated object structure model and a SPH-based fluid model;

[0138] A characterization unit 71 is used to discretize the structure of the slender object into particles for characterization based on the slender object structure model and the fluid model and in combination with the interface coupling mode between the slender object and the liquid;

[0139] A simulation unit 72, used for simulating the slender object through a two-dimensional slender object unit, simulating the fluid through a fluid model of SPH, simulating the pressure transmission of the coupling interface between the slender object and the liquid through a transmission unit, and simulating the displacement coordination of the coupling interface through a coupling unit;

[0140] A force analysis unit 73 is used to perform force analysis on discrete particles of the slender object, obtain the virtual reverse motion separation structure deformation and rigid body displacement of the slender object, and obtain the deformation of the slender object in two-dimensional directions and the internal force it is subjected to;

[0141] A determination unit 74, for determining the particle approximate fluid control equations, the discrete fluid continuity equation and the momentum equation of the slender object based on the transfer unit and the SPH fluid model;

[0142] The processing unit 75 is used to perform stretching stability control on the approximate fluid control equation based on the Shepard Filter algorithm and the particle correction technology; solve the discrete fluid continuity equation by leapfrog time integration to obtain the particle physical quantity of the SPH particle at the next moment; solve the momentum equation by the central difference method to obtain the particle motion equation of the finite particle method FPM of the slender object;

[0143] A construction unit 76 is used to uniformly distribute multiple layers of virtual particles on the coupling interface by using a coupling interface particle arrangement method, and determine the simulated physical quantities of the virtual particles at the coupling interface and the corresponding relationship between the physical quantities based on the transfer unit and the coupling unit; and obtain the pressure distribution transmission of the coupling interface by analyzing the transfer unit, and obtain the displacement of the virtual particles by analyzing the coupling unit, so as to build a two-dimensional fluid-solid coupling analysis framework for slender objects;

[0144] The analysis unit 77 is used to analyze the fluid-structure coupling of the slender object based on the analysis framework to obtain corresponding analysis results.

[0145] In some executable embodiments, the force analysis unit 73 is further used for:

[0146] By means of virtual inverse motion of the slender object, the rigid body translation and rotation of the inverse motion of the slender object are calculated;

[0147] Deduct the rigid body translation and rotation of the mass point to determine the unit deformation information of the slender object;

[0148] The unit axial force is determined by unit deformation, and the internal forces of the mass points at both ends of the slender object unit are determined based on the force balance relationship.

[0149] In some executable embodiments, the simulation unit 72 is further configured to:

[0150] Based on the interpolation principle and kernel estimation method, the partial differential equation of the SPH fluid model is transformed into an integral equation. The physical quantities of discrete particles are determined based on the integral equation. The fluid calculation domain is discretized into a series of particles carrying physical information by adding the physical quantities. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area around the particle.

[0151] And the attribute information of the particles at the previous moment is iteratively obtained to obtain the attribute information of the particles at the next moment.

[0152] In some executable embodiments, the building unit 76 is further used for:

[0153] At the coupling interface, along the axis direction of the elongated object, multiple layers of virtual particles with a distribution density close to that of the fluid particles are arranged with the same particle spacing.

[0154] In some executable embodiments, the simulation unit 72 is further configured to:

[0155] Determine the effect on virtual particle B i The interface pressure on the virtual particle B i The interface pressure on the plane is decomposed into the mass points of the slender object unit. Specifically, it is assumed that the relative position relationship between the plane slender object unit and the corresponding virtual particle always remains unchanged. The virtual particle B i The projection position of the slender object element A0A1 on the coupling boundary is B ip , then the coupling force transmitted to the mass points at both ends of the slender object unit is in The virtual particle coupling force is Along the local coordinate system of the slender object The direction component, d is the distance from the virtual particle projection point to the virtual particle, is the equivalent coupling force acting on the particle at the end of the slender object, N is the shape function matrix, N1=1-3ξ 2 +2ξ 3 ,N2=(ξ-2ξ 2 +ξ 3 )l, N3=3ξ 2 -2ξ 3 ,N4=(-ξ 2 +ξ 3 )l,N′ k N k The derivative of (k=1,2,3,4) with respect to ξ, l is the length of the slender object unit A0A1, A0 to B ip The length of the object is , and A0 and A1 are the two end points of the slender object unit.

[0156] In the embodiment of the present application, the position of the virtual particle at the coupling interface is updated according to the displacement of the coupling unit, that is, the displacement of the slender object particle. Specifically, assuming that the distance from the virtual particle at the coupling interface to the slender object unit remains unchanged during the movement, the angle of the slender object unit rotating counterclockwise at time t+1 relative to time t is θ, and the virtual particle B belonging to the slender object unit is i , the updated position at time t+1 for: d′=R(θ)·d, in, are the positions of the two end mass points of the slender object unit at time t+1, R(θ) is the rotation matrix, and d is the rotation matrix from B at time t. ip Point to B i Vector.

[0157] In the embodiment of the present application, the force analysis unit 73 is also used for:

[0158] Assuming that in each time iteration step during the structural motion deformation process, the particles are in a dynamic equilibrium state, and the motion of any particle follows Newton's second law, the equation is: m α is the mass of particle α, and They represent the external force, internal force and damping force of the particle α respectively, μ is the damping coefficient, which is a set constant. Through the central difference algorithm, the displacement of the particle in the path unit is directly obtained, and the position and deformation information of the structure at the next moment are obtained.

[0159] In an exemplary embodiment, the aforementioned units and the like may be implemented by one or more central processing units (CPU), graphics processing units (GPU), application specific integrated circuits (ASIC), DSPs, programmable logic devices (PLD), complex programmable logic devices (CPLD), field programmable gate arrays (FPGA), general-purpose processors, controllers, microcontrollers (MCU), microprocessors, or other electronic components.

[0160] Regarding the device in the above embodiment, the specific manner in which each module and unit performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0161] According to an embodiment of the present application, the present application also provides an electronic device and a readable storage medium.

[0162] Figure 8 FIG. 8 is a schematic block diagram of an example network element 800 that can be used to implement an embodiment of the present application. Figure 8As shown, the network element 800 includes a computing unit 801, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 802 or a computer program loaded from a storage unit 808 to a random access memory (RAM) 803. In the RAM 803, various programs and data required for the operation of the network element 800 can also be stored. The computing unit 801, the ROM 802, and the RAM 803 are connected to each other via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0163] Multiple components in the network element 800 are connected to the I / O interface 805, including: an input unit 806, such as a keyboard, a mouse, etc.; an output unit 807, such as various types of displays, speakers, etc.; a storage unit 808, such as a disk, an optical disk, etc.; and a communication unit 809, such as a network card, a modem, a data processing transceiver, etc. The communication unit 809 allows the network element 800 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0164] The computing unit 801 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 801 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 801 performs the various methods and processes described above, such as a fluid-solid coupling analysis method for a slender object based on a finite particle method and SPH. For example, in some embodiments, a fluid-solid coupling analysis method for a slender object based on a finite particle method and SPH may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit 808. In some embodiments, part or all of the computer program may be loaded and / or installed on the network element 800 via the ROM 802 and / or the communication unit 809. When the computer program is loaded into the RAM 803 and executed by the computing unit 801, one or more steps of the fluid-solid coupling analysis method for a slender object based on the finite particle method and SPH described above may be executed. Alternatively, in other embodiments, the computing unit 801 may be configured in any other appropriate manner (for example, by means of firmware) to execute the fluid-structure interaction analysis method for the slender object based on the finite particle method and SPH.

[0165] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0166] The program code for implementing the method of the present application can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code, when executed by the processor or controller, implements the functions / operations specified in the flow chart and / or block diagram. The program code can be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0167] In the context of the present application, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0168] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0169] The systems and techniques described herein may be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), and the Internet.

[0170] A computer system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The relationship of client and server is generated by computer programs running on respective computers and having a client-server relationship with each other. The server may be a cloud server, a server of a distributed system, or a server combined with a blockchain.

[0171] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in this application can be achieved, and this document is not limited here.

[0172] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0173] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A fluid-structure interaction analysis method for slender objects based on finite particle method and SPH, characterized in that: Create finite particle slender object structure model and smooth particle method SPH based fluid model; Based on the slender object structure model and the fluid model, combined with the interface coupling mode between the slender object and the liquid, the slender object structure is discretized into particles for representation; the method includes: The slender object is simulated by two-dimensional slender object unit, the fluid is simulated by SPH fluid model, the pressure transmission of the coupling interface between the slender object and the liquid is simulated by the transmission unit, and the displacement coordination of the coupling interface is simulated by the coupling unit; the discrete particles of the slender object are subjected to force analysis to obtain the virtual reverse motion separation structure deformation and rigid body displacement of the slender object, and the deformation of the slender object in the two-dimensional direction and the internal force it is subjected to are obtained; Determine the particle approximate fluid control equations for slender objects based on the transfer unit and SPH fluid model, and the discrete fluid continuity equation and momentum equation; Based on the Shepard Filter algorithm and particle correction technology, the approximate fluid control equation is subjected to tensile stability control; the discrete fluid continuity equation is solved by leapfrog time integration to obtain the particle physical quantity of the SPH particle at the next moment; the momentum equation is solved by the central difference method to obtain the particle motion equation of the finite particle method FPM of the slender object; The coupling interface particle arrangement method is used to evenly distribute multiple layers of virtual particles on the coupling interface, and the simulated physical quantities of the virtual particles at the coupling interface and the corresponding relationship between the physical quantities are determined based on the transfer unit and the coupling unit; the pressure distribution transmission of the coupling interface is obtained by analyzing the transfer unit, and the displacement of the virtual particles is obtained by analyzing the coupling unit, thereby building a two-dimensional fluid-solid coupling analysis framework for slender objects; Based on the analysis framework, the fluid-structure coupling of the slender object is analyzed to obtain corresponding analysis results.

2. The fluid-structure coupling determination method according to claim 1, characterized in that: The method of obtaining the virtual reverse motion of the slender object to separate the structural deformation and the rigid body displacement to obtain the deformation of the slender object in two-dimensional directions and the internal force it is subjected to includes: By means of virtual inverse motion of the slender object, the rigid body translation and rotation of the inverse motion of the slender object are calculated; Deduct the rigid body translation and rotation of the mass point to determine the unit deformation information of the slender object; The unit axial force is determined by unit deformation, and the internal forces of the mass points at both ends of the slender object unit are determined based on the force balance relationship.

3. The fluid-structure coupling determination method according to claim 1, characterized in that: The fluid simulation by the smooth particle method SPH includes: Based on the interpolation principle and kernel estimation method, the partial differential equation of the SPH fluid model is transformed into an integral equation. The physical quantities of discrete particles are determined based on the integral equation. The fluid calculation domain is discretized into a series of particles carrying physical information by adding the physical quantities. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area around the particle. And the attribute information of the particles at the previous moment is iteratively obtained to obtain the attribute information of the particles at the next moment.

4. The fluid-structure coupling determination method according to claim 1, characterized in that: The method of using the coupling interface particle arrangement method to uniformly distribute multiple layers of virtual particles on the coupling interface includes: At the coupling interface, along the axial direction of the elongated object, multiple layers of virtual particles with a distribution density close to that of the fluid particles are arranged with the same particle spacing.

5. The fluid-structure coupling determination method according to claim 1, characterized in that: The coupled interface pressure transmission between the slender object and the liquid is simulated by a transmission unit, including: Determine the effect on virtual particle B i The interface pressure on the virtual particle B i The interface pressure on the plane is decomposed into the mass points of the slender object unit. Specifically, it is assumed that the relative position relationship between the plane slender object unit and the corresponding virtual particle always remains unchanged. The virtual particle B i The projection position of the slender object element A0A1 on the coupling boundary is B ip , then the coupling force transmitted to the mass points at both ends of the slender object unit is in The virtual particle coupling force is Along the local coordinate system of the slender object The direction component, d is the distance from the virtual particle projection point to the virtual particle, is the equivalent coupling force acting on the particle at the end of the slender object, N is the shape function matrix, N1=1-3ξ 2 +2ξ 3 ,N2=(ξ-2ξ 2 +ξ 3 )l, N3=3ξ 2 -2ξ 3 ,N4=(-ξ 2 +ξ 3 )l,N′ k N k The derivative of (k=1, 2, 3, 4) with respect to ξ, l is the length of the slender object unit A0A1, A0 to B ip The length of the object is , and A0 and A1 are the two end points of the slender object unit.

6. The fluid-structure coupling determination method according to claim 1, characterized in that: The method further includes: updating the position of the virtual particle at the coupling interface according to the displacement of the coupling unit, that is, the displacement of the slender object particle. Specifically, assuming that the distance between the virtual particle at the coupling interface and the slender object unit remains unchanged during the movement, the angle of the slender object unit rotating counterclockwise at time t+1 relative to time t is θ, and updating the position of the virtual particle B belonging to the slender object unit i , the updated position at time t+1 for: d′=R(θ)·d, in, are the positions of the two end mass points of the slender object unit at time t+1, R(θ) is the rotation matrix, and d is the rotation matrix from B at time t. ip Point to B i Vector.

7. The fluid-structure coupling determination method according to claim 1, characterized in that: The method of obtaining the particle motion equation of the finite particle method FPM of the slender object includes: Assuming that in each time iteration step during the structural motion deformation process, the particles are in a dynamic equilibrium state, and the motion of any particle follows Newton's second law, the equation is: m α is the mass of particle α, and They represent the external force, internal force and damping force of the particle α respectively, μ is the damping coefficient, which is a set constant. Through the central difference algorithm, the displacement of the particle in the path unit is directly obtained, and the position and deformation information of the structure at the next moment are obtained.

8. A fluid-structure coupling analysis device for slender objects based on finite particle method and SPH, characterized in that: The device comprises: Creation unit for creating finite mass slender object structure model and SPH-based fluid model; A characterization unit, configured to discretize the structure of the slender object into particles for characterization based on the slender object structure model and the fluid model and in combination with the interface coupling mode between the slender object and the liquid; A simulation unit is used to simulate the slender object through a two-dimensional slender object unit, simulate the fluid through an SPH fluid model, simulate the pressure transmission of the coupling interface between the slender object and the liquid through a transmission unit, and simulate the displacement coordination of the coupling interface through a coupling unit; A force analysis unit is used to perform force analysis on discrete particles of the slender object, obtain the virtual reverse motion separation structure deformation and rigid body displacement of the slender object, and obtain the deformation of the slender object in two-dimensional directions and the internal force it is subjected to; Determine the unit, which is used to determine the particle approximate fluid control equations of the slender object based on the transfer unit and the SPH fluid model, and the discrete fluid continuity equation and momentum equation; A processing unit is used to perform tensile stability control on the approximate fluid control equation based on the Shepard Filter algorithm and the particle correction technology; solve the discrete fluid continuity equation by leapfrog time integration to obtain the particle physical quantity of the SPH particle at the next moment; solve the momentum equation by the central difference method to obtain the particle motion equation of the finite particle method FPM of the slender object; A construction unit is used to uniformly distribute multiple layers of virtual particles on the coupling interface by using a coupling interface particle arrangement method, and determine the simulated physical quantities of the virtual particles at the coupling interface, as well as the corresponding relationship between the physical quantities based on the transfer unit and the coupling unit; and obtain the pressure distribution transmission of the coupling interface by analyzing the transfer unit, and obtain the displacement of the virtual particles by analyzing the coupling unit, thereby building a two-dimensional fluid-solid coupling analysis framework for slender objects; The analysis unit is used to analyze the fluid-solid coupling situation of the slender object based on the analysis framework to obtain corresponding analysis results.

9. The fluid-structure coupling determination device according to claim 8, characterized in that: The force analysis unit is further used for: By means of virtual inverse motion of the slender object, the rigid body translation and rotation of the inverse motion of the slender object are calculated; Deduct the rigid body translation and rotation of the mass point to determine the unit deformation information of the slender object; The unit axial force is determined by unit deformation, and the internal forces of the mass points at both ends of the slender object unit are determined based on the force balance relationship.

10. The fluid-structure coupling determination device according to claim 8, characterized in that: The simulation unit is further used for: Based on the interpolation principle and kernel estimation method, the partial differential equation of the SPH fluid model is transformed into an integral equation. The physical quantities of discrete particles are determined based on the integral equation. The fluid calculation domain is discretized into a series of particles carrying physical information by adding the physical quantities. The physical quantity of each particle is obtained by weighting the physical quantities of other particles in a certain area around the particle. And the attribute information of the particles at the previous moment is iteratively obtained to obtain the attribute information of the particles at the next moment.

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