A CFD and modal superposition hydroelastic two-way strong coupling calculation method and system

Abstract

The application discloses a kind of CFD and modal superposition's water elasticity two-way strong coupling calculation method and system, wherein, the method comprises: establishing marine structure flow area model in CFD solver;Marine structure three-dimensional finite element model is established in solid domain solver;Fluid domain grid and solid domain grid information two-way strong coupling matching method are constructed;The surface load and its motion time history value of the preset marine structure are output in CFD solver to simulate;Through the matching method, the surface load is transmitted to the three-dimensional finite element model, and the modal motion equation is solved using implicit parallel modal superposition method, and the displacement response time history value of the preset marine structure solid grid is obtained;The displacement response time history value is reversely transmitted to the fluid grid associated in CFD solver, and the first two steps are iteratively executed until the result meets the preset displacement residual value.The method improves the calculation accuracy of marine structure fluid-structure coupling problem.

Description

Technical Field

[0001] This invention relates to the field of ship hydroelasticity prediction technology, and in particular to a two-way strongly coupled calculation method and system for hydroelasticity based on CFD and modal superposition. Background Technology

[0002] Hydroelasticity, as a strongly nonlinear fluid-structure interaction problem, has been extensively studied in recent years. Multiphysics coupling, as a novel method for solving fluid-structure interaction problems, has shown great applicability in marine loads, aerospace loads, and biomedical devices. With the increasing complexity of the problems being solved, open-source, flexible, efficient, and scalable multiphysics coupling methods have gradually emerged, mainly including global coupling and partitioned coupling. Global coupling methods solve all equations from each physics domain together in a single system, leading to low computational efficiency. Partitioned coupling methods have proven to be very popular. They couple existing independent physical simulation solvers together to solve novel simulation problems.

[0003] In practical marine engineering, the increasing size of marine structures and the use of high-strength steel have made them more flexible. For example, large openings on ships lower the natural frequency of the hull, while high ship speeds increase the frequency of wave encounters. These combined effects result in significant high-frequency vibrations in the ship, thereby increasing the amplitude of bending moments in waves. Because marine structures exhibit significant elastic effects under wave excitation, and traditional assumptions are no longer applicable, the interaction between the structure and the marine environment must be considered. Therefore, the theory of hydroelastic analysis has emerged.

[0004] Currently, hydroelastic analysis of marine structures mainly employs potential flow theory and coupled computational fluid dynamics / finite element method (CFD-FEM). Due to the limitations of potential flow theory, it cannot effectively simulate strongly nonlinear waves, and therefore cannot accurately model the fluid-structure interaction of marine structures under severe sea conditions. CFD technology has stronger physical modeling and nonlinear free surface processing capabilities, especially in handling large-amplitude waves and induced violent motion and breaking waves. The finite element method (FEM) can be used to study the structural strength and deformation effects of marine structures under wave loads. However, the general form of CFD-FEM hydroelastic method has high computational time cost, low computational efficiency, and high computational resource requirements.

[0005] Therefore, when comprehensively considering structural loads and hydroelastic response, there is an urgent need for a marine structure material-structure coupling analysis algorithm that can both ensure computational accuracy and further improve computational efficiency while reducing time costs. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, one objective of this invention is to propose a hydroelastic two-way strongly coupled calculation method that combines CFD and modal analysis. This method can accurately simulate the motion and elastic loads of marine structures in wind, wave, and current environments, and can also greatly improve the calculation accuracy of material-structure coupling problems of marine structures.

[0008] Another objective of this invention is to propose a hydroelastic bidirectional strongly coupled computational system that superimposes CFD and modal analysis.

[0009] Another aspect of the present invention is to provide a computer device.

[0010] Another aspect of this invention is to provide a non-transitory computer-readable storage medium.

[0011] To achieve the above objectives, one embodiment of the present invention proposes a hydroelastic bidirectional strongly coupled calculation method combining CFD and modal superposition, comprising the following steps: Step S1, establishing a watershed model of the marine structure in the CFD fluid domain solver, discretizing the watershed model into a watershed mesh, and setting physical parameters, initial conditions, and boundary conditions; Step S2, establishing a three-dimensional finite element model of the marine structure in the solid domain solver, discretizing the three-dimensional finite element model into a solid mesh, and applying constraints to the solid mesh to calculate the natural frequencies and mode shapes of the marine structure under constraint conditions; Step S3, constructing a bidirectional strongly coupled matching method for the fluid domain mesh and the solid domain mesh information to match each fluid mesh on the marine structure with its optimal solid element mesh. The process is as follows: Step S4: Simulate the preset marine structure in the CFD fluid domain solver, and output the surface load and motion history of the preset marine structure; Step S5: Transfer the surface load of the preset marine structure to the solid three-dimensional finite element model of the marine structure through the bidirectional strong coupling matching method of the fluid domain mesh and the solid domain mesh, and use the implicit parallel modal superposition method to numerically solve the modal motion equations to obtain and derive the displacement response history of the preset marine structure solid mesh; Step S6: Transfer the displacement response history of the preset marine structure solid mesh back to the fluid mesh associated in the CFD fluid domain solver, and iterate through steps S5-S6 until the calculation result satisfies the preset displacement residual value.

[0012] The hydroelastic bidirectional strongly coupled calculation method of CFD and modal superposition in this invention strongly couples the CFD method with the modal superposition method in both directions. It comprehensively considers the combined effects of marine structure motion, wave load, and structural response. While accurately simulating the motion and load of ships during navigation, it also greatly improves the solution efficiency of hydroelastic problems.

[0013] In addition, the hydroelastic two-way strong coupling calculation method of CFD and modal superposition according to the above embodiments of the present invention may also have the following additional technical features:

[0014] Furthermore, in one embodiment of the present invention, the CFD fluid domain solver is used to simulate the wave field of a numerical water tank and the fluid flow in the surrounding area of ​​a preset marine structure to obtain the surface stress field of the preset marine structure and its motion history.

[0015] Furthermore, in one embodiment of the present invention, the solid domain solver is used to simulate the structural deformation, bending moment and shear force of marine structures under wave loads.

[0016] Further, in one embodiment of the present invention, step S1 specifically includes: step S101, establishing a numerical pool in the CFD fluid domain solver, wherein the numerical pool is a cuboid spatial domain enclosed by four side walls, a bottom surface, and a top surface; step S102, establishing a preset CAD three-dimensional solid model of the marine structure, and performing a Boolean subtraction operation between the preset CAD three-dimensional solid model of the marine structure and the fluid domain of the pool to obtain the fluid computation domain; step S103, setting the six degrees of freedom, weight, center of gravity position, and moment of inertia of the preset CAD three-dimensional solid model of the marine structure, as well as the position of the preset CAD three-dimensional solid model of the marine structure in the numerical pool; step S104, dividing the fluid computation domain into an upper air layer, a free surface layer, and a lower water layer using the fluid domain volume method; step S105, setting the mesh deformation method, and simulating the CAD three-dimensional solid model of the marine structure using overlapping mesh and deformed mesh techniques respectively. The model's motion and structural deformation enable hybrid deformation of the mesh; Step S106: Discretize the fluid computation domain into a watershed mesh, and refine the mesh in the free liquid surface layer and the CAD 3D solid model of the marine structure; Step S107: Select 3D, implicit unsteady state, multiphase, turbulent, watershed volume, k-epsilon turbulence, VOF wave, gravity, and element mass correction as the physical properties of the computation domain; Step S108: Set the boundary conditions of the computation domain, designating the four side walls and the bottom surface as walls, the top surface as a pressure outlet, the left side as a velocity inlet, the right side as a pressure outlet, and the outer surface of the marine structure as a non-slip wall; Step S109: Set the wave generation and wave dissipation methods, wherein momentum source terms are used for watershed wave generation, and force wave dissipation technology is used for wave dissipation; Step S110: Set the incoming flow velocity of the pool fluid domain to achieve the forward speed of the marine structure.

[0017] Further, in one embodiment of the present invention, step S2 specifically includes: step S201, establishing a three-dimensional finite element model of the marine structure in the solid domain solver, wherein the three-dimensional finite element model of the marine structure includes the outer shell and reinforcing frame of the marine structure; step S202, discretizing the three-dimensional finite element model of the marine structure into a solid mesh, wherein the outer shell of the marine structure is meshed using shell elements, and the reinforcing frame is meshed using beam elements; step S203, setting the material properties of the outer shell and the reinforcing frame of the marine structure, wherein the material properties include mass, density, stiffness, elastic modulus, Poisson's ratio, number of modes, and structural damping; step S204, applying gravity loads to all mesh nodes, applying fluid loads to the mesh nodes on the surface of the marine structure in contact with the external flow field, and applying displacement constraints to all mesh nodes in combination with the degrees of freedom of motion of the marine structure; step S205, calculating the natural frequencies and natural modes of the marine structure based on the discretized three-dimensional finite element model of the marine structure according to the material properties and displacement constraints.

[0018] Furthermore, in one embodiment of the present invention, the bidirectional strong coupling matching method for constructing the watershed grid and the structural grid specifically involves: transmitting the fluid load acting on the surface of the marine structural material flow body grid through the CFD fluid domain solver to the associated solid grid element in the solid domain solver via an m2n sockets communication link; the solid domain solver performs grid displacement calculation based on a parallel implicit modal superposition method, and the obtained displacement calculation value is then transmitted back to the associated fluid grid via the m2nsockets communication link, performing multiple iterations within a single time step until the residual of the calculated values ​​of two adjacent displacements is less than a user-defined residual value.

[0019] Further, in one embodiment of the present invention, step S5 specifically includes: step S501, transferring the surface load of the preset marine structure mesh element to the three-dimensional finite element model of the marine structure through the bidirectional strong coupling matching method of the fluid domain mesh and the solid domain mesh information, and performing equation decoupling; step S502, preset the calculation time step, the total simulation time, and the number of data exchanges within each time step, and simultaneously running the CFD fluid domain solver and the solid domain solver to perform numerical simulation calculations; step S503, using the modal superposition method to obtain the displacement, bending moment, and shear force of any cross section of the preset marine structure; step S504, outputting the real-time response data, outputting the wave surface elevation and the surface load of the marine structure fluid mass mesh element in the CFD fluid domain solver, and outputting the cross section load, local stress, and structural deformation of the marine structure in the solid domain solver.

[0020] To achieve the above objectives, another embodiment of the present invention proposes a hydroelastic bidirectional strongly coupled computational system combining CFD and modal superposition, comprising: a fluid domain model construction module, used to establish a fluid domain model of the marine structure in the CFD fluid domain solver, discretize the fluid domain model of the marine structure into a fluid domain mesh, and set physical parameters, initial conditions, and boundary conditions; a solid domain model construction module, used to establish a three-dimensional finite element model of the marine structure in the solid domain solver, discretize the three-dimensional finite element model of the marine structure into a solid mesh, and apply constraints to the solid mesh to calculate the natural frequencies and mode shapes of the marine structure under constraint conditions; a construction association module, used to construct a bidirectional strongly coupled matching method for fluid domain mesh and solid domain mesh information to associate each fluid mesh on the marine structure with its optimal solid element mesh; and a simulation module. The system is used to simulate a preset marine structure in the CFD fluid domain solver, outputting the surface load and time history values ​​of the preset marine structure's motion; the modal superposition module, through a bidirectional strong coupling matching method between the fluid domain mesh and the solid domain mesh information, transfers the surface load of the preset marine structure to the solid three-dimensional finite element model of the marine structure, and uses an implicit parallel modal superposition method to numerically solve the modal motion equations, obtaining and deriving the displacement response time history values ​​of the preset marine structure's solid mesh; the reverse transmission and iteration module is used to reversely transmit the displacement response time history values ​​of the preset marine structure's solid mesh to the fluid mesh associated in the CFD fluid domain solver, iteratively executing the modal superposition module and the reverse transmission and iteration module until the calculation results meet the user-defined displacement residual values.

[0021] The CFD and modal superposition hydroelastic bidirectional strongly coupled computational system of this invention combines the CFD method with the modal superposition method in a bidirectional strong coupling. It comprehensively considers the combined effects of marine structure motion, wave load, and structural response, and while accurately simulating the motion and load of ships during navigation, it also greatly improves the solution efficiency of hydroelastic problems.

[0022] To achieve the above objectives, another aspect of the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the hydroelastic bidirectional strong coupling calculation method of CFD and modal superposition as described in the above embodiments.

[0023] To achieve the above objectives, one aspect of the present invention provides a non-transitory computer-readable storage medium storing a computer program thereon, wherein the computer program, when executed by a processor, implements the hydroelastic bidirectional strong coupling calculation method of CFD and modal superposition as described in the above embodiments.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 This is a flowchart of a hydroelastic bidirectional strong coupling calculation method based on CFD and modal superposition according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram illustrating the principle of a hydroelastic two-way strong coupling calculation method combining CFD and modal superposition according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the geometric model of a marine structure upright panel according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the flow domain in a CFD fluid domain solver according to an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the flow domain mesh generation in a CFD fluid domain solver according to an embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of fluid mesh generation on the surface of a vertical plate in a CFD fluid domain solver according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the solid mesh of the vertical plate in a solid domain solver according to an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram of the dam-break water flow motion simulated by a CFD fluid domain solver according to an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram of a water tank dam failure test device according to an embodiment of the present invention;

[0035] Figure 10 This is a schematic diagram of a dam failure test apparatus according to an embodiment of the present invention;

[0036] Figure 11 This is a schematic diagram comparing the displacement result of the top of the vertical plate according to an embodiment of the present invention with the experimental results;

[0037] Figure 12 This is a schematic diagram of the structure of a hydroelastic bidirectional strongly coupled system of CFD and modal superposition according to an embodiment of the present invention.

[0038] Figure labeling: 1-Water layer, 2-Air layer, 3-Vertical plate, 4-Water tank baffle, 100-Watershed model construction module, 200-Marine structure model construction module, 300-Construction association module, 400-Simulation module, 500-Modal overlay module, and 600-Reverse transmission and iteration module. Detailed Implementation

[0039] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0040] The following describes, with reference to the accompanying drawings, a hydroelastic bidirectional strong coupling calculation method and system based on CFD and modal superposition proposed according to an embodiment of the present invention. First, the hydroelastic bidirectional strong coupling calculation method based on CFD and modal superposition proposed according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0041] Figure 1 This is a flowchart of a hydroelastic two-way strong coupling calculation method for CFD and modal superposition according to an embodiment of the present invention.

[0042] like Figure 1 As shown, the hydroelastic two-way strongly coupled calculation method of CFD and modal superposition includes the following steps:

[0043] In step S1, a marine structure flow domain model is established in the CFD fluid domain solver. The marine structure flow domain model is discretized into a flow domain mesh, and physical parameters, initial conditions, and boundary conditions are set.

[0044] The CFD fluid domain solver is used to simulate the wave field of the numerical water tank and the fluid flow in the surrounding area of ​​the preset marine structure, so as to obtain the surface stress field of the preset marine structure and its motion history.

[0045] In one embodiment of the present invention, step S1 specifically includes:

[0046] Step S101: Establish a numerical pool in the CFD fluid domain solver. The numerical pool is a cuboid space domain, which is enclosed by 6 faces: 4 side walls, 1 bottom face, and 1 top face.

[0047] Step S102: Establish a preset CAD three-dimensional solid model of the marine structure, and perform a Boolean subtraction operation between the CAD three-dimensional solid model of the marine structure and the fluid domain of the pool to obtain the fluid calculation domain.

[0048] Step S103: Set the six degrees of freedom, weight, center of gravity position and moment of inertia of the preset marine structure CAD three-dimensional solid model, as well as the position of the marine structure CAD three-dimensional solid model in the numerical water tank;

[0049] Step S104: The fluid computational domain is divided into an upper air layer, a free liquid surface layer, and a lower water layer using the watershed volume method.

[0050] Step S105: Set the mesh deformation method, and use overlapping mesh and deformable mesh technology to simulate the movement and structural deformation of the CAD three-dimensional solid model of the marine structure, so as to realize the hybrid deformation of the mesh;

[0051] Step S106: Discretize the fluid computation domain into a watershed mesh and refine the CAD 3D solid model of the free liquid surface and marine structures.

[0052] Step S107: Select three-dimensional, implicit unsteady state, multiphase, turbulence, watershed volume, k-epsilon turbulence, VOF wave, gravity, and element mass correction as physical properties of the computational domain;

[0053] Step S108: Set the boundary conditions of the computational domain, set the front and rear two side walls (i.e., four side walls) and the bottom surface as walls, set the top surface as a pressure outlet, set the left side as a velocity inlet, set the right side as a pressure outlet, and set the outer surface of the marine structure as a no-slip wall.

[0054] Step S109: Set the wave generation and wave suppression methods, wherein momentum source term is used for watershed wave generation and force wave suppression technology is used for wave suppression;

[0055] Step S110: Set the inflow velocity of the water tank fluid domain to achieve the forward speed of the marine structure.

[0056] In step S2, a three-dimensional finite element model of the marine structure is established in the solid domain solver. The three-dimensional finite element model of the marine structure is discretized into a solid mesh, and constraints are applied to the solid mesh to calculate the natural frequencies and mode shapes of the marine structure when it vibrates under the constraints.

[0057] Among them, the solid domain solver is used to simulate the structural deformation, bending moment and shear force of marine structures under wave loads.

[0058] In one embodiment of the present invention, step S2 specifically includes:

[0059] Step S201: Establish a three-dimensional finite element model of the marine structure in the solid domain solver, wherein the three-dimensional finite element model of the marine structure includes the outer shell and reinforcing skeleton of the marine structure;

[0060] Step S202: Discretize the three-dimensional finite element model of the marine structure into a solid mesh, wherein the outer shell of the marine structure is meshed with shell elements and the reinforcing frame is meshed with beam elements.

[0061] Step S203: Set the material properties of the outer shell and reinforcing skeleton of the marine structure, wherein the material properties include mass, density, stiffness, elastic modulus, Poisson's ratio, number of modes and structural damping;

[0062] Step S204: Apply gravity loads to all grid nodes, apply fluid loads to the grid nodes on the surface of the marine structure in contact with the external flow field, and apply displacement constraints to all grid nodes in combination with the motion degrees of freedom of the marine structure.

[0063] Step S205: Based on the three-dimensional finite element model of the marine structure after mesh discretization, calculate the natural frequency and natural mode shape of the marine structure according to material properties and displacement constraints.

[0064] In step S3, a bidirectional strong coupling matching method for fluid domain mesh and solid domain mesh information is constructed to associate each fluid mesh on the marine structure with its best solid element mesh.

[0065] The specific method for constructing a two-way strong coupling matching of information between the watershed grid and the structural grid is as follows:

[0066] The fluid loads acting on the mesh surface of the marine structure's fluid volume are transmitted to the associated solid mesh elements in the solid domain solver via the m2nsockets communication link through the CFD fluid domain solver.

[0067] The solid domain solver performs mesh displacement calculations based on the parallel implicit modal superposition method. The calculated displacement values ​​are then transmitted back to the associated fluid mesh via the m2n sockets communication link. The calculations are repeated multiple times within a single time step until the residual between two adjacent displacement calculations is less than the user-defined residual value.

[0068] It should be noted that steps S1-S3 involve setting up the environment and the overall program. Subsequent steps S4 and S5 involve using the program. Specifically, the CFD fluid domain solver uses the OpenFOAM open-source software, the solid domain solver uses the Calculix open-source software, and the preCICE software is used as the coupling platform.

[0069] In step S4, the preset marine structure is simulated in the CFD fluid domain solver, and the surface load of the preset marine structure and the time history value of the motion of the preset marine structure are output.

[0070] Specifically, the pre-built CFD fluid domain solver is used to simulate the preset marine structure, and the pre-built CFD fluid domain solver also outputs the surface load of the preset marine structure's fluid mass mesh element and the time history value of the preset marine structure's motion.

[0071] In step S5, the pre-set surface load of the marine structure is transferred to the solid three-dimensional finite element model of the marine structure through a two-way strong coupling matching method of fluid domain mesh and solid domain mesh information. The modal motion equation is numerically solved by an implicit parallel modal superposition method to obtain and derive the displacement response time history value of the pre-set marine structure solid mesh.

[0072] In one embodiment of the present invention, step S5 specifically includes:

[0073] Step S501: Through the m2n sockets communication link and the bidirectional strong coupling matching method (i.e., the bidirectional strong coupling matching method between fluid domain mesh and solid domain mesh), the surface load of the preset marine structure mesh element is transferred to the three-dimensional finite element model of the marine structure, and the equations are decoupled.

[0074] Step S502: Preset the calculation time step, total simulation duration, and number of data exchanges within each time step, and simultaneously run the CFD fluid domain solver and solid domain solver for numerical simulation calculation;

[0075] Step S503: Use the modal superposition method to obtain the displacement, bending moment and shear force of any cross section of the preset marine structure;

[0076] Step S504: Output real-time response data. Output wave surface elevation and surface load of marine structure material mass mesh element in the CFD fluid domain solver, and output marine structure profile load, local stress, and structural deformation in the solid domain solver.

[0077] The specific method for decoupling the equations is as follows:

[0078] Assuming the fluid is compressible and inviscid, the fluid motion equilibrium equations are proposed:

[0079]

[0080] Among them, K f p is the fluid bulk modulus. rgh ρ is the fluid dynamic pressure, γ is the volume constant of the dissipation effect, and ρ is the fluid dynamic pressure. f Let ∠ be the fluid density, and ∠ be the Laplace operator;

[0081] Based on equation (1), the structural finite element discretization equation is derived.

[0082]

[0083] Among them, M f Let C be the fluid mass matrix. f K is the fluid damping matrix. f Let p be the fluid restoring force matrix, p be the pressure vector of the fluid mesh node, d be the displacement vector at the fluid-structure interface, and S be the displacement vector at the fluid-structure interface. fs The effective surface area coupling matrix associated with each node on the interface;

[0084] Based on the fluid pressure acting on the interface, the structural motion equations are proposed:

[0085]

[0086] Among them, M s Let C be the structural mass matrix. s Let K be the structural damping matrix. s Let F be the structural stiffness matrix. s For structural surface pressure;

[0087] Based on equations (2) and (3), the complete finite element equations for the fluid-structure interaction problem in ship waves are proposed:

[0088]

[0089] Introduce auxiliary variables:

[0090] ψ=p / ω 2 (5)

[0091] Where ω is the characteristic value of equation (3), i.e., the natural frequency of the ship;

[0092] Substituting equation (5) into equation (3), we obtain the symmetric eigenvalue equation:

[0093]

[0094] The Lanczos algorithm is used to solve equation (6) to obtain ω;

[0095] neglect The term simplifies the structural motion equation (3) to:

[0096]

[0097] Define the displacement vector d at the fluid-structure interface as

[0098]

[0099] Where n is the modal order, Let z be the vector of the i-th mode shape. iLet i be the coordinates of the i-th mode shape;

[0100] Based on the orthogonality of modal mass and stiffness, equation (7) is decoupled as follows:

[0101]

[0102] Where, ω i Let be the i-th natural frequency.

[0103] In step S6, the displacement response time history value of the preset marine structure solid mesh is transmitted in reverse to the fluid mesh associated in the CFD fluid domain solver, and steps S5-S6 are executed iteratively until the calculation result meets the preset displacement residual value.

[0104] like Figure 2 As shown below, the hydroelastic two-way strong coupling calculation method of CFD and modal superposition proposed in this invention will be further described in detail through a specific embodiment.

[0105] Taking the vertical plate dam-break impact model as an example, the model has a total length of 1.0m, a width of 0.01m, and a height of 0.1m. The simulation process considers the structural flexibility deformation of the vertical plate structure under the impact of dam-break waves.

[0106] In this embodiment, the CFD fluid domain solver uses OpenFOAM software, and the solid domain solver uses Calculix software. preCICE software is used as the coupling platform to achieve bidirectional, strongly coupled data exchange between the fluid and solid domain solvers.

[0107] like Figure 3-10 As shown, in step one, a numerical simulation water tank model and a vertical plate solid model (i.e., a marine structure water flow domain model) are established in the CFD fluid domain solver. The water flow domain model is obtained through Boolean subtraction. After setting the mesh parameters of the water flow domain model, the water flow domain is discretized. Physical parameters, initial conditions, and boundary conditions are set. In this embodiment, the specific steps include:

[0108] A fluid domain is established within the pool. This fluid domain is a rectangular space bounded by six surfaces: four side walls, a bottom surface, and a top surface. The dimensions of the fluid domain along the longitudinal x-axis, transverse y-axis, and vertical z-axis of the vertical plate are 2m, 1m, and 1m, respectively. The dimensions of the breach tank are 0.5m long, 1m wide, and 0.6m high. Figure 10 As shown.

[0109] The 6 degrees of freedom, weight, center of gravity position, and moment of inertia of the vertical plate CAD 3D solid model are set. The position of the vertical plate CAD 3D solid model 3 in the fluid domain is set. In this embodiment, the lower end of the vertical plate is fixed. The longitudinal position of the center of gravity of the vertical plate CAD 3D solid model is 0.005m, and the vertical position of the center of gravity is 0.05m from the baseline.

[0110] like Figure 4 As shown, the fluid domain of the pool is divided into two parts, water layer 1 and air layer 2, using the volumetric fluid flow (VOF) method. The free surface is located at the junction of the water layer and the air layer.

[0111] like Figure 5 and Figure 6 As shown, fluid meshes are generated for the fluid domain and the vertical plate CAD 3D solid model, and mesh refinement is performed near the vertical plate CAD 3D solid model 3. Figure 5 and Figure 6 As shown, a hexahedral unstructured mesh is used to divide the computational domain, employing an overlapping mesh scheme. The computational domain comprises a background region and an overlapping region. To accurately capture the drastic changes in physical quantities such as turbulence around the free surface and the vertical plate, local mesh refinement is applied to the free surface and around the vertical plate. The wave height range contains 10 mesh layers, the wavelength range contains 60 mesh layers, and 6 boundary layer mesh layers are set at the outer wall of the vertical plate.

[0112] The mesh deformation method was set up, employing both overlapping mesh and deformable mesh techniques to simulate the motion of the vertical plate and structural deformation, achieving hybrid mesh deformation. Specifically, overlapping mesh technology was used to simulate the large-scale motion of marine structures in waves, while deformable mesh technology was used to simulate the elastic deformation of the marine structure.

[0113] Set boundary conditions, designate the front and rear two side walls and the bottom surface as walls, the top surface as a pressure outlet, the left side as a velocity inlet, the right side as a pressure outlet, and the outer surface of the marine structure as a non-slip wall.

[0114] The wave generation and suppression modes are set up, and the momentum source term is used for numerical wave generation, while the force suppression technology is used for wave suppression.

[0115] Step two involves establishing a three-dimensional finite element model of the solid plate in the solid domain solver, discretizing the finite element model into a structural mesh, applying constraints to the mesh, defining the structural element parameters, and then calculating the natural frequencies and mode shapes of the marine structure under the constraints. In this embodiment, the specific steps include:

[0116] like Figure 7 As shown, the finite element mesh is generated for the vertical plate structure in the solid domain solver, and the solid element mesh is generated for the shell of the vertical plate.

[0117] The structural material properties of the vertical plate are defined, including the shell mass, density, stiffness, elastic modulus, Poisson's ratio, number of modes, and structural damping. In this embodiment, the mass of each structural unit is set according to the actual mass distribution of the vertical plate; the stiffness of the structural units is set according to the actual stiffness distribution of the vertical plate. The vertical plate is made of silicone rubber with a density of 1.4 g / cm³, a fracture stress of 7 MPa, an elastic modulus of 3.5 MPa, a Poisson's ratio of 0.3, and a hardness of 55. The DIRECT damping model is used.

[0118] Displacement constraints are applied to the mesh nodes based on the degrees of freedom of the vertical plate's motion. In this embodiment, only the lateral displacement of the vertical plate after being impacted by water flow is considered, and a completely fixed constraint is applied to the bottom of the vertical plate.

[0119] Gravity loads are applied to all grid nodes, and corresponding fluid loads are applied to the grid nodes on the vertical plate surface in contact with the external flow field. These fluid loads are calculated by the CFD fluid domain solver.

[0120] Step 3: Establish an M2N stock communication link. Based on the radial basis function method, construct a bidirectional strong coupling matching method between the watershed grid and the structural grid, associating each fluid grid with the most suitable structural element grid. In this embodiment, this specifically includes the following steps:

[0121] The CFD fluid domain solver transmits the fluid pressure and shear force acting on the surface of the vertical plate to the solid domain solver;

[0122] The solid domain solver performs modal superposition dynamic analysis on marine structures based on external flow field forces, rigid body inertial forces, and structural elastic forces.

[0123] Step four: Simulate the vertical plate model in the CFD fluid domain solver, and output the time history values ​​of the surface loads and motion of the vertical plate fluid mesh elements. In this embodiment, specifically:

[0124] In the CFD fluid domain solver, a solution time of 1s is set, the time step is 0.0001s, the PIMPLE algorithm is used, the number of iterations within each time step is 10, and the number of data exchanges between the fluid and structure solvers is 2.

[0125] The output results data, in OpenFOAM, include the wavefront elevation, the load on the vertical plate surface, and its motion history values, such as... Figure 8 The wave field shown, Figure 11 The results of the lateral displacement at the top of the vertical plate are shown in the figure, and the experimental results are compared.

[0126] Step 5: The surface load of the fluid mesh element of the vertical plate is transferred to the solid mesh element of the vertical plate through the bidirectional strong coupling matching method. In the solid solution, the modal superposition method is used to numerically solve the modal motion equations to obtain the real-time response of the vertical plate structure and export the data.

[0127] Step six involves transmitting the real-time response of the vertical plate structure back to the fluid mesh associated with it in the fluid domain solver. Steps five and six are repeated until the calculation results meet the user-defined displacement residual value. In this embodiment, the vertical plate section load, local stress, and structural deformation are output in the solid domain solver, and the lateral displacement results at the top of the vertical plate are compared with the experimental results. Figure 11 As shown.

[0128] The hydroelastic bidirectional strong coupling calculation method based on CFD and modal superposition proposed in this invention comprehensively considers the combined effects of marine structure motion, wave loads, and structural response, enabling accurate simulation of the motion and stress conditions of ships navigating in waves. It combines the advantages of both CFD fluid domain solvers and modal superposition methods. Compared to potential flow theory methods, CFD can simulate strongly nonlinear wave fields, while solid domain solvers can obtain the ship's natural frequencies and mode shapes. Modal superposition can obtain the structural loads and deformations of marine structures, thus fully considering the fluid-structure interaction between ships and waves. Compared to unidirectional coupling methods, this invention offers higher computational accuracy, enabling precise analysis of the elasticity and flutter responses of flexible marine structures under strongly nonlinear wave action. Compared to general fluid-structure interaction simulation methods, this method provides accurate simulation of the hydroelasticity of ships with minimal structural deformation while significantly improving computational efficiency, offering a reliable method for the design and development of marine structures.

[0129] Next, referring to the accompanying drawings, a hydroelastic bidirectional strongly coupled computing system based on CFD and modal superposition proposed according to an embodiment of the present invention is described.

[0130] Figure 12 This is a schematic diagram of the structure of a hydroelastic bidirectional strongly coupled computing system with CFD and modal superposition according to an embodiment of the present invention.

[0131] like Figure 12 As shown, the system 10 includes: a fluid domain model construction module 100, a solid domain model construction module 200, a construction association module 300, a simulation module 400, a modal superposition module 500, and a reverse transmission and iteration module 600.

[0132] The fluid domain model construction module 100 is used to establish a fluid domain model of the marine structure in the CFD fluid domain solver, discretize the fluid domain model of the marine structure into a fluid domain mesh, and set physical parameters, initial conditions, and boundary conditions. The solid domain model construction module 200 is used to establish a three-dimensional finite element model of the marine structure in the solid domain solver, discretize the three-dimensional finite element model of the marine structure into a solid mesh, and apply constraints to the solid mesh to calculate the natural frequencies and mode shapes of the marine structure under constraint conditions. The association module 300 is used to construct a two-way strong coupling matching method between the fluid domain mesh and the solid domain mesh information to associate each fluid mesh on the marine structure with its best solid element mesh. The simulation module 400 is used to simulate the preset marine structure in the CFD fluid domain solver and output the preset marine structure surface loads and the time history values ​​of the preset marine structure motion. The modal superposition module 500 uses a bidirectional strong coupling matching method between fluid domain mesh and solid domain mesh information to transfer the preset surface load of the marine structure to the solid three-dimensional finite element model of the marine structure. It then employs an implicitly parallel modal superposition method to numerically solve the modal motion equations, obtaining and deriving the displacement response time history values ​​of the preset marine structure solid mesh. The reverse transmission and iteration module 600 is used to reverse transmit the displacement response time history values ​​of the preset marine structure solid mesh to the associated fluid mesh in the CFD fluid domain solver, iteratively executing the modal superposition module and the reverse transmission and iteration module until the calculation results meet the user-defined displacement residual values.

[0133] It should be noted that the explanation of the above-described embodiment of the hydroelastic two-way strong coupling calculation method of CFD and modal superposition also applies to the hydroelastic two-way strong coupling calculation system of CFD and modal superposition in this embodiment, and will not be repeated here.

[0134] The hydroelastic bidirectional strongly coupled computational system based on CFD and modal superposition proposed in this invention comprehensively considers the combined effects of marine structure motion, wave loads, and structural response, enabling accurate simulation of the motion and stress conditions of ships navigating in waves. It combines the advantages of both CFD fluid domain solvers and modal superposition methods. Compared to potential flow theory methods, CFD can simulate strongly nonlinear wave fields, FEM can obtain the ship's natural frequencies and mode shape matrices, and modal superposition can obtain the structural loads and deformations of marine structures, thus fully considering the fluid-structure interaction between ships and waves. Compared to unidirectional coupling methods, this invention offers higher computational accuracy, enabling precise analysis of the elasticity and flutter responses of flexible marine structures under strongly nonlinear wave action. Compared to general fluid-structure interaction simulation methods, this method provides accurate simulation of the hydroelasticity of ships with minimal structural deformation while significantly improving computational efficiency, providing a reliable method for ship design and development.

[0135] To implement the above embodiments, the present invention also proposes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the hydroelastic bidirectional strong coupling calculation method and system of CFD and modal superposition as described in the foregoing embodiments.

[0136] To implement the above embodiments, the present invention also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the hydroelastic bidirectional strongly coupled calculation method and system of CFD and modal superposition as described in the foregoing embodiments.

[0137] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0138] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0139] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0140] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0141] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0142] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0143] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0144] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A hydroelastic two-way strongly coupled calculation method combining CFD and modal analysis, characterized in that, Includes the following steps: Step S1: Establish a marine structure flow domain model in the CFD fluid domain solver, discretize the marine structure flow domain model into a flow domain mesh, and set physical parameters, initial conditions, and boundary conditions. Step S2: Establish a three-dimensional finite element model of the marine structure in the solid domain solver, discretize the three-dimensional finite element model of the marine structure into a solid mesh, and apply constraints to the solid mesh to calculate the natural frequencies and mode shapes of the marine structure when it vibrates under constraints. Step S3: Construct a two-way strongly coupled matching method for fluid domain mesh and solid domain mesh information to associate each fluid mesh on the marine structure with its optimal solid element mesh. Specifically, the method involves: The fluid loads acting on the marine structure's material flow mesh surface are transmitted to the associated solid mesh cells in the solid domain solver via the m2nsockets communication link through the CFD fluid domain solver. The solid domain solver performs mesh displacement calculation based on the parallel implicit modal superposition method. The calculated displacement value is then transmitted back to the associated fluid mesh via the m2n sockets communication link. The calculation is repeated multiple times within a single time step until the residual of the calculated values ​​of two adjacent displacements is less than the user-defined residual value. Step S4: Simulate the preset marine structure in the CFD fluid domain solver and output the surface load of the preset marine structure and the time history value of the motion of the preset marine structure. Step S5: The surface load of the preset marine structure is transferred to the solid three-dimensional finite element model of the marine structure through the bidirectional strong coupling matching method of the fluid domain mesh and the solid domain mesh. The modal motion equation is numerically solved by the implicit parallel modal superposition method to obtain and derive the displacement response time history value of the preset marine structure solid mesh. Step S6: The displacement response time history value of the preset marine structure solid mesh is transmitted in reverse to the fluid mesh associated in the CFD fluid domain solver, and steps S5-S6 are executed iteratively until the calculation result meets the preset displacement residual value.

2. The hydroelastic two-way strong coupling calculation method based on CFD and modal superposition as described in claim 1, characterized in that, The CFD fluid domain solver is used to simulate the wave field of a numerical water tank and the fluid flow in the surrounding area of ​​a preset marine structure, so as to obtain the surface stress field of the preset marine structure and its motion history.

3. The hydroelastic two-way strongly coupled calculation method based on CFD and modal superposition as described in claim 1, characterized in that, The solid domain solver is used to simulate the structural deformation, bending moment, and shear force of marine structures under wave loads.

4. The hydroelastic two-way strong coupling calculation method based on CFD and modal superposition as described in claim 1, characterized in that, Step S1 specifically includes: Step S101: Establish a numerical pool in the CFD fluid domain solver, wherein the numerical pool is a cuboid spatial domain, which is enclosed by four side walls, a bottom surface and a top surface. Step S102: Establish a preset CAD three-dimensional solid model of the marine structure, and perform a Boolean subtraction operation between the CAD three-dimensional solid model of the marine structure and the fluid domain of the pool to obtain the fluid computation domain; Step S103: Set the six degrees of freedom, weight, center of gravity position and moment of inertia of the preset marine structure CAD three-dimensional solid model, as well as the position of the marine structure CAD three-dimensional solid model in the numerical water tank; Step S104: The fluid computational domain is divided into an upper air layer, a free liquid surface layer, and a lower water layer using the watershed volume method; Step S105: Set the mesh deformation mode, and use overlapping mesh and deformable mesh technology respectively to simulate the movement and structural deformation of the CAD three-dimensional solid model of the marine structure to achieve hybrid mesh deformation; Step S106: Discretize the fluid computation domain into a watershed mesh, and perform densification processing on the free liquid surface layer and the CAD three-dimensional solid model of the marine structure; Step S107: Select three-dimensional, implicit unsteady state, multiphase, turbulence, watershed volume, k-epsilon turbulence, VOF wave, gravity, and element mass correction as the physical properties of the computational domain; Step S108: Set the boundary conditions of the computational domain, set the four side walls and the bottom surface as walls, set the top surface as a pressure outlet, set the left side as a velocity inlet, set the right side as a pressure outlet, and set the outer surface of the marine structure as a non-slip wall. Step S109: Set the wave generation and wave suppression methods, wherein momentum source term is used for watershed wave generation and force wave suppression technology is used for wave suppression; Step S110: Set the inflow velocity of the fluid domain in the pool to achieve the forward speed of the marine structure.

5. The hydroelastic two-way strong coupling calculation method based on CFD and modal superposition as described in claim 1, characterized in that, Step S2 specifically includes: Step S201: Establish a three-dimensional finite element model of the marine structure in the solid domain solver, wherein the three-dimensional finite element model of the marine structure includes the outer shell and reinforcing skeleton of the marine structure; Step S202: Discretize the three-dimensional finite element model of the marine structure into a solid mesh, wherein the outer shell of the marine structure is meshed into shell elements and the reinforcing frame is meshed into beam elements. Step S203: Set the material properties of the outer shell of the marine structure and the reinforcing skeleton, wherein the material properties include mass, density, stiffness, elastic modulus, Poisson's ratio, number of modes and structural damping; Step S204: Apply gravity loads to all grid nodes, apply fluid loads to the grid nodes on the surface of the marine structure in contact with the external flow field, and apply displacement constraints to all grid nodes in combination with the motion degrees of freedom of the marine structure. Step S205: Based on the three-dimensional finite element model of the marine structure after mesh discretization, calculate the natural frequencies and natural mode shapes of the marine structure according to the material properties and displacement constraints.

6. The hydroelastic two-way strong coupling calculation method based on CFD and modal superposition according to claim 1, characterized in that, Step S5 specifically includes: Step S501: Using the bidirectional strong coupling matching method between the fluid domain mesh and the solid domain mesh information, the surface load of the preset marine structure mesh element is transferred to the three-dimensional finite element model of the marine structure, and the equations are decoupled. Step S502: Preset the calculation time step, total simulation duration, and number of data exchanges within each time step, and simultaneously run the CFD fluid domain solver and the solid domain solver to perform numerical simulation calculations; Step S503: Use the modal superposition method to obtain the displacement, bending moment and shear force of any cross section of the preset marine structure; Step S504: Output real-time response data. Output wavefront elevation and surface load of marine structure material mass grid cells in the CFD fluid domain solver, and output marine structure profile load, local stress, and structural deformation in the solid domain solver.

7. A hydroelastic two-way strongly coupled computational system combining CFD and modal analysis, characterized in that, include: The fluid domain model construction module is used to build a marine structure flow domain model in the CFD fluid domain solver, discretize the marine structure flow domain model into a flow domain mesh, and set physical parameters, initial conditions, and boundary conditions. The solid domain model construction module is used to build a three-dimensional finite element model of the marine structure in the solid domain solver, discretize the three-dimensional finite element model of the marine structure into a solid mesh, and apply constraints to the solid mesh to calculate the natural frequencies and mode shapes of the marine structure when it vibrates under constraints. A correlation module is constructed to build a bidirectional strongly coupled matching method for fluid domain mesh and solid domain mesh information, so as to associate each fluid mesh on a marine structure with its best solid element mesh. Specifically, the bidirectional strongly coupled matching method for fluid domain mesh and solid domain mesh information is as follows: The fluid loads acting on the marine structure's material flow mesh surface are transmitted to the associated solid mesh cells in the solid domain solver via the m2nsockets communication link through the CFD fluid domain solver. The solid domain solver performs mesh displacement calculation based on the parallel implicit modal superposition method. The calculated displacement value is then transmitted back to the associated fluid mesh via the m2n sockets communication link. The calculation is repeated multiple times within a single time step until the residual of the calculated values ​​of two adjacent displacements is less than the user-defined residual value. The simulation module is used to simulate a preset marine structure in the CFD fluid domain solver and output the surface load of the preset marine structure and the time history value of the motion of the preset marine structure. The modal superposition module uses a bidirectional strong coupling matching method between the fluid domain mesh and the solid domain mesh to transfer the surface load of the preset marine structure to the solid three-dimensional finite element model of the marine structure, and uses an implicit parallel modal superposition method to numerically solve the modal motion equations to obtain and derive the displacement response time history of the preset marine structure solid mesh. The reverse transmission and iteration module is used to reverse transmit the displacement response time history value of the preset marine structure solid mesh to the fluid mesh associated in the CFD fluid domain solver, and iteratively execute the modal superposition module and the reverse transmission and iteration module until the calculation result meets the user-defined displacement residual value.

8. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the hydroelastic bidirectional strongly coupled calculation method of CFD and modal superposition as described in any one of claims 1-6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the hydroelastic two-way strong coupling calculation method of CFD and modal superposition as described in any one of claims 1-6.

Images