Ultra-large UUV floating ice breaking numerical simulation method and system in ice breaking environment

Abstract

The invention discloses a numerical simulation method and system for upward-floating icebreaking of an ultra-large UUV (Unmanned Underwater Vehicle) in a crushed ice environment, and the method comprises the steps: introducing a volume fraction filling-hydrostatic pressure joint initialization strategy, a crushed ice-ultra-large UUV multi-substance group coupling solving mechanism and a local grid encryption technology; and multiphase flow-solid coupling unified solution of a water area, an air area, crushed ice and an ultra-large UUV is realized. Compared with the prior art, the method is closer to the real working condition of the ultra-large UUV working in the periglacial region or under the ice ridge, and the obtained contact force data of the crushed ice and the ultra-large UUV has higher engineering reference value. Through an interface initialization mode based on a volume fraction filling method and hydrostatic pressure, phase interface geometric consistency is effectively kept, and simulation stability is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of computational fluid dynamics technology, specifically relating to a numerical simulation method and system for the floating and icebreaking of ultra-large UUVs in a broken ice environment. Background Technology

[0002] With the global development of polar resources and the increasing strategic value of the Arctic shipping routes, unmanned underwater vehicles (UUVs) are being used more and more widely in polar ice regions, especially in scientific research, resource exploration, and environmental monitoring. Among them, ultra-large UUVs, with their ultra-long endurance, high payload, and strong autonomy, have become important equipment for performing long-term and complex missions.

[0003] During operations in polar ice regions, emergency ascents or communication / positioning by UUVs not only occur under flat ice sheets but also in areas with accumulated ice, such as the ice periphery or below ice ridges. Due to the large size of ultra-large UUVs, their ascent process requires dispersing or pushing aside a large amount of ice debris. This process involves complex dynamic interactions between the ultra-large UUV structure, the surrounding fluid, and a large number of ice fragments, representing a typical fluid-structure interaction and multibody dynamics coupling problem, posing a severe challenge to the structural safety of ultra-large UUVs.

[0004] Currently, research methods for addressing the icebreaking mechanism of UUVs mainly include physical model experiments and numerical simulations. While physical model experiments (such as scaled-down ice-water tank experiments) can visually reproduce physical phenomena, they suffer from high costs, long cycles, and difficulty in precisely controlling ice fragment distribution. In contrast, numerical simulation methods offer advantages such as flexible modeling, controllable operating conditions, and high visualization, making them an important technical approach for studying the icebreaking mechanism of UUVs.

[0005] However, existing numerical methods still have shortcomings in handling the coupling problem between ultra-large UUVs and ice fragments. Lagrangian-grid-based algorithms (such as the finite element method, FEM) suffer from enormous computational costs and are prone to mesh distortion when dealing with large amounts of ice contact, collision, and accumulation. While Eulerian-based algorithms can adapt to large deformation flows, they struggle to accurately capture the boundaries of UUVs and ice fragments, resulting in insufficient accuracy in calculating momentum exchange between fluid and solid. The Arbitrary Lagrangian-Eulerian (ALE) method, while offering some capability in simulating fluid-solid interface tracking, requires frequent re-meshing of the fluid domain mesh when ice fragments undergo significant overturning and breakage, leading to low computational efficiency and potential mesh quality degradation and interruption. Meshless methods such as Smoothed Particle Hydrodynamics (SPH), while suitable for simulating ice fragmentation, have extremely low computational efficiency in large-scale fluid domains and struggle to maintain the stability of the pressure field and the accuracy of boundary conditions. Especially in the scenario of low-speed ascent of ultra-large UUVs, if only an initial velocity is applied, it is difficult to break thick ice floes, resulting in the inability to observe ice cracks. Furthermore, existing numerical methods often treat ultra-large UUVs as rigid bodies, making structural analysis impossible.

[0006] In summary, there is currently a lack of numerical simulation methods capable of achieving stable interface tracking, efficient computation, and reflecting the structural response of ultra-large UUVs in a three-phase environment of ice-water-air. Traditional methods suffer from problems such as high computational cost, severe interface penetration, and poor fluid-structure interaction stability, which limit the accurate prediction and design optimization of the ice-breaking process of ultra-large UUVs. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a numerical simulation method and system for the floating and icebreaking of ultra-large UUVs in a broken ice environment. By introducing a volume fraction filling-hydrostatic pressure joint initialization strategy, a multi-material coupling solution mechanism for ice fragmentation and ultra-large UUVs, and local mesh refinement technology, a unified solution for multiphase flow-solid coupling is achieved for the water domain, air domain, ice fragmentation, and ultra-large UUVs. Compared with existing technologies, the method of this invention more closely reflects the actual working conditions of ultra-large UUVs operating in the ice periphery or below ice ridges, and the obtained contact force data between ice fragmentation and ultra-large UUVs has greater engineering reference value. By using an interface initialization method based on volume fraction filling and hydrostatic pressure, the geometric consistency of the phase interface is effectively maintained, significantly improving the stability of the simulation.

[0008] The technical solution adopted by this invention to solve its technical problem is as follows: Step 1: Establish the geometric model and mesh generation; A three-dimensional geometric model of the ultra-large UUV and ice fragments is constructed, and then the three-dimensional geometric model of the ultra-large UUV and ice fragments is meshed to obtain the floating icebreaking calculation model. The floating icebreaking calculation model is imported into explicit dynamic analysis finite element software, and Lagrangian solid element algorithms are defined for the ultra-large UUV and ice fragments respectively. Materials are selected for the ultra-large UUV and ice fragments, and the state equations and physical parameters of the air domain and water domain are set. By defining a multi-material group, the unified modeling of the two-phase fluids in the air domain and water domain is achieved. Step 2: Generate the fluid domain and set the boundary set; The fluid domain includes an air domain and a water domain; a structured mesh is established for the air domain and the water domain, and local mesh refinement is performed in the floating path of the ultra-large UUV and the area where ice fragments are distributed; a node set and a cell set are created and constrained, the node set includes all the node sets at the bottom of the water domain, and the cell set includes the segment sets of the four sides around the air domain and the water domain, and the segment sets of the ultra-large UUV and the ice fragments; a solid set is created inside the air domain and the water domain and the solid set of the surrounding boundaries; Step 3: Define the physics field and initialize the volume fraction; Gravitational acceleration is applied to the three-dimensional geometric model of the ultra-large UUV and ice fragments. The magnitude and direction of the upward velocity of the ultra-large UUV are set, and the hydrostatic pressure of the water area is initialized. The volume fraction filling method is used to realize the layering of the air domain and the water area in the computational domain. The ultra-large UUV and ice fragments are embedded in the layered air domain and water area to achieve the consistency of the air domain and water area interface and the fluid-solid interface. Step 4: Fluid-structure interaction algorithm and numerical stability control; Select a fluid-structure interaction algorithm, including the coupling between ice fragments and the fluid domain, and the coupling between the ultra-large UUV and the fluid domain; establish the contact between ice fragments and the ultra-large UUV, as well as the self-contact between ice fragments, and set the hourglass control parameters, simulation termination time, and time step control conditions; define the ASCII and binary files for output contact force and fluid-structure interaction force, and set the keyword file for generating animation frames; extract the force and ice load data of the ultra-large UUV.

[0009] Further, step 1 specifically includes: Step 1-1: Create a super-large UUV geometric model in 3D modeling software; select the area where the ice rink is to be built, randomly generate a certain number of distribution points in the area, generate polygons of different shapes based on the distribution points according to Voronoi theory, set the scaling factor to enlarge or shrink the polygons, and finally stretch the thickness to obtain the ice rink composed of polygons. Steps 1-2: Mesh the ice fragmentation geometry model and the ultra-large UUV geometry model; The geometric model of the ultra-large UUV is divided into mapped meshes. First, it is decomposed into regular mapped bodies. After decomposition, the number of mesh points is set on each mapped body. The number of points is increased in the shell region and the stern region. Finally, the size and shape of the mesh are set to automatically generate a hexahedral solid mesh. The geometric model of the ice fragments is divided into hexahedral meshes. At the same time, the mesh is refined for the floating path of the ultra-large UUV. Steps 1-3: Define the Lagrangian solid element algorithm for the mesh of the ultra-large UUV and ice fragments; use the *MAT_PLASTIC_KINEMATIC material model to simulate the shell material of the ultra-large UUV as aluminum alloy, and use an isotropic elastic failure constitutive model to simulate the ice fragment geometry by setting the failure strain and cutoff pressure; when the pressure or strain of the ice fragment geometry exceeds the failure strain or cutoff pressure, the ice fragments will be deleted, forming cracks, represented as: or ,in p n+1 for t n+1 The pressure value at any moment, For effective plastic strain, p t To cut off the pressure, For plastic failure strain; Set the material parameters and equations of state for the air and water domains, as well as the multi-material groups for the air and water domains.

[0010] Furthermore, step 2 specifically includes: Step 2-1: The meshes for the air and water domains are implemented using the S-ALE algorithm; the flow field control equations of the S-ALE algorithm consist of the continuity equation (1), the momentum equation (2), and the energy equation (3), which are the Navier-Stokes control equations. (1) (2) (3) In the formula, t For time; ρ It is fluid density. ρ r for ρ The reference domain function; x i for i To Euler coordinates; x j for j To Euler coordinates; u i It is the material speed. yes ui The reference material velocity function; w i for i Directional relative velocity; w j for j Directional relative velocity; b i Force per unit volume; e r for e The reference domain function, e For internal energy; σ ij,j , σ ij All are stress tensors; u i,j Let be the strain rate tensor.

[0011] The *STRUCTURED_MESH_CONTROL_POINTS keyword is used to set numbers and coordinates in the X, Y, and Z directions. The number of numbers is increased to encrypt the floating path and ice fragmentation area of ​​the ultra-large UUV. Finally, the encrypted mesh is generated by the *STRUCTURED_MESH keyword. Step 2-2: Create a node set for all nodes on the bottom surface of the super-large UUV in the water area and apply six-degree-of-freedom constraints. After creating the segment sets for the air domain and the water area, set the surrounding area as a non-reflective boundary. At the same time, create segment sets for the super-large UUV and the ice fragments. Continue to add boundary layers and set the solid set inside and the solid set of the surrounding boundary using the *SET_SOLID_GENERAL keyword.

[0012] Preferably, step 3 specifically comprises: Step 3-1: Define the curve of gravitational acceleration, set the direction of gravitational acceleration downward along the negative Y-axis, define the keyword *LOAD_BODY_Y, and apply the defined gravitational acceleration to the entire physical model; set the buoyancy speed of the ultra-large UUV along the positive Y-axis; Step 3-2: Define the keyword *ALE_AMBIENT_HYDROSTATIC; create air domain vertices and water domain vertices, and then fix the internal solid set and the solid set of the surrounding boundary defined in Step 2-2 using air domain vertices and water domain vertices; Step 3-3: Define the keyword *ALE_STRUCTURED_MESH_VOLUME_FILLING to fill the entire internal region of the computational domain with water. Then, create a plane and fill the upper half with air, where the water vertices are on this plane. The air domain extends upwards from this plane to the air domain vertex, and downwards to the water domain. Using the segment set of ultra-large UUVs and ice fragments created in Step 2-2, embed ultra-large UUVs and ice fragments into the water domain.

[0013] Preferably, step 4 specifically comprises: Step 4-1: Define the keyword *ALE_STRUCTURED_FSI, set the coupling parameters between the ice fragmentation mesh and the ultra-large UUV mesh and the fluid domain mesh; select the penalty function contact algorithm for the contact algorithm; Interface contact force F From formula (4): F = kδ (4) in, k Indicates the stiffness of the unit contact surface. δ Indicates the amount of penetration; k The calculation formula (5) is as follows: (5) in, This represents the stiffness penalty factor. K Represents the bulk modulus of elasticity. A Indicates the contact area. V Indicates the principal area; The contact between the ultra-large UUV and the ice fragments, as well as the contact between the contents of the ice fragments, are defined using the keywords *CONTACT_ERODING_SURFACE_TO_SURFACE and *CONTACT_ERODING_SINGLE_SURFACE, respectively. Step 4-2: By setting independent hourglass control parameters for the water area, air area, and ice fragments, and combining them with time step adaptive control, the computational stability control during the deformation process is achieved; ASCII and binary files for output contact force and fluid-structure interaction force are defined, and keyword files for generating animation frames are set to extract the stress and ice load data of the ultra-large UUV.

[0014] A numerical simulation system for the buoyancy and icebreaking of an ultra-large UUV in a crushed ice environment includes: Automatic ice crushing module: Generates ice crushing groups of different sizes, thicknesses, and densities according to actual working conditions; Mesh generation module: Used to create physical models of ultra-large UUVs, mesh the ice crushing physical model and the ultra-large UUV physical model, and then import them into explicit dynamic analysis finite element software. Numerical simulation module: used to define fluid materials and equations of state, as well as automatic mesh generation of the ensemble model of the computational domain, set fluid-structure interaction model and contact algorithm, configure boundary conditions and numerical solution model, and solve the contact force and fluid-structure interaction force based on the numerical simulation method of ultra-large UUV floating and icebreaking in the ice-breaking environment and the configured numerical calculation conditions of the ultra-large UUV floating and icebreaking numerical model. Results Export Module: Used to post-process contact forces and fluid-structure interaction forces to obtain ice load calculation results of ultra-large UUVs under different ice-breaking conditions; The automatic ice crushing module, mesh generation module, numerical simulation module, and result export module are connected sequentially through a data interface to form an automated simulation process of "input working parameters - geometric modeling - mesh generation - simulation solution - result output".

[0015] An electronic device includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to enable the electronic device to perform the above-described floating and ice-breaking numerical simulation method.

[0016] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described numerical simulation method for icebreaking and buoyancy.

[0017] A chip includes a processor for retrieving and running a computer program from a memory, causing a device equipped with the chip to perform the above-described numerical simulation method for ice-breaking and buoyancy.

[0018] A computer program product includes a computer storage medium storing a computer program, the computer program including instructions executable by at least one processor, which, when executed by the at least one processor, implement the above-described numerical simulation method for icebreaking and buoyancy.

[0019] The beneficial effects of this invention are as follows: This invention couples water, air, ice fragments, and ultra-large UUVs within a unified framework using the S-ALE algorithm, enabling convenient simulation of random ice fragmentation environments with varying ice thicknesses, sizes, and densities. Compared to existing techniques (such as ignoring hydrodynamics or simulating only smooth ice), this method more closely approximates the actual working conditions of ultra-large UUVs operating in ice periphery zones or beneath ice ridges, and the obtained contact force data between ice fragments and ultra-large UUVs has greater engineering reference value. By employing an interface initialization method based on volume fraction filling and hydrostatic pressure, the geometric consistency of the phase interface is effectively maintained, significantly improving the stability of the simulation.

[0020] This invention constructs a three-domain contact system of ice fragments, ultra-large UUVs, and fluids. By combining a penalty function algorithm with an hourglass control strategy, it effectively avoids mesh distortion and solution divergence caused by ice fragment accumulation.

[0021] This invention designs an integrated computing system consisting of an automatic ice fragmentation generation module, a mesh generation module, a numerical simulation module, and a result export module. This system can automatically complete simulation configuration based on input operating parameters, enabling batch calculations under different ice thicknesses, ice densities, and ultra-large UUV speeds, and possesses good engineering adaptability and scalability. Attached Figure Description

[0022] Figure 1 This is a flowchart of the steps of the method of the present invention; Figure 2 Automatically generate program diagrams for crushed ice; Figure 3 For grid partitioning; Figure 4 Diagram showing the initialization of hydrostatic pressure; Figure 5 This is a diagram showing the results of ice breakage. Figure 6 Equivalent stress cloud diagram of the structure at the moment of collision of the ultra-large UUV; Figure 7 The diagram shows the calculated contact force results during the buoyancy and icebreaking process of an ultra-large UUV. Figure 8 This is a schematic diagram of the structure of a numerical simulation system for the floating and icebreaking of an ultra-large UUV. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] This invention provides a numerical simulation method and system for the floating and icebreaking of ultra-large UUVs in a broken ice environment. By introducing a volume fraction filling-hydrostatic pressure joint initialization strategy, a multi-material group coupling solution mechanism for broken ice and ultra-large UUVs, and local mesh refinement technology, a unified solution for multiphase flow-solid coupling of water, air, broken ice, and ultra-large UUVs is achieved, thereby significantly improving the simulation stability, accuracy, and engineering applicability.

[0025] A numerical simulation method for the buoyancy and icebreaking of ultra-large UUVs in a broken ice environment, the specific scheme is as follows: S1: Establish the geometric model and mesh generation; A three-dimensional geometric model of a super-large UUV and ice fragments was constructed. The model was then meshed to obtain a preliminary calculation model for icebreaking and floating. The calculation model was imported into an explicit dynamic analysis finite element software. Lagrangian solid element algorithms were defined for both the super-large UUV and ice fragments, and suitable materials were selected. The state equations and physical parameters for both the air and water domains were set. By defining a multi-material group, a unified modeling of the two-phase fluids in the air and water domains was achieved.

[0026] S2: Generate the fluid domain and set the boundary set; Structured meshes were established for the air and water domains, with local mesh refinement applied along the floating path of the ultra-large UUV and in areas with ice fragmentation to improve the accuracy of fluid-solid interface capture and better capture ice crack propagation. Corresponding node and element sets were created and constrained, including all node sets at the bottom of the water domain, segment sets for the air domain and the four surrounding surfaces of the water domain, and segment sets for the ultra-large UUV and ice fragments. To add boundary layers, solid sets were created for the air and water domains and the surrounding boundaries. This setup ensures the topological continuity of the fluid-solid interface, providing a boundary foundation for subsequent volume fraction initialization and fluid-solid coupling solutions.

[0027] S3: Definition of physical fields and initialization of volume fraction; Gravitational acceleration is applied to the entire physical model, and the magnitude and direction of the buoyancy velocity of the ultra-large UUV are set. Hydrostatic pressure is initialized for the water area. A volume fraction filling method is used to stratify the air and water domains within the computational domain. The ultra-large UUV and ice fragments are then embedded into the stratified air and water domains, ensuring consistency at the air-water interface and the fluid-solid interface. This effectively guarantees the multiphase dynamic interactive simulation of the ultra-large UUV's buoyancy, ice impact, and breakup processes.

[0028] S4: Fluid-structure interaction algorithm and numerical stability control; Select appropriate fluid-structure interaction (FSI) algorithms, including the coupling between ice fragments and the fluid domain, and the coupling between the ultra-large UUV and the fluid domain; establish contact between ice fragments and the ultra-large UUV, as well as self-contact between ice fragments; set hourglass control parameters, simulation termination time, and time step control conditions; define ASCII and binary files for output contact forces and FSI forces, and set keyword files for generating animation frames. Extract the force and ice load data of the ultra-large UUV through a post-processing module.

[0029] A numerical simulation system for the buoyancy and icebreaking of an ultra-large UUV in a crushed ice environment includes: Automatic ice crushing module: Based on the actual working conditions required, it can generate ice crushing groups of different sizes, thicknesses and densities.

[0030] Mesh generation module: Used to create physical models of ultra-large UUVs, meshing the ice crushing physical model and the ultra-large UUV physical model, and then importing them into explicit dynamic analysis finite element software.

[0031] Numerical simulation module: used to define fluid materials and equations of state, as well as the automatic mesh generation of the ensemble model of the computational domain, set the fluid-structure interaction model and contact algorithm, configure boundary conditions and numerical solution model, and solve the numerical model of ultra-large UUV floating and icebreaking under numerical calculation conditions to obtain contact force and fluid-structure interaction force.

[0032] Results Export Module: Used for post-processing of contact force and fluid-structure interaction force to obtain the ice load calculation results of ultra-large UUV under different ice crushing conditions.

[0033] Each module is connected sequentially through a data interface, forming an automated simulation process of "input working parameters - geometric modeling - mesh generation - simulation solution - result output".

[0034] Example: See Figure 1 This is a flowchart illustrating the steps of a numerical simulation method for the buoyancy and icebreaking of an ultra-large UUV in a broken ice environment, which can accurately obtain the contact force and fluid-structure interaction force during the buoyancy and icebreaking of an ultra-large UUV, including: S1: Establish the geometric model and mesh generation; S11: Consult relevant materials and, based on the existing proportions of ultra-large UUVs, create a similar geometric model in 3D modeling software. Since the distribution of ice fragments in nature follows certain patterns, using 3D modeling software, select the area where the ice fragment field will be built, randomly generate a certain number of distribution points in that area, and generate polygons of different shapes based on the distribution points using Voronoi theory. Set a scaling factor to enlarge or shrink the polygons, and finally stretch the thickness to obtain the ice fragment field composed of polygons. Figure 2 It is a geometric model of broken ice generated by an automatic ice-generating program. Compared with a broken ice field composed of regular ice blocks, this broken ice field is closer to the real situation and can better simulate the collision between ultra-large UUVs and broken ice.

[0035] S12: Mesh generation is performed on the ice fragmentation geometry model and the ultra-large UUV geometry model. Specifically, the ultra-large UUV geometry model uses a mapping mesh generation method. It is first decomposed into regular mapping volumes. After decomposition, the number of mesh points is set on each mapping volume, with a slightly increased number of points in the shell and stern regions to facilitate subsequent mesh refinement. Finally, the size and shape of the mesh are set, automatically generating a hexahedral solid element mesh. Due to its regular shape, the ice fragmentation geometry model can be directly meshed using hexahedral mesh generation. Mesh refinement is also performed on the ultra-large UUV's ascent path. After mesh generation, the mesh quality is checked. The mesh generation results are as follows: Figure 3 As shown.

[0036] S13: Define the Lagrangian solid element algorithm for the mesh elements of the ultra-large UUV and ice fragments. Considering that the ultra-large UUV will be subjected to huge impact loads during the buoyancy and ice breaking process, structural deformation and dynamic response will occur. The *MAT_PLASTIC_KINEMATIC material model is used to simulate the shell material of the ultra-large UUV as aluminum alloy. An isotropic elastic failure constitutive model is used to simulate the ice fragment material model. By setting the failure strain and cutoff pressure, when the pressure or strain of the ice fragment element exceeds the failure strain or cutoff pressure, the ice fragment element will be deleted to form a crack, which is expressed as: or Setting the material parameters and equations of state for the air and water domains, as well as the multi-material groups for the air and water domains, lays the foundation for subsequent automatic mesh generation of the computational domain using the S-ALE algorithm.

[0037] S2: Generate the fluid domain and set the boundary set; S21: The meshes for the air and water domains are implemented using the S-ALE algorithm, a second-order accurate advection algorithm based on the momentum conservation equation of a unified continuous medium, which has high advection accuracy and mesh regularity. The S-ALE method still uses Euler variables to describe the fluid and Lagrangian variables to describe the structure. Compared with the ALE method, the fluid domain of the S-ALE method is automatically generated based on the fluid boundary, which means that the S-ALE method does not need to deal with the coordinate and mesh transformation between the physical plane and the computational plane in the calculation. When dealing with dynamic boundary problems, it does not need to update the mesh in real time at every time step, thus reducing the number of calculation loops and greatly improving the calculation speed. The flow field control equations of the S-ALE algorithm consist of the continuity equation (1), the momentum equation (2), and the energy equation (3), all of which are derived from classical fluid dynamics theory, namely the Navier-Stokes control equations.

[0038] (1) (2) (3) The *STRUCTURED_MESH_CONTROL_POINTS keyword is used to set appropriate numbers and coordinates in the X, Y, and Z directions. The number of numbers is increased to encrypt the floating path and ice fragmentation area of ​​the ultra-large UUV. Finally, the encrypted mesh is generated using the *STRUCTURED_MESH keyword.

[0039] S22: Since the real-world scenario of ultra-large UUVs surfacing and breaking ice involves nearly infinitely large bodies of water, to avoid fluid leakage and wave reflection, a node set is created for all nodes on the bottom surface, and six-degree-of-freedom constraints are applied. After creating segment sets for the air and water domains, the surrounding area is set as a non-reflective boundary. Simultaneously, segment sets for both the ultra-large UUV and the ice fragments are created to make the subsequent hydrostatic pressure initialization more realistic. Boundary layers are then added, and the *SET_SOLID_GENERAL keyword is used to set the internal solid set and the solid set for the surrounding boundaries to ensure topological continuity.

[0040] S3: Definition of physical fields and initialization of volume fraction; S31: Define the curve of gravitational acceleration, set the direction of gravitational acceleration downward along the negative Y-axis, define the keyword *LOAD_BODY_Y, and apply the defined gravitational acceleration to the entire physical model. Since submarine icebreaking is mostly done by vertical surfacing, the same applies to ultra-large UUVs, setting their surfacing speed along the positive Y-axis.

[0041] S32: Define the keyword *ALE_AMBIENT_HYDROSTATIC and set the gravitational acceleration to 9.80002 m / s². 2 The standard atmospheric pressure is 1.013 × 10⁻⁶. 5 Pa; Create the vertices of the air and water domains to create a layered structure. Then, fix the internal solid set and the surrounding boundary solid sets defined in S2 using the newly created vertices of the air and water domains. The hydrostatic pressure initialization is complete. Figure 4 As shown.

[0042] S33: Define the keyword *ALE_STRUCTURED_MESH_VOLUME_FILLING. First, fill the entire computational domain with water. Then, create a plane and fill its upper half with air. The water vertices established in S32 lie on this plane. Above this plane, up to the air domain vertex, is the air domain; below, it is the water domain. Finally, using the segment set of ultra-large UUVs and ice fragments created in S22, embed ultra-large UUVs and ice fragments into the water domain. This initialization method maintains the consistency of the air domain–water domain–solid interface and prevents numerical divergence caused by discontinuous volume fractions.

[0043] S4: Fluid-structure interaction algorithm and numerical stability control; S41: Define the keyword *ALE_STRUCTURED_FSI to set the coupling parameters between the ice fragmentation mesh and the ultra-large UUV mesh and the fluid domain mesh. The contact algorithm selected is the penalty function contact algorithm. This algorithm defines the two free surfaces that may come into contact as the master surface and the slave surface, respectively. When the two surfaces are about to come into contact and cause penetration, some normal "springs" will be generated between the master surface and the slave surface. These "springs" can limit the occurrence of penetration. The force generated by the "springs" is called the interface contact force, i.e., the interaction force.

[0044] The interfacial contact force is calculated using the following formula (4): F = kδ (4) k The calculation formula (5) is as follows: (5) Based on the above contact algorithm, the contact between ice fragments and ultra-large UUVs, as well as the contact between ice fragments themselves, are defined using the keywords *CONTACT_ERODING_SURFACE_TO_SURFACE and *CONTACT_ERODING_SINGLE_SURFACE, respectively.

[0045] S42: By setting independent hourglass control parameters for the water, air, and ice fragments, combined with time-step adaptive control, computational stability control is achieved during large deformation processes. ASCII and binary files for output contact forces and fluid-structure interaction forces are defined, and keyword files for generating animation frames are set to facilitate subsequent post-processing analysis. The post-processing module extracts the stress and ice load data of the ultra-large UUV.

[0046] Figure 5 This is a picture showing the result of ice breakage. It can be seen that after the shell of the super-large UUV came into contact with ice, the cracks expanded rapidly, and some of the ice fragments shattered and splashed.

[0047] Figure 6 This is an equivalent stress cloud diagram of the structure at the moment of collision of the super-large UUV. It can be seen that the stress of the bow, the shell and the fins of the stern of the super-large UUV is relatively large. This is because the super-large UUV collided with the ice fragments.

[0048] Figure 7 This is a diagram showing the calculated contact force during the icebreaking process of an ultra-large UUV.

[0049] This invention, based on the S-ALE algorithm and fluid-structure interaction theory, considers the unique scenario of ultra-large UUVs operating in polar ice regions, specifically in the ice-breaking zone below the ice edge or ridge. It incorporates the coupling effects of both air and water media with the ice-breaking and ultra-large UUVs. Compared to some numerical methods that neglect fluid dynamics, this invention more closely approximates real-world physical conditions. The isotropic elastic failure constitutive model used to simulate ice breaking allows for the design of failure strain and cutoff pressure, simulating ice crack propagation and better reflecting the physical properties of real ice. Currently, most ultra-large UUVs rely on the ALE and SPH methods for icebreaking. This invention creatively introduces the S-ALE algorithm, improving simulation efficiency and accuracy. Furthermore, this invention provides a program for automatically generating ice-breaking geometry models, allowing for user-defined ice size, thickness, and density settings, offering convenience and speed.

[0050] This invention also provides a computational system for a numerical simulation method of icebreaking on the surface of ultra-large UUVs based on the S-ALE algorithm, such as... Figure 8 As shown, the system includes: an automatic ice fragmentation generation module 801, a mesh generation module 802, a numerical simulation module 803, and a result export module 804. The automatic ice fragmentation generation module 801 is used to automatically generate a geometric model with preset ice fragmentation size, thickness, and density. The mesh generation module 802 is used to mesh the ice fragmentation geometric model and the ultra-large UUV geometric model to initially obtain the floating and icebreaking calculation model. The numerical simulation module 803 is used to define the fluid-structure interaction relationship, contact algorithm, boundary conditions, and initial physical field of the floating and icebreaking calculation model, and to simulate the floating and icebreaking situation of the ultra-large UUV under different working conditions. The result export module is used to post-process the contact force and ultra-large UUV structural response data in the simulation results to obtain the numerical calculation results of the ultra-large UUV floating and icebreaking under different working conditions.

Claims

1. A numerical simulation method for the floating and icebreaking of ultra-large UUVs in a broken ice environment, characterized in that, Includes the following steps: Step 1: Establish the geometric model and mesh generation; A three-dimensional geometric model of the ultra-large UUV and ice fragments is constructed, and then the three-dimensional geometric model of the ultra-large UUV and ice fragments is meshed to obtain the floating icebreaking calculation model. The floating icebreaking calculation model is imported into explicit dynamic analysis finite element software, and Lagrangian solid element algorithms are defined for the ultra-large UUV and ice fragments respectively. Materials are selected for the ultra-large UUV and ice fragments, and the state equations and physical parameters of the air domain and water domain are set. By defining a multi-material group, the unified modeling of the two-phase fluids in the air domain and water domain is achieved. Step 2: Generate the fluid domain and set the boundary set; The fluid domain includes an air domain and a water domain; a structured mesh is established for the air domain and the water domain, and local mesh refinement is performed in the floating path of the ultra-large UUV and the area where ice fragments are distributed; a node set and a cell set are created and constrained, the node set includes all the node sets at the bottom of the water domain, and the cell set includes the segment sets of the four sides around the air domain and the water domain, and the segment sets of the ultra-large UUV and the ice fragments; a solid set is created inside the air domain and the water domain and the solid set of the surrounding boundaries; Step 3: Define the physics field and initialize the volume fraction; Gravitational acceleration is applied to the three-dimensional geometric model of the ultra-large UUV and ice fragments. The magnitude and direction of the upward velocity of the ultra-large UUV are set, and the hydrostatic pressure of the water area is initialized. The volume fraction filling method is used to realize the layering of the air domain and the water area in the computational domain. The ultra-large UUV and ice fragments are embedded in the layered air domain and water area to achieve the consistency of the air domain and water area interface and the fluid-solid interface. Step 4: Fluid-structure interaction algorithm and numerical stability control; Select a fluid-structure interaction algorithm, including the coupling between ice fragments and the fluid domain, and the coupling between the ultra-large UUV and the fluid domain; establish the contact between ice fragments and the ultra-large UUV and the self-contact between ice fragments, and set the hourglass control parameters, simulation termination time and time step control conditions. It also defines ASCII and binary files for outputting contact force and fluid-structure interaction force, and sets keyword files for generating animation frames; Extract stress and ice load data for ultra-large UUVs.

2. The numerical simulation method for the floating and icebreaking of an ultra-large UUV in a broken ice environment according to claim 1, characterized in that, Step 1 specifically involves: Step 1-1: Create a super-large UUV geometric model in 3D modeling software; select the area where the ice rink is to be built, randomly generate a certain number of distribution points in the area, generate polygons of different shapes based on the distribution points according to Voronoi theory, set the scaling factor to enlarge or shrink the polygons, and finally stretch the thickness to obtain the ice rink composed of polygons. Steps 1-2: Mesh the ice fragmentation geometry model and the ultra-large UUV geometry model; The geometric model of the ultra-large UUV is divided into mapped meshes. First, it is decomposed into regular mapped bodies. After decomposition, the number of mesh points is set on each mapped body. The number of points is increased in the shell region and the stern region. Finally, the size and shape of the mesh are set to automatically generate a hexahedral solid mesh. The geometric model of the ice fragments is divided into hexahedral meshes. At the same time, the mesh is refined for the floating path of the ultra-large UUV. Steps 1-3: Define the Lagrangian solid element algorithm for the mesh of the ultra-large UUV and ice fragments; use the *MAT_PLASTIC_KINEMATIC material model to simulate the shell material of the ultra-large UUV as aluminum alloy, and use an isotropic elastic failure constitutive model to simulate the ice fragment geometry by setting the failure strain and cutoff pressure; when the pressure or strain of the ice fragment geometry exceeds the failure strain or cutoff pressure, the ice fragments will be deleted, forming cracks, represented as: or ,in p n+1 for t n+1 The pressure value at any moment, For effective plastic strain, p t To cut off the pressure, For plastic failure strain; Set the material parameters and equations of state for the air and water domains, as well as the multi-material groups for the air and water domains.

3. The numerical simulation method for icebreaking of ultra-large UUVs in a broken ice environment according to claim 2, characterized in that, Step 2 specifically involves: Step 2-1: The meshes for the air and water domains are implemented using the S-ALE algorithm; the flow field control equations of the S-ALE algorithm consist of the continuity equation (1), the momentum equation (2), and the energy equation (3), which are the Navier-Stokes control equations. (1) (2) (3) In the formula, t For time; ρ It is fluid density. ρ r for ρ The reference domain function; x i for i To Euler coordinates; x j for j To Euler coordinates; u i It is the material speed. yes u i The reference material velocity function; w i for i Directional relative velocity; w j for j Directional relative velocity; b i Force per unit volume; e r for e The reference domain function, e For internal energy; σ ij,j , σ ij All are stress tensors; u i,j For strain rate tensor; The *STRUCTURED_MESH_CONTROL_POINTS keyword is used to set numbers and coordinates in the X, Y, and Z directions. The number of numbers is increased to encrypt the floating path and ice fragmentation area of ​​the ultra-large UUV. Finally, the encrypted mesh is generated by the *STRUCTURED_MESH keyword. Step 2-2: Create a node set for all nodes on the bottom surface of the super-large UUV in the water area and apply six-degree-of-freedom constraints. After creating the segment sets for the air domain and the water area, set the surrounding area as a non-reflective boundary. At the same time, create segment sets for the super-large UUV and the ice fragments. Continue to add boundary layers and set the solid set inside and the solid set of the surrounding boundary using the *SET_SOLID_GENERAL keyword.

4. The numerical simulation method for the floating and icebreaking of an ultra-large UUV in a broken ice environment according to claim 3, characterized in that, Step 3 specifically involves: Step 3-1: Define the curve of gravitational acceleration, set the direction of gravitational acceleration downward along the negative Y-axis, define the keyword *LOAD_BODY_Y, and apply the defined gravitational acceleration to the entire physical model; set the buoyancy speed of the ultra-large UUV along the positive Y-axis; Step 3-2: Define the keyword *ALE_AMBIENT_HYDROSTATIC; create air domain vertices and water domain vertices, and then fix the internal solid set and the solid set of the surrounding boundary defined in Step 2-2 using air domain vertices and water domain vertices; Step 3-3: Define the keyword *ALE_STRUCTURED_MESH_VOLUME_FILLING to fill the entire internal region of the computational domain with water. Then create a plane and fill the upper half with air. The vertex of the water area is on this plane. The area above the plane is the air area, and the area below it is the water area. Using the segment set of ultra-large UUVs and ice fragments created in step 2-2, ultra-large UUVs and ice fragments are embedded in the water.

5. The numerical simulation method for the floating and icebreaking of an ultra-large UUV in a crushed ice environment according to claim 4, characterized in that, Step 4 specifically involves: Step 4-1: Define the keyword *ALE_STRUCTURED_FSI to set the coupling parameters between the ice fragmentation mesh and the ultra-large UUV mesh and the fluid domain mesh; Contact algorithm selection penalty function contact algorithm; Interface contact force F From formula (4): F = kδ (4) in, k Indicates the stiffness of the unit contact surface. δ Indicates the amount of penetration; k The calculation formula (5) is as follows: (5) in, This represents the stiffness penalty factor. K Represents the bulk modulus of elasticity. A Indicates the contact area. V Indicates the principal area; The contact between the ultra-large UUV and the ice fragments, as well as the contact between the contents of the ice fragments, are defined using the keywords *CONTACT_ERODING_SURFACE_TO_SURFACE and *CONTACT_ERODING_SINGLE_SURFACE, respectively. Step 4-2: By setting independent hourglass control parameters for the water area, air area, and ice fragments, and combining them with time step adaptive control, the computational stability control during the deformation process is achieved; ASCII and binary files for output contact force and fluid-structure interaction force are defined, and keyword files for generating animation frames are set to extract the stress and ice load data of the ultra-large UUV.

6. A floating icebreaking numerical simulation system employing the icebreaking numerical simulation method as described in claim 5, characterized in that, include: Automatic ice crushing module: Generates ice crushing groups of different sizes, thicknesses, and densities according to actual working conditions; Mesh generation module: Used to create physical models of ultra-large UUVs, mesh the ice crushing physical model and the ultra-large UUV physical model, and then import them into explicit dynamic analysis finite element software. Numerical simulation module: used to define fluid materials and equations of state, as well as automatic mesh generation of the ensemble model of the computational domain, set fluid-structure interaction model and contact algorithm, configure boundary conditions and numerical solution model, and solve the contact force and fluid-structure interaction force based on the numerical simulation method of ultra-large UUV floating and icebreaking in the ice-breaking environment and the configured numerical calculation conditions of the ultra-large UUV floating and icebreaking numerical model. Results Export Module: Used to post-process contact forces and fluid-structure interaction forces to obtain ice load calculation results of ultra-large UUVs under different ice-breaking conditions; The automatic ice crushing module, mesh generation module, numerical simulation module, and result export module are connected sequentially through a data interface to form an automated simulation process of "input working parameters - geometric modeling - mesh generation - simulation solution - result output".

7. An electronic device, characterized in that, include: Processor and memory; The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to cause the electronic device to perform the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 5.

9. A chip, characterized in that, include: A processor for retrieving and running a computer program from memory, causing a device on which the chip is mounted to perform the method as described in any one of claims 1 to 5.

10. A computer program product, characterized in that, The computer program product includes a computer storage medium storing a computer program, the computer program including instructions executable by at least one processor, which, when executed by the at least one processor, implement the method as described in any one of claims 1 to 5.

Images