Ice load calculation method for super large vehicle floating in ice environment

Abstract

The application discloses a method for calculating ice load of super-large vehicle in the process of floating and breaking ice in the layered ice environment, and the method comprises the following steps: carrying out mesh division on the layered ice environment and the geometric model of the super-large UUV (unmanned underwater vehicle) to obtain a floating and ice-breaking calculation model of the super-large UUV; the floating and ice-breaking calculation model comprises the mesh-divided geometric model of the layered ice field and the mesh-divided model of the super-large UUV; the fluid-structure coupling relationship of the floating and ice-breaking calculation model is defined, the multi-phase flow-structure coupling unified solution of the water area, the air area, the ice layer and the hull is realized, and the ice load in the process of floating and ice-breaking is identified, separated and calculated under the unified solution framework, so that the stability, the precision and the engineering applicability of the load result are remarkably improved; the floating and ice-breaking calculation model is used to simulate and calculate the floating and ice-breaking of the super-large UUV under various working conditions, and the ice load borne by the super-large UUV at each moment is obtained.

Description

Technical Field

[0001] This invention belongs to the field of computational fluid dynamics technology, specifically relating to a method for calculating ice loads for ultra-large vehicles surfacing and breaking ice in layered ice environments. Background Technology

[0002] With the increase in polar navigation and marine engineering activities, ultra-large unmanned underwater vehicles (UUVs) are increasingly performing "surfacing-ice contact-ice breaking-through" operations in sea ice-covered waters. This process involves unsteady confined water flow, brittle failure and block redistribution of ice under bending and shearing, and strong transient contact loads on the ultra-large UUV structure, constituting a significant three-phase coupling problem between water, ice, and the ultra-large UUV. Traditional pool / sea trials are costly, risky, and difficult to cover the combination of operating conditions; simplified estimates based on experience or standards cannot reflect the time-domain peak and frequency-domain characteristics caused by confined flow fields, added mass, and viscous dissipation; pure Lagrangian or pure Euler descriptions are prone to mesh distortion or interface dispersion during large deformation and fracture of ice, and are also difficult to characterize the impact response and energy dissipation of contact-separation-re-contact. Existing research still lacks a systematic and robust numerical approach for obtaining the time history of ice loads under near-ice surface / icebreaking floating conditions. There is an urgent need for a calculation method that can simultaneously handle fluid motion, large solid deformation, and contact fracture within a unified framework, so as to provide a reliable basis for the evaluation of icebreaking loads and engineering design of ultra-large UUVs. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a method for calculating ice loads during the surfacing and icebreaking of ultra-large UUVs in layered ice environments. The method involves meshing the layered ice environment and the geometric model of the ultra-large UUV to obtain a calculation model for its surfacing and icebreaking. This calculation model includes both a meshed layered ice field geometric model and a meshed ultra-large UUV model. The fluid-structure interaction relationship of the calculation model is defined, enabling a unified solution for multiphase fluid-solid coupling involving the water area, air domain, ice layer, and hull. Within this unified solution framework, the ice loads during the surfacing and icebreaking process are identified, separated, and calculated, significantly improving the stability, accuracy, and engineering applicability of the load results. The surfacing and icebreaking calculation model is then used to simulate the surfacing and icebreaking of the ultra-large UUV under various operating conditions, obtaining the ice loads experienced by the ultra-large UUV at different times.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows:

[0005] Step 1: Establish the geometric model and mesh generation;

[0006] A three-dimensional geometric model of the ultra-large UUV and the ice layer is constructed, and the three-dimensional geometric model of the ultra-large UUV and the ice layer is meshed to obtain the floating and icebreaking calculation model.

[0007] The floating icebreaking calculation model is imported into explicit dynamic / explicit fluid-structure interaction analysis software. Lagrange solid element algorithm is defined for ultra-large UUV, arbitrary Lagrange-Euler ALE fluid element algorithm is defined for water and air domains, ice constitutive model or equivalent solid model is selected for ice layer, and state equations and physical parameters of air and water domains are set at the same time.

[0008] Step 2: Generate the fluid domain and set the boundary set;

[0009] The grid is locally refined along the expected ascent trajectory of the ultra-large UUV and in the areas where the ultra-large UUV may come into contact with the ice layer;

[0010] Multiple feature regions are defined and constrained based on the grid topology, including the node set at the bottom of the water area, the unit surface segment set in the air domain and the periphery of the water area, and the contact surface segment set corresponding to the outer surface of the ultra-large UUV and the bottom surface of the ice layer.

[0011] Define corresponding solid sets within and around the water and air domains to describe the continuous transition between fluid volume and boundaries;

[0012] Step 3: Setting fluid-structure interaction and boundary conditions;

[0013] In explicit dynamic / explicit fluid-structure interaction analysis software, the coupling relationship between the fluid domain and the solid domain is established; the fluid domain includes the air domain and the water domain; the solid domain includes ultra-large UUVs and ice layers.

[0014] Select a coupling algorithm for the interaction between LE fluid elements and Lagrange solid elements;

[0015] Appropriate velocity constraints or non-reflective boundary conditions are applied to the bottom, side walls, and outer boundary of the air domain. Initial buoyancy conditions are applied to the ultra-large UUV. Gravity and constraint conditions are applied to the ice layer to ensure that all materials are at rest or in a predetermined equilibrium state at the initial moment of calculation.

[0016] Based on the ascent path and expected contact area of ​​the ultra-large UUV, establish the contact constraints between the ice layer and the ultra-large UUV, and set the contact stiffness and contact damping parameters.

[0017] Step 4: Solve for control and ice load data output;

[0018] Set the simulation termination time and time step control conditions, and enable the ALE mesh smoothing and remapping function to keep the fluid mesh normal during the process of the ultra-large UUV floating, colliding and breaking ice layers.

[0019] The solution process is initiated, and time history data of the pressure field on the outer surface of the ultra-large UUV, the contact reaction force between the ice layer and the hull of the ultra-large UUV, and the fluid-structure coupling force are output according to the pre-set output control card. At the same time, animation frame files for visualization are generated.

[0020] By integrating the normal pressure and tangential shear stress of the surface unit of the ultra-large UUV hull in different regions and subtracting the hydrodynamic background component under the corresponding working conditions, the ice load time history and its peak characteristic quantity of the entire process of the ultra-large UUV floating and breaking ice are obtained.

[0021] Preferably, step 1 specifically comprises:

[0022] Step 1-1: Based on the external proportions of the super-large UUV, establish the geometric model of the super-large UUV in 3D modeling software; establish a continuous ice layer with a given thickness, length and width above the super-large UUV, and regard the ice layer as a horizontally distributed whole ice layer; set the planar dimensions of the ice layer as a multiple of the length of the super-large UUV.

[0023] Steps 1-2: Mesh the ice layer geometry model and the ultra-large UUV geometry model. The ultra-large UUV model uses a mapping meshing method, first decomposing it into several regular mapping volumes, then refining the mesh in the shell region, the bow curvature variation region, and the stern region, ultimately generating a hexahedral solid element mesh. The ice layer is a regular geometry, so a structured hexahedral mesh is directly used. Simultaneously, local mesh refinement is performed along the ultra-large UUV's ascent path. After meshing, the mesh quality is checked.

[0024] Steps 1-3: Define the Lagrangian solid element algorithm for the mesh elements of the ultra-large UUV and the ice layer; describe the shell of the ultra-large UUV using the *MAT RIGID material model; describe the ice layer using an isotropic elastic-brittle or elastic-plastic failure constitutive model, and simulate the local fracture or damage of the ice layer under compression and bending by setting the failure strain and cutoff pressure; set the material parameters and equations of state for the air domain and the water domain respectively, and establish a multi-material group for the air domain and the water domain.

[0025] Preferably, step 2 specifically comprises:

[0026] The water and air domains are described using arbitrary Lagrange-Euler ALE, and the ALE form equations for mass conservation, momentum conservation, and energy conservation are written as follows:

[0027] (1)

[0028] (2)

[0029] (3)

[0030] In the formula, ρ is the fluid density, with dimensions of kg / m³. 3 V is the fluid velocity, with dimensions in m / s; V g ρ is the grid velocity, in m / s; p is the pressure, in N / m. 2 σ is the stress tensor, with dimensions in N / m. 2 f is the volume force per unit mass, with dimensions in m / s². 2 E is the total energy, with dimensions in J / m³. 3 q is heat flux, with dimensions W / m. 3 ; Indicates time, Represents the divergence operator; This represents the tensor product, used to perform operations on two vectors.

[0031] Six-degree-of-freedom constraints are applied to the node set at the bottom of the computational domain, and non-reflective or transmissive boundary conditions are applied to the segment sets surrounding the air and water domains.

[0032] Preferably, step 3 specifically comprises:

[0033] Step 3-1: Apply an initial buoyancy velocity or velocity-time history along the positive Y-axis to the ultra-large UUV;

[0034] Step 3-2: Bind the solid set of solid elements created in Step 2 to the boundary vertices to ensure that the hydrostatic pressure field is consistently applied inside the fluid domain and on the bottom and sidewall boundaries, so that the water body is in an approximately hydrostatic equilibrium state at the start of the calculation; embed the ultra-large UUV and the whole ice layer into the flow field to realize the continuous representation of the multiphase interface of air domain-water domain-ultra-large UUV-ice layer.

[0035] Preferably, step 4 specifically comprises:

[0036] Step 4-1: Define the coupling relationship between the ultra-large UUV mesh and the fluid domain mesh, and between the ice layer mesh and the fluid domain mesh using the *CONSTRAINED_LAGRANGE_IN_SOLID keyword;

[0037] The contact between ice and water, and between ultra-large UUVs and water, is set to *AUTOMATIC_NODES_TO_SURFACE under the CONTACT keyword in LS-DYNA; the contact between ultra-large UUVs and ice is set to erosion contact, i.e., *ERODING_SURFACE_TO_SURFACE. The contact force is obtained by F= kδ, with the dimension N, where k is the contact surface stiffness, with the dimension N / m; δ is the penetration amount, with the dimension m.

[0038] Step 4-2: Set hourglass control parameters for water, air, and ice respectively, and combine them with time step adaptive control; define output contact force, fluid-structure interaction force, and stress and displacement data files of key sections, and set keywords for generating animation frames to facilitate visualization analysis of the entire process of floating, ice contact, and breaking.

[0039] A system for calculating ice loads for surfacing and breaking ice in a layered ice environment for ultra-large vehicles includes:

[0040] Load acquisition and identification module: After the numerical calculation is completed, the pressure, shear stress and contact state information of each time step on the outer surface of the ultra-large UUV hull are automatically read from the explicit solution results. The surface of the ultra-large UUV hull is divided into regions, the unit regions affected by ice and the regions that only bear hydrodynamic effects are identified, and the load data is filtered and separated, retaining the effective loads related to the ice layer.

[0041] Mesh generation module: Used to create a three-dimensional solid model of the ultra-large UUV and a whole ice layer model, and to discretize the ultra-large UUV three-dimensional solid model and the whole ice layer model in the computer preprocessing environment; the generated mesh model and related properties are imported into the explicit dynamic solver to provide a discretization basis for subsequent ALE solution;

[0042] The ALE Solver and Fluid-Structure Coupling Module is used to define material parameters and equations of state for the water and air domains in the solver, construct the ALE fluid computation domain, set the fluid-structure interaction relationship and contact calculation scheme between the fluid domain and the ultra-large UUV and ice layer, configure boundary conditions and numerical control parameters for time step and termination time; and simulate the icebreaking process of the ultra-large UUV under given working conditions to obtain the instantaneous pressure field, shear stress field and fluid-structure interaction reaction time history of the outer surface of the ultra-large UUV.

[0043] Feature index generation module: Automatically post-processes load data obtained under different times, different ascent speeds and different ice thicknesses, integrates, statistically analyzes and merges ice loads on the surface of ultra-large UUVs, generates ice load time history curves, peak load summary tables, load envelope curves, and load files that can be directly called for structural finite element analysis, and outputs corresponding charts and data reports.

[0044] The modules exchange information sequentially through data files or interfaces, forming an overall automated calculation process from input of working condition parameters, geometric and mesh modeling, ALE simulation solution, automatic identification and extraction of ice loads, to output of feature quantities.

[0045] 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 method for calculating ice load during ice breaking.

[0046] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method for calculating ice load during ice breaking.

[0047] A chip includes a processor for calling and running a computer program from a memory, causing a device equipped with the chip to perform the above-described method for calculating ice load during ice breaking.

[0048] 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 method for calculating ice load during ice breaking and buoyancy.

[0049] The beneficial effects of this invention are as follows:

[0050] 1. This invention couples water, air, ice, and hull within a unified framework using the ALE algorithm, enabling convenient simulation of actual icebreaking conditions with different ice thicknesses, ice strengths, ascent speeds, and diving depths. The obtained ice-ship contact force data has higher engineering reference value.

[0051] 2. This invention constructs a three-domain contact and coupling system of ice layer-ultra-large UUV-fluid, and combines penalty function algorithm and hourglass control strategy to effectively avoid mesh distortion and solution divergence caused by large deformation or local crushing of ice layer, and ensure the continuity and reliability of load output.

[0052] 3. This invention designs an integrated computing system consisting of a "load acquisition and identification module, a mesh generation module, an ALE solution and fluid-structure interaction module, and a characteristic index generation module." This system can automatically complete simulation configuration based on input ice thickness, ascent velocity, ice layer distribution, and the external parameters of the ultra-large UUV, enabling batch calculations under different working conditions and exhibiting good engineering adaptability and scalability. Compared with existing technologies that only provide the overall icebreaking process without distinguishing the load source, this invention can separate and statistically analyze ice loads and fluid-structure interaction loads, outputting time-history loads and characteristic loads that can be directly used for structural design and experimental comparison, providing a more direct numerical basis for the ice-resistant structural design of ultra-large UUVs. Attached Figure Description

[0053] Figure 1 This is a flowchart of the method of the present invention;

[0054] Figure 2 A grid map showing the layout of ultra-large UUVs and ice layers;

[0055] Figure 3 The curve of contact force versus time for an ultra-large UUV;

[0056] Figure 4 A top-down view of the ice layer destruction caused by the ascent and ice breaking of an ultra-large UUV;

[0057] Figure 5 Equivalent stress cloud diagram of the structure at the moment of collision of the ultra-large UUV;

[0058] Figure 6 A schematic diagram showing the change of pitch angle over time during the surfacing and icebreaking process of an ultra-large UUV.

[0059] Figure 7 A cloud map showing the attitude changes of an ultra-large UUV during its ascent and icebreaking process. Detailed Implementation

[0060] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0061] See Figure 1 This embodiment provides a flowchart of a numerical simulation method for the surfacing and icebreaking of ultra-large UUVs based on the ALE algorithm. This method can be used to obtain the contact forces and fluid-structure interaction forces of ultra-large UUVs during the surfacing and icebreaking process, more realistically reflecting the surfacing conditions in polar or ice-covered waters. It includes:

[0062] S1: Establish the geometric model and mesh generation;

[0063] A three-dimensional geometric model of the ultra-large UUV and the ice layer is constructed. The three-dimensional geometric model of the ultra-large UUV and the ice layer is meshed to obtain the floating icebreaking calculation model. The floating icebreaking calculation model is imported into explicit dynamic / explicit fluid-structure interaction analysis software. Lagrange solid element algorithm is defined for ultra-large UUV, arbitrary Lagrange-Eulerian ALE fluid element algorithm is defined for water and air domains, and ice constitutive model or equivalent solid model is selected for ice layer. At the same time, the state equations and physical parameters of air and water domains are set.

[0064] S11: Based on relevant materials and the proportions of a typical ultra-large UUV, create a geometric model of the ultra-large UUV in 3D modeling software that is similar in scale, shape, and structural layout. To adapt to the surfacing and icebreaking scenario, create a continuous ice layer with a given thickness, length, and width above the ultra-large UUV. This ice layer can be considered as a horizontally distributed monolithic ice layer. The planar dimensions of the ice layer are set as a multiple of the length of the ultra-large UUV to avoid boundary effects.

[0065] S12: Mesh generation is performed on the ice layer geometry model and the ultra-large UUV geometry model. The ultra-large UUV model uses a mapping meshing method, first decomposing it into several regular mapping volumes. Appropriate mesh refinement is applied in the shell region, the bow curvature variation region, and the stern region to improve the accuracy of contact and local stress calculations, ultimately generating a hexahedral solid element mesh. The ice layer, being a regular geometry, can be directly meshed using a structured hexahedral mesh. Simultaneously, local mesh refinement is performed along the ultra-large UUV's ascent path to ensure the calculation accuracy at the ultra-large UUV-ice layer contact interface during ascent. After mesh generation, the mesh quality is checked, and the mesh generation results are as follows: Figure 2 As shown.

[0066] S13: Define the Lagrangian solid element algorithm for the mesh elements of the ultra-large UUV and the ice layer. Considering that the ultra-large UUV will be subjected to large impact loads and structural responses during the buoyancy and icebreaking process, the shell of the ultra-large UUV can be described using the *MATRIGID material model; the ice layer is described using an isotropic elastic-brittle or elastic-plastic failure constitutive model. By setting the failure strain and cutoff pressure, the local fracture or damage of the ice layer under compression and bending conditions can be simulated, avoiding the use of expressions such as "ice fragment deletion" and "fragment scattering". Material parameters and state equations are set for the air domain and water domain respectively, and a multi-material group for the air domain and water domain is established to create conditions for subsequent adaptive mesh control of the computational domain using the ALE algorithm.

[0067] S2: Generate the fluid domain and set the boundary set;

[0068] Structured meshes were established for the air and water domains, with local mesh refinement applied along the ascent path of the ultra-large UUV and near the ice layer above it to improve the accuracy of fluid-structure interface capture and better reflect the multi-field coupling characteristics of the entire process of the ultra-large UUV's ascent, ice contact, and ice breaking. Corresponding node sets and element sets were created and necessary constraints were applied, including the node set at the bottom of the water domain, the segment sets around the air and water domains, and the segment set between the ultra-large UUV and the ice layer. Simultaneously, solid sets were created within the water and air domains and at the surrounding boundaries to ensure the correctness of topological continuity.

[0069] The air and water domains are meshed using the Arbitrary-Lagrangian-Eulerian (ALE) algorithm. The ALE fluid-structure interaction algorithm is commonly used for the coupling effects between multiple materials. It combines the advantages of the Lagrangian and Eulerian methods, allowing the handling of fluid and solid motion within the same framework. This enables the mesh to be adjusted as needed, avoiding numerical problems caused by large deformations. In the numerical calculation method of this invention, the water and air domains are described using ALE. Their governing equations are essentially derived from the fundamental laws of mass, momentum, and energy conservation in continuum mechanics and fluid mechanics, belonging to the original governing equations within the scope of classical physics. In the Eulerian coordinate system, these are written as the continuity equation, the Navier-Stoke equation, and the energy equation, respectively. Based on this, by explicitly introducing the mesh velocity Vg into the control volume, the original Eulerian form is generalized to the ALE form, allowing the computational mesh to move independently relative to the materials, thereby reducing mesh distortion caused by large deformations. The ALE form of the mass, momentum, and energy conservation equations can be written as follows:

[0070] (1)

[0071] (2)

[0072] (3)

[0073] Since the actual icebreaking operation of ultra-large UUVs can be considered as being in an approximately infinite water area, to avoid fluid leakage and wave reflection, six-degree-of-freedom constraints are applied to the node set at the bottom of the computational domain, and non-reflective or transmissive boundary conditions are applied to the segment sets around the air domain and the water area. Segment sets are established separately on the ultra-large UUV and the ice layer to make the subsequent hydrostatic pressure initialization more stable and facilitate subsequent fluid-structure interaction calculations.

[0074] S3: Fluid-structure interaction and boundary condition settings;

[0075] The magnitude and direction of the buoyancy velocity of the ultra-large UUV are set, and the fluid-structure interaction relationship and boundary conditions between the water area, air domain, ultra-large UUV and ice layer are defined in the solver. This ensures that the calculation is in hydrostatic equilibrium at the initial moment, providing an initial field for the multiphase dynamic simulation of buoyancy contact with ice and ice breaking. Thus, numerical calculations can be carried out directly after the mesh generation and boundary constraints are completed.

[0076] S31: Apply an initial buoyancy velocity or velocity-time history along the positive Y-axis to the ultra-large UUV.

[0077] S32: Bind the internal solid set and the surrounding boundary solid set created in S2 to the aforementioned boundary vertices, ensuring that the hydrostatic pressure field is consistently applied within the fluid domain and on the bottom and sidewall boundaries, guaranteeing that the water body is in approximately hydrostatic equilibrium at the start of the calculation. Using the previously created segment sets of the ultra-large UUV and ice layer, embed the ultra-large UUV and the entire ice layer into the aforementioned flow field, achieving a continuous representation of the multiphase interface between the air domain, water area, ultra-large UUV, and ice layer.

[0078] S4: Solve for control and ice load data output;

[0079] After completing the fluid-structure interaction and boundary condition settings, the ALE fluid-structure interaction algorithm suitable for the floating and icebreaking conditions of ultra-large UUVs is selected. At the same time, the contact algorithm, hourglass control parameters, simulation termination time, and time step adaptive control conditions are set. The output contact force and fluid-structure interaction force files are defined to facilitate the extraction of the curves of force and ice load change of ultra-large UUVs over time in post-processing.

[0080] S41: Define the coupling relationships between the ultra-large UUV mesh and the fluid domain mesh, and between the ice layer mesh and the fluid domain mesh using the *CONSTRAINED_LAGRANGE_IN_SOLID keyword. The preferred contact algorithm is the penalty function contact algorithm, defining the two surfaces that may come into contact as the master surface and slave surface, respectively. Specifically, the contact between ice layer and water area, and between ultra-large UUV and water area, is set to *AUTOMATIC_NODES_TO_SURFACE under the automatic contact function in the CONTACT keyword of LS-DYNA. To more closely approximate the realistic ice-breaking effect, the ultra-large UUV-ice contact is set to erosion contact, i.e., *ERODING_SURFACE_TO_SURFACE. Considering the erosion effect between the two, when the ultra-large UUV floats and contacts the entire ice layer or the ice layer locally deflects and tends to contact, a normal equivalent "spring" is generated between the two surfaces to prevent penetration. The interface contact force is calculated, and its dimension is N, which can be obtained by F = kδ. Where k is the contact surface stiffness, in N / m; δ is the penetration amount, in m; k can be calculated based on the material's bulk modulus, contact area, and penalty factor. Based on the above contact algorithm, the contact between ultra-large UUVs and ice layers and the forced deformation of local areas of the ice layer under high pressure can be described simultaneously without discretizing the ice layer into a large number of ice fragments.

[0081] S42: Appropriate hourglass control parameters are set for the water, air, and ice regions respectively. Combined with time-step adaptive control, numerical stability is achieved under large deformation and strong contact conditions. Data files such as output contact force, fluid-structure interaction force, and stress and displacement of key sections are defined. At the same time, keywords for generating animation frames are set to facilitate visualization and analysis of the entire process of buoyancy, ice contact, and breakage.

[0082] Studies of ultra-large UUVs at the same ice thickness and different ascent velocities reveal that the peak contact force experienced by ultra-large UUVs continuously increases, such as... Figure 3 The figure shows the curve of contact force versus time after the ultra-large UUV floats and comes into contact with the whole ice layer; Figure 4 A top-down view of the ice layer damage after a super-large UUV floats and breaks through the ice; Figure 5 An equivalent stress cloud map of an ultra-large UUV in contact with a continuous ice layer; Figure 6 The pitch angle varies with time during the icebreaking process of the ultra-large UUV under various working conditions; Figure 7 A cloud map showing the attitude changes of an ultra-large UUV during its ascent and icebreaking process.

[0083] This invention, based on the Arbitrary Lagrange-Euler (ALE) algorithm and fluid-structure interaction theory, addresses the unique operational conditions of ultra-large UUVs surfacing and breaking ice beneath polar ice caps. It constructs a multiphase fluid-structure integrated numerical model that simultaneously incorporates the water domain, air domain, continuous whole ice layer, and the ultra-large UUV itself. Compared to existing numerical methods that neglect fluid interactions or simply treat the ice cap as a rigid boundary, this invention can simultaneously characterize the spatiotemporal distribution of hydrodynamic loads and ice layer reactions during surfacing, more realistically reflecting the actual physical process of ultra-large UUV surfacing and icebreaking. By employing a whole ice material model with failure criteria for the ice layer, the evolution of fracture, crushing, or damage in localized areas of the ice layer can be described without pre-discretizing the ice cap into numerous independent ice fragment units, thereby reducing modeling complexity and improving computational stability. Given that current numerical simulations of ultra-large UUV surfacing and icebreaking often employ the ALE method or Smoothed Particle Hydrodynamics (SPH) method, this invention effectively improves simulation efficiency and load prediction accuracy while maintaining the robustness of the ALE method.

Claims

1. A method for calculating the ice load of a super-large vehicle in a layer 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 the ice layer is constructed, and the three-dimensional geometric model of the ultra-large UUV and the ice layer is meshed to obtain the floating and icebreaking calculation model. The floating icebreaking calculation model is imported into explicit dynamic / explicit fluid-structure interaction analysis software. Lagrange solid element algorithm is defined for ultra-large UUV, arbitrary Lagrange-Euler ALE fluid element algorithm is defined for water and air domains, ice constitutive model or equivalent solid model is selected for ice layer, and state equations and physical parameters of air and water domains are set at the same time. Step 2: Generate the fluid domain and set the boundary set; The grid is locally refined along the expected ascent trajectory of the ultra-large UUV and in the areas where the ultra-large UUV may come into contact with the ice layer; Multiple feature regions are defined and constrained based on the grid topology, including the node set at the bottom of the water area, the unit surface segment set in the air domain and the periphery of the water area, and the contact surface segment set corresponding to the outer surface of the ultra-large UUV and the bottom surface of the ice layer. Define corresponding solid sets within and around the water and air domains to describe the continuous transition between fluid volume and boundaries; Step 3: Setting fluid-structure interaction and boundary conditions; In explicit dynamic / explicit fluid-structure interaction analysis software, the coupling relationship between the fluid domain and the solid domain is established; the fluid domain includes the air domain and the water domain; the solid domain includes ultra-large UUVs and ice layers. Select a coupling algorithm for the interaction between LE fluid elements and Lagrange solid elements; Appropriate velocity constraints or non-reflective boundary conditions are applied to the bottom, side walls, and outer boundary of the air domain. Initial buoyancy conditions are applied to the ultra-large UUV. Gravity and constraint conditions are applied to the ice layer to ensure that all materials are at rest or in a predetermined equilibrium state at the initial moment of calculation. Based on the ascent path and expected contact area of ​​the ultra-large UUV, establish the contact constraints between the ice layer and the ultra-large UUV, and set the contact stiffness and contact damping parameters. Step 4: Solve for control and ice load data output; Set the simulation termination time and time step control conditions, and enable the ALE mesh smoothing and remapping function to keep the fluid mesh normal during the process of the ultra-large UUV floating, colliding and breaking ice layers. The solution process is initiated, and time history data of the pressure field on the outer surface of the ultra-large UUV, the contact reaction force between the ice layer and the hull of the ultra-large UUV, and the fluid-structure coupling force are output according to the pre-set output control card. At the same time, animation frame files for visualization are generated. By integrating the normal pressure and tangential shear stress of the surface unit of the ultra-large UUV hull in different regions and subtracting the hydrodynamic background component under the corresponding working conditions, the ice load time history and its peak characteristic quantity of the entire process of the ultra-large UUV floating and breaking ice are obtained.

2. The method according to claim 1, wherein, Step 1 specifically involves: Step 1-1: Based on the external proportions of the super-large UUV, establish the geometric model of the super-large UUV in 3D modeling software; establish a continuous ice layer with a given thickness, length and width above the super-large UUV, and regard the ice layer as a horizontally distributed whole ice layer; set the planar dimensions of the ice layer as a multiple of the length of the super-large UUV. Steps 1-2: Mesh the ice layer geometric model and the ultra-large UUV geometric model. The ultra-large UUV model is meshed using a mapping meshing method, first decomposing it into several regular mapping volumes, then refining the mesh in the shell region, the bow curvature variation region, and the stern region, ultimately generating a hexahedral solid element mesh. The ice layer is a regular geometry, so a structured hexahedral mesh is directly used. At the same time, local mesh refinement is performed along the upward path of the ultra-large UUV. After the mesh is generated, check the quality of the mesh. Steps 1-3: Define the Lagrangian solid element algorithm for the mesh elements of the ultra-large UUV and the ice layer; describe the shell of the ultra-large UUV using the *MAT RIGID material model; describe the ice layer using an isotropic elastic-brittle or elastic-plastic failure constitutive model, and simulate the local fracture or damage of the ice layer under compression and bending by setting the failure strain and cutoff pressure; set the material parameters and equations of state for the air domain and the water domain respectively, and establish a multi-material group for the air domain and the water domain.

3. The method according to claim 2, wherein, Step 2 specifically involves: The water and air domains are described using arbitrary Lagrange-Euler ALE, and the ALE form equations for mass conservation, momentum conservation, and energy conservation are written as follows: (1) (2) (3) where p is the fluid density, dimension kg / m 3 ; V is the fluid velocity, dimension m / s; V g is the mesh velocity, dimension m / s; p is the pressure, dimension N / m 2 ; σ is the stress tensor, dimension N / m 2 ; f is the volume force per unit mass, dimension m / s 2 ; E is the total energy, with dimensions J / m³. 3 q is heat flux, with dimensions W / m. 3 ; Indicates time, Represents the divergence operator; This represents the tensor product, used to perform operations on two vectors. Six-degree-of-freedom constraints are applied to the node set at the bottom of the computational domain, and non-reflective or transmissive boundary conditions are applied to the segment sets surrounding the air and water domains.

4. The method according to claim 3, wherein, Step 3 specifically involves: Step 3-1: Apply an initial buoyancy velocity or velocity-time history along the positive Y-axis to the ultra-large UUV; Step 3-2: Bind the solid set of solid elements created in Step 2 to the boundary vertices so that the hydrostatic pressure field is consistently applied inside the fluid domain and on the bottom and sidewall boundaries, ensuring that the water body is in an approximately hydrostatic equilibrium state at the start of the calculation. By embedding ultra-large UUVs and whole ice layers into the flow field, a continuous representation of the multiphase interface between the air domain, water domain, ultra-large UUV, and ice layer is achieved.

5. The method according to claim 4, wherein, Step 4 specifically involves: Step 4-1: Define the coupling relationship between the ultra-large UUV mesh and the fluid domain mesh, and between the ice layer mesh and the fluid domain mesh using the *CONSTRAINED_LAGRANGE_IN_SOLID keyword; The contact between ice and water, and between ultra-large UUVs and water, is set to *AUTOMATIC_NODES_TO_SURFACE under the CONTACT keyword in LS-DYNA; the contact between ultra-large UUVs and ice is set to erosion contact, i.e., *ERODING_SURFACE_TO_SURFACE. The contact force is obtained by F= kδ, with the dimension N, where k is the contact surface stiffness, with the dimension N / m; δ is the penetration amount, with the dimension m. Step 4-2: Set hourglass control parameters for water, air, and ice respectively, and combine them with time step adaptive control; define output contact force, fluid-structure interaction force, and stress and displacement data files of key sections, and set keywords for generating animation frames to facilitate visualization analysis of the entire process of floating, ice contact, and breaking.

6. A super large vehicle ice load calculation system for floating ice breaking using the calculation method according to claim 1, characterized in that, include: Load acquisition and identification module: After the numerical calculation is completed, the pressure, shear stress and contact state information of each time step on the outer surface of the ultra-large UUV hull are automatically read from the explicit solution results. The surface of the ultra-large UUV hull is divided into regions, the unit regions affected by ice and the regions that only bear hydrodynamic effects are identified, and the load data is filtered and separated, retaining the effective loads related to the ice layer. Mesh generation module: Used to create a three-dimensional solid model of the ultra-large UUV and a whole ice layer model, and to discretize the ultra-large UUV three-dimensional solid model and the whole ice layer model in the computer preprocessing environment; the generated mesh model and related properties are imported into the explicit dynamic solver to provide a discretization basis for subsequent ALE solution; The ALE Solver and Fluid-Structure Coupling Module is used to define material parameters and equations of state for the water and air domains in the solver, construct the ALE fluid computation domain, set the fluid-structure interaction relationship and contact calculation scheme between the fluid domain and the ultra-large UUV and ice layer, configure boundary conditions and numerical control parameters for time step and termination time; and simulate the icebreaking process of the ultra-large UUV under given working conditions to obtain the instantaneous pressure field, shear stress field and fluid-structure interaction reaction time history of the outer surface of the ultra-large UUV. Feature index generation module: Automatically post-processes load data obtained under different times, different ascent speeds and different ice thicknesses, integrates, statistically analyzes and merges ice loads on the surface of ultra-large UUVs, generates ice load time history curves, peak load summary tables, load envelope curves, and load files that can be directly called for structural finite element analysis, and outputs corresponding charts and data reports. The modules exchange information sequentially through data files or interfaces, forming an overall automated calculation process from input of working condition parameters, geometric and mesh modeling, ALE simulation solution, automatic identification and extraction of ice loads, to output of feature quantities.

7. An electronic device, comprising: 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 by 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, characterised 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.

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