LBM large-deformation fluid-solid interface stabilization method and system based on energy flux adjustment

Abstract

The invention provides an LBM large-deformation fluid-solid interface stabilization method and system based on energy flux regulation, and belongs to the technical field of computational fluid mechanics and solid mechanics coupling numerical simulation. Identifying a fluid-solid boundary area, and constructing a buffer layer area; solving fluid in a buffer layer area, and embedding an energy flux regulation mechanism; applying a load to the structure through fluid, and calculating a structure response; fluid is fed back, and the dynamic boundary is updated; and iterating repeatedly, and stopping and outputting after a set termination condition is reached. Active regulation and control of the fluid-structure interface energy exchange process are achieved, the numerical stability and physical precision of fluid-structure interaction simulation under the large deformation condition are remarkably improved, and the method has the advantages of being simple in structure, high in expandability and low in calculation overhead; the method is suitable for complex coupling scenes such as flexible structural body propulsion, airfoil pitching motion and high Reynolds number structural response analysis, and has wide engineering application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of coupled numerical simulation of computational fluid dynamics and solid mechanics, and specifically relates to a LBM large deformation fluid-solid interface stabilization method and system based on energy flux regulation, and more particularly to a strong coupling numerical simulation technology based on the lattice Boltzmann method (LBM), which improves the stability of the large deformation fluid-solid interface through energy flux regulation. Background Art

[0002] With the development of cutting-edge engineering applications such as biomimetic propulsion, flexible aircraft, and aerodynamic load analysis of membrane structures, fluid-structure interaction (FSI) numerical simulation has become a key research tool. Among them, the lattice Boltzmann method (LBM) has gradually become an important development direction in the field of CFD due to its high degree of parallelism and good adaptability to complex boundaries.

[0003] However, when simulating the coupling behavior between large deformation flexible structures and fluids, the traditional LBM method has the following problems:

[0004] Instability of the fluid-solid interface: Due to high-speed motion or severe deformation of the structural boundary, the fluid variables at the interface show obvious oscillation or numerical non-conservation;

[0005] Density or momentum drift: LBM is prone to unrealistic numerical dissipation or accumulation near the interface, leading to error diffusion;

[0006] Local non-physical behavior: For example, spurious solutions such as negative density and velocity reversal, which are especially noticeable when using nested grids or moving boundary algorithms.

[0007] Existing improvements include: improving boundary treatment (such as the discontinuous boundary method and the immersed boundary method); using relaxation factors to control stability; and introducing damping terms or interface lubrication models. However, most of these methods suffer from computational complexity, difficulty in strong coupling with structural modules, and excessive dissipation, making it difficult to balance physical accuracy and numerical stability.

[0008] The patent document "High-performance large-scale fluid-solid coupling fluid simulation method based on statistical dynamics" (CN111695309A) discloses that by optimizing high-order parameters on the NO-CMLBM model and combining immersed boundary processing, high precision and stability are achieved in complex turbulence and fluid-solid coupling simulations. This solves the problems of large numerical dissipation and dispersion errors in the prior art, and achieves efficient fluid-solid coupling simulation, which is suitable for multi-node and multi-GPU environments. However, as a high-order parameter optimization model, this method requires the construction of a mapping and the performance of mapping-recovery operations in each sub-step. The code implementation is complex and debugging is difficult. The algorithm has higher requirements for parallel performance, and the parameters set based on experience are difficult to correspond to the actual working conditions. At the same time, stability and accuracy depend on the fitting quality of the boundaries and high-order interpolation, and have low applicability.

[0009] The patent document "A Separated Coupling Numerical Simulation Method and Apparatus for Multi-Physical Field Applications" (CN115526091A) discloses the use of the lattice Boltzmann method and the finite volume method in combination with the open source coupling library preCICE to achieve real-time coupling of multiple physical fields in fluid-solid coupling scenarios, solving the problems of low efficiency and poor scalability in existing technologies, improving simulation efficiency and accuracy, and making it suitable for high-performance computing. However, for flexible bodies, structures with large displacements or topological changes (such as bionic fins, soft robotic arms, etc.), it will encounter problems such as iterative oscillation and loose coupling non-convergence. The main goal is the collaborative efficiency of multiple physical fields and the scalability of parallel computing, and the path mechanism and scope of application are different.

[0010] Therefore, there is an urgent need for a simple, stable, and highly compatible interface control strategy, especially suitable for lattice Boltzmann method fluid-solid coupling simulation under extreme conditions such as high Reynolds number, strong nonlinearity, and large deformation structural motion. Summary of the Invention

[0011] In view of the defects in the prior art, the purpose of the present invention is to provide a LBM large deformation fluid-solid interface stabilization method and system based on energy flux regulation.

[0012] According to the present invention, a LBM large deformation fluid-solid interface stabilization method based on energy flux regulation includes:

[0013] Step 1: Initialize the model and divide the grid;

[0014] Step 2: Identify the fluid-solid interface area of ​​the model and construct the buffer layer area;

[0015] Step 3: Solve the fluid in the buffer layer region and embed the energy flux regulation mechanism;

[0016] Step 4: Apply load to the structure through the fluid and calculate the structural response;

[0017] Step 5: Feedback the structural response to the fluid and update the moving boundary;

[0018] Repeat steps 3 to 5 and stop when the set termination condition is reached.

[0019] Preferably, the initialization model includes constructing a calculation area, initializing the fluid distribution function, structural displacement, velocity and material model parameters, and setting the initial density and velocity field.

[0020] The calculation domain includes a fluid domain and a solid structure domain.

[0021] The grid division is to construct a grid in the fluid domain using the standard lattice Boltzmann method, and to establish a discrete model in the structural domain using the finite element method or other structural mechanics methods.

[0022] In step 4, the momentum exchange method or the pressure integration method is used to extract the fluid force acting on the boundary of the structural domain from the fluid domain, and the force is mapped to the corresponding nodes or surface elements on the solid structural domain. The deformation of the solid is calculated based on the force on the solid calculated by the fluid, and the structural deformation and velocity state are updated to obtain the structural position and boundary velocity information of the updated velocity field.

[0023] In step five, the updated velocity field is used to set the dynamic boundary conditions of the fluid.

[0024] The moving boundary condition is set by fitting velocity interpolation, immersed boundary method or indirect boundary method.

[0025] The termination condition is to reach the set simulation termination time or the structural stable state, and output the fluid-solid interface flow field, structural deformation and coupling force data.

[0026] Preferably, the embedded energy flux regulation mechanism is to update the fluid nodes in the buffer layer region using the LBM evolution equation in BGK format:

[0027]

[0028] Add adjustments to correct the collision process:

[0029]

[0030] Among them, f i represents the distribution function in the i-th velocity direction;

[0031] represents the local equilibrium distribution function;

[0032] is the distribution function in the i-th velocity direction after the collision;

[0033] x represents the grid spacing;

[0034] t represents the time step;

[0035] represents the energy regulation factor;

[0036] β represents the regulatory factor;

[0037] represents the discrete velocity direction;

[0038] τ represents the relaxation time;

[0039] Δ i Indicates additional adjustment items.

[0040] Preferably, in step 2, the fluid grid points in the fluid-solid interface region are identified according to the current position of the structure, and the buffer layer region Ω is set. c , record the minimum distance between the grid point and the structure boundary in each buffer layer area

[0041] The buffer layer region is located outside the boundary of the solid structure and is updated in the Euler coordinate system as the solid structure moves. The thickness is δ c .

[0042] For the fluid node in the buffer layer area, the energy adjustment factor is defined according to the distance from the node to the structure boundary

[0043]

[0044] in, and α both represent adjustment coefficients;

[0045] x represents the grid spacing;

[0046] t represents the time step;

[0047] Indicates the minimum distance from a fluid node to a solid boundary.

[0048] The energy adjustment factor is in the form of a hyperbolic tangent, piecewise linear or polynomial function.

[0049] Preferably, the iteration further comprises:

[0050] Step 6: Embed a dynamic feedback regulation mechanism in the model for adaptive control and monitor the density disturbance σ in the fluid-solid interface area in real time. ρ , boundary node velocity gradient or local kinetic energy change rate Dynamically adjust the adjustment coefficient α or the buffer layer thickness δ c .

[0051] The density disturbance in the buffer layer is counted at every set time step:

[0052]

[0053] Among them, σ ρ (t) represents the density perturbation in the buffer layer region at time step t;

[0054] Ω c represents the buffer layer area;

[0055] x represents the grid spacing;

[0056] t represents the time step;

[0057] ρ represents density.

[0058] When the density disturbance exceeds the preset threshold σ th When σ ρ >σ th , increase the adjustment coefficient or α;

[0059] When the density perturbation is in a stable state for a long time, the decay

[0060] When the velocity gradient of the boundary node reaches the set threshold, the adjustment coefficient α is increased and the buffer layer thickness δ is expanded. c ;

[0061] When the local kinetic energy change rate reaches the set rate, immediately increase α and expand the buffer layer thickness δ c

[0062] When the structural acceleration exceeds the set threshold, the thickness of the buffer layer area is expanded;

[0063] When the convergence speed is too fast, reduce the adjustment intensity.

[0064] The adjustment strength includes an adjustment coefficient Adjustment coefficient α, buffer zone thickness δ c and\or the strength of the additional adjustment items.

[0065] According to the present invention, a LBM large deformation fluid-solid interface stabilization system based on energy flux regulation is provided, comprising:

[0066] Module 1: Initialize the model and divide the grid;

[0067] Module 2: Identify the fluid-solid interface area of ​​the model and construct the buffer layer area;

[0068] Module 3: Solve the fluid in the buffer layer region and embed the energy flux regulation mechanism;

[0069] Module 4: Apply loads to structures through fluids and calculate structural responses;

[0070] Module 5: Feedback the structural response to the fluid and update the moving boundary;

[0071] Repeat the iteration to trigger module three to module five, and stop after the set termination condition is reached.

[0072] Preferably, the initialization model includes constructing a calculation area, initializing the fluid distribution function, structural displacement, velocity and material model parameters, and setting the initial density and velocity field.

[0073] The calculation domain includes a fluid domain and a solid structure domain.

[0074] The grid division is to construct a grid in the fluid domain using the standard lattice Boltzmann method, and to establish a discrete model in the structural domain using the finite element method or other structural mechanics methods.

[0075] In the fourth module, the momentum exchange method or the pressure integration method is used to extract the fluid force acting on the boundary of the structural domain from the fluid domain, and the force is mapped to the corresponding nodes or surface elements on the solid structural domain. The deformation of the solid is calculated based on the force on the solid calculated by the fluid, and the structural deformation and velocity state are updated to obtain the structural position and boundary velocity information of the updated velocity field.

[0076] In the module five, the updated velocity field is used to set the dynamic boundary conditions of the fluid.

[0077] The moving boundary condition is set by fitting velocity interpolation, immersed boundary method or indirect boundary method.

[0078] The termination condition is to reach the set simulation termination time or the structural stable state, and output the fluid-solid interface flow field, structural deformation and coupling force data.

[0079] Preferably, the embedded energy flux regulation mechanism is to update the fluid nodes in the buffer layer region using the LBM evolution equation in BGK format:

[0080]

[0081] Add adjustments to correct the collision process:

[0082]

[0083] Among them, f i represents the distribution function in the i-th velocity direction;

[0084] represents the local equilibrium distribution function;

[0085] is the distribution function in the i-th velocity direction after the collision;

[0086] x represents the grid spacing;

[0087] t represents the time step;

[0088] represents the energy regulation factor;

[0089] β represents the regulatory factor;

[0090] represents the discrete velocity direction;

[0091] τ represents the relaxation time;

[0092] Δ i Indicates additional adjustment items.

[0093] Preferably, in the second module, the fluid grid points in the fluid-solid interface region are identified according to the current position of the structure, and the buffer layer region Ω is set. c , record the minimum distance between the grid point and the structure boundary in each buffer layer area

[0094] The buffer layer region is located outside the boundary of the solid structure and is updated in the Euler coordinate system as the solid structure moves. The thickness is δ c .

[0095] For the fluid node in the buffer layer area, the energy adjustment factor is defined according to the distance from the node to the structure boundary

[0096]

[0097] in, and α both represent adjustment coefficients;

[0098] x represents the grid spacing;

[0099] t represents the time step;

[0100] Indicates the minimum distance from a fluid node to a solid boundary.

[0101] The energy adjustment factor is in the form of a hyperbolic tangent, piecewise linear or polynomial function.

[0102] Preferably, the iteration further comprises:

[0103] Module 6: Adaptive control based on dynamic feedback regulation mechanism, real-time monitoring of density disturbance σ in the fluid-solid interface area ρ , boundary node velocity gradient or local kinetic energy change rate Dynamically adjust the adjustment coefficient α or the buffer layer thickness δ c .

[0104] The density disturbance in the buffer layer is counted at every set time step:

[0105]

[0106] Among them, σ ρ (t) represents the density perturbation in the buffer layer region at time step t;

[0107] Ω c represents the buffer layer area;

[0108] x represents the grid spacing;

[0109] t represents the time step;

[0110] ρ represents density.

[0111] When the density disturbance exceeds the preset threshold σ th When σ ρ >σ th , increase the adjustment coefficient or α;

[0112] When the density perturbation is in a stable state for a long time, the decay

[0113] When the velocity gradient of the boundary node reaches the set threshold, the adjustment coefficient α is increased and the buffer layer thickness δ is expanded. c ;

[0114] When the local kinetic energy change rate reaches the set rate, immediately increase α and expand the buffer layer thickness δ c

[0115] When the structural acceleration exceeds the set threshold, the thickness of the buffer layer area is expanded;

[0116] When the convergence speed is too fast, reduce the adjustment intensity.

[0117] The adjustment strength includes an adjustment coefficient Adjustment coefficient α, buffer zone thickness δ c and\or the strength of the additional adjustment items.

[0118] Compared with the prior art, the present invention has the following beneficial effects:

[0119] 1. The adjustment method proposed in the present invention has good locality and can be directly embedded in the existing LBM framework to realize modular calling without changing the original structural modeling method. It can be used with any structural motion model (rigid or flexible), is suitable for a variety of fluid-solid coupling boundary conditions, and has minimal impact on the original LBM core evolution logic.

[0120] 2. The present invention adjusts the regulation intensity or buffer layer thickness by real-time monitoring of physical quantities (such as density fluctuations, structural acceleration, etc.). It has a clear physical meaning and dynamic response mechanism, does not require manual adjustment, and the parameters are easy to interpret and control. It effectively suppresses non-physical velocity fluctuations and negative density that appear in the fluid under high-speed movement or severe deformation of the structure.

[0121] 3. The present invention does not affect the efficiency of parallel computing through local node adjustment operations, has low computational overhead, is suitable for large-scale parallel computing and large-scale supercomputing environment deployment, and does not require precise fitting of structural boundaries, only rough regional judgment is required, which can significantly improve the accuracy and stability of fluid-solid coupling simulation in strong coupling and large deformation scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0123] Figure 1 Schematic diagram of the flow chart of the LBM large deformation fluid-solid interface stabilization method based on energy flux regulation. DETAILED DESCRIPTION

[0124] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0125] In response to the existing LBM-FSI algorithm's propensity to exhibit density perturbations, momentum loss, and numerical oscillations under conditions of highly nonlinear structural responses or large-scale interface motion, the present invention provides an LBM large-deformation fluid-solid interface stabilization method based on energy flux regulation. This method addresses the interface instability, numerical oscillation, and unphysical behavior that can occur with traditional LBM when simulating large-deformation fluid-solid interaction problems, thereby enhancing the robustness and physical consistency of the simulation. In particular, under extreme conditions such as high Reynolds numbers, strong nonlinearities, and large-deformation structural motion, the method exhibits low computational overhead, is suitable for large-scale parallel computing, and can significantly improve the accuracy and stability of large-deformation fluid-solid interaction simulations.

[0126] By introducing an energy buffer layer near the fluid-solid interface and spatially regulating the energy flux in the region during the propagation of fluid particles in the region, the problem of uneven energy input / output caused by violent interface motion is suppressed. By constructing a spatially distributed regulation function, the regulation factor is used to dynamically adjust the velocity and kinetic energy in the fluid-solid interface region to ensure local conservation and global stability. It has good locality and can be embedded in the existing LBM framework. It is suitable for a variety of fluid-solid coupling boundary conditions and has minimal impact on the original LBM core evolution logic. Specifically, Figure 1 For example, the following steps are included:

[0127] Step 1: Model initialization and mesh division.

[0128] Specifically, the calculation area is constructed, including the fluid domain and the solid structure domain; the standard lattice Boltzmann method (LBM) is used to construct the grid in the fluid domain; and the finite element method (FEM) or other structural mechanics methods are used to establish a discrete model in the structure domain.

[0129] Initialize the fluid distribution function and set the initial density and velocity field; initialize the structural displacement, velocity and material model parameters.

[0130] Step 2: Identification of the fluid-solid interface area and construction of the buffer layer area.

[0131] Specifically, according to the current position of the structure, the fluid grid point at the fluid-solid interface is identified; with the structure boundary as the center, a buffer layer area Ω is set around it. c , the preferred width is 2 to 3 grid points.

[0132] Record each buffer zone, that is, the minimum distance between the grid point and the structure boundary in the buffer zone This is used for subsequent calculation of adjustment strength.

[0133] The energy buffer layer is located outside the boundary of the solid structure and is updated in the Euler coordinate system as the solid structure moves. Its thickness is δ c For the fluid nodes in the buffer layer, the minimum normal distance from the node to the structure boundary is Define an energy adjustment factor Used to control the energy input intensity during the distribution function update process of this point.

[0134] Step 3: Fluid solution and energy flux regulation mechanism embedding.

[0135] The energy flux regulation mechanism adopted does not rely on high-order expansion of the lattice structure and can be directly embedded in traditional mainstream lattice systems such as D2Q9 and D3Q19. It only needs to add a regulation term controlled by kinetic energy density to the collision term, without the need for additional matrix transformation or orthogonal basis expansion. It is suitable for integration and deployment in a wide range of engineering environments and general LBM platforms (such as Palabos and OpenLB), and has strong versatility. Specifically, the energy regulation factor The distance from the grid point to the structure boundary is set as:

[0136]

[0137] in, and α are adjustment coefficients, which control the adjustment intensity and attenuation speed. x represents the grid spacing. Indicates the minimum distance from the fluid node to the solid boundary, in grid points.

[0138] In further preferred embodiments, the energy adjustment factor can be configured as a hyperbolic tangent, piecewise linear, or polynomial function, depending on the operating conditions, to accommodate varying response speeds and adjustment capabilities. This factor is activated only near areas of intense kinetic energy disturbance, softening the velocity gradient at the fluid-solid interface. Furthermore, it has a clear physical meaning and dynamic response mechanism, eliminating the need for manual adjustment and making its parameters easy to interpret and control.

[0139] Perform the standard LBM deduction steps for the fluid region:

[0140]

[0141] Here, t represents the time step.

[0142] The update process of the fluid nodes adopts the LBM evolution equation in the BGK (Bhatnagar-Gross-Krook) format. For the grid points in the buffer area, an adjustment term is added to the evolution formula to correct the collision process, forming a corrected format:

[0143]

[0144] Among them, f i is the distribution function in the i-th velocity direction, is the local equilibrium distribution function, and β is the adjustment factor. is the discrete velocity direction; τ is the relaxation time; Δ i It is an additional adjustment item with kinetic energy dissipation characteristics; is the distribution function in the i-th velocity direction after the collision.

[0145] The adjustment factor β is a constant or a local tensor used to control the kinetic energy dissipation intensity. Under this structure, the flux term is adjusted Δ i This is equivalent to introducing a type of "physically consistent local viscous damping" in the buffer layer to suppress excessive changes in local velocity or penetration of fluid particles.

[0146] In areas near the interface, dissipation is automatically adjusted based on changes in local kinetic energy flux. This eliminates the need for precise fitting of structural boundaries and only requires rough regional determination, stabilizing fluid disturbances induced by large deformation structures. By introducing an energy buffer layer near the fluid-solid interface and spatially regulating the energy flux in this area, the uneven energy input / output caused by violent interface motion is suppressed, thereby improving the stability and accuracy of large-deformation fluid-solid coupling simulations. When dealing with violently moving boundaries such as membrane structures and flexible fins, the numerical stability is far superior to high-order boundary processing methods that rely on precise fitting, and is more suitable for fluid-solid interfaces with large-scale deformations or topological changes (such as folding, collisions, free surface fluctuations, etc.).

[0147] By regulating the flux of energy exchange at the fluid-structure interface, this approach significantly reduces density fluctuations at the fluid-solid interface under large deformations and improves the overall stability of the LBM solver. Because it relies entirely on local node regulation, it minimally impacts the existing LBM core evolutionary logic and can be directly embedded into existing code systems for modular implementation.

[0148] Step 4: The fluid applies load to the structure and the structural response is calculated.

[0149] Specifically, the momentum exchange method or pressure integration method is used to extract the fluid force acting on the structural boundary from the fluid side; the force is mapped to the structural model, that is, the corresponding nodes or surface elements on the solid structure domain; the structural solution is performed, and the structural deformation and velocity state are updated; and a new round of structural position and boundary velocity is obtained.

[0150] The structural solution calculates the deformation of the solid based on the force on the solid calculated by the fluid. This is a solid calculation step and can be performed using any solid calculation software or method.

[0151] Step 5: Structural feedback acts on the fluid to complete the dynamic boundary update.

[0152] Specifically, the velocity field after structural update is used to set the dynamic boundary conditions of the fluid (e.g., based on the fitted velocity interpolation method or the immersed boundary method);

[0153] If the immersed boundary method or indirect boundary method is used, the structural motion effect is converted into a source term and embedded in the LBM.

[0154] After the process is completed, it advances to the next time step.

[0155] In more preferred embodiments, an adaptive control step of adjusting intensity is also included.

[0156] Specifically, a dynamic feedback regulation mechanism is further introduced to ensure the adaptability and physical consistency of the regulation behavior. ρ , boundary node velocity gradient or local kinetic energy change rate Dynamically adjust the adjustment coefficient α or buffer layer thickness δ using physical quantities such as c , to adapt to different types of deformation situations.

[0157] When the velocity gradient is large, it is often accompanied by problems such as shear discontinuity, numerical instability, or insufficient grid scale. When the boundary velocity gradient reaches a certain threshold, the adjustment coefficient α should be appropriately increased to enhance the dissipation effect and suppress velocity mutations. At the same time, the buffer layer thickness δ should be appropriately increased. c , so that the regulation term works in a larger range near the interface, thereby suppressing the outward propagation of gradient-induced velocity fluctuations.

[0158] The local kinetic energy change rate reflects the speed of kinetic energy change of the fluid unit per unit time. If the kinetic energy change rate increases rapidly, it indicates that there may be severe disturbance or unsteady impact. At this time, α must be increased rapidly to prevent local instability from propagating to the entire domain. At the same time, the buffer layer thickness δ c It should also be enlarged so that the stabilization mechanism can act over a larger area, forming a "damping zone" or "buffer zone".

[0159] Statistics are taken on the buffer density disturbance every several time steps (e.g. 50 steps):

[0160]

[0161] Where ρ represents the density. If the disturbance is too large (exceeding the preset threshold σ ρ >σ th ), then increase the adjustment coefficient Or α; if the disturbance is in a stable state for a long time, it will decay appropriately Avoid excessive numerical diffusion. When the local structural acceleration exceeds a certain threshold, the buffer thickness is expanded; if the system converges too quickly, indicating excessive damping, the regulation intensity is reduced.

[0162] The stable state usually refers to the buffer density perturbation σ ρ Maintain within a small and limited range for a period of time. Specifically, when σ ρ The 500 consecutive time steps are all below 5×10 -4If the fluctuation range does not exceed ±10, the disturbance is considered to be in a long-term stable state. If the key residuals (such as the residual of density or the residual of velocity gradient) drop rapidly by 2 to 3 orders of magnitude within 100 time steps, it means that the convergence is too fast, and non-physical damping or excessive regulation may be introduced. In this case, the regulation intensity needs to be appropriately reduced.

[0163] The regulation intensity refers to multiple factors involved in numerical stability in the entire regulation mechanism, mainly including the regulation coefficient (or α), buffer zone thickness δ c , as well as the strength of additional adjustment items, etc. These adjustment intensities can be adjusted individually or in combination to achieve more refined energy flux management.

[0164] By real-time monitoring of physical quantities (such as density fluctuations and structural acceleration), the regulation intensity or buffer layer thickness is adjusted to ensure numerical stability. Since all regulation operations only act on the local buffer zone, the parallel computing efficiency is not affected, and it can be deployed on a large scale in supercomputing environments.

[0165] Repeat the iteration until the termination condition.

[0166] Specifically, the above steps are repeated until the simulation ends or the structure stabilizes. The output fluid-solid interface flow field, structural deformation, and coupling force data are used for analysis. This method is widely applicable to large-deformation fluid-structure coupling problems and exhibits excellent numerical stability in the face of various deformation scenarios (such as flexible vibration, sudden displacement, and wave propulsion). It is also compatible with various fluid-structure coupling boundary treatment methods, including the submerged boundary method, the moving boundary method, and the immersed volume method.

[0167] Taking the fluid-solid coupling calculation task of a typical two-dimensional flexible structure moving in a fluid as an example, it is particularly suitable for simulation tasks in which the flexible structure interacts strongly with the fluid, resulting in non-physical instabilities at the fluid-solid interface. All coupling behaviors occur inside the LBM solver, and the fluid-solid interaction is directly processed through momentum / energy exchange, without the need for data mapping or additional synchronous communication. The method provided by the present invention belongs to an internal coupling strategy, with a more compact numerical mechanism and lower dependence on parallel communication and synchronization. It is suitable for single-frame integrated deployment and does not rely on external coupling libraries. In complex coupling scenarios such as flexible structure propulsion, airfoil pitching motion, and high Reynolds number structural response analysis, it can significantly improve the numerical stability of the fluid-solid interface area, improve the overall simulation stability and accuracy, significantly reduce the density fluctuation in the interface area, and improve the overall stability of the LBM solver by more than 50%.

[0168] The present invention also provides an LBM large deformation fluid-solid interface stabilization system based on energy flux regulation. The LBM large deformation fluid-solid interface stabilization system based on energy flux regulation can be realized by executing the process steps of the LBM large deformation fluid-solid interface stabilization method based on energy flux regulation, that is, those skilled in the art can understand the LBM large deformation fluid-solid interface stabilization method based on energy flux regulation as a preferred embodiment of the LBM large deformation fluid-solid interface stabilization system based on energy flux regulation.

[0169] By introducing an energy flux regulation factor at the fluid-solid interface and embedding the LBM evolution equation, the active regulation of the energy exchange process at the fluid-structure interface is effectively achieved, which significantly improves the numerical stability and physical accuracy of fluid-solid coupling simulation under large deformation conditions. It has the advantages of simple structure, strong scalability and low computational overhead. It is suitable for complex coupling scenarios such as flexible structure propulsion, airfoil pitching motion, and high Reynolds number structural response analysis, and has broad engineering application value.

[0170] According to the present invention, a LBM large deformation fluid-solid interface stabilization system based on energy flux regulation is provided, comprising:

[0171] Module 1: Initialize the model and divide the grid;

[0172] Module 2: Identify the fluid-solid interface area of ​​the model and construct the buffer layer area;

[0173] Module 3: Solve the fluid in the buffer layer region and embed the energy flux regulation mechanism;

[0174] Module 4: Apply loads to structures through fluids and calculate structural responses;

[0175] Module 5: Feedback the structural response to the fluid and update the moving boundary;

[0176] Repeat the iteration to trigger module three to module five, and stop after the set termination condition is reached.

[0177] In more preferred examples, the initialization model includes constructing a calculation area, initializing the fluid distribution function, structural displacement, velocity and material model parameters, and setting the initial density and velocity field.

[0178] The calculation domain includes a fluid domain and a solid structure domain.

[0179] The grid division is to construct a grid in the fluid domain using the standard lattice Boltzmann method, and to establish a discrete model in the structural domain using the finite element method or other structural mechanics methods.

[0180] In the fourth module, the momentum exchange method or the pressure integration method is used to extract the fluid force acting on the boundary of the structural domain from the fluid domain, and the force is mapped to the corresponding nodes or surface elements on the solid structural domain. The deformation of the solid is calculated based on the force on the solid calculated by the fluid, and the structural deformation and velocity state are updated to obtain the structural position and boundary velocity information of the updated velocity field.

[0181] In the module five, the updated velocity field is used to set the dynamic boundary conditions of the fluid.

[0182] The moving boundary condition is set by fitting velocity interpolation, immersed boundary method or indirect boundary method.

[0183] The termination condition is to reach the set simulation termination time or the structural stable state, and output the fluid-solid interface flow field, structural deformation and coupling force data.

[0184] In more preferred embodiments, the embedded energy flux regulation mechanism is to update the fluid nodes in the buffer layer region using the LBM evolution equation in BGK format:

[0185]

[0186] Add adjustments to correct the collision process:

[0187]

[0188] Among them, f i represents the distribution function in the i-th velocity direction;

[0189] represents the local equilibrium distribution function;

[0190] is the distribution function in the i-th velocity direction after the collision;

[0191] x represents the grid spacing;

[0192] t represents the time step;

[0193] represents the energy regulation factor;

[0194] β represents the regulatory factor;

[0195] represents the discrete velocity direction;

[0196] τ represents the relaxation time;

[0197] Δ i Indicates additional adjustment items.

[0198] In more preferred embodiments, the module 2 identifies the fluid grid points in the fluid-solid interface region according to the current position of the structure, and sets the buffer layer region Ω c , record the minimum distance between the grid point and the structure boundary in each buffer layer area

[0199] The buffer layer region is located outside the boundary of the solid structure and is updated in the Euler coordinate system as the solid structure moves. The thickness is δ c .

[0200] For the fluid node in the buffer layer area, the energy adjustment factor is defined according to the distance from the node to the structure boundary

[0201]

[0202] in, and α both represent adjustment coefficients;

[0203] x represents the grid spacing;

[0204] t represents the time step;

[0205] Indicates the minimum distance from a fluid node to a solid boundary.

[0206] The energy adjustment factor is in the form of a hyperbolic tangent, piecewise linear or polynomial function.

[0207] In more preferred embodiments, the iteration further includes:

[0208] Module 6: Adaptive control based on dynamic feedback regulation mechanism, real-time monitoring of density disturbance σ in the fluid-solid interface area ρ , boundary node velocity gradient or local kinetic energy change rate Dynamically adjust the adjustment coefficient α or the buffer layer thickness δ c .

[0209] The density disturbance in the buffer layer is counted at every set time step:

[0210]

[0211] Among them, σ ρ (t) represents the density perturbation in the buffer layer region at time step t;

[0212] Ω c represents the buffer layer area;

[0213] x represents the grid spacing;

[0214] t represents the time step;

[0215] ρ represents density.

[0216] When the density disturbance exceeds the preset threshold σ th When σ ρ >σ th , increase the adjustment coefficient or α;

[0217] When the density perturbation is in a stable state for a long time, the decay

[0218] When the velocity gradient of the boundary node reaches the set threshold, the adjustment coefficient α is increased and the buffer layer thickness δ is expanded. c ;

[0219] When the local kinetic energy change rate reaches the set rate, immediately increase α and expand the buffer layer thickness δ c

[0220] When the structural acceleration exceeds the set threshold, the thickness of the buffer layer area is expanded;

[0221] When the convergence speed is too fast, reduce the adjustment intensity.

[0222] The adjustment strength includes an adjustment coefficient Adjustment coefficient α, buffer zone thickness δ c and\or the strength of the additional adjustment items.

[0223] Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same functions of the system and its various devices, modules, and units provided by the present invention in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; the devices, modules, and units for implementing various functions can also be considered as both software modules implementing the method and structures within the hardware component.

[0224] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A LBM large deformation fluid-solid interface stabilization method based on energy flux regulation, characterized in that: include: Step 1: Initialize the model and divide the grid; Step 2: Identify the fluid-solid interface area of ​​the model and construct the buffer layer area; Step 3: Solve the fluid in the buffer layer region and embed the energy flux regulation mechanism; Step 4: Apply load to the structure through the fluid and calculate the structural response; Step 5: Feedback the structural response to the fluid and update the moving boundary; Repeat steps 3 to 5 iteratively and stop when the set termination condition is reached.

2. The LBM large deformation fluid-solid interface stabilization method based on energy flux regulation according to claim 1 is characterized in that: The initialization model includes constructing a calculation area, initializing the fluid distribution function, structural displacement, velocity and material model parameters, and setting the initial density and velocity field; The calculation area includes a fluid domain and a solid structural domain; The grid division is to construct a grid in the fluid domain using the standard lattice Boltzmann method, and to establish a discrete model in the structural domain using the finite element method or other structural mechanics methods; In step 4, the momentum exchange method or the pressure integration method is used to extract the fluid force on the boundary of the structural domain from the fluid domain, and the force is mapped to the corresponding nodes or panels on the solid structural domain. The deformation of the solid is calculated based on the force on the solid calculated by the fluid, and the structural deformation and velocity state are updated to obtain the structural position and boundary velocity information of the updated velocity field; In step 5, the updated velocity field is used to set the dynamic boundary conditions of the fluid; The dynamic boundary condition is set by using the fitting velocity interpolation, the immersed boundary method or the indirect boundary method; The termination condition is to reach the set simulation termination time or the structural stable state, and output the fluid-solid interface flow field, structural deformation and coupling force data.

3. The LBM large deformation fluid-solid interface stabilization method based on energy flux regulation according to claim 1 is characterized in that: The embedded energy flux regulation mechanism is to update the fluid nodes in the buffer layer region using the LBM evolution equation in BGK format: Add adjustments to correct the collision process: Among them, f i represents the distribution function in the i-th velocity direction; represents the local equilibrium distribution function; is the distribution function in the i-th velocity direction after the collision; x represents the grid spacing; t represents the time step; represents the energy regulation factor; β represents the regulatory factor; represents the discrete velocity direction; τ represents the relaxation time; Δ i Indicates additional adjustment items.

4. The LBM large deformation fluid-solid interface stabilization method based on energy flux regulation according to claim 1 is characterized in that: In the second step, the fluid grid points in the fluid-solid interface region are identified according to the current position of the structure, and the buffer layer region Ω is set. c , record the minimum distance between the grid point and the structure boundary in each buffer layer area The buffer layer region is located outside the boundary of the solid structure and is updated in the Euler coordinate system as the solid structure moves. The thickness is δ c ; For the fluid node in the buffer layer area, the energy adjustment factor is defined according to the distance from the node to the structure boundary in, and α both represent adjustment coefficients; x represents the grid spacing; t represents the time step; Indicates the minimum distance from the fluid node to the solid boundary; The energy adjustment factor is in the form of a hyperbolic tangent, piecewise linear or polynomial function.

5. The LBM large deformation fluid-solid interface stabilization method based on energy flux regulation according to claim 4 is characterized in that: The iteration also includes: Step 6: Embed a dynamic feedback regulation mechanism in the model for adaptive control and monitor the density disturbance σ in the fluid-solid interface area in real time. ρ , boundary node velocity gradient or local kinetic energy change rate Dynamically adjust the adjustment coefficient α or the buffer layer thickness δ c ; The density disturbance in the buffer layer is counted at every set time step: Among them, σ ρ (t) represents the density perturbation in the buffer layer region at time step t; Ω c represents the buffer layer area; x represents the grid spacing; t represents the time step; ρ represents density; When the density disturbance exceeds the preset threshold σ th When σ ρ >σ th , increase the adjustment coefficient or α; When the density perturbation is in a stable state for a long time, the decay When the velocity gradient of the boundary node reaches the set threshold, the adjustment coefficient α is increased and the buffer layer thickness δ is expanded. c ; When the local kinetic energy change rate reaches the set rate, immediately increase α and expand the buffer layer thickness δ c When the structural acceleration exceeds the set threshold, the thickness of the buffer layer area is expanded; When the convergence speed is too fast, reduce the adjustment intensity; The adjustment strength includes an adjustment coefficient Adjustment coefficient α, buffer zone thickness δ c and\or the strength of the additional adjustment items.

6. An LBM large deformation fluid-solid interface stabilization system based on energy flux regulation, characterized in that: include: Module 1: Initialize the model and divide the grid; Module 2: Identify the fluid-solid interface area of ​​the model and construct the buffer layer area; Module 3: Solve the fluid in the buffer layer region and embed the energy flux regulation mechanism; Module 4: Apply loads to structures through fluids and calculate structural responses; Module 5: Feedback the structural response to the fluid and update the moving boundary; Repeat the iteration to trigger module three to module five, and stop after the set termination condition is reached.

7. The LBM large deformation fluid-solid interface stabilization system based on energy flux regulation according to claim 6 is characterized in that: The initialization model includes constructing a calculation area, initializing the fluid distribution function, structural displacement, velocity and material model parameters, and setting the initial density and velocity field; The calculation area includes a fluid domain and a solid structural domain; The grid division is to construct a grid in the fluid domain using the standard lattice Boltzmann method, and to establish a discrete model in the structural domain using the finite element method or other structural mechanics methods; In the fourth module, the fluid force acting on the boundary of the structural domain is extracted from the fluid domain by using the momentum exchange method or the pressure integration method, and the force is mapped to the corresponding nodes or elements on the solid structural domain. The deformation of the solid is calculated based on the force on the solid calculated by the fluid, and the structural deformation and velocity state are updated to obtain the structural position and boundary velocity information of the updated velocity field; In the module 5, the updated velocity field is used to set the dynamic boundary conditions of the fluid; The dynamic boundary condition is set by using the fitting velocity interpolation, the immersed boundary method or the indirect boundary method; The termination condition is to reach the set simulation termination time or the structural stable state, and output the fluid-solid interface flow field, structural deformation and coupling force data.

8. The LBM large deformation fluid-solid interface stabilization system based on energy flux regulation according to claim 6 is characterized in that: The embedded energy flux regulation mechanism is to update the fluid nodes in the buffer layer region using the LBM evolution equation in BGK format: Add adjustments to correct the collision process: Among them, f i represents the distribution function in the i-th velocity direction; represents the local equilibrium distribution function; is the distribution function in the i-th velocity direction after the collision; x represents the grid spacing; t represents the time step; represents the energy regulation factor; β represents the regulatory factor; represents the discrete velocity direction; τ represents the relaxation time; Δ i Indicates additional adjustment items.

9. The LBM large deformation fluid-solid interface stabilization system based on energy flux regulation according to claim 6 is characterized in that: In the second module, the fluid grid points in the fluid-solid interface region are identified according to the current position of the structure, and the buffer layer region Ω is set. c , record the minimum distance between the grid point and the structure boundary in each buffer layer area The buffer layer region is located outside the boundary of the solid structure and is updated in the Euler coordinate system as the solid structure moves. The thickness is δ c ; For the fluid node in the buffer layer area, the energy adjustment factor is defined according to the distance from the node to the structure boundary in, and α both represent adjustment coefficients; x represents the grid spacing; t represents the time step; Indicates the minimum distance from the fluid node to the solid boundary; The energy adjustment factor is in the form of a hyperbolic tangent, piecewise linear or polynomial function.

10. The LBM large deformation fluid-solid interface stabilization system based on energy flux regulation according to claim 9 is characterized in that: The iteration also includes: Module 6: Adaptive control based on dynamic feedback regulation mechanism, real-time monitoring of density disturbance σ in the fluid-solid interface area ρ , boundary node velocity gradient or local kinetic energy change rate Dynamically adjust the adjustment coefficient α or the buffer layer thickness δ c ; The density disturbance in the buffer layer is counted at every set time step: Among them, σ ρ (t) represents the density perturbation in the buffer layer region at time step t; Ω c represents the buffer layer area; x represents the grid spacing; t represents the time step; ρ represents density; When the density disturbance exceeds the preset threshold σ th When σ ρ >σ th , increase the adjustment coefficient or α; When the density perturbation is in a stable state for a long time, the decay When the velocity gradient of the boundary node reaches the set threshold, the adjustment coefficient α is increased and the buffer layer thickness δ is expanded. c ; When the local kinetic energy change rate reaches the set rate, immediately increase α and expand the buffer layer thickness δ c When the structural acceleration exceeds the set threshold, the thickness of the buffer layer area is expanded; When the convergence speed is too fast, reduce the adjustment intensity; The adjustment strength includes an adjustment coefficient Adjustment coefficient α, buffer zone thickness δ c and\or the strength of the additional adjustment items.

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