A ship navigation flow field simulation method, device, equipment and storage medium

Abstract

The application discloses a kind of ship navigation flow field simulation method, device, equipment and storage medium, applied in flow field simulation field, based on LBM method in analog flow area Analog liquid flow field and gaseous flow field in the process of ship navigation;CLSVOF method is based on The gas-liquid interface between liquid flow field and gaseous flow field is captured and the surface tension of gas-liquid interface is determined, and the density distribution function of gas-liquid interface grid point is corrected based on surface tension;Capture the solid-liquid interface between ship model and liquid flow field;IBM method is based on The volume force term of solid boundary in solid-liquid interface to liquid flow field is determined, and the density distribution function of solid-liquid interface grid point is corrected based on volume force term;DEM method is based on The volume fraction of DEM model in solid-liquid interface grid point is determined, and the density distribution function of solid-liquid interface grid point is corrected based on volume fraction.Compared with prior art, the flow field simulated is more accurate, so that the ship accurately predicts the sea working condition in the process of navigation and avoids risk.

Description

Technical Field

[0001] This invention relates to the field of flow field simulation, and in particular to a method, apparatus, equipment, and computer-readable storage medium for simulating the flow field of ship navigation. Background Technology

[0002] During ship navigation, simulating the flow field around the ship can predict sea surface conditions and help avoid risks in a timely manner, ensuring navigational safety. Currently, the Lattice Boltzmann (LBM) method is used to simulate the liquid and gaseous flow fields during ship navigation. However, due to the low simulation accuracy of the LBM method, the output results are not very reliable. Consequently, when sea surface conditions are dangerous, the simulation results cannot accurately predict the dangers that may be encountered, thus failing to avoid risks and causing economic losses. Summary of the Invention

[0003] The purpose of this invention is to provide a method, apparatus, device, and computer-readable storage medium for simulating the flow field of ship navigation. Applied to the field of flow field simulation, this method corrects the density distribution function of the gas-liquid interface grid points through the CLSVOF method during the LBM iteration process, and corrects the density distribution function of the solid-liquid interface grid points through the IBM and DEM methods. Compared with the prior art, the simulated flow field is more accurate, enabling ships to accurately predict sea surface conditions and avoid risks in a timely manner during navigation.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for simulating the flow field of ship navigation, comprising:

[0005] The LBM method is used to simulate the liquid and gaseous flow fields during ship navigation in a simulated watershed.

[0006] The CLSVOF method is used to capture the gas-liquid interface between the liquid flow field and the gas flow field and to determine the surface tension of the gas-liquid interface. The density distribution function of the gas-liquid interface grid points is then corrected based on the surface tension.

[0007] Capture the solid-liquid interface between the ship model and the liquid flow field;

[0008] The volume force term of the solid boundary in the solid-liquid interface on the liquid flow field is determined based on the IBM method, and the density distribution function of the solid-liquid interface grid points is corrected based on the volume force term.

[0009] The volume fraction of the DEM model at the solid-liquid interface grid points is determined based on the DEM method, and the density distribution function of the solid-liquid interface grid points is corrected based on the volume fraction.

[0010] Optional, also includes:

[0011] After the LBM method iterates for a preset number of iterations, the difference between the simulated physical quantity and the real physical quantity at the grid point is determined.

[0012] When the difference is greater than the difference threshold, the density distribution function of the grid points is corrected based on the difference.

[0013] Optionally, the surface tension of the gas-liquid interface is determined based on the CLSVOF method, including:

[0014] Based on the CLSVOF method, a horizontal field is set up in the simulated watershed, and the distance function of the horizontal field is determined.

[0015] The curvature of the gas-liquid interface and the Dirac function centered on the gas-liquid interface are determined based on the distance function.

[0016] The surface tension is determined based on the curvature, the Dirac function, the surface tension coefficient, and the gradient of the distance function;

[0017] Accordingly, the density distribution function of the gas-liquid interface grid points based on the surface tension correction includes:

[0018] The first correction coefficient is determined based on the surface tension and the iteration step size;

[0019] The density distribution function of the gas-liquid interface grid points in the next iteration step is corrected based on the first correction coefficient.

[0020] Optional, also includes:

[0021] The flow rate difference between the gas-liquid interface grid points during the LBM method iteration process is determined based on the velocity of the grid points at the gas-liquid interface.

[0022] Determine the difference between the density distribution function of the gas-liquid interface grid points in the next iteration step and the density distribution function in the current step;

[0023] The density distribution function of the gas-liquid interface grid points in the next iteration step is corrected based on the difference between the flow rate difference and the density distribution function.

[0024] Optionally, determining the volume force term of the solid boundary at the solid-liquid interface on the liquid flow field based on the IBM method includes:

[0025] Based on the IBM method, a ship grid is constructed using Lagrange points, and the force density of the Lagrange points is determined.

[0026] The solid-liquid interaction force at the solid-liquid interface lattice point is determined based on the force density.

[0027] The volume force term of the solid boundary at the solid-liquid interface on the liquid flow field is determined based on the solid-liquid interaction force.

[0028] Accordingly, the density distribution function of the solid-liquid interface grid points modified based on the volume force term includes:

[0029] The second correction coefficient is determined based on the volume force term and the iteration step size;

[0030] The density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected based on the second correction coefficient.

[0031] Optionally, determining the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method includes:

[0032] Connect the intersection of the DEM model and the side length of the grid points at the solid-liquid interface to form the base of a pyramid;

[0033] The grid vertex corresponding to the opposite direction of the surface normal vector of the DEM model inside the grid point of the solid-liquid interface is taken as the first pyramid vertex;

[0034] The surface stationary point of the DEM model inside the grid points of the solid-liquid interface is taken as the vertex of the second pyramid;

[0035] The volume of the first pyramid is determined based on the base of the pyramid and the vertex of the first pyramid; the volume of the second pyramid is determined based on the base of the pyramid and the vertex of the second pyramid.

[0036] The volume fraction of the solid-liquid interface grid points is determined based on the volume of the first pyramid and the volume of the second pyramid.

[0037] Accordingly, the step of correcting the density distribution function of the solid-liquid interface grid points based on the volume fraction includes:

[0038] The weighting function of the solid-liquid interface grid points is determined based on the volume fraction.

[0039] The third correction coefficient is determined based on the weighting function and the LBM collision operator;

[0040] The density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected based on the third correction coefficient.

[0041] Optionally, the mesh model of the LBM method is the D3Q19 model, and the collision model is the MRT model.

[0042] To solve the above-mentioned technical problems, the present invention provides a ship navigation flow field simulation device, comprising:

[0043] The first module is used to simulate the liquid and gaseous flow fields during ship navigation in a simulated watershed based on the LBM method.

[0044] The second module is used to capture the gas-liquid interface between the liquid flow field and the gas flow field based on the CLSVOF method and determine the surface tension of the gas-liquid interface, and to correct the density distribution function of the grid points of the gas-liquid interface based on the surface tension.

[0045] The third module is used to capture the solid-liquid interface between the ship model and the liquid flow field.

[0046] The fourth module is used to determine the volume force term of the solid boundary in the solid-liquid interface on the liquid flow field based on the IBM method, and to correct the density distribution function of the solid-liquid interface grid points based on the volume force term.

[0047] The fifth module is used to determine the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method, and to correct the density distribution function of the solid-liquid interface grid points based on the volume fraction.

[0048] To solve the above-mentioned technical problems, the present invention provides a ship navigation flow field simulation device, comprising:

[0049] Memory, used to store computer programs;

[0050] A processor for implementing any of the ship navigation flow field simulation methods when executing the computer program.

[0051] To address the aforementioned technical problems, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement any of the ship navigation flow field simulation methods described above.

[0052] As can be seen, this invention simulates the liquid and gaseous flow fields during ship navigation in a simulated flow domain using the LBM method; it captures the gas-liquid interface between the liquid and gaseous flow fields and determines the surface tension of the gas-liquid interface using the CLSVOF method, and corrects the density distribution function of the grid points at the gas-liquid interface based on the surface tension; it captures the solid-liquid interface between the ship model and the liquid flow field; it determines the volume force term of the solid boundary on the liquid flow field at the solid-liquid interface using the IBM method, and corrects the density distribution function of the grid points at the solid-liquid interface based on the volume force term; and it determines the volume fraction of the DEM model at the solid-liquid interface grid points, and corrects the density distribution function of the solid-liquid interface grid points based on the volume fraction. Compared with existing technologies, the simulated flow field is more accurate, enabling ships to accurately predict sea surface conditions and avoid risks during navigation. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0054] Figure 1 A flowchart of a ship navigation flow field simulation method provided in an embodiment of the present invention;

[0055] Figure 2 This is a structural block diagram of a ship navigation flow field simulation device provided in an embodiment of the present invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] The following combination Figure 1 , Figure 1 A flowchart of a ship navigation flow field simulation method provided in an embodiment of the present invention, the method may include:

[0058] S101: Simulating liquid and gaseous flow fields during ship navigation in a simulated watershed using the LBM method.

[0059] This embodiment simulates the liquid and gaseous flow fields of a ship during navigation in a simulated flow domain based on the LBM method. It uses an anemometer and wind vane to collect real-time wind speed and direction information, calculates the additional force of the incoming wind on the water flow, generates a grid, uses the collected information as the initial input to the LBM flow field, and imports the ship model into the simulated flow domain. The simulation accuracy is matched based on the computational resource scale, a simulated flow domain of appropriate size is set, and initial parameters such as fluid density and velocity are set within the simulated flow domain to initialize the environment. The LBM method is a method for simulating fluids at a mesoscopic scale. It discretizes velocity and time, and its main variable is the density distribution function, which allows for the determination of macroscopic physical information at each lattice point in the flow field. The lattice Boltzmann method is based on the Boltzmann equations and describes the evolution of particles in the flow field through the processes of particle collision and migration. The formula used to iterate the lattice density distribution function can be:

[0060] f i (x+e i δt, t+δt)=fi (x, t) - Ω i (f i (x, t), f i eq (x, t));

[0061] In the formula, f i (x, t) is the density distribution function of the grid point at coordinate x in direction i and at iteration step t, f i (x+e i δt, t+δt) is the density distribution function at iteration step t+1, x is the grid coordinate, δt is the LBM iteration step size, and e i Ω represents the discrete velocity direction of the grid points, where i is the index of the discrete direction. i For the LBM collision operator, f i eq (x, t) is the equilibrium density distribution function of the lattice point at iteration step t.

[0062] During the iteration of the LBM method, the density distribution function of grid points in the flow field can be iterated using the above formula. In this embodiment, the grid model of the LBM method can adopt the D3Q19 model, which is a grid model in fluid simulation. The collision model can adopt the MRT (Multi Relaxation Time) model.

[0063] S102: Based on the CLSVOF method, capture the gas-liquid interface between the liquid flow field and the gas flow field and determine the surface tension of the gas-liquid interface. Based on the surface tension, correct the density distribution function of the grid points of the gas-liquid interface.

[0064] This embodiment can correct the density distribution function of the gas-liquid interface grid points during the iteration process. This embodiment does not limit the specific correction method. The density distribution function of the gas-liquid interface grid points in the next iteration step can be obtained by correcting the surface tension of the gas-liquid interface in each iteration step.

[0065] CLSVOF (Coupling between VOF and LS) is a coupling method of VOF (Volume of Fluid) and LS (Level sets). In this embodiment, the CLSVOF method can capture the gas-liquid interface between the liquid flow field and the gas flow field and determine the surface tension of the gas-liquid interface.

[0066] The level set method uses a signed distance function to simulate different fluids in multiphase flow, where positive and negative values ​​represent two different fluids, and the 0 level set represents the interface location. The absolute value represents the shortest distance from the current grid center to the interface. The interface is obtained by solving the transport equations, and after the first time step, the level set function needs to be reinitialized to restore the distance attribute.

[0067] The fluid volumetric method for capturing the motion of a free interface requires an indicator function θ. The indicator function is defined as the liquid volume fraction at each grid point. If θ = 1, the grid point is in the liquid phase; if θ = 0, the grid point is in the gas phase; if it is between 0 and 1, it belongs to the interface layer. In this embodiment, grid points with a volume fraction between 0 and 1 can be identified as gas-liquid interface grid points.

[0068] A new horizontal field is set up in the simulated watershed. As a distance function, the horizontal set field is initialized based on a grid of points with a liquid volume fraction θ of 0.5. Initial values ​​for the horizontal set function are first assigned using the formula shown below:

[0069]

[0070] In the formula, Let Γ be the initial value of the distance function, θ be the liquid volume fraction at the grid point, and Γ be the grid length coefficient, typically taken as 0.75δx, where δx is the grid point length in the gas phase. Obtaining a negative value in the liquid phase A positive value was obtained.

[0071] Furthermore, the distance function is substituted into the following equation for initialization:

[0072]

[0073] In the formula, Let Δt1 be the gradient of the distance function, and Δt1 be the time step required for the initialization process. It is a symbolic function, and its value is... The symbol. Choosing an appropriate time step Δt1, the solution converges to... To ensure that the distance function near the interface does not change sharply. Number of reinitializations. The value is determined by the following formula:

[0074]

[0075] In the formula, d1 is the average interface thickness, which is the transition distance between the gas phase and the liquid phase. In this embodiment, the value is generally taken as 1.5Δx.

[0076] This embodiment can determine the curvature of the gas-liquid interface based on a distance function. Since the distance functions of each gas-liquid interface grid point are not necessarily the same, the corresponding curvatures are also not necessarily the same. The curvature can be calculated as follows:

[0077]

[0078] In the formula, · is the divergence operator, and n is the normal vector of the gas-liquid interface. The calculation formula is as follows:

[0079]

[0080] In this embodiment, the Dirac function can be determined based on the distance function. In this embodiment, the Dirac function is centered on the gas-liquid interface, and its determination method is as follows:

[0081] In the formula, d2 is the Dirac function, and d2 is the surface tension thickness, which is generally taken as 6Δx, that is, the surface tension is corrected for the grid points within the thickness of the six-layer grid close to the interface.

[0082] This embodiment can determine the surface tension of the gas-liquid interface based on the gradient of curvature, Dirac function, surface tension coefficient, and distance function, as shown in the following formula:

[0083]

[0084] In the formula, F σ Let σ be the surface tension at the gas-liquid interface, and σ be the surface tension coefficient.

[0085] In this embodiment, the first correction coefficient F can be determined based on surface tension and iteration step size. σ In each iteration of the LBM method, δt can be adjusted based on the first correction coefficient to modify the density distribution function at the gas-liquid interface grid point in the next iteration step, as shown in the following equation:

[0086] f i (x+e i δt, t+δt)=f i (x, t) - Ω i (f i (x, t), f i eq (x, t))+F σ δt;

[0087] When using the above formula to correct the density distribution function, i is taken as the direction perpendicular to the gas-liquid interface, i.e., the direction with the smallest angle to the interface normal vector n. That is, the density distribution function of the gas-liquid interface grid points in the direction perpendicular to the gas-liquid interface is corrected by surface tension.

[0088] For compressible fluids, when using the above method for flow field simulation, the compressibility of the simulated fluid may cause some liquid phase volume to be lost at the interface. To reduce the volume error caused by compressibility, this embodiment requires a second correction to the density distribution function after the first correction coefficient. Firstly, the flow rate difference between the gas-liquid interface grid points during the LBM method iteration process can be determined based on the velocity of the grid points, as shown in the following equation:

[0089]

[0090] In the formula, ε1 is the flow rate difference between the gas-liquid interface grid point in the next iteration step and the current iteration step, and u is the grid point velocity.

[0091] Furthermore, this embodiment needs to determine the difference between the density distribution function of the gas-liquid interface grid points in the next iteration step and the density distribution function of the current step, as shown in the following formula:

[0092] ε2=(∑f i (x+e i δt,t+δt)) t+1 -(∑f i (x, t)) t ;

[0093] In the formula, ε2 is the difference in density distribution function between the gas-liquid interface grid points in the next iteration step and the current iteration step.

[0094] This embodiment can correct the density distribution function after the first correction coefficient is applied based on the difference between the flow rate difference and the density distribution function, as shown in the following formula:

[0095]

[0096] In the formula, f i new (x+e i δt, t+δt) is the density distribution function of the next point in the gas-liquid interface grid after two corrections.

[0097] S103: Captures the solid-liquid interface between the ship model and the liquid flow field.

[0098] S104: Based on the IBM method, determine the volume force term of the solid boundary on the liquid flow field in the solid-liquid interface, and correct the density distribution function of the solid-liquid interface grid points based on the volume force term.

[0099] This embodiment does not limit the specific method of capturing the solid-liquid interface between the ship model and the liquid flow field; the capture method can be set according to the actual application scenario. In this embodiment, the volume force term of the solid boundary on the liquid flow field in the solid-liquid interface can be determined based on the IBM (Immersed Boundary method). First, a flow field grid is constructed based on Eulerian points, and a ship grid is constructed based on Lagrange points. The position of the Lagrange points will also change with the movement of the ship grid. The density distribution function of the Lagrange points is generally obtained by numerical extrapolation from the surrounding fluid grid, as shown in the following equation:

[0100]

[0101] In the formula, X l (X l Y l Z l ) represents the coordinates of the Lagrange point, h max j max and k max f represents the number of Euler points used in each direction. i (X l Let x(t) be the density distribution function of the Lagrange point, and x(t) be the density distribution function of the Lag hjk Let x be the x-coordinate of the Euler point at index (h, j, k), and y be the y-coordinate of the Euler point at index (h, j, k). hjk Let y be the y-coordinate of the Euler point at index (h, j, k), and z be the z-coordinate of the Euler point at index (h, j, k). hjk Let be the z-coordinate of the Euler point at the index (h, j, k).

[0102] The fluid density distribution function outside the Lagrange lattice is modified to consider the influence of the ship lattice on the surrounding flow field, as shown in the following equation:

[0103]

[0104] In the formula, u is the opposite direction of i. l Let ω be the velocity at the Lagrange point. i Let be the weight in the i-th direction, and c be the speed of sound at the grid point.

[0105] In this embodiment, u l The formula for calculating can be shown in the following equation:

[0106] u l =u p +w p ×(X l -X p );

[0107] In the formula, u p and w pX represents the translational and angular velocities of the ship's grid points. p The coordinates of the centroid of the ship's grid points.

[0108] Based on the interaction between fluid grid points and ship grid points, i.e., changes in the ship grid point's motion attitude, such as translation or rotation, are affected by the surrounding flow field, and the flow field is also affected by the ship grid point's motion attitude, this embodiment can determine the force density at the Lagrange point, as shown in the following formula:

[0109]

[0110] In the formula, g(X) l , where t is the force density at the Lagrange point. For e i The opposite discrete velocity direction.

[0111] The solid-liquid interaction force is further determined based on the force density, as shown in the following equation:

[0112] F(x,t)=∑ l g(X l ,t)D hjk (x hjk -X l )S l ;

[0113] In the formula, F(x, t) is the solid-liquid interaction force at the solid-liquid interface lattice point with coordinate x at time step t, and D... hjk S is the solid-liquid interaction force coefficient. l This represents the cross-sectional area where the current Eulerian and Lagrange meshes intersect.

[0114] In this embodiment, the solid-liquid interaction force coefficient can be determined as shown in the following formula:

[0115]

[0116] In the formula, r is the thickness of the solid-liquid interface lattice, β is the angle between the direction of the current Lagrange point normal vector and the direction of the vector pointing from the current Lagrange point to the Euler point, and δ is the solid-liquid interface lattice thickness. r This is the coefficient of interaction force.

[0117] In this embodiment, δ r The calculation formula can be:

[0118]

[0119] Furthermore, this embodiment can calculate the volume force term of the solid boundary on the liquid flow field at the solid-liquid interface grid point based on the solid-liquid interaction force. Since the solid-liquid interaction force at each solid-liquid interface grid point is not necessarily the same, the corresponding volume force term calculated for each solid-liquid interface grid point is also not necessarily the same. The calculation method of the volume force term in this embodiment can be shown in the following formula:

[0120]

[0121] In the formula, F b Let τ be the volume force term, τ be the relaxation time, and u be the lattice velocity.

[0122] In this embodiment, the second correction coefficient F can be determined based on the volume force term and the iteration step size. b δt; and based on the second correction coefficient, the density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected, as shown in the following equation:

[0123] f i (x+e i δt, t+δt)=f i (x, t) - Ω i (f i (x, t), f i eq (x, t))+F b δt;

[0124] Because volume forces are applied to the flow field, this embodiment requires updating the velocities of the grid points:

[0125]

[0126] In the formula, ρ is the grid density.

[0127] S105: Determine the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method, and correct the density distribution function of the solid-liquid interface grid points based on the volume fraction.

[0128] Furthermore, this embodiment can correct the grid points of the solid-liquid interface based on the DEM (Discrete Element method). This embodiment does not limit the correction order of the DEM method and the IBM method, and can be set according to the actual application.

[0129] This embodiment first determines the volume fraction of the DEM model at the solid-liquid interface grid points. The intersection of the DEM model and the edge lengths of the solid-liquid interface grid points is used as the base of a pyramid. The grid vertex corresponding to the opposite direction of the surface normal vector of the DEM model inside the solid-liquid interface grid points is taken as the first pyramid vertex. The surface stationary point of the DEM model inside the solid-liquid interface grid points is taken as the second pyramid vertex. The volume V1 of the first pyramid is determined based on the pyramid base and the first pyramid vertex. The volume V2 of the second pyramid is determined based on the pyramid base and the second pyramid vertex. This embodiment can determine the volume fraction of the solid-liquid interface grid points based on the first pyramid volume and the second pyramid volume, as shown in the following formula:

[0130]

[0131] In the formula, η is the volume fraction of the grid points at the solid-liquid interface, and S is the empirical coefficient for calculating the surface area. The value is less than 1 when calculating concave surfaces and greater than 1 when calculating convex surfaces.

[0132] To ensure a smooth transition between the DEM model and the LBM grid, this embodiment can determine the weighting function of the solid-liquid interface grid points based on the volume fraction. The calculation method is shown in the following formula:

[0133]

[0134] In the formula, B q (η) is η q The weight function is given by q, where q represents the grid point number.

[0135] Furthermore, the third correction coefficient B can be determined based on the weighting function and the LBM collision operator. q Ω i The density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected based on the third correction coefficient, as shown in the following equation:

[0136]

[0137] Wherein, the i-direction is taken as the cosine value of the angle between the velocity discrete directions of the outer surface of the DEM model and the grid points of the solid-liquid interface, cosβ. d Discrete velocity directions > 0.5 It is the collision operator of the DEM algorithm.

[0138] In this embodiment, The calculation method can be shown in the following formula:

[0139]

[0140] In the formula, u p For DEM model speed, u d This represents the velocity of the DEM model at the grid point with coordinate x. Let the density be ρ and the velocity be u in direction i. d The lattice equilibrium density distribution function, It is the opposite direction of velocity i.

[0141] In this embodiment, the velocity of the DEM model at the grid point with coordinate x can be calculated as follows:

[0142] u d =w p ×(xX p )+u p ;

[0143] In the formula, w p X represents the angular velocity of the DEM model. p Let u be the centroid of the DEM model. d When η = 0 and η = 1, the solid-liquid interface boundary treatment can be simplified to a common rebound model, that is, the magnitude of the velocity at the boundary remains unchanged, but the direction is reversed.

[0144] This embodiment can modify the interface grid density distribution function at each step of the LBM iteration process. In each LBM iteration, that is, in the process of obtaining the density distribution function of the next iteration step from the density distribution function of the current step:

[0145] The CLSVOF method is used to capture the gas-liquid interface and obtain the surface tension of the gas-liquid interface.

[0146] The first correction coefficient is calculated based on the surface tension of each gas-liquid interface grid point, and the density distribution function of the gas-liquid interface grid point in the next iteration step is corrected based on the first correction coefficient.

[0147] Based on the difference in flow rate and density distribution function at each gas-liquid interface grid point during the iteration process, the density distribution function of the next iteration step is corrected again; during the second correction process, the density distribution function of the next iteration step is the density distribution function after surface tension correction.

[0148] Capture the solid-liquid interface, determine the volume force term of the solid boundary on the liquid flow field in the solid-liquid interface based on the IBM method, and determine the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method.

[0149] The density distribution function of solid-liquid interface lattice points is modified based on the volume force term and volume fraction of solid-liquid interface lattice points.

[0150] Furthermore, this embodiment can introduce a self-feedback adjustment mechanism for flow field simulation. After iterating the LBM method for a preset time step, the difference between the simulated physical quantity and the actual physical quantity at the grid point is determined. In this embodiment, the grid point can be selected from a preset region. When the difference exceeds the difference threshold, the simulation result can be considered to have a serious deviation. This embodiment can correct the density distribution function of the corresponding grid point based on the difference. This embodiment does not limit the specific correction method. Generally, the difference in physical quantities can be converted into an external force, and the difference correction coefficient can be determined based on the external force and the iteration step size. The difference distribution coefficient is then introduced into the density distribution function for correction, prompting subsequent iterations to evolve towards the correct result. This embodiment can record the error and the external force used for correction in a log as reference learning material for subsequent simulations, allowing for faster error correction in subsequent simulations.

[0151] Based on the above embodiments, the present invention corrects the density distribution function of the gas-liquid interface grid points by using the CLSVOF method during the LBM iteration process, and corrects the density distribution function of the solid-liquid interface grid points by using the IBM and DEM methods. Compared with the prior art, the simulated flow field is more accurate, enabling ships to accurately predict sea surface conditions and avoid risks in a timely manner during navigation.

[0152] The following is a specific embodiment of the method provided by the present invention, which may include:

[0153] The LBM method is used to simulate the liquid and gaseous flow fields during ship navigation in a simulated watershed.

[0154] In the LBM method, the collision model is set to a multi-relaxation time model, and the mesh model is set to the D3Q19 model.

[0155] Based on the CLSVOF method, grid points with liquid volume fraction between 0 and 1 are identified as gas-liquid interface grid points.

[0156] The curvature of the gas-liquid interface and the Dirac function with the gas-liquid interface as the execution point are calculated based on the distance function of each gas-liquid interface node.

[0157] The surface tension of the gas-liquid interface at the corresponding gas-liquid interface grid point is calculated based on the divergence of curvature, Dirac function, surface tension coefficient and distance function of each gas-liquid interface node.

[0158] The surface tension is multiplied by the iteration step size to obtain the first correction coefficient, and the first correction coefficient is added to the density fraction function of the next iteration step of the gas-liquid interface grid point for correction.

[0159] The divergence of the velocity in the next iteration step at each gas-liquid interface grid point is subtracted from the divergence of the velocity in the current step to obtain the corresponding flow rate difference.

[0160] Subtract the density distribution function of the current step from the density distribution function of each gas-liquid interface grid point in the next iteration step to obtain the corresponding density distribution function difference;

[0161] The error value is obtained by subtracting the density distribution function difference from the flow rate difference, and then the error value is discretized to the density distribution function of the gas-liquid interface grid points in each direction.

[0162] Capture the solid-liquid interface and determine the volume force terms of the solid boundary on the liquid flow field based on the IBM method;

[0163] The volume force term corresponding to each solid-liquid interface grid point is multiplied by the iteration step size to obtain the second correction coefficient. The second correction coefficient is then added to the density fraction function of the next iteration step of the corresponding solid-liquid interface grid point for correction.

[0164] The volume fraction of the DEM model at each solid-liquid interface grid point is determined based on the DEM method, and the weight function of each solid-liquid interface grid point is calculated based on the volume fraction.

[0165] The weighting function is multiplied by the LBM collision operator to obtain the third correction coefficient. The third correction coefficient is then added to the density fraction function of the next iteration for the corresponding solid-liquid interface lattice point for a second correction.

[0166] The following combination Figure 2 , Figure 2 This is a structural block diagram of a ship navigation flow field simulation device provided in an embodiment of the present invention. The device may include:

[0167] The first module 100 is used to simulate the liquid and gaseous flow fields during ship navigation in a simulated water domain based on the LBM method.

[0168] The second module 200 is used to capture the gas-liquid interface between the liquid flow field and the gas flow field based on the CLSVOF method and determine the surface tension of the gas-liquid interface, and correct the density distribution function of the grid points of the gas-liquid interface based on the surface tension.

[0169] The third module 300 is used to capture the solid-liquid interface between the ship model and the liquid flow field.

[0170] The fourth module 400 is used to determine the volume force term of the solid boundary in the solid-liquid interface on the liquid flow field based on the IBM method, and to correct the density distribution function of the grid points of the solid-liquid interface based on the volume force term.

[0171] The fifth module 500 is used to determine the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method, and to correct the density distribution function of the solid-liquid interface grid points based on the volume fraction.

[0172] Based on the above embodiments, the present invention corrects the density distribution function of the gas-liquid interface grid points by using the CLSVOF method during the LBM iteration process, and corrects the density distribution function of the solid-liquid interface grid points by using the IBM and DEM methods. Compared with the prior art, the simulated flow field is more accurate, enabling ships to accurately predict sea surface conditions and avoid risks in a timely manner during navigation.

[0173] Based on the above embodiments, the device may further include:

[0174] The sixth module is used to determine the difference between the simulated physical quantity and the real physical quantity at the grid point after the LBM method iterates a preset number of iterations.

[0175] The seventh module is used to correct the density distribution function of the grid points based on the difference when the difference is greater than the difference threshold.

[0176] Based on the above embodiments, the second module 200 may include:

[0177] The first unit is used to set up a horizontal field in the simulated watershed based on the CLSVOF method and determine the distance function of the horizontal field.

[0178] The second unit is used to determine the curvature of the gas-liquid interface and the Dirac function centered on the gas-liquid interface based on the distance function.

[0179] The third unit is used to determine the surface tension based on the curvature, the Dirac function, the surface tension coefficient, and the gradient of the distance function;

[0180] The fourth unit is used to determine the first correction coefficient based on the surface tension and the iteration step size;

[0181] The fifth unit is used to correct the density distribution function of the gas-liquid interface grid points in the next iteration step based on the first correction coefficient.

[0182] Based on the above embodiments, the second module 200 may further include:

[0183] The sixth unit is used to determine the flow rate difference of the gas-liquid interface grid points during the LBM method iteration process based on the velocity of the gas-liquid interface grid points.

[0184] The seventh unit is used to determine the difference between the density distribution function of the gas-liquid interface grid points in the next iteration step and the density distribution function of the current step.

[0185] The eighth unit is used to correct the density distribution function of the gas-liquid interface grid points in the next iteration step based on the difference between the flow rate difference and the density distribution function.

[0186] Based on the above embodiments, the fourth module 400 may include:

[0187] The ninth unit is used to construct a ship grid using Lagrange points based on the IBM method and to determine the force density of the Lagrange points.

[0188] The tenth unit is used to determine the solid-liquid interaction force at the solid-liquid interface grid point based on the force density;

[0189] The eleventh unit is used to determine the volume force term of the solid boundary in the solid-liquid interface on the liquid flow field based on the solid-liquid interaction force.

[0190] The twelfth unit is used to determine the second correction coefficient based on the volume force term and the iteration step size;

[0191] The thirteenth unit is used to correct the density distribution function of the solid-liquid interface grid points in the next iteration step based on the second correction coefficient.

[0192] Based on the above embodiments, the fifth module 500 may include:

[0193] The fourteenth unit is used to connect the intersection of the DEM model and the side length of the solid-liquid interface grid points to form the base of a pyramid.

[0194] The fifteenth unit is used to take the grid vertex corresponding to the opposite direction of the surface normal vector of the DEM model inside the solid-liquid interface grid as the first pyramid vertex.

[0195] The sixteenth unit is used to take the surface stationary point of the DEM model inside the grid of the solid-liquid interface as the second pyramid vertex;

[0196] The seventeenth unit is used to determine the volume of the first pyramid based on the base of the pyramid and the vertex of the first pyramid; and to determine the volume of the second pyramid based on the base of the pyramid and the vertex of the second pyramid.

[0197] The eighteenth unit is used to determine the volume fraction of the solid-liquid interface grid points based on the volume of the first pyramid and the volume of the second pyramid;

[0198] The nineteenth unit is used to determine the weighting function of the solid-liquid interface grid points based on the volume fraction.

[0199] The twentieth unit is used to determine the third correction coefficient based on the weighting function and the LBM collision operator.

[0200] The twenty-first unit is used to correct the density distribution function of the solid-liquid interface grid points in the next iteration step based on the third correction coefficient.

[0201] Based on the above embodiments, the mesh model of the LBM method is the D3Q19 model, and the collision model is the MRT model.

[0202] Based on the above embodiments, the present invention also provides a ship navigation flow field simulation device. This device may include a memory and a processor. The memory stores a computer program, and when the processor calls the computer program in the memory, it can implement the steps provided in the above embodiments. Of course, the device may also include various necessary network interfaces, power supplies, and other components.

[0203] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by an execution terminal or processor, can implement the method provided in the embodiments of the present invention; the storage medium may include various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0204] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0205] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for simulating the flow field during ship navigation, characterized in that, include: The LBM method is used to simulate the liquid and gaseous flow fields during ship navigation in a simulated watershed. The CLSVOF method is used to capture the gas-liquid interface between the liquid flow field and the gas flow field and to determine the surface tension of the gas-liquid interface. The density distribution function of the gas-liquid interface grid points is then corrected based on the surface tension. Capture the solid-liquid interface between the ship model and the liquid flow field; The volume force term of the solid boundary in the solid-liquid interface on the liquid flow field is determined based on the IBM method, and the density distribution function of the solid-liquid interface grid points is corrected based on the volume force term. The volume fraction of the DEM model at the solid-liquid interface grid points is determined based on the DEM method, and the density distribution function of the solid-liquid interface grid points is corrected based on the volume fraction. The determination of the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method includes: Connect the intersection of the DEM model and the side length of the grid points at the solid-liquid interface to form the base of a pyramid; The grid vertex corresponding to the opposite direction of the surface normal vector of the DEM model inside the grid point of the solid-liquid interface is taken as the first pyramid vertex; The surface stationary point of the DEM model inside the grid points of the solid-liquid interface is taken as the vertex of the second pyramid; The volume of the first pyramid is determined based on the base of the pyramid and the vertex of the first pyramid; the volume of the second pyramid is determined based on the base of the pyramid and the vertex of the second pyramid. The volume fraction of the solid-liquid interface grid points is determined based on the volume of the first pyramid and the volume of the second pyramid. Accordingly, the step of correcting the density distribution function of the solid-liquid interface grid points based on the volume fraction includes: The weighting function of the solid-liquid interface grid points is determined based on the volume fraction. The third correction coefficient is determined based on the weighting function and the LBM collision operator; The density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected based on the third correction coefficient.

2. The ship navigation flow field simulation method according to claim 1, characterized in that, Also includes: After the LBM method iterates for a preset number of iterations, the difference between the simulated physical quantity and the real physical quantity at the grid point is determined. When the difference is greater than the difference threshold, the density distribution function of the grid points is corrected based on the difference.

3. The ship navigation flow field simulation method according to claim 1, characterized in that, Determining the surface tension of the gas-liquid interface based on the CLSVOF method includes: Based on the CLSVOF method, a horizontal field is set up in the simulated watershed, and the distance function of the horizontal field is determined. The curvature of the gas-liquid interface and the Dirac function centered on the gas-liquid interface are determined based on the distance function. The surface tension is determined based on the curvature, the Dirac function, the surface tension coefficient, and the gradient of the distance function; Accordingly, the density distribution function of the gas-liquid interface grid points based on the surface tension correction includes: The first correction coefficient is determined based on the surface tension and the iteration step size; The density distribution function of the gas-liquid interface grid points in the next iteration step is corrected based on the first correction coefficient.

4. The ship navigation flow field simulation method according to claim 3, characterized in that, Also includes: The flow rate difference between the gas-liquid interface grid points during the LBM method iteration process is determined based on the velocity of the gas-liquid interface grid points. Determine the difference between the density distribution function of the gas-liquid interface grid points in the next iteration step and the density distribution function in the current step; The density distribution function of the gas-liquid interface grid points in the next iteration step is corrected based on the difference between the flow rate difference and the density distribution function.

5. The ship navigation flow field simulation method according to claim 1, characterized in that, The determination of the volume force term of the solid boundary on the liquid flow field at the solid-liquid interface based on the IBM method includes: Based on the IBM method, a ship grid is constructed using Lagrange points, and the force density of the Lagrange points is determined. The solid-liquid interaction force at the solid-liquid interface lattice point is determined based on the force density. The volume force term of the solid boundary at the solid-liquid interface on the liquid flow field is determined based on the solid-liquid interaction force. Accordingly, the density distribution function of the solid-liquid interface grid points modified based on the volume force term includes: The second correction coefficient is determined based on the volume force term and the iteration step size; The density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected based on the second correction coefficient.

6. The ship navigation flow field simulation method according to claim 1, characterized in that, The mesh model for the LBM method is the D3Q19 model, and the collision model is the MRT model.

7. A device for simulating the flow field of ship navigation, characterized in that, include: The first module is used to simulate the liquid and gaseous flow fields during ship navigation in a simulated watershed based on the LBM method. The second module is used to capture the gas-liquid interface between the liquid flow field and the gas flow field based on the CLSVOF method and determine the surface tension of the gas-liquid interface, and to correct the density distribution function of the grid points of the gas-liquid interface based on the surface tension. The third module is used to capture the solid-liquid interface between the ship model and the liquid flow field. The fourth module is used to determine the volume force term of the solid boundary in the solid-liquid interface on the liquid flow field based on the IBM method, and to correct the density distribution function of the solid-liquid interface grid points based on the volume force term. The fifth module is used to determine the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method, and to correct the density distribution function of the solid-liquid interface grid points based on the volume fraction. The determination of the volume fraction of the DEM model at the solid-liquid interface grid points based on the DEM method includes: Connect the intersection of the DEM model and the side length of the grid points at the solid-liquid interface to form the base of a pyramid; The grid vertex corresponding to the opposite direction of the surface normal vector of the DEM model inside the grid point of the solid-liquid interface is taken as the first pyramid vertex; The surface stationary point of the DEM model inside the grid points of the solid-liquid interface is taken as the vertex of the second pyramid; The volume of the first pyramid is determined based on the base of the pyramid and the vertex of the first pyramid; the volume of the second pyramid is determined based on the base of the pyramid and the vertex of the second pyramid. The volume fraction of the solid-liquid interface grid points is determined based on the volume of the first pyramid and the volume of the second pyramid. Accordingly, the step of correcting the density distribution function of the solid-liquid interface grid points based on the volume fraction includes: The weighting function of the solid-liquid interface grid points is determined based on the volume fraction. The third correction coefficient is determined based on the weighting function and the LBM collision operator; The density distribution function of the solid-liquid interface lattice points in the next iteration step is corrected based on the third correction coefficient.

8. A ship navigation flow field simulation device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the ship navigation flow field simulation method as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, implement the ship navigation flow field simulation method as described in any one of claims 1 to 6.

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