A ship hydroelastic one-way coupling numerical algorithm based on viscous flow theory

Abstract

The application provides a ship hydroelastic one-way coupling numerical algorithm based on a viscous flow theory, comprising the following steps: determining external force and external torque of a ship under the action of a wave flow, and determining the speed and acceleration of six-degree-of-freedom motion of the ship; inputting ship segmented hydrodynamic load into a one-dimensional beam model of a ship beam elastic deformation module, and calculating the bending deformation of the ship beam through the one-dimensional beam model; determining the rigid body displacement of the time step according to the speed of the six-degree-of-freedom motion of the ship, updating the node coordinates of the flow field body grid according to the rigid body displacement of the time step, and then updating the flow field calculation domain grid by solving Laplace equation; and iteratively calculating the updated flow field calculation domain grid; the application has the beneficial effects that the application can realize the hydroelastic one-way coupling numerical calculation considering the elastic effect of the ship, can better capture the hydroelastic response influence brought by strong nonlinear wave slamming, and can further provide data support for the strength analysis of the ship structure.

Description

Technical Field

[0001] This invention relates to the field of fluid-structure interaction research technology in numerical simulation of ship hydroelasticity, and in particular to a unidirectional coupling numerical algorithm for ship hydroelasticity based on viscous flow theory. Background Technology

[0002] In severe sea conditions, ships undergo significant motion, with the bow frequently entering and exiting the water, and phenomena such as slamming at the bottom and flanks, and waves on the deck are very pronounced. The hull experiences high-frequency vibrations and flutter responses from these severe impacts, resulting in highly unsteady and strongly nonlinear interactions between the ship and the waves. Currently, to improve the economic performance of civilian ships and the long-range operational capabilities of naval vessels, surface ships are trending towards larger size, higher speed, and lighter weight. Furthermore, the application of high-strength steel and new materials makes ships more susceptible to more severe impact responses in severe sea conditions, exacerbating the ship's elastic effects and flutter responses. Traditional potential flow methods have limitations in accuracy in addressing this highly nonlinear problem, while viscous flow methods struggle to account for the ship's elastic effects. Currently, methods based on segmented force integration are used to calculate the internal forces of rigid ships, but these numerical prediction methods neglect the influence of the ship's elastic effects. For large, lightweight ships, such as container ships up to 400 meters in length, the elastic effects can be extremely severe, making it difficult to guarantee the accuracy of hull section bending moment calculations using force integration methods.

[0003] The invention patent with application number CN202111069155.7, entitled "A Simulation Method for Hydroelastic Response of Liquid-Loaded Ships Based on CFD-FEM-SPH Four-Way Coupling", discloses a numerical simulation method for hydroelasticity of ships based on CFD-FEM-SPH, taking into account the sloshing of the liquid tanks they carry. This patent uses the open-source FEM solver deal.ii to simulate the rigid body motion and elastic deformation of the ship. For program development, this method has the disadvantages of long development cycle and difficulty in timely and effective verification. Moreover, compared with unidirectional coupling, bidirectional coupling has low computational efficiency and long computation time. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a one-way coupled numerical algorithm for ship hydroelasticity based on viscous flow theory, which solves the problem that numerical prediction methods in the prior art ignore the influence of ship elasticity.

[0005] To achieve the above and other related objectives, the present invention provides the following technical solution:

[0006] A one-way coupled numerical algorithm for hydroelasticity of ships based on viscous flow theory is proposed. The calculation results of the flow field and structure in the previous time step are used as the initial values ​​for the current time step. The calculation process for each time step includes the following steps: First, the external forces and moments of the ship under wave and current action are obtained through hydrodynamic integration. The ship is treated as a rigid body, and the velocity and acceleration of the ship's six-degree-of-freedom motion are obtained according to the six-degree-of-freedom motion calculation formula. Second, the segmented hydrodynamic loads of the ship are input into a one-dimensional beam model within the hull beam elastic deformation module. The bending deformation of the hull beam is calculated using the one-dimensional beam model, where parameters related to the bending deformation include node displacements. Third, the rigid body displacement of the time step is determined based on the velocity of the ship's six-degree-of-freedom motion, and the node coordinates of the flow field mesh are updated based on the rigid body displacement of the time step. Then, the flow field computational domain mesh is updated by solving the Laplace equation. Fourth, iterative calculations are performed on the updated flow field mesh. Based on the iterative calculation results and the bending deformation calculation results of the hull beam, a one-way coupled numerical calculation considering the elastic action of the hull is achieved.

[0007] An electronic device includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to execute the numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory as described above.

[0008] In one embodiment of the present invention, obtaining the external forces and torques of the ship under the action of waves and currents through hydrodynamic integration includes: obtaining the external forces and torques of the ship under the action of waves and currents according to the following formulas:

[0009] Among them, F e M is the resultant force of the ship under the action of waves and currents. e The resultant moment of the ship under the action of waves and currents, where the subscript e indicates that it is in the geodetic coordinate system, m is the total mass of the ship, g is the gravitational acceleration vector, and r is the net moment of the ship under the action of waves and currents. cg is the vector from the center of rotation to the center of gravity of the ship, and r is the position vector from any point mass to the center of gravity of the ship.

[0010] In one embodiment of the present invention, obtaining the velocity and acceleration of the ship undergoing six degrees of freedom motion according to the six-degree-of-freedom motion calculation formula includes: obtaining the velocity and acceleration of the ship undergoing six degrees of freedom motion according to the following formula: Where (u,v,w) represents the ship's linear velocity vector, (p,q,r) represents the ship's angular velocity vector, and the value with a point added represents the derivative with respect to time, i.e., the corresponding component of the acceleration vector, (X... s ,Y s Z s(K) represents the resultant force acting on the ship; s M s N s (I) represents the resultant torque acting on the ship. x ,I y ,I z Let (x) be the moment of inertia of the ship about its three rotational axes around its center of rotation. g ,y g ,z g ) represents the three components of the vector from the center of gravity of the ship model to the center of rotation.

[0011] In one embodiment of the present invention, calculating the bending deformation of the hull beam using the one-dimensional beam model includes: calculating the bending deformation of the hull beam according to the following formula: Where M is the mass matrix, C is the damping matrix, K is the stiffness matrix, F is the load vector, and x, and These are the generalized displacement, velocity, and acceleration vectors of the nodes, which include linear deformation and angular deformation components.

[0012] In one embodiment of the present invention, determining the rigid body displacement of the time step based on the speed of the ship's six-degree-of-freedom motion, and updating the flow field body-fitted mesh node coordinates based on the rigid body displacement of the time step, includes: multiplying the speed of the ship's six-degree-of-freedom motion by the time step to obtain the rigid body displacement of the time step, and obtaining the body-fitted mesh node coordinate update amount caused by the rigid body motion based on the rigid body displacement of the time step; converting the mesh node coordinate update amount into the mesh node coordinate update amount in the geodetic coordinate system according to the coordinate transformation matrix. This technical solution, by converting the mesh node coordinate update amount into the mesh node coordinate update amount in the geodetic coordinate system according to the coordinate transformation matrix, facilitates the updating of the flow field computation domain mesh.

[0013] In one embodiment of the present invention, updating the flow field computational domain mesh by solving the Laplace equation includes: updating the flow field computational domain mesh according to the following formula: in, The divergence operator is denoted as γ, which can perform divergence operations on any vector. γ is the diffusion coefficient, and u is the deformation velocity of the grid node. Based on the grid update function provided by the open-source software OpenFOAM, the flow field computational domain grid can be updated based on the deformed grid, and the topological relationship does not change during the grid update process.

[0014] In one embodiment of the present invention, the iterative calculation of the updated flow field computational domain grid includes: updating the free surface by solving the VOF equation and then calculating the velocity equation; then updating the pressure equation according to the set number of iterations within PIMPLE; until the iterations within PIMPLE are completed, the turbulence term of the flow field is corrected, thereby completing the data update of the flow field. This technical solution is based on the PIMPLE algorithm flow, thereby completing the data update of the flow field and providing data support for the flow field and structure calculations in the next time step.

[0015] As described above, the present invention provides a unidirectional coupling numerical algorithm for hydroelasticity of ships based on viscous flow theory, which has the following advantages: The present invention obtains the external forces and torques of the ship under the action of waves and currents through hydrodynamic integration, and then obtains the velocity and acceleration of the ship's six-degree-of-freedom motion according to the six-degree-of-freedom motion calculation formula. The segmented hydrodynamic loads of the ship are used as inputs to the one-dimensional beam model in the elastic deformation module of the hull beam. The bending deformation of the hull beam is calculated through the one-dimensional beam model. Then, the rigid body displacement of the time step is obtained according to the velocity of the ship's six-degree-of-freedom motion, and the coordinates of the flow field body-fitted mesh nodes are updated according to the rigid body displacement of the time step. The flow field calculation domain mesh is updated by solving the Laplace equation, and iterative calculation is performed on the updated flow field calculation domain mesh. Thus, it is possible to realize unidirectional coupling numerical calculation of hydroelasticity considering the elastic action of the ship, which can better capture the influence of hydroelastic response caused by strong nonlinear wave impact, thereby providing data support for the strength analysis of the hull structure and providing better assurance for the safety verification of the ship. Attached Figure Description

[0016] Figure 1 This is a flowchart of the numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory in the first embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of an electronic device according to the second embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the finite element elements of the hull beam model in this invention;

[0019] Figure 4 This is a flowchart of the solution strategy for unidirectional fluid-structure interaction of ship hydroelasticity based on viscous flow theory in this invention;

[0020] Figure 5 This is a schematic diagram of the force transmission and deformation solution in fluid-structure interaction in this invention;

[0021] Figure 6 This is a schematic diagram illustrating the relationship between the various numerical solution modules in this invention;

[0022] Figure 7This is a schematic diagram illustrating the computational domain setup in a practical application of the present invention;

[0023] Figure 8 This is a schematic diagram of the hull segmentation in practical application of the present invention;

[0024] Figure 9 This is a schematic diagram comparing the heave amplitude response curves in practical applications of the present invention;

[0025] Figure 10 This is a comparison chart of the pitch amplitude response curves in practical applications of the present invention;

[0026] Figure 11 This is a schematic diagram comparing the amplitude response curves of the vertical bending moment amidships in the practical application of the present invention. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features described herein can be combined with each other.

[0028] The first embodiment of the present invention relates to a numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory, the process of which is as follows: Figure 1 As shown, the details are as follows:

[0029] Step 101: Obtain the external forces and torques of the ship under the action of waves and currents by hydrodynamic integration, and treat the ship as a rigid body. Calculate the velocity and acceleration of the ship during six-degree-of-freedom motion according to the six-degree-of-freedom motion calculation formula.

[0030] Specifically, the main formulas for numerical integration calculation of hydrodynamic loads are as follows: The flow field is solved in the geodetic coordinate system, therefore the forces and moments are also calculated in the geodetic coordinate system; First, the hydrodynamic force on each element surface of the ship's body-fitted mesh is: dF e =τ·d|S f |+pdS f , of which S f This is the normal vector of the platform surface unit surface, pointing inwards. Its magnitude is equal to the area of ​​the platform surface unit surface. The subscript 'e' indicates that it is in the geodetic coordinate system. τ is the shear stress, and p is the total pressure. The formulas for calculating shear stress and total pressure are as follows:

[0031] After calculating the total force on each element surface of the platform, the resultant force and resultant moment acting on the entire platform can be obtained by integration: Among them, F e M is the resultant force of the ship under the action of waves and currents. eThe resultant moment of the ship under the action of waves and currents, where the subscript e indicates that it is in the geodetic coordinate system, m is the total mass of the ship, g is the gravitational acceleration vector, and r is the net moment of the ship under the action of waves and currents. cg is the vector from the center of rotation to the ship's center of gravity, and r is the position vector from any point mass to the ship's center of gravity. cg The formula for calculating r is: cg =(x g ,y g ,z g )=(x cog ,y cog ,z cog )-(x rot ,y rot ,z rot ).

[0032] After calculating the forces and moments in the geodetic coordinate system, it needs to be transformed to the ship's coordinate system. When the ship model is upright, the coordinate axes of the ship's coordinate system are in the same direction as the geodetic coordinate system. The displacement of the ship in the geodetic coordinate system, that is, the position of the ship's coordinate system relative to the geodetic coordinate system, is defined as: η=(η1,η2)=(x1,x2,x3,φ,θ,ψ), representing the sway, heave, roll, pitch, and bow motions, respectively; where (φ,θ,ψ) are the three Euler angles. The velocities of the six degrees of freedom in the ship's coordinate system are defined as: v=(v1,v2)=(u,v,w,p,q,r). The velocities in the two coordinate systems can be converted using a transformation matrix based on Euler angles. and Here, J1 and J2 and their inverse matrices are transformation matrices, which can be obtained by multiplying the rotation matrices around the z-axis, y-axis, and x-axis in sequence. The expressions for J1, J2, and their inverse matrices are as follows:

[0033]

[0034]

[0035]

[0036]

[0037] Transform the forces and moments acting on the hull into the hull coordinate system: In this context, the subscript 'e' represents the force and torque in the Earth coordinate system, while 's' represents the ship's coordinate system.

[0038] The acceleration of a ship can be calculated in the ship's coordinate system using the six-degree-of-freedom rigid body motion equations:

[0039]

[0040] Where (u,v,w) represents the ship's linear velocity vector, where u represents the x-component of linear acceleration, and v and w are similarly represented by the y and z-components; (p,q,r) represents the ship's angular velocity vector, and similarly, p, q, and r correspond to the components of rotation about the x, y, and z coordinate axes, respectively. Adding a point to the physical quantity represents the derivative with respect to time, i.e., the corresponding component of the acceleration vector, (X... s ,Y s Z s (K) represents the resultant force acting on the ship, corresponding to its three directional components; s M s N s (x) represents the resultant torque acting on the ship, about its center of gravity, corresponding to its three directional components; g ,y g ,z g (I) represents the three components of the vector from the center of gravity of the ship model to the center of rotation; x ,I y ,I z Let be the moment of inertia of the ship about its three rotational axes around its center of rotation, calculated by the following formula: Among them, (I) xcg ,I ycg ,I zcg Based on the principal rotational inertia of the ship's center of gravity, after calculating the accelerations of the six degrees of freedom, we integrate them to obtain the velocities of the six degrees of freedom in the ship's coordinate system, v = (u, v, w, p, q, r). Then, we transform these velocities to the Earth's coordinate system using a coordinate transformation matrix. According to the requirements of the Laplace mesh solver, further integration yields the displacement η = (x1, x2, x3, φ, θ, ψ).

[0041] Step 102: Input the hydrodynamic load of the ship section into the one-dimensional beam model in the elastic deformation module of the hull beam, and calculate the bending deformation of the hull beam through the one-dimensional beam model.

[0042] Specifically, in this embodiment, the hydrodynamic load refers to the external forces and moments of the ship under the action of waves and currents in step 101. To calculate the elastic deformation of the hull beams, a one-dimensional beam model with two degrees of freedom at each node is used. The Newmark method is used to solve the dynamic equations. The specific solution process is as follows: First, the hull is simplified into a hull beam model, using a one-dimensional Timoshenko beam model with two degrees of freedom at each node (vertical displacement and angular deformation). Numerical discretization is performed based on the finite element method. Each beam element consists of two nodes and has a total of four degrees of freedom, such as... Figure 3 As shown.

[0043] The resultant force obtained by hydrodynamic integration on each hull section is denoted as F.h In this embodiment, the resultant force and resultant moment also refer to the external forces and moments of the ship under the action of waves and currents in step 101. This resultant force needs to be converted into the equivalent structural load acting at the finite element node positions in the structural finite element calculation, denoted as F. In each segment of the finite element, F... h The following transformation relationship exists between F and F: Among them, F h Let F be the resultant force obtained by hydrodynamic integration on a certain hull section, F be the finite element nodal equivalent load on the structure, and L be the length of the structural section.

[0044] The governing equations for the structural dynamics of an elastic hull beam are: Where M is the mass matrix, C is the damping matrix, K is the stiffness matrix, F is the load vector, and x, and These are the generalized displacement, velocity, and acceleration vectors of the nodes, including linear and angular deformation components. That is, displacement includes linear and angular displacement, velocity includes linear and angular velocity, and acceleration includes linear and angular acceleration. The damping matrix C adopts the Rayleigh damping form, i.e., C = αM + βK, where α and β are determined by the two natural frequencies of the beam structure's vibration. The damping ratio ζ is defaulted to 0.03, and the calculation formula is as follows:

[0045] The solution to the structural dynamics equations is based on the Newmark method, which is generally considered a generalization of the linear acceleration method. It assumes that the following two formulas hold true: and At each time step, the structural dynamics equations to be solved are: Substituting the Newmark method's assumed formula and rearranging, we get: Among them, K * =a0M+a1C+K, Where a0 to a7 are Newmark coefficients: a6=Δt(1-γ), a7=γΔt, thus the generalized displacements (linear and angular displacements) of the nodal beams of the hull at the time step to be solved can be calculated. Then, based on the assumed formula, the generalized velocities (linear and angular velocities) and accelerations (linear and angular accelerations) of the nodal beams at that time step can be calculated.

[0046] In particular, unlike the general Newmark method, a relaxation algorithm is added to the calculation to enhance the stability of the structure calculation: and x i+1 =(1-α)x i+αx i+1 The coefficient α represents the relaxation factor, which is selected from 0 to 1. When the value is 1, it indicates that the data update is performed using the structural calculation results of the new time step. When the value is 0, it indicates that the data update is performed using the structural calculation results of the old time step. The smaller the value of the relaxation factor, the more stable the structural numerical calculation process. Generally, the value is above 0.9. The relaxation factor recommended by this unidirectional fluid-structure interaction calculation method is 0.95.

[0047] Step 103: Determine the rigid body displacement of the time step based on the speed of the ship's six-degree-of-freedom motion, update the flow field body-fitted mesh node coordinates based on the rigid body displacement of the time step, and then update the flow field computational domain mesh by solving the Laplace equation.

[0048] Specifically, the velocity of the ship undergoing six-degree-of-freedom motion is first multiplied by the time step to obtain the rigid body displacement at that time step. Based on the rigid body displacement at that time step, the update amount of the body-fitted mesh node coordinates caused by the rigid body motion is obtained. Then, the update amount of the mesh node coordinates is converted into the update amount of the mesh node coordinates in the geodetic coordinate system according to the coordinate transformation matrix. Finally, the flow field computational domain mesh is updated by solving the Laplace equation.

[0049] More specifically, the velocity of the body-fitted mesh nodes on the hull surface, calculated from the rigid body's six-degree-of-freedom motion, is first multiplied by the time step to obtain the coordinate update amount d of the body-fitted mesh nodes caused by the rigid body motion. r For the mesh node coordinate update caused by rigid body motion, it can be easily calculated based on the linear and angular velocities of the rigid body's translation and rotation around its center of gravity. Based on this, and using coordinate transformation matrices J1 and J2, the update amount of the body-fitted mesh node coordinates in the geodetic coordinate system can be calculated. After obtaining the update amount of the body-fitted mesh node coordinates on the hull surface in the geodetic coordinate system, the coordinate updates of other internal mesh nodes within the flow field computational domain can be obtained by solving the Laplace equation. in, The divergence operator represents the operator that performs divergence operations on any vector. This operator requires a point after it; otherwise, it's the gradient operator, as shown in the formula. This involves performing gradient calculations on a scalar, specifically the grid coordinate node u, which yields a vector and two... In the calculation, one is divergence calculation and the other is gradient calculation, which form a Laplacian operator, where γ is the diffusion coefficient and u is the deformation velocity of the grid node. The grid update function provided by the open-source software OpenFOAM can be used to update the flow field calculation domain grid based on the deformed grid, and the topological relationship does not change during the grid update process.

[0050] Step 104: Iterative calculation is performed on the updated flow field mesh. Based on the iterative calculation results and the bending deformation calculation results of the hull beam, the hydroelastic unidirectional coupling numerical calculation considering the elastic action of the hull is realized.

[0051] Specifically, after the flow field computational domain mesh is updated, the process based on the PIMPLE algorithm first updates the free surface by solving the VOF equation, then calculates the velocity equation (U equation), and then updates the pressure equation (p equation) according to the set number of iterations within PIMPLE, until the calculation of the iterations within PIMPLE is completed. After that, the turbulence term of the flow field is corrected, thereby completing the data update of the flow field and providing data support for the flow field and structural calculations in the next time step. Finally, the hydroelastic unidirectional coupling numerical calculation considering the elastic action of the ship is realized based on the bending deformation of the beam.

[0052] More specifically, the physical quantities in the computational domain of the flow field after mesh deformation were updated based on the PIMPLE algorithm. The specific steps were as follows: First, the phase fraction distribution of the flow field was updated by solving the VOF equations captured by the free surface. Where α represents the phase fraction, U represents the flow field velocity, and U c The relative velocity of the fluid at the compressible interface is represented by the value of 'R'. After calculating the updated phase fractional field distribution, the velocity-pressure decoupling calculation of the flow field is performed based on the PIMPLE algorithm. First, the velocity distribution of the flow field is calculated. Then, based on the set number of iterations within the PIMPLE algorithm, the pressure equation is corrected to obtain the accurate pressure distribution of the flow field. Finally, the turbulence terms in the flow field are corrected, thus completing the update of the physical quantity information in the computational domain of the flow field after the mesh update. Please refer to the overall flowchart. Figure 4 .

[0053] Furthermore, in the algorithm disclosed in this invention, the flow field and structural field are first initialized separately. Then, within each time step, the forces on the hull segments are obtained through force integration. Based on these forces, the six-degree-of-freedom motion of the ship is calculated. Simultaneously, the force integration is converted into structural nodal loads in the finite element method, thereby performing structural numerical calculations and outputting the results, such as... Figure 5 As shown, where F h F represents the hydrodynamic integral experienced in the segment. gThe algorithm represents the gravitational integral experienced by each segment. Then, based on rigid body motion, the mesh node deformation update is calculated, and the mesh is updated based on the Laplace equation. Finally, flow field calculations are performed on the updated mesh. The system corresponding to the algorithm disclosed in this invention includes a hull force integration and six-degree-of-freedom motion calculation module, a hull beam elastic deformation calculation module, and a flow field mesh deformation update module. The hull force integration and six-degree-of-freedom motion calculation module obtains the external forces and moments of the ship under wave and current action through hydrodynamic integration, treating the ship as a rigid body and obtaining the velocity and acceleration of the ship's six-degree-of-freedom motion according to the six-degree-of-freedom motion calculation formula. The hull beam elastic deformation calculation module calculates the bending deformation of the hull beam. The flow field mesh deformation update module iteratively calculates the updated flow field mesh, and realizes a hydroelastic unidirectional coupling numerical calculation considering the elastic action of the hull based on the iterative calculation results and the bending deformation calculation results of the hull beam. For details, please refer to [link to relevant documentation]. Figure 6 ,from Figure 6 As can be seen, this method separates the calculation of the ship's six degrees of freedom motion from the numerical solution of the elastic hull beam into two modules, which is more advantageous for program development and verification. Therefore, the advantage of this invention is that it solves the interaction between the ship and the waves under the viscous flow framework, which makes the ship's motion and load prediction have high calculation accuracy. In addition, at the code level, separating the six degrees of freedom motion calculation module of the ship as a rigid body from the elastic deformation solution module of the ship is conducive to carrying out numerical calculations based on their respective mature algorithms.

[0054] In practical applications, ships move significantly in rough seas, with the bow and stern entering and exiting the water, and waves slamming on the deck being very pronounced. Highly unsteady and strongly nonlinear interactions occur between the ship and the waves, severely impacting the safety of ship navigation. Based on a hull beam model, conducting unidirectional fluid-structure interaction numerical simulations considering the elastic deformation of the hull is an effective technical means to address the hydroelasticity problem of ships. To better understand the above-mentioned objectives, features, and advantages of this invention, the following examples further illustrate the invention. The specific implementation process of the examples is described in detail below: 1. Constructing a numerical simulation model of a 20kTEU ship model: This example conducts unidirectional coupled hydroelasticity numerical calculations based on a 20kTEU ship model at the model scale. The main scale parameters of the example are shown in Table 1:

[0055] Table 1 Main Scale Parameters of the Embodiment

[0056]

[0057] The computing domain settings in this embodiment are as follows: Figure 7 As shown, 001 represents the inlet boundary, 002 represents the outlet boundary, 003 represents the air boundary, and 004 represents the seabed boundary. In the numerical calculation, the hull is divided into 40 beam segments for calculation. Figure 8 As shown, in this embodiment, the wavelength-to-length ratio is set to 0.8–1.2, and five calculation examples under different working conditions are performed. The results are compared and verified with those from ship model experiments. The corresponding actual ship speed is 11.5 knots, the wave height is 5 meters, and the volume grid number is approximately 1.99 million. In this embodiment, since the ship is sailing against the waves, the rigid body degrees of freedom for pitch and heave are released, while the other four rigid body degrees of freedom are restricted. Based on the viscous flow theory-based unidirectional strongly coupled numerical algorithm for ship hydroelasticity used in this invention, the motion and load history of the elastic ship are simulated and compared with experimental results and potential flow simulation results. The ship heave amplitude response curve is compared as follows: Figure 9 As shown, the pitch amplitude response curve is compared to... Figure 10 As shown, the bending moment at the midship section is extracted, and the calculated amplitude response curve is compared with the experimental and potential flow simulation results. Figure 11 As shown, the method of the present invention can effectively predict the motion and load of the ship under the interaction between the ship and the waves. By comparing with the results of the hydroelastic test of the ship model, the calculation accuracy and stability of the developed method are verified. In addition, hydroelastic fluid-structure interaction calculation for ships can analyze the internal force response of the ship in real time while obtaining the fluid load.

[0058] The second embodiment of the present invention relates to an electronic device; please refer to [link / reference]. Figure 2 ,include:

[0059] At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to execute the above-described numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory.

[0060] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.

[0061] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.

[0062] The third embodiment of the present invention relates to a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-described method embodiments.

[0063] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes 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.

[0064] This invention obtains the external forces and moments of a ship under the action of waves and currents through hydrodynamic integration. Then, it calculates the velocity and acceleration of the ship's six-degree-of-freedom motion using the six-degree-of-freedom motion calculation formula. The segmented hydrodynamic loads of the ship are used as inputs to a one-dimensional beam model within the hull beam elastic deformation module. The bending deformation of the hull beam is calculated using the one-dimensional beam model. Then, the rigid body displacement at that time step is obtained based on the velocity of the ship's six-degree-of-freedom motion, and the coordinates of the flow field mesh nodes are updated based on the rigid body displacement at that time step. The flow field computational domain mesh is then updated by solving the Laplace equation, and iterative calculations are performed on the updated flow field computational domain mesh. This enables unidirectional coupling numerical calculation of hydroelasticity considering the elastic action of the ship, better capturing the hydroelastic response influence of strong nonlinear wave impact, thus providing data support for the strength analysis of the hull structure and providing better assurance for the safety verification of the ship.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. All equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A numerical algorithm for one-way coupling of hydroelasticity in ships based on viscous flow theory, characterized in that, The flow field and structure calculation results from the previous time step are used as the initial values ​​for the current time step. The calculation process for each time step includes the following steps: The external forces and torques of the ship under the action of waves and currents are obtained by hydrodynamic integration. The ship is regarded as a rigid body, and the velocity and acceleration of the ship in six degrees of freedom motion are obtained according to the six-degree-of-freedom motion calculation formula. The hydrodynamic loads of the ship sections are input into the one-dimensional beam model in the elastic deformation module of the hull beam. The bending deformation of the hull beam is calculated through the one-dimensional beam model. The parameters related to the bending deformation include the displacement of the nodes. The rigid body displacement at the time step is determined based on the velocity of the ship during its six-degree-of-freedom motion. The coordinates of the flow field mesh nodes are then updated based on the rigid body displacement at the time step, and the flow field computational domain mesh is updated by solving the Laplace equation. The updated flow field mesh is iteratively calculated, and the hydroelastic unidirectional coupling numerical calculation considering the elastic action of the hull beam is realized based on the iterative calculation results and the bending deformation calculation results of the hull beam.

2. The numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory according to claim 1, characterized in that: The method of obtaining the external forces and moments of a ship under the action of waves and currents through hydrodynamic integration includes: The external forces and moments of a ship under the action of waves and currents can be obtained from the following formulas: Among them, F e M is the resultant force of the ship under the action of waves and currents. e The resultant moment of the ship under the action of waves and currents, where the subscript e indicates that it is in the geodetic coordinate system, m is the total mass of the ship, g is the gravitational acceleration vector, and r is the net moment of the ship under the action of waves and currents. cg It is a vector from the center of rotation to the center of gravity of the ship, and r is a position vector from any point mass to the center of gravity of the ship.

3. The numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory according to claim 1, characterized in that: The calculation of the ship's velocity and acceleration during six-degree-of-freedom motion, based on the six-degree-of-freedom motion calculation formula, includes: The velocity and acceleration of a ship undergoing six degrees of freedom motion can be obtained using the following formulas: Where (u,v,w) represents the ship's linear velocity vector, (p,q,r) represents the ship's angular velocity vector, and the value with a point added represents the derivative with respect to time, i.e., the corresponding component of the acceleration vector, (X... s ,Y s Z s (K) represents the resultant force acting on the ship; s M s N s (I) represents the resultant torque acting on the ship. x ,I y ,I z Let (x) be the moment of inertia of the ship about its three rotational axes around its center of rotation. g ,y g ,z g ) represents the three components of the vector from the center of gravity of the ship model to the center of rotation.

4. The numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory according to claim 1, characterized in that: The calculation of the bending deformation of the hull beam using the one-dimensional beam model includes: The bending deformation of the hull beams can be calculated using the following formula: Where M is the mass matrix, C is the damping matrix, K is the stiffness matrix, F is the load vector, and x, and These are the generalized displacement, velocity, and acceleration vectors of the nodes, which include linear deformation and angular deformation components.

5. The numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory according to claim 1, characterized in that: The process of determining the rigid body displacement at a given time step based on the velocity of the ship's six-degree-of-freedom motion, and updating the flow field body-fitted mesh node coordinates based on that rigid body displacement, includes: Multiply the velocity of the ship during its six-degree-of-freedom motion by the time step to obtain the rigid body displacement at that time step, and then use the rigid body displacement at that time step to obtain the update amount of the body-fitted mesh node coordinates caused by the rigid body motion. The grid node coordinate update values ​​are converted into grid node coordinate update values ​​in the geodetic coordinate system based on the coordinate transformation matrix.

6. The numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory according to claim 5, characterized in that: The process of updating the computational domain mesh of the flow field by solving the Laplace equation includes: Update the flow field computational domain mesh according to the following formula: in, The divergence operator is denoted as γ, which can perform divergence operations on any vector. γ is the diffusion coefficient, and u is the deformation velocity of the grid node. Based on the grid update function provided by the open-source software OpenFOAM, the flow field computational domain grid can be updated based on the deformed grid, and the topological relationship does not change during the grid update process.

7. The numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory according to claim 1, characterized in that: The iterative calculation of the updated flow field computational domain mesh includes: After updating the free surface by solving the VOF equation, the velocity equation is calculated. Then, the pressure equation is updated according to the set number of iterations within PIMPLE. After the calculation of the iterations within PIMPLE is completed, the turbulence term of the flow field is corrected, thus completing the data update of the flow field.

8. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to execute the numerical algorithm for unidirectional coupling of ship hydroelasticity based on viscous flow theory as described in any one of claims 1 to 7.

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