CN111428434B - Numerical simulation method and system for object falling in ocean current - Google Patents

Abstract

The invention provides a numerical simulation method and system for objects falling in ocean currents, wherein a pool model and an object model are established according to initial pool parameters and initial object parameters; the pool model is divided into grids according to preset grid parameters ; According to the preset ocean current parameters, set the boundary conditions and fluid motion parameters of the pool model to form a simulated ocean current model; According to the preset physical parameters, establish a free fall model of the object model in the liquid; The step of establishing the free fall model includes setting The moving mesh of the falling object model: generate the background mesh of the hexahedral area; embed the falling sub mesh of the object model into the background mesh through the offset mesh; import the free fall model of the object model in the liquid into the simulated ocean current model, Start the simulation step; the present invention conveniently simulates the falling process of different objects under different ocean currents, and the cost is lower.

Description

A numerical simulation method and system for objects falling in ocean currents

technical field

The invention belongs to the field of numerical modeling and simulation, and particularly relates to the establishment and method analysis of a numerical simulation model for objects falling in ocean currents.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

With the gradual increase in the exploration of deep-sea resources, the operation of deep-sea cranes to lower objects in the ocean is more and more widely used. Due to the increasingly complex operating environment, when deep-sea cranes are operating at sea, there are many interference problems in the process of falling loads after entering the water. Loads may not reach the intended placement point safely due to waves, currents, and the ship's own navigation. This can lead to a collision between the deck and the load, resulting in damage, or the cable breaking due to excessive tension, resulting in a more serious safety problem. Therefore, it is necessary to study the force and motion of the load in the water flow during the ocean lifting process. At the same time, studying the motion of rigid bodies in fluid has extensive scientific significance and technical application value, and also provides a valuable reference for practical hydraulic engineering design.

The inventor found that, in order to make the object fall smoothly in the ocean current and realize the effective control of the falling object in the ocean current, the motion path, the motion speed and the force of the ocean current on the object when it falls in the ocean current should be obtained in advance. Therefore, the numerical simulation and model establishment of objects falling in ocean currents are very necessary.

At present, most researches on offshore cranes mainly focus on the analysis of the crane hull, while ignoring the movement of the underwater payload and the influence of the underwater ocean current on the movement of the payload, how to ensure the safety of the falling process of the loaded object, especially When the water has a certain flow rate, it is a technical problem that needs to be solved urgently at present.

SUMMARY OF THE INVENTION

In order to solve the above problems, the research on the falling of underwater objects in the ocean current is very important. The present invention takes the ocean current model into consideration, and can accurately predict the motion state of the object so as to better control the object. By setting the ocean current model, it is possible to extremely It greatly facilitates and simplifies the huge and expensive physical experiments, and the experimental results will be more accurate.

In this regard, the purpose of the present invention is to provide a method for establishing a numerical simulation model of objects falling in ocean currents based on OpenFOAM, which can easily simulate the falling situation of objects of any shape and size under the conditions of ocean currents with different parameters, with lower cost, The establishment and setting of the model are also more flexible, with great flexibility and wide practicability.

In order to achieve the above object, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a numerical simulation method for objects falling in ocean currents, including:

According to the initial pool parameters and initial object parameters, the pool model and the object model are established;

The pool model is meshed according to the preset grid parameters; according to the preset ocean current parameters, the boundary conditions and fluid motion parameters of the pool model are set to form a simulated ocean current model;

According to the preset physical parameters, a free fall model of the object model in the liquid is established; the step of establishing the free fall model includes setting the moving grid of the falling object model: generating the background mesh of the hexahedral area; Embedding into the background grid via the offset grid;

Import the free fall model of the object model in the liquid into the simulated ocean current model, start the simulation step, and simulate the output of the object model's movement trajectory, movement speed and changes in force parameters in all directions.

In a second aspect, the present invention provides a numerical simulation system for objects falling in ocean currents, including:

A model building module, which is used to establish a pool model and an object model according to the initial pool parameters and object parameters, form a simulated pool environment, and divide the pool model according to preset grid parameters;

The simulation ocean current environment forming module is used to set the boundary conditions of the model according to the preset ocean current parameters to form a simulated ocean current model;

The simulation gravity environment module is used to set the gravity parameters according to the preset object parameters, form the gravity environment, and establish the model of the object falling freely in the liquid;

The simulation module is used to import the preset free-fall model of the object model with the initial velocity into the ocean current model, start the simulation step, perform simulation calculations, and output the movement trajectory, movement speed and changes of the force parameters of the object in all directions situation and get an image of these parameters as a function of time.

In a third aspect, the present invention provides a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, implements the steps in the numerical simulation method for objects falling in ocean currents according to the first aspect.

In a fourth aspect, the present invention provides a computer terminal, including a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the program described in the first aspect when the processor executes the program. Steps in a numerical simulation method for objects falling in ocean currents.

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

1. The numerical simulation method of the object falling in the ocean current of the present invention can easily simulate the falling situation of objects of any shape and size under the conditions of ocean currents with different parameters, the cost is lower, and the establishment and setting of the model are also more flexible, Great flexibility and broad utility.

2. A numerical simulation method for objects falling in ocean currents provided by the present invention, in order to make objects fall smoothly in ocean currents and realize effective control of falling objects in ocean currents, a model including objects is established according to preset physical parameters. The free fall model of the falling moving grid can cooperate with the ocean current model to achieve high-precision simulation of the state of the object falling into the ocean current, and efficiently and accurately obtain the moving path, speed and force of the ocean current when the object falls in the ocean current. , the error is very small, and it has a technical reference for the numerical simulation and model establishment of objects falling in ocean currents.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

1 is a flowchart of a numerical simulation method for an object falling in ocean currents according to an embodiment of the present invention;

Fig. 2 is the pool model of the embodiment of the present invention;

Fig. 3 is the simulation model coordinate system of the embodiment of the present invention;

Fig. 4 is the schematic diagram of the offset grid of the embodiment of the present invention;

Fig. 5 is the evolution process of the vertical position of the cylinder falling from the static state;

Fig. 6 is the simulation result of the object falling in the ocean current according to the embodiment of the present invention;

Figure 7(a) is the cylinder trajectory data of the horizontal cylinder falling in the ocean current according to the embodiment of the present invention;

Figure 7(b) is the horizontal velocity data of the horizontal cylinder falling in the ocean current according to the embodiment of the present invention;

Figure 7(c) is the vertical velocity data of the horizontal cylinder falling in the ocean current according to the embodiment of the present invention;

Figure 7(d) is the horizontal force data of the horizontal cylinder falling in the ocean current according to the embodiment of the present invention;

Figure 7(e) is the vertical force data of the horizontal cylinder falling in the ocean current according to the embodiment of the present invention;

8 is a schematic structural diagram of a numerical simulation system for an object entering water according to an embodiment of the present invention.

Detailed ways:

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

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", etc. The orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only a relational word determined for the convenience of describing the structural relationship of each component or element of the present invention, and does not specifically refer to any component or element in the present invention, and should not be construed as a reference to the present invention. Invention limitations.

In the present invention, terms such as "fixed connection", "connected", "connected", etc. should be understood in a broad sense, indicating that it can be a fixed connection, an integral connection or a detachable connection; it can be directly connected, or it can be connected through the middle media are indirectly connected. For the relevant scientific research or technical personnel in the field, the specific meanings of the above terms in the present invention can be determined according to the specific situation, and should not be construed as a limitation of the present invention.

Example 1

The invention provides a numerical simulation method for objects falling in ocean currents, including: establishing a pool model and an object model according to initial pool parameters and initial object parameters;

The pool model is meshed according to the preset grid parameters; according to the preset ocean current parameters, the boundary conditions and fluid motion parameters of the pool model are set to form a simulated ocean current model;

According to the preset physical parameters, a free fall model of the object model in the liquid is established; the step of establishing the free fall model includes setting the moving grid of the falling object model: generating the background mesh of the hexahedral area; Embedding into the background grid via the offset grid;

Import the free fall model of the object model in the liquid into the simulated ocean current model, start the simulation step, and simulate the output of the object model's movement trajectory, movement speed and changes in force parameters in all directions.

Further, the step of establishing the pool module includes: determining the coordinate values of each point on the pool and the object by blockMesh, and establishing the boundary conditions of the pool and the object; the grid parameters of the pool and the object are the grid in the three-dimensional coordinate system. Spacing, set the spacing value to a value that varies evenly according to the preset situation.

Further, the simulated ocean current model simulates a uniform flow with the same speed and direction of fluid flow; for the setting of the boundary conditions of the ocean current model, the boundary conditions of the upper and lower walls of the pool are set to wall to prevent leakage from the upper and lower boundaries; The boundary conditions of fluid velocity U and pressure p are set to zero gradient.

Further, the preset physical parameters include: gravity parameters of the object.

Further, in order to represent the posture of the object model in the ocean current model, two Cartesian coordinate systems are defined, namely the world coordinate system and the load coordinate system.

Further, (o _g x _g y _g ) is the world coordinate system, in which the origin is fixed on the left side of the bottom of the numerical slot, O _g x g is parallel to the free surface, and O _g y _g is vertically upward; (O _c x _c y _c ) is Load coordinate system, its O _c is fixed at the center of mass of the load, O _c x _c is parallel to O _g x _g , in the same direction, O _g y _g is parallel to O _c y _c , in opposite directions; the load speed is determined by the horizontal speed u and the vertical downward direction Velocity v composition.

Further, the ocean current model includes a fixed cylindrical flow model and an ocean current-air model; the fixed cylindrical flow model is an ocean current model in which the upper and lower boundaries of the pool model are solid walls, and is used to simulate and verify the data of the cylindrical flow; The ocean current-air model is based on the cylindrical flow model, and a small amount of air is arranged on the upper part of the ocean current to prevent the unbalance of gas-liquid pressure; the ocean current-air model can be used for later merging with the free-falling object model.

Further, the specific steps of setting the moving grid of the falling object include:

Use blockMesh to generate the background mesh of the hexahedral area;

The sub-grid of the object model is embedded in the background grid through the offset grid; the sub-grid can move freely in the background grid, and the sub-grid and the background grid are independent of each other;

Set the size and shape of the payload, by setting the initial position coordinates of the object mesh and generating the object mesh.

Construct the equation for where the object model falls.

Example 2

This embodiment discloses a method for establishing a numerical simulation model for objects falling in ocean currents, specifically:

FIG. 1 is a flowchart of a numerical simulation method for objects falling in ocean currents according to this embodiment.

As shown in FIG. 1 , the numerical simulation method for objects falling in ocean currents in this embodiment includes:

According to the initial pool parameters and object parameters, the pool model and the object model are established to form a simulated pool environment, and the pool model is meshed according to the preset grid parameters;

According to the preset ocean current parameters, set the boundary conditions of the pool model and the parameters of the fluid flow to form a simulated ocean current model;

According to the preset object parameters, set the gravity parameters to form the gravity environment, and establish the model of the object falling freely in the liquid;

Import the preset free-fall model of the object with initial velocity into the preset ocean current model, start the simulation step, carry out the simulation calculation, output the movement trajectory, movement speed and change of the force parameters of the object in all directions, and Get images of these parameters as a function of time.

Set the number of grids in the z-axis direction to 1, and the resulting numerical pool is shown in Figure 2.

To represent the pose of objects in ocean currents, two Cartesian coordinate systems are defined. This embodiment simulates a two-dimensional object falling in an ocean current. As shown in Figure 3, (o _g x _g y _g ) is the world coordinate system, in which the origin is fixed on the left side of the bottom of the numerical slot, O _g x _g is parallel to the free surface, and O _g y _g is vertically upward. (O _c x _c y _c ) is the load coordinate system whose O _c is fixed at the center of mass of the load, O _c x _c is parallel to O _g x _g in the same direction, and O _g y _g is parallel to O _c y _c in opposite directions. The load speed consists of the horizontal speed u and the vertical downward speed v.

(1) Set the size and grid size of the numerical pool

The setting of the numerical pool uses the mesh generation tool blockMesh that comes with OpenFOAM to generate meshes. blockMesh is a program for generating meshes in blocks. The present invention regards the entire computational domain as a large block. In the calculation process, the calculation area is set as large as possible, so that the calculation is not affected by the surrounding fixed walls.

(2) Ocean current model

In the whole simulation model, it is very important to realize the fluid flow of the numerical pool by setting the initial conditions and boundary conditions of the entire numerical pool. The ocean current model we set up simulates a uniform flow with the same velocity and direction of fluid flow. Ocean currents flow in on the left and flow out on the right. Therefore, in the setting of the entire ocean current model, the setting of boundary conditions is particularly important.

Default current parameters:

1) Fixed flow model around cylinder

blockmesh:

Since the set pool is a two-dimensional model, on the front and back surfaces, the boundary type is set to empty; the boundary condition of the cylinder is set to wall; the upper and lower boundaries of the flow field use symmetrical boundary conditions to reduce the influence of the blocking rate on the flow; The rest of the boundary conditions are set to patch.

U:

The inlet boundary condition is set to fixedValue, and the internal velocity of the flow field internalField is set to the same value as the inlet velocity; at the outlet of the flow field model, the velocity U is set to zeroGradient. The solid cylinder is set to a fixed value of zero.

p:

At the inlet of the flow field model, the boundary condition of the fluid pressure p is set to zeroGradient. At the outlet of the flow field model, the pressure p is set to fixedValue.

2) Ocean current-air model

alpha.water:

The upper and upper left air boundary conditions are set to a fixed value of zero; the inlet is set to a fixed value and the value is set to internalField; the type is set to variableHeightFlowRate at the outlet (and lowerBound is set to 1; upperBound is set to 0), the boundary Conditions provide phase fraction conditions based on local flow conditions, constraining values to lie between user-specified upper and lower limits. The solid wall boundary condition at the bottom of the pool is set to slip.

blockmesh:

Since the set pool is a two-dimensional model, on the front and back surfaces, the boundary type is set to empty; the rest of the boundary conditions are set to wall to prevent leakage from the boundary.

U:

The upper and upper left air boundary conditions are set to pressureInletOutletVelocity; at the inlet, the velocity U of the specified boundary condition is set to fixedValue, and the internal velocity of the flow field internalField is set to the same value as the inlet velocity. For the exit, the speed U is set to zeroGradient, and the bottom of the pool is set to slip.

p:

The air boundary conditions on the upper and upper left sides are set to totalPressure; at the inlet, the boundary conditions of the fluid pressure p are set to fixedFluxPressure (where both gradient and value are set to uniform0). At the outlet, the pressure p is set to zeroGradient. The bottom of the pool is set to slip.

Here we set up two ocean current models successively. The first is an ocean current model in which the upper and lower boundaries of the pool model are solid walls, which are used to simulate and verify the data of the current around the cylinder to ensure the correctness of the ocean current parameter settings. The second is based on the first, a small amount of air is set on the upper part of the ocean current to prevent the imbalance of gas-liquid pressure. This model can be used for later merging with the free-falling object model.

The uniform flow set by the simulation software is relatively stable and easy to control. The change of the flow velocity only needs to modify the parameter settings. During the experiment, the measured experimental data have small errors and high reference, whether for fixed objects or sinking objects.

(3) Dynamic grid settings for falling objects

In order to correctly obtain the speed and trajectory of the object, this paper uses blockMesh to generate the background mesh of the hexahedral area. On this basis, the sub-grid of the object is embedded into the background grid through the offset grid. Due to the simple structure of the object, the grid density of the background is uniform. Figure 4 is an overset mesh used to simulate objects falling in a fluid. The subgrid can move freely within the background grid, but the two grids are independent of each other. Although the object displacement is large throughout the calculation, only the relative positions of the two meshes change, and the mesh shapes of the two meshes do not change. Each part of the grid can exchange data, so we can calculate the entire flow field.

Set the size and shape of the payload. The present invention adopts a relatively regular and simple load, so it also directly uses the blockMesh in OpenFOAM to directly set the initial position coordinates of the object mesh and generate the object mesh. However, the current model can also handle loads with complex and irregular shapes. Faced with this situation, you can first use a third-party CAD drawing software to draw the object mesh and then import it into OpenFOAM.

(4) Construct the equation of the falling object

The water in our experiments is set to be a two-dimensional viscous incompressible fluid, so the basic governing equations of the continuity equation and the Navier-Stokes equation are as follows:

是拉普拉斯算子，t是时间，x是位置向量，u是速度向量，g是重力加速度，ρ是流体密度，μ是流体粘度。p^*可以定义为：in

is the Laplace operator, t is the time, x is the position vector, u is the velocity vector, g is the acceleration of gravity, ρ is the fluid density, and μ is the fluid viscosity. p ^* can be defined as:

p ^* = p-ρg x

Add the g file to set the gravity field in the constant folder, and set the size and direction of the gravitational acceleration in the file. If you want to simulate free fall motion you can set the density, center of gravity and mass of the object. Adding constraints according to the actual situation can simulate the process of hoisting objects down by cables.

(5) Add ocean currents to the model and use the solver to solve

After setting the dynamic grid, gravity field and solver of the gravity model, we set the initial conditions and boundary conditions of the gravity model according to the initial conditions and boundary conditions of the entire numerical pool in the ocean current model. This example uses the incompressible multiphase flow solver overInterDyMFoam. The multiphase flow solver overInterDyMFoam is based on the law of conservation of mass, the law of conservation of momentum, and the law of volume fraction transport.

In each time step, the motion parameters of the object are first solved by the six-degree-of-freedom (6-DOF) motion equation, and then the offset moving grid is updated by the motion parameters. The solver first discretizes the mass conservation equation and momentum conservation equation that describe the fluid motion into a series of algebraic equations by integrating over the entire computational space domain and time domain, so that each tiny grid cell has an equation to describe , and then solve these equations through simultaneous iterations, get the approximate solution of each equation, then get the physical parameters of each tiny unit, and then get the physical parameters of the entire ocean current pool, then update the parameters and perform the next iteration until The iteration is complete.

(6) Data processing and analysis methods

After the solution is completed, the software paraview software is used to view the result information, and observe the movement of the object in the ocean current, the speed change, and the pressure change of the fluid. Extract the specific numerical information into the Excel file, and organize the data through MATLAB software to obtain the horizontal and vertical force of the load, the movement speed of the load, and the time-varying image of the movement trajectory, which is convenient for comparison of movements in different situations. analyze.

The following is a specific simulation experiment of objects falling in ocean currents based on OpenFOAM:

The horizontal cylinder falls into the vertical water surface (water velocity is zero):

Set up a numerical calculation pool according to the above steps, and set the initial falling speed of the cylinder to 0 at the initial moment. Data is output every 0.1s during the calculation process. We start at time t=0 and extract the position of the cylinder every 0.2s. Figure 5 shows the evolution of the vertical position of the cylinder as it descends from the resting state and compares it with the actual experiment. It can be seen from the position evolution of the cylindrical drop that, under the same premise, it is basically consistent with the results of the reference experiment, and also with the actual state of motion, which is more convenient and economical than physics.

The horizontal cylinder falls into the vertical water surface (water velocity is not zero):

Set up a numerical calculation pool according to the above steps. At the initial moment, the lowest point of the horizontal cylinder coincides with the horizontal plane. The falling velocity of the cylinder is set to 0.5m/s, and the water velocity is set to 0.1m/s and 0.2m/s, respectively. Data is output every 0.001s during the calculation process. The resulting simulation results of the cylinder falling freely in the ocean current. Figure 6 shows the paraview display results.

The position change, speed change and force data of the cylinder are extracted, and the data graph of their change with time is drawn through MATLAB, as shown in Figure 7:

It can be seen that the speed of the ocean current has a great influence on the movement of objects in the horizontal direction, but the influence in the vertical direction can be ignored. The measured position change, speed change and force data have very important reference value in actual engineering.

This embodiment can not only simulate the free fall of cylindrical objects in the ocean current, but also import various shapes of object meshes through blockMesh in OpenFOAM or third-party CAD drawing software, and then import them in the numerical pool. The process of free fall in ocean currents. Therefore, according to the shape of the cargo in the actual project, simulation simulation and hydrodynamic analysis can be carried out in advance, and the optimal control scheme can be determined in advance.

Example 3

FIG. 8 is a schematic structural diagram of a numerical simulation system for objects falling in ocean currents according to this embodiment.

As shown in FIG. 8 , this embodiment provides a numerical simulation system for objects falling in ocean currents, including:

(1) A model building module, which is used to establish a pool model and an object model according to the initial pool parameters and object parameters, form a simulated pool environment, and divide the pool model according to preset grid parameters; The initial conditions and boundary conditions of the pool are set to realize the flow of the fluid in the numerical pool.

The grid parameter is the grid spacing in the XYZ three-dimensional coordinate system, the spacing values are all equal, and the spacing value is an adjustable value.

(2) A simulation ocean current environment forming module, which is used to set the boundary conditions of the model according to the preset ocean current parameters to form a simulated ocean current model; the object wall and the pool wall are set to noSlip. At the inlet of the flow field model, set the velocity U of the specified boundary condition to fixedValue, and set the internal velocity of the flow field internalField to the same value as the inlet velocity. The boundary condition of the fluid pressure p is set to zero gradient. At the outlet of the flow field model, the velocity U is set to zeroGradient and the pressure p is set to fixedValue. Symmetrical boundary conditions are used for the upper and lower boundaries of the flow field to reduce the influence of the blocking rate on the flow. The model does not account for gravity and only simulates the interaction between fluids and objects. Set the free surface in the pool model so that the free surface is filled with water below and air above.

(3) A simulation gravity environment module, which is used to set gravity parameters according to preset object parameters, form a gravity environment, and establish a model of objects falling freely in liquid;

(4) Simulation module, which is used to import the preset free fall model of the object with initial velocity into the ocean current model, start the simulation step, perform simulation calculation, and output the movement trajectory, movement speed and force parameters of the object in all directions , and get the images of these parameters changing with time.

Also provided in other embodiments:

This embodiment provides a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, implements the steps in the numerical simulation method for an object falling in an ocean current as described in Embodiment 1.

This embodiment provides a computer terminal, including a memory, a processor, and a computer program stored in the memory and running on the processor, when the processor executes the program, the object according to Embodiment 1 is implemented in ocean currents Steps in the numerical simulation method of the fall.

As will be appreciated by one skilled in the art, embodiments of the present disclosure may be provided as a method, system, or computer program product. Accordingly, the present disclosure may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present disclosure may take the form of a computer program product embodied on one or more computer-usable storage media having computer-usable program code embodied therein, including but not limited to disk storage, optical storage, and the like.

The present disclosure is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be implemented by instructing relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. During execution, the processes of the embodiments of the above-mentioned methods may be included. The storage medium may be a magnetic disk, an optical disk, a read-only memory (Read-Only Memory, ROM), or a random access memory (Random Access Memory, RAM) or the like.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative work. Various modifications or deformations that can be made are still within the protection scope of the present invention.

Claims (10)

1. the numerical simulation method that an object falls in ocean current, it is characterized in that, comprise: according to initial pool parameter and initial object parameter, establish pool model and object model; The pool model is meshed according to the preset grid parameters; according to the preset ocean current parameters, the boundary conditions and fluid motion parameters of the pool model are set to form a simulated ocean current model; According to the preset physical parameters, a free fall model of the object model in the liquid is established; the step of establishing the free fall model includes setting the moving grid of the falling object model: generating the background mesh of the hexahedral area; Embedding into the background grid via the offset grid; Import the free fall model of the object model in the liquid into the simulated ocean current model, start the simulation step, and simulate the output of the object model's movement trajectory, movement speed and changes in force parameters in all directions; The free fall model of the object model in the liquid is imported into the simulated ocean current model, and the solver is used to solve the problem. In each time step, the motion parameters of the object are first solved through the six-degree-of-freedom motion equation, and then the overset dynamic network is updated through the motion parameters. Grid; the solver first discretizes the mass conservation equation and momentum conservation equation that describe fluid motion into a series of algebraic equations by integrating over the entire computational space and time domains, so that each tiny grid cell has an equation To describe, and then solve these equations through simultaneous iteration, get the approximate solution of each equation, then get the physical parameters of each tiny unit, then get the physical parameters of the entire ocean current pool, then update the parameters and go to the next time Iterate until the iteration is complete. 2. The numerical simulation method according to claim 1, wherein the specific steps of setting the moving grid of the falling object model include: Use blockMesh to generate the background mesh of the hexahedral area; The sub-grid of the object model is embedded in the background grid through the offset grid; the sub-grid can move freely in the background grid, and the sub-grid and the background grid are independent of each other; Set the size and shape of the payload, by setting the initial position coordinates of the object mesh and generating the object mesh. 3. Numerical simulation method as claimed in claim 1, is characterized in that, the described step of establishing pool model comprises: determine the coordinate value of each point on pool and object by blockMesh, set up the boundary condition of pool and object; Pool and object; The grid parameter of the object is the spacing of the grid in the 3D coordinate system, and the spacing value is set to a value that varies uniformly according to the preset situation. 4. The numerical simulation method according to claim 1, wherein the simulated ocean current model simulates a uniform flow with the same speed and direction of fluid flow; the setting of the boundary conditions of the ocean current model, the upper and lower walls of the pool The boundary conditions are set to wall to prevent leakage from the upper and lower boundaries; the boundary conditions of fluid velocity U and pressure p at the outlet are set to zero gradient. 5 . The numerical simulation method according to claim 1 , wherein the preset physical parameters include: gravity parameters of the object. 6 . 6 . The numerical simulation method according to claim 1 , wherein, in order to represent the posture of the object model in the ocean current model, two Cartesian coordinate systems are defined, namely the world coordinate system and the load coordinate system. 7 . 7. The numerical simulation method of claim 1, wherein the ocean current model comprises a fixed cylindrical flow model and an ocean current-air model; the fixed cylindrical flow model is that the upper and lower boundaries of the pool model are all solid walls. The ocean current model is used to simulate and verify the data of the flow around the cylinder; the ocean current-air model is based on the current model around the cylinder, and a small amount of air is set on the upper part of the ocean current to prevent the imbalance of gas-liquid pressure; the ocean current-air model can be Used for later merging with free-falling object models. 8. A numerical simulation system for objects falling in ocean currents, comprising: A model building module, which is used to establish a pool model and an object model according to the initial pool parameters and object parameters, form a simulated pool environment, and divide the pool model according to preset grid parameters; The simulation ocean current environment forming module is used to set the boundary conditions of the pool model and the parameters of the fluid flow according to the preset ocean current parameters to form a simulated ocean current model; The simulation gravity environment module is used to set the gravity parameters according to the preset object parameters, form the gravity environment, and establish the model of the object model falling freely in the liquid; The simulation module is used to import the preset free-fall model of the object model with the initial velocity into the preset simulated ocean current model, start the simulation steps, perform simulation calculations, and output the movement trajectory and movement speed of the object in all directions and the changes of the force parameters, and obtain the images of these parameters changing with time; import the object model in the liquid free fall model into the simulated ocean current model, use the solver to solve, first pass six degrees of freedom in each time step The equation of motion solves the motion parameters of the object, and then updates the offset dynamic grid through the motion parameters; the solver first discretizes the mass conservation equation and momentum conservation equation that describe the fluid motion into one by integrating over the entire computational space domain and time domain. A series of algebraic equations, so that each tiny grid cell has an equation to describe, and then solve these equations through simultaneous iteration, get the approximate solution of each equation, and then get the physical parameters of each tiny cell, and then The physical parameters of the entire ocean current pool are obtained, and then the parameters are updated and the next iteration is performed until the iteration is completed. 9. A computer-readable storage medium on which a computer program is stored, characterized in that, when the program is executed by a processor, the numerical simulation of the falling of an object in an ocean current as claimed in any one of claims 1-7 is realized steps in the method. 10. A computer terminal, comprising a memory, a processor and a computer program stored on the memory and running on the processor, wherein the processor implements any one of claims 1-7 when the processor executes the program. Steps in a numerical simulation method of a described object falling in ocean currents.

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