CN111428434A - Numerical simulation method and system for object falling in ocean current - Google Patents
Numerical simulation method and system for object falling in ocean current Download PDFInfo
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Abstract
The invention provides a numerical simulation method and a numerical simulation system for falling of an object in ocean current, wherein a pool model and an object model are established according to initial pool parameters and initial object parameters; carrying out mesh division on the pool model according to preset mesh parameters; setting boundary conditions and fluid motion parameters of the pool model according to preset ocean current parameters to form a simulation ocean current model; establishing a free falling model of the object model in the liquid according to preset physical parameters; the free fall model building step comprises the steps of setting a falling moving grid of the object model: generating a background grid of the hexahedral area; embedding the sub-grid of the object model falling into the background grid through the overset grid; introducing the free falling model of the object model in the liquid into a simulation ocean current model, and starting a simulation step; the device can conveniently simulate the falling process of different objects under different ocean current conditions, and has lower cost.
Description
Technical Field
The invention belongs to the field of numerical modeling and simulation, and particularly relates to establishment of a numerical simulation model and method analysis of object falling in ocean current.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the increasing exploration of deep sea resources, the deep sea crane is widely used for lowering objects in the sea. Because of the increasingly complex working environment, the process of the load falling after entering water presents a plurality of interference problems when the deep sea crane works at sea. The load may not be able to safely reach the destination point due to sea waves, ocean currents, and the vessel's own voyage. This can cause a collision between the deck and the load, resulting in damage, or the cable can break due to excessive tension, which can present a more serious safety problem. It is necessary to study the stress and movement of the load in the water flow during the ocean going up and down. Meanwhile, the research on the motion of the rigid body in the fluid has wide scientific significance and technical application value, and provides valuable reference for the actual hydraulic engineering design.
The inventor finds that in order to make the object fall smoothly in the ocean current and realize effective control of the falling object in the ocean current, the motion path, the motion speed and the ocean current acting force of the object when the object falls in the ocean current should be obtained in advance. Therefore, numerical simulation and modeling of the falling of objects in ocean currents are necessary.
At present, most of research on offshore cranes mainly focuses on analysis of crane hulls, neglects the motion of underwater effective loads and the influence of underwater ocean currents on the motion of the effective loads, and how to ensure the safety of the falling process of the load objects, particularly when water has certain flow velocity, is a technical problem which is urgently needed to be solved at present.
Disclosure of Invention
In order to solve the problems, the study on the falling of underwater objects in ocean currents is of great importance, the invention considers an ocean current model, can accurately predict the motion state of the objects so as to better control the objects, can greatly facilitate and simplify the physical experiment with huge engineering and high price by setting the ocean current model, and the experimental result is more accurate.
Therefore, the invention aims to provide a method for establishing a numerical simulation model of object falling in ocean current based on OpenFOAM, which can conveniently simulate the falling condition of objects with any shape and size under the ocean current conditions with different parameters, has lower cost, more flexible model establishment and setting, and great flexibility and wide practicability.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for numerically simulating the falling of an object in an ocean current, comprising:
establishing a pool model and an object model according to the initial pool parameters and the initial object parameters;
carrying out mesh division on the pool model according to preset mesh parameters; setting boundary conditions and fluid motion parameters of the pool model according to preset ocean current parameters to form a simulation ocean current model;
establishing a free falling model of the object model in the liquid according to preset physical parameters; the free fall model building step comprises the steps of setting a falling moving grid of the object model: generating a background grid of the hexahedral area; embedding the sub-grid of the object model falling into the background grid through the overset grid;
and (3) introducing the free falling model of the object model in the liquid into the simulation ocean current model, starting a simulation step, and simulating and outputting the motion trail, the motion speed and the change condition of the stress parameters of the object model in each direction.
In a second aspect, the present invention provides a numerical simulation system for the falling of an object in an ocean current, comprising:
the model building module is used for building a pool model and an object model according to the initial pool parameters and the object parameters, forming a simulated pool environment and carrying out meshing on the pool model according to preset mesh parameters;
the simulation ocean current environment forming module is used for setting boundary conditions of the model according to preset ocean current parameters to form a simulation ocean current model;
the simulated gravity environment module is used for setting gravity parameters according to preset object parameters, forming a gravity environment and establishing a model of free falling of an object in liquid;
and the simulation module is used for introducing a preset object model free falling model with initial speed into the ocean current model, starting a simulation step, performing simulation calculation, outputting the motion trail, the motion speed and the change condition of stress parameters of the object in each direction, and obtaining images of the parameters changing along with time.
In a third aspect, the present invention provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps in the method for numerical simulation of the descent of an object in an ocean current as set forth in the first aspect.
In a fourth aspect, the present invention provides a computer terminal, comprising a memory, a processor and a computer program stored on the memory and operable on the processor, wherein the processor executes the program to implement the steps of the method for numerical simulation of the falling of an object in an ocean current according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
1. the numerical simulation method for the object falling in the ocean current can conveniently simulate the falling condition of the object with any shape and size under the ocean current conditions with different parameters, has lower cost, more flexible model establishment and setting, and has great flexibility and wide practicability.
2. The invention provides a numerical simulation method for falling of an object in ocean current, which aims to enable the object to fall in the ocean current stably and realize effective control of the falling object in the ocean current.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a flow chart of a numerical simulation method for the falling of an object in an ocean current according to an embodiment of the present invention;
FIG. 2 is a pool model of an embodiment of the present invention;
FIG. 3 is a simulation model coordinate system of an embodiment of the present invention;
FIG. 4 is a schematic diagram of an overset grid in accordance with an embodiment of the present invention;
FIG. 5 is the evolution of the vertical position of the cylinder descending from a resting state;
FIG. 6 is a simulation of an object falling in an ocean current according to an embodiment of the present invention;
FIG. 7(a) is cylinder trajectory data of a horizontal cylinder falling in an ocean current according to an embodiment of the present invention;
fig. 7(b) is horizontal velocity data of a horizontal cylinder falling in an ocean current according to an embodiment of the present invention;
FIG. 7(c) is vertical velocity data of a horizontal cylinder falling in an ocean current according to an embodiment of the present invention;
FIG. 7(d) is horizontal force data of a horizontal cylinder falling in an ocean current according to an embodiment of the present invention;
FIG. 7(e) is vertical force data of a horizontal cylinder falling in an ocean current according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a numerical simulation system for object water entry according to an embodiment of the present invention.
The specific implementation mode is as follows:
the invention is further described with reference to the following figures and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, 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 is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only terms of relationships determined for convenience of describing structural relationships of the parts or elements of the present invention, and are not intended to refer to any parts or elements of the present invention, and are not to be construed as limiting the present invention.
In the present invention, terms such as "fixedly connected", "connected", and the like are to be understood in a broad sense, and may be a fixed connection, or may be an integral connection or a detachable connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be determined according to specific situations by persons skilled in the relevant scientific or technical field, and are not to be construed as limiting the present invention.
Example 1
The invention provides a numerical simulation method for falling of an object in ocean current, which comprises the following steps: establishing a pool model and an object model according to the initial pool parameters and the initial object parameters;
carrying out mesh division on the pool model according to preset mesh parameters; setting boundary conditions and fluid motion parameters of the pool model according to preset ocean current parameters to form a simulation ocean current model;
establishing a free falling model of the object model in the liquid according to preset physical parameters; the free fall model building step comprises the steps of setting a falling moving grid of the object model: generating a background grid of the hexahedral area; embedding the sub-grid of the object model falling into the background grid through the overset grid;
and (3) introducing the free falling model of the object model in the liquid into the simulation ocean current model, starting a simulation step, and simulating and outputting the motion trail, the motion speed and the change condition of the stress parameters of the object model in each direction.
Further, the step of establishing the pool module comprises: determining coordinate values of all points on the pool and the object through the blockMesh, and establishing boundary conditions of the pool and the object; the grid parameters of the pool and the object are the distance between grids in a three-dimensional coordinate system, and the distance value is set to be a uniformly-changed value according to a preset condition.
Further, the simulation ocean current model simulates a uniform flow with uniform fluid flowing speed and direction; setting boundary conditions of the ocean current model, and setting boundary conditions of upper and lower wall surfaces of the pool as wall to prevent water from leaking out of the upper and lower boundaries; the boundary conditions of the fluid velocity U and the pressure p at the outlet are set to zero gradient.
Further, the preset physical parameters include: a gravity parameter of the object.
Further, in order to represent the pose of the object model in the ocean current model, two cartesian coordinate systems, a world coordinate system and a load coordinate system, are defined.
Further, (o)gxgyg) Is a world coordinate system in which the origin is fixed to the left of the bottom of the numerical slot, Ogxg parallel to the free surface, OgygVertically upwards; (O)cxcyc) Is a load coordinate system, OcFixed at the center of mass of the load, OcxcAnd OgxgParallel, in the same direction, OgygAnd OcycParallel and opposite in direction; the load speed is controlled by the horizontal speed u and the vertical directionLower velocity v composition.
Further, the ocean current model comprises a fixed cylindrical streaming model and an ocean current-air model; the fixed cylindrical streaming model is an ocean current model with the upper and lower boundaries of the pool model being fixed walls, and is used for simulating and verifying data of cylindrical streaming; the ocean current-air model is based on the cylindrical streaming model, and a small amount of air is arranged at the upper part of ocean current to prevent the imbalance of gas-liquid pressure; the ocean current-air model may be used for later merging with a free-falling object model.
Further, the specific steps of the moving grid setting of the object falling include:
generating a background grid of the hexahedral region by using blockMesh;
embedding the sub-grid of the object model into the background grid through the overset grid; the sub-grid can move freely in the background grid, and the sub-grid and the background grid are independent from each other;
the size and shape of the load is set by setting the initial position coordinates of the object grid and generating the object grid.
Equation for building the object model descent.
Example 2
The embodiment discloses a method for establishing a numerical simulation model of object falling in ocean current, which specifically comprises the following steps:
fig. 1 is a flowchart of a numerical simulation method for falling of an object in an ocean current according to the present embodiment.
As shown in fig. 1, the method for simulating the falling of an object in an ocean current according to the present embodiment includes:
establishing a pool model and an object model according to the initial pool parameters and the object parameters to form a simulated pool environment, and performing grid division on the pool model according to preset grid parameters;
setting boundary conditions of the pool model and parameters of fluid flow according to preset ocean current parameters to form a simulation ocean current model;
setting gravity parameters according to preset object parameters to form a gravity environment and establish a model of free fall of an object in liquid;
and introducing a preset object free falling model with initial speed into a preset ocean current model, starting a simulation step, carrying out simulation calculation, outputting the motion trail, the motion speed and the change condition of stress parameters of the object in each direction, and obtaining an image of the parameters changing along with time.
The number of grids in the z-axis direction was set to 1, and the resulting numerical pool was as shown in fig. 2.
To represent the pose of an object in an ocean current, two cartesian coordinate systems are defined. This embodiment simulates the falling of a two-dimensional object in an ocean current. As shown in FIG. 3, (o)gxgyg) Is a world coordinate system in which the origin is fixed to the left of the bottom of the numerical slot, OgxgParallel to the free surface, OgygVertically upwards. (O)cxcyc) Is a load coordinate system, OcFixed at the center of mass of the load, OcxcAnd OgxgParallel, in the same direction, OgygAnd OcycParallel and opposite in direction. The load velocity consists of a horizontal velocity u and a vertical downward velocity v.
(1) Setting the size and grid size of a numerical pool
The numerical value pool is set to generate a grid by using a grid generation tool blockMesh carried by OpenFOAM, wherein the blockMesh is a program for generating the grid in a blocking mode, and the whole calculation domain is regarded as a large block. The calculation area is set as large as possible during the calculation, so that the calculation is not affected by the surrounding fixed wall surface.
(2) Ocean current model
In the whole simulation model, the flow of the numerical value pool fluid is realized by setting the initial conditions and the boundary conditions of the whole numerical value pool. The ocean current model set by us simulates a uniform flow with uniform speed and direction of fluid flow. Ocean currents flow in from the left side and out from the right side. Therefore, in setting the entire ocean current model, setting of the boundary condition is particularly important.
The preset ocean current parameters are as follows:
1) fixed cylinder streaming model
blockmesh：
Since the set pool is a two-dimensional model, the boundary type is set to empty on the front and back surfaces; setting the boundary condition of the cylinder to wall; the upper and lower boundaries of the flow field adopt symmetric boundary conditions to reduce the influence of the blockage rate on the flow; the remaining boundary conditions are set to patch.
U：
The inlet boundary condition is set to fixedValue and the internal velocity of the flow field interfield is set to the same value as the inlet velocity; at the exit 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 entrance of the flow field model, the boundary condition of the fluid pressure p is set to zeroGradient. At the exit 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 entry is set to a fixed value and the value is set to internalField; the exit type is set to variable height flowrate (and lowerBound to 1; upperBound to 0), which provides a phase fraction condition based on local flow conditions, limiting the value to lie between user specified upper and lower limits. The fixed wall boundary condition of the bottom of the pool is set to slip.
blockmesh：
Since the set pool is a two-dimensional model, the boundary type is set to empty on the front and back surfaces; the remaining boundary conditions are set to wall to prevent water from leaking out of the boundary.
U：
The air boundary conditions at the top and left top are set to pressurelnletoutetlettvelocity; at the inlet, the velocity U specifying the boundary condition is set to fixedValue, and the internal velocity of the flow field interfield is set to the same value as the inlet velocity. And the outlet, the speed U is set to zeroGradient, and the bottom of the water tank is set to slip.
p:
The upper and upper left air boundary conditions are set to totalPresure; at the inlet, the boundary condition for the fluid pressure p is set to fixedFluxPressure (where both the value of gradient and value are set to uniform 0). At the outlet, the pressure p is set to zeroGradient. The bottom of the water pool is set to be slip.
Here we have set two ocean current models in succession. The first is an ocean current model with fixed walls on the upper and lower boundaries of the pool model, which is used for simulating and verifying the data of cylindrical streaming so as to ensure the correctness of ocean current parameter setting. The second is that on the basis of the first, a small amount of air is arranged above the ocean current to prevent the imbalance of the gas-liquid pressure. This model can be used for later merging with a model of a free-falling object.
The uniform flow set by the simulation software is stable and convenient to control, and the change of the flow rate can be realized only by modifying the setting of the parameters. In the experimental process, the measured experimental data have small errors and high referential performance no matter for a fixed object or a sinking object.
(3) Moving grid arrangement for object falling
To correctly obtain the velocity and trajectory of the object, a background mesh of hexahedral regions is generated using blockMesh herein. On this basis, the sub-grid of the object is embedded into the background grid through the overset grid. Due to the simple structure of the object, the grid density of the background is uniform. FIG. 4 is an overset grid for simulating the fall of an object in a fluid. The submesh may move freely in 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 compute the entire flow field.
Setting the size and shape of the load. The invention adopts the load with relatively regular and simple shape, so that the initial position coordinates of the object grid are directly set by directly utilizing the blockMesh in OpenFOAM and the object grid is generated. However, the current model can also handle loads with complex and irregular shapes, and in this case, the object mesh can be guided into OpenFOAM after being drawn by CAD drawing software of a third party.
(4) Building equations for object descent
The water in our experiments was set as a two-dimensional viscous incompressible fluid, so the basic governing equations of the continuity equation and the Navier-Stokes equation are as follows:
wherein
Is the laplacian, t is time, x is the position vector, u is the velocity vector, g is the gravitational acceleration, ρ is the fluid density, μ is the fluid viscosity. p is a radical of*Can be defined as:
p*＝p-ρg·x
and adding a g file for setting a gravity field into the constant folder, and setting the magnitude and the direction of the gravity acceleration in the file. The density, center of gravity and mass of the object can be set if one wants to simulate free fall movements. Constraint conditions are added according to actual conditions, and the process that the mooring rope hoists the object downwards can be simulated.
(5) Adding ocean currents to a model and solving using a solver
After the dynamic grid, the gravity field and the solver of the set gravity model are set, the initial condition and the boundary condition of the gravity model are set according to the setting of the initial condition and the boundary condition of the whole numerical pool in the ocean current model. The present embodiment uses an incompressible InterDyMFoam, which is based on the law of conservation of mass, the law of conservation of momentum, and the law of transport of volume fractions.
In each time step, firstly, solving the motion parameters of the object through a six-degree-of-freedom (6-DOF) motion equation, and then updating the overjet motion grid through the motion parameters. The solver firstly disperses a mass conservation equation formula and a momentum conservation equation formula for describing fluid motion into a series of algebraic equations in an integral mode on the whole calculation space domain and the whole calculation time domain, so that each tiny grid unit is described by an equation, then solves the equations through simultaneous iteration to obtain an approximate solution of each equation, then obtains physical parameters of each tiny unit, then obtains physical parameters of the whole ocean current pool, and then updates the parameters and carries out next iteration until the iteration is completed.
(6) Data processing and analysis method
And after the solution is completed, the software paraview software is used for checking result information and observing the motion condition, the speed change condition, the fluid pressure change condition and the like of an object in the ocean current, the specific numerical information is extracted into an Excel file, and MAT L AB software is used for sorting data to obtain images and the like of horizontal force and vertical force applied to the load, the motion speed of the load and the motion track changing along with time, so that the motion of different conditions can be conveniently compared and analyzed.
The following specific simulation experiments of OpenFOAM-based object falling in ocean currents:
horizontal cylinder vertical surface falling water (water velocity is zero):
and (4) establishing a numerical calculation water pool according to the steps, and setting the initial falling speed of the cylinder to be 0 at the initial time. Data is output every 0.1s during the calculation. We extract the position of the cylinder every 0.2s, starting from time t-0. Fig. 5 shows the evolution of the vertical position of the cylinder from a rest state, and compared with the actual experiment. It can be seen from the evolution of the position of the cylindrical droplet that, on the same premise, it substantially coincides with the results of the reference experiment and also with the actual state of motion, which is more convenient and economical than physics.
Horizontal cylinder vertical surface falling water (water velocity is not zero):
and (3) establishing a numerical calculation water pool according to the steps, wherein at the initial moment, the lowest point of the horizontal cylinder is superposed with the horizontal plane, the falling speed of the cylinder is set to be 0.5m/s, and the water flow speed is respectively 0.1m/s and 0.2 m/s. Data were output every 0.001s during the calculation. And finally obtaining a simulation result of free falling of the cylinder in the ocean current. Fig. 6 shows the paraview display result.
The position change, speed change and stress data of the cylinder are extracted, and the data of the cylinder along with the change of time is drawn by a MAT L AB, as shown in FIG. 7:
it can be seen that the velocity of the ocean current has a large effect on the movement of the object in the horizontal direction, but a negligible effect in the vertical direction. The tested position change, speed change and stress data have very important reference values in practical engineering.
The method can simulate the free falling of the cylindrical object in the ocean current, import the object grids in various shapes after drawing is completed through blockMesh in OpenFOAM or CAD drawing software of a third party, and simulate the free falling process of the cylindrical object in the ocean current in a numerical pool. Therefore, simulation can be carried out in advance according to the shape of the goods in the actual engineering, hydrodynamic analysis is carried out, and the optimal control scheme is determined in advance.
Example 3
Fig. 8 is a schematic structural diagram of a numerical simulation system for the object falling in the ocean current according to the embodiment.
As shown in fig. 8, the present embodiment provides a numerical simulation system for an object falling in an ocean current, including:
(1) the model building module is used for building a pool model and an object model according to the initial pool parameters and the object parameters, forming a simulated pool environment and carrying out meshing on the pool model according to preset mesh parameters; the flow of the numerical value pool fluid is realized by setting the initial conditions and the boundary conditions of the whole numerical value pool.
The grid parameters are the intervals of the grids in an XYZ three-dimensional coordinate system, the interval values are all equal, and the interval values are adjustable numerical values.
(2) The simulation ocean current environment forming module is used for setting boundary conditions of the model according to preset ocean current parameters to form a simulation ocean current model; the object wall surface and the pool wall surface are set to be nonslip. At the entrance of the flow field model, the velocity U specifying the boundary condition is set to fixedValue, and the internal velocity of the flow field interfield is set to the same value as the entrance velocity. The boundary condition of the fluid pressure p is set to zero gradient. At the exit of the flow field model, the velocity U is set to zeroGradient and the pressure p is set to fixedValue. Symmetric boundary conditions are adopted by the upper and lower boundaries of the flow field to reduce the influence of the blockage rate on the flow. The model only simulates the interaction between the fluid and the object, without considering gravity. A free liquid level is set in the pool model, so that the lower part of the free liquid level is filled with water, and the upper part is filled with air.
(3) The simulated gravity environment module is used for setting gravity parameters according to preset object parameters, forming a gravity environment and establishing a model of free falling of an object in liquid;
(4) and the simulation module is used for introducing a preset object free falling model with an initial speed into the ocean current model, starting a simulation step, performing simulation calculation, outputting the motion trail, the motion speed and the change condition of stress parameters of the object in each direction, and obtaining an image of the parameters changing along with time.
Also provided in other embodiments are:
the present embodiment provides a computer-readable storage medium on which a computer program is stored, which when executed by a processor, implements the steps in the numerical simulation method of the object falling in an ocean current as described in embodiment 1.
This embodiment provides a computer terminal, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the program, the steps in the numerical simulation method for the object falling in the ocean current according to embodiment 1 are implemented.
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 (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.
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 of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (10)
1. A numerical simulation method for the falling of an object in an ocean current is characterized by comprising the following steps: establishing a pool model and an object model according to the initial pool parameters and the initial object parameters;
carrying out mesh division on the pool model according to preset mesh parameters; setting boundary conditions and fluid motion parameters of the pool model according to preset ocean current parameters to form a simulation ocean current model;
establishing a free falling model of the object model in the liquid according to preset physical parameters; the free fall model building step comprises the steps of setting a falling moving grid of the object model: generating a background grid of the hexahedral area; embedding the sub-grid of the object model falling into the background grid through the overset grid;
and (3) introducing the free falling model of the object model in the liquid into the simulation ocean current model, starting a simulation step, and simulating and outputting the motion trail, the motion speed and the change condition of the stress parameters of the object model in each direction.
2. A numerical simulation method according to claim 1, wherein the specific step of setting the dynamic mesh of the object model drop comprises:
generating a background grid of the hexahedral region by using blockMesh;
embedding the sub-grid of the object model into the background grid through the overset grid; the sub-grid can move freely in the background grid, and the sub-grid and the background grid are independent from each other;
the size and shape of the load is set by setting the initial position coordinates of the object grid and generating the object grid.
3. The numerical simulation method of claim 1, wherein the step of establishing a pool module comprises: determining coordinate values of all points on the pool and the object through the blockMesh, and establishing boundary conditions of the pool and the object; the grid parameters of the pool and the object are the distance between grids in a three-dimensional coordinate system, and the distance value is set to be a uniformly-changed value according to a preset condition.
4. A numerical simulation method according to claim 1, wherein the simulated ocean current model simulates a uniform flow of fluid flow having a uniform velocity and direction; setting boundary conditions of the ocean current model, and setting boundary conditions of upper and lower wall surfaces of the pool as wall to prevent water from leaking out of the upper and lower boundaries; the boundary conditions of the fluid velocity U and the pressure p at the outlet are set to zero gradient.
5. The numerical simulation method of claim 1, wherein the preset physical parameters include: a gravity parameter of the object.
6. A numerical simulation method according to claim 1, wherein in order to represent the pose of the object model in the ocean current model, two cartesian coordinate systems are defined, a world coordinate system and a load coordinate system, respectively.
7. The numerical simulation method of claim 1, wherein the ocean current model comprises a fixed cylindrical streaming model and an ocean current-air model; the fixed cylindrical streaming model is an ocean current model with the upper and lower boundaries of the pool model being fixed walls, and is used for simulating and verifying data of cylindrical streaming; the ocean current-air model is based on the cylindrical streaming model, and a small amount of air is arranged at the upper part of ocean current to prevent the imbalance of gas-liquid pressure; the ocean current-air model may be used for later merging with a free-falling object model.
8. A numerical simulation system for the descent of an object in an ocean current, comprising:
the model building module is used for building a pool model and an object model according to the initial pool parameters and the object parameters, forming a simulated pool environment and carrying out meshing on the pool model according to preset mesh parameters;
the simulation ocean current environment forming module is used for setting boundary conditions of the pool model and parameters of fluid flow according to preset ocean current parameters to form a simulation ocean current model;
the simulated gravity environment module is used for setting gravity parameters according to preset object parameters, forming a gravity environment and establishing a model of the object model falling freely in liquid;
and the simulation module is used for introducing a preset free falling model of an object model with an initial speed into a preset ocean current model, starting a simulation step, performing simulation calculation, outputting the motion trail, the motion speed and the change condition of stress parameters of the object in each direction, and obtaining images of the parameters changing along with time.
9. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, is characterized by carrying out the steps of the method for numerical simulation of the descent of an object in an ocean current according to any one of claims 1 to 7.
10. A computer terminal comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor, when executing the program, implements the steps in the method for numerical simulation of the falling of an object in an ocean current according to any one of claims 1-7.
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