CN111783368B

CN111783368B - Shallow sea water physical parameter simulation method

Info

Publication number: CN111783368B
Application number: CN202010678064.2A
Authority: CN
Inventors: 常志邈; 韩复兴; 孙章庆; 王雪秋; 刘明忱
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2020-07-15
Filing date: 2020-07-15
Publication date: 2023-04-28
Anticipated expiration: 2040-07-15
Also published as: CN111783368A

Abstract

The invention provides a sea water physical parameter simulation method based on a smooth particle fluid dynamics algorithm (Smoothed Particle Hydrodynamics algorithm, hereinafter referred to as an SPH method) and a Gerstner wave sea surface simulation method (hereinafter referred to as a Gerstner method), which is used for generating initial sea water particles (the sea water particles do not refer to a single water molecule or substances consisting of a plurality of water molecules, but consider sea water in a certain volume as a whole from a macroscopic angle) by using the Gerstner method, so that the sea water particles conform to common sense distribution, and then the density estimation algorithm in the SPH method is used for combining the particle distribution and the density at a certain point of the sea water from the physical angle by considering the influence of an action range (namely smooth core and smooth radius). By utilizing the method, a complex and various seawater speed or density distribution model can be theoretically simulated, and data support basically conforming to reality is provided for the research of geophysical field simulation and the like.

Description

Shallow sea water physical parameter simulation method

Technical Field

The invention relates to the technical field of wave field simulation, in particular to a method for simulating physical parameters of shallow sea water.

Background

In previous studies, researchers have typically set parameters such as the velocity of sea water to a constant value to simulate the geophysical field, and in so doing, the manner of wave field propagation in sea water may be simulated, but the effect of sea water fluctuations on the numerical simulation is not considered. And another disadvantage of setting the sea water velocity to a constant value is the singleness of the model, which can only be tested by changing the magnitude and boundary of the sound wave velocity, and cannot simulate the physical parameters of the sea water which are complicated and diverse in real situations.

In order to solve the problem, the invention designs a model capable of generating complex shallow seawater sound wave speed and density parameter distribution by combining an SPH method and a Gerstner wave method, and the specific background technology is as follows.

In both the chemical and micro-physical fields, there is a relationship between micro-particles and macro-mass, which means that from the particle motion point of view, macro-physical parameters can be estimated in some way.

The Gerstner model was first introduced in 1986 by Fournier et al into the field of computer graphics processing, and this model describes the motion states of individual particles on the sea surface primarily from a kinetic perspective.

The basic idea of Gerstner wave is to consider the sea water movement as the movement of water particles, which in non-offshore ocean segments can be seen as circular (spherical in three dimensions), so that the collection of all water particles is displayed, thus effectively simulating the sea surface. Since the Gerstner wave describes particle motion, the basic description formula of the wave is written as a parametric equation. For the Gerstner wave, it produces a concentration of particles in the wave peak, that is, more closely fitting the sharp peak seen as the wave progresses. In practice this is also similar to waves in real large water depth environments.

The core of SPH is a smooth core. The particles will always interact with their surrounding particles during movement, which is effective and includes various types of chemical interactions, the range of which is known as smooth nuclei, which are usually circles or spheres, and the radius of this geometry is the smooth nuclei radius, representing the radius of maximum influence of the particles.

Although in the SPH algorithm the fluid is regarded as individually dispersed particles, in practice the fluid is continuous and if calculations are to be performed on the basis of particles, it must be considered that the effect of all relevant particles at a certain point is taken together as a calculated value.

Consider the presence of a point in a fluid

(of course, there is not necessarily a particle at this location), within the smooth core radius hA plurality of particles are arranged in the enclosure, and the corresponding positions of the particles are respectively +>

Then the cumulative formula for some item of attribute X at this place is:

x in the formula _j For a certain attribute needing accumulation, m _j ，ρ _j For the mass and density of the surrounding particles,

the position of the particles, h, is the smooth kernel radius, and the function W is the smooth kernel function.

In order to generate the speed model which is consistent with the reality, the invention combines the two methods to generate the model.

Disclosure of Invention

This section is intended to outline some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description summary and in the title of the application, to avoid obscuring the purpose of this section, the description summary and the title of the invention, which should not be used to limit the scope of the invention.

Therefore, the invention aims to provide a shallow sea water physical parameter simulation method which can improve the operation efficiency, simulate complex and various sea water speed or density distribution models, and provide data support basically consistent with reality for research in geophysical field simulation and the like.

In order to solve the technical problems, according to one aspect of the present invention, the following technical solutions are provided:

a method of shallow sea water physical parameter simulation, comprising: the method comprises the following steps:

step one: generating a random fluid particle distribution by using a Gerstner wave method;

step two: setting an attenuation function;

step three: calculating the physical parameter value of each grid point by utilizing an SPH method;

step four: the data before boundary removal of the density distribution of the shallow seawater is obtained, the density distribution can be obtained through removing the boundary effect, the pressure change of the shallow seawater is ignored by utilizing the density distribution data, and the sound wave speed distribution data of the shallow seawater is obtained through a sea water sound wave speed empirical calculation formula.

As a preferable scheme of the method for simulating the physical parameters of the shallow sea water, the invention comprises the following steps: step one: the fluid particle distribution displays the sea surface morphology, and a form of adding random phases is adopted in the generation process, so that the model is more in line with common sense.

As a preferable scheme of the method for simulating the physical parameters of the shallow sea water, the invention comprises the following steps: step two: and setting an attenuation function, and selecting an inverse proportion function attenuation.

As a preferable scheme of the method for simulating the physical parameters of the shallow sea water, the invention comprises the following steps: step three: the calculated physical parameter is an average value over a smooth core range.

Compared with the prior art, the method has the advantages that the Gerstner method is used for generating initial seawater particles (the seawater particles do not refer to a single water molecule or substances consisting of a plurality of water molecules, but the seawater in a certain volume is regarded as a whole from a macroscopic angle), so that the seawater particles are ensured to conform to common sense distribution, then the influence of an action range (namely smooth core and smooth radius) is considered by utilizing a density estimation algorithm in the SPH method, the particle distribution and the density at a certain point of the seawater are combined from the physical angle, the operation efficiency is improved, a complicated and various seawater speed or density distribution model is simulated, and data support basically conforming to reality is provided for the research in the aspects of geophysical field simulation and the like.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings, which are to be understood as merely some embodiments of the present invention, and from which other drawings can be obtained by those skilled in the art without inventive faculty. Wherein:

FIG. 1 is a simulated flow chart of the present invention;

FIG. 2 is a Gerstner base waveform diagram of the present invention;

FIG. 3 is a morphology of a smooth core of the present invention;

FIG. 4 is a graph showing the simulated density distribution of sea water at a wind speed of 8 units according to the present invention;

FIG. 5 is a simulated velocity profile of sea water sound waves at a wind speed of 8 units according to the present invention;

FIG. 6 is a graph of simulated sea water sonic velocity distribution (small) for a wind speed of 15 units according to the present invention;

FIG. 7 is an enlarged view of the simulated sonic velocity profile of seawater at 15 units of wind speed in accordance with the present invention;

FIG. 8 is a graph of simulated sea water sonic velocity distribution (including sea surface wave conditions) for 20 units of wind speed according to the present invention.

Detailed Description

In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.

Next, the present invention will be described in detail with reference to the drawings, wherein the sectional view of the device structure is not partially enlarged to general scale for the convenience of description, and the drawings are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

The invention provides a method for simulating physical parameters of shallow sea water, which can improve the operation efficiency, simulate complex and various sea water speed or density distribution models, provide data support basically consistent with reality for the research of geophysical field simulation and the like, and refer to fig. 1-8, and comprises the following steps:

step one: the Gerstner wave method is used for generating the random fluid particle distribution, and the Gerstner wave is a gravitational wave in the mathematical description sense, so that the Gerstner wave can basically show the sea surface morphology, and a mode of adding random phases is adopted during generation, so that the model is more in line with common knowledge. The Gerstner wave is generated through a parameter equation, and the position of each water particle is calculated, so that the sea surface fluctuation condition is obtained;

step two: giving an attenuation function, namely, assuming that the sea water energy is attenuated according to a certain rule from top to bottom, which is the key of converting the water surface into the water body, selecting an inverse proportion function attenuation, namely, the rule that the energy is reduced along with the depth is an inverse proportion function change rule;

step three: the physical parameter value of each grid point is calculated point by point using the SPH method, in which a method of calculating a physical parameter using water particle distribution is given. It is worth mentioning that there is not necessarily a particle at each grid point, i.e. the calculated physical parameter is simply an average value over a smooth kernel. The density calculation formula in the SPH method is utilized in calculation;

step four: the data before boundary removal of the density distribution of the shallow seawater is obtained, the density distribution can be obtained through removing the boundary effect, the pressure change of the shallow seawater is ignored by utilizing the density distribution data, the sound wave velocity distribution data of the shallow seawater is obtained through a sea water sound wave velocity empirical calculation formula, the sound wave calculation is carried out by utilizing the empirical formula commonly used in ocean science, and the pressure is regarded as a constant value (the assumption is made because the sea water is shallow).

In order to better explain the effects of the above embodiment, a specific example is given below:

examples: assuming that the wind speed of a sea area is 8 units and 15 units (the grid spacing is set to be 0.1m multiplied by 0.1 m), programming calculation is performed by the method, the grid size is set to be 100 multiplied by 100, the obtained grid size is 42 multiplied by 37 after boundary cutting processing, and the sound wave velocity distribution can be obtained through an empirical calculation formula of the density-to-sound wave velocity, and the simulation flow is shown in fig. 1. The density distribution of 8 unit wind speeds is shown in fig. 4, the sonic velocity distribution of 8 unit wind speeds is shown in fig. 5, the sonic velocity distribution of 15 unit wind speeds is shown in fig. 6, the sonic velocity enlargement of 15 unit wind speeds is shown in fig. 7, and the model comprising the rough sea surface is shown in fig. 8. (all abscissas in the figure represent lateral extent, and ordinates represent longitudinal depth).

Although the invention has been described hereinabove with reference to embodiments, various modifications thereof may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the features of the disclosed embodiments may be combined with each other in any manner as long as there is no structural conflict, and the exhaustive description of these combinations is not given in this specification merely for the sake of omitting the descriptions and saving resources. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. The method for simulating the physical parameters of the shallow sea water is characterized by comprising the following steps of:

step one: generating random fluid particle distribution by using a Gerstner wave method, and generating initial seawater particles by using the Gerstner wave method, wherein the seawater particles do not refer to a single water molecule or a substance consisting of a plurality of water molecules, but consider seawater in a certain volume as a whole from a macroscopic angle, so that the seawater particles are ensured to accord with common sense distribution;

step two: setting an attenuation function, namely, assuming that the sea water energy is attenuated according to a certain rule from top to bottom, which is the key of converting the water surface into the water body, selecting an inverse proportion function attenuation, namely, the rule that the energy is reduced along with the depth is an inverse proportion function change rule;

step three: calculating the physical parameter value of each grid point by using an SPH method, wherein the calculated physical parameter is an average value in a smooth nuclear range;

2. The method for simulating physical parameters of shallow sea water according to claim 1, wherein the first step is: the fluid particle distribution exhibits sea morphology, in the form of adding random phase at the time of generation.