CN-122021433-A - Method for simulating aquaculture net structure based on immersion boundary correction method

CN122021433ACN 122021433 ACN122021433 ACN 122021433ACN-122021433-A

Abstract

The invention provides a method for simulating a aquaculture net structure based on a method for correcting submerged boundary, and belongs to the field of mariculture. The method comprises the steps of selecting a grid unit penetrated by a aquaculture net interface as an immersed boundary unit, calculating a continuous forced source item of the immersed boundary unit by adopting an improved Darcy-Forchheimer equation, applying the continuous forced source item to a momentum equation in the immersed boundary unit by adopting a semi-implicit processing method, and finally solving and updating field quantities such as speed, pressure and the like in a calculation domain by adopting a computational fluid mechanics method to realize simulation calculation of an aquaculture net structure. According to the invention, the submerged boundary method is adopted to simulate the aquaculture net structure, so that the generation difficulty of a calculation grid is reduced, the Darcy-Forchheimer equation for calculating the continuous forced source term is improved, the semi-implicit processing method of the continuous forced source term is adopted, the simulation capability of the aquaculture net box with a complex shape is improved, the calculation efficiency is remarkably improved, and the hydrodynamic characteristics and the distribution characteristics of surrounding flow fields of the aquaculture net structure can be accurately simulated.

Inventors

ZHAO HAISHENG
Hu Dieyang
LENG ZHIPENG
LENG SHUDONG
LI XIN
SHI WEI
ZHAO MEIXIA

Assignees

大连理工大学
大连理工大学宁波研究院

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (7)

1. The method for simulating the structure of the aquaculture net based on the method for correcting the immersed boundary is characterized by comprising the following steps of: S1, establishing a net numerical simulation model based on actual parameters of the aquaculture net; s2, selecting an immersed boundary unit based on the numerical simulation model of the netting; s3, calculating continuous forced source items of the immersed boundary units according to the latest calculated domain velocity field based on the improved Darcy-Forchheimer equation; s4, discretizing a control equation of a calculation domain of the numerical simulation model of the net to obtain a discretization momentum equation and a discretization pressure poisson equation in each grid unit of the calculation domain; s5, applying continuous forced source items to the discretization momentum equation in the immersed boundary unit, and performing semi-implicit treatment on the source items to obtain the continuous forced discretization momentum equation; s6, solving a discretization momentum equation and a discretization pressure poisson equation in all grid cells including the immersed boundary cell to obtain a calculation domain speed field and a pressure field under the current time step; And S7, circularly executing the steps S3-S6 until the speed field and the pressure field of all time steps in the calculation domain are calculated, and obtaining the final distribution condition of the netting stress and the flow field.
2. The method for simulating a structure of a aquaculture net according to claim 1, wherein in step S1, the modeling of the net based on actual parameters of the aquaculture net comprises: Creating a corresponding geometric model file based on the actual shape and size of the aquaculture net; Determining a global coordinate system and a corresponding grid computing domain in an OpenFOAM environment, and encrypting grids near the aquaculture netting according to computing requirements; Boundary conditions are set for the numerical simulation model, and initial conditions are set for the velocity field and the pressure field of the computational domain.
3. The method for simulating a structure of a aquaculture net based on a modified immersion boundary method according to claim 2, wherein in step S2, said selecting immersion boundary cells based on a net numerical simulation model comprises: selecting grid units penetrated by a aquaculture net interface as immersed boundary units in a calculation domain based on a geometric model file of the aquaculture net and the established calculation domain grid; recording the interface between the aquaculture net structure and the immersed boundary units, and calculating the area and unit normal vector of the interface in each immersed boundary unit.
4. A method for simulating a structure of a aquaculture net based on a modified immersion boundary method according to claim 3, wherein in step S2, in step S3, a continuous forced source term of the immersion boundary element is calculated, specifically as follows: (1) (2) In the formula, Forcing a source term for each submerged boundary element in succession; Is hydrodynamic viscosity; a fluid velocity vector within each submerged boundary unit; is the fluid density; An area of interface within each submerged boundary element; And Respectively an improved viscosity coefficient matrix and an improved inertia Darcy-Forchheimer coefficient matrix; And Improved Darcy-Forchheimer viscosity coefficients for normal and tangential, respectively; And Improved inertia coefficients of Darcy-Forchheimer in normal and tangential directions, respectively, and improved And The following conversion relation exists between the traditional Darcy-Forchheimer coefficient matrix and the traditional Darcy-Forchheimer coefficient matrix: (3) In the formula, And Conventional Darcy-Forchheimer viscosity coefficients, normal and tangential, respectively; And The inertia coefficients of the traditional Darcy-Forchheimer are normal and tangential respectively; virtual thickness in a traditional porous medium model; In actual calculation, the improved Darcy-Forchheimer coefficient matrix is subjected to coordinate transformation: (4) (5) In the formula, A unit normal vector for each submerged boundary element inner interface; Is a unit matrix; And The modified Darcy-Forchheimer coefficient matrix after coordinate transformation is respectively used.
5. The method for simulating a structure of a aquaculture net according to claim 4, wherein in step S4, the discretized momentum equation and the discretized pressure poisson equation in each grid cell are as follows: based on a finite volume method, discretizing a control equation of a calculation domain of a numerical simulation model of the netting to obtain a discretization momentum equation and a discretization pressure poisson equation in each grid unit: (6) (7) In the formula, And Is the influence coefficient of the grid unit itself; And The influence coefficients of each adjacent cell of the grid cells; Is a constant vector; Is a constant; Representing a velocity vector within the current time step grid cell; a velocity vector within each adjacent cell of the current time step grid cell; representing the pressure within the current time step grid cell; is the pressure within each adjacent cell of the current time step grid cell.
6. The method for simulating a structure of a aquaculture net based on a modified submerged boundary method according to claim 5, wherein in step S5, said continuously forced discretized momentum equation is obtained based on the following method: Applying a continuous forcing source term to the discretized momentum equation within the submerged boundary element, yields: In the formula, The influence coefficient of the immersed boundary unit; The influence coefficients of each adjacent unit of the immersed boundary unit; Is a constant vector; And Respectively representing velocity vectors in the boundary units immersed in the current time step and the last time step; immersing velocity vectors in each adjacent cell of the boundary cell for the current time step; Semi-implicitly processing the continuous forced source term in the formula (8) to obtain a continuous forced discretization momentum equation: (9) In the formula, And Respectively as a matrix And Is a trace of (1).
7. The method for simulating a structure of a aquaculture net based on a modified immersion boundary method according to claim 6, wherein in step S6, the solving process of the calculated domain velocity field and the pressure field at the current time step comprises: Based on a turbulence theory, respectively obtaining a turbulence equation of turbulence kinetic energy and turbulence dissipation ratio, discretizing the turbulence equation by adopting a finite volume method, and carrying out iterative solution on the discretized turbulence equation in each grid unit in a calculation domain to obtain an updated turbulence kinetic energy field and a updated turbulence dissipation ratio field; and solving a discretization momentum equation and a discretization pressure poisson equation in all grid cells including the immersed boundary cells by adopting a pressure implicit operator splitting algorithm, introducing an updated turbulence kinetic energy field and a turbulence dissipation rate field in the solving process to carry out turbulence correction on the velocity field, and obtaining a velocity field and a pressure field in the current time step after updating.

Description

Method for simulating aquaculture net structure based on immersion boundary correction method Technical Field The invention belongs to the technical field of mariculture, and relates to a culture netting structure simulation method based on a modified submerged boundary method. Background With the rapid development of marine pasture and deep-open sea cultivation, cultivation facilities gradually develop to large-scale and deep-water, wherein the cultivation netting is used as a core bearing and enclosing structure, and the hydrodynamic characteristics of the cultivation netting directly influence the structural safety, the running stability and the cultivation environment quality of a cultivation system. Therefore, the hydrodynamic action mechanism of the aquaculture net is studied deeply, the influence of the hydrodynamic action mechanism on the flow field and the stress characteristic is accurately described, and the method has important engineering significance for improving the safety of an aquaculture system and improving the aquaculture water environment. At present, compared with a culture netting model test, the numerical simulation means has the advantages of low cost and easy implementation, and is widely developed and applied. The computational fluid dynamics method based on the porous medium model can effectively simulate hydrodynamic properties of the netting and distribution of surrounding flow fields. However, the computing method has the defects of complex computing domain meshing process, insufficient processing capacity for complex shapes and low computing efficiency. Disclosure of Invention In view of the above, the invention develops a method for simulating the structure of the aquaculture net based on a method for correcting the immersion boundary, which adopts a continuous forced immersion boundary method to simulate the aquaculture net, can realize the rapid simulation of the structure of the aquaculture net, can accurately calculate the hydrodynamic characteristics and wake characteristics of the structure of the aquaculture net under the action of water flow, and analyzes the influence of the structure of the aquaculture net on the distribution of surrounding flow fields. The technical scheme adopted by the invention is as follows: A method for simulating a aquaculture net structure based on a method for correcting immersion boundary comprises the following steps: S1, establishing a net numerical simulation model based on actual parameters of the aquaculture net; s2, selecting an immersed boundary unit based on the numerical simulation model of the netting; s3, calculating continuous forced source items of the immersed boundary units according to the latest calculated domain velocity field based on the improved Darcy-Forchheimer equation; s4, discretizing a control equation of a calculation domain of the numerical simulation model of the net to obtain a discretization momentum equation and a discretization pressure poisson equation in each grid unit of the calculation domain; s5, applying continuous forced source items to the discretization momentum equation in the immersed boundary unit, and performing semi-implicit treatment on the source items to obtain the continuous forced discretization momentum equation; s6, solving a discretization momentum equation and a discretization pressure poisson equation in all grid cells including the immersed boundary cell to obtain a calculation domain speed field and a pressure field under the current time step; And S7, circularly executing the steps S3-S6 until the speed field and the pressure field of all time steps in the calculation domain are calculated, and obtaining the final distribution condition of the netting stress and the flow field. Further, in step S1, the establishing a net numerical simulation model based on the actual parameters of the aquaculture net includes: Creating a corresponding geometric model file based on the actual shape and size of the aquaculture net; Determining a global coordinate system and a corresponding grid computing domain in an OpenFOAM environment, and encrypting grids near the aquaculture netting according to computing requirements; According to the simulation requirement, boundary conditions are set for the numerical simulation model, and initial conditions are set for the velocity field and the pressure field of the calculation domain. Further, in step S2, the selecting a submerged boundary unit based on the numerical simulation model of the netting includes: selecting grid units penetrated by a aquaculture net interface as immersed boundary units in a calculation domain based on a geometric model file of the aquaculture net and the established calculation domain grid; recording the interface between the aquaculture net structure and the immersed boundary units, and calculating the area and unit normal vector of the interface in each immersed boundary unit. Further, in step S3, based on the modified Dar