CN-117236224-B - Three-dimensional gridless numerical simulation method for hydrodynamic characteristics of netting

CN117236224BCN 117236224 BCN117236224 BCN 117236224BCN-117236224-B

Abstract

The invention discloses a three-dimensional gridless numerical simulation method for hydrodynamic characteristics of a netting. The method comprises the steps of obtaining a netting to be numerically simulated, constructing a fluid motion control equation according to a continuity equation and a momentum equation, carrying out discrete processing on the fluid motion control equation based on a smooth particle fluid dynamics method, combining a wave-making function to construct a gridless numerical water tank, carrying out Lagrange type particle discrete processing on the netting according to the shape of the netting, combining a screen model to construct a Lagrange type netting particle model, reading the Lagrange type netting particle model into the gridless numerical water tank, and carrying out gridless coupling calculation on the netting and fluid in each time step to obtain the fluid resistance suffered by the netting. The invention adopts a smooth particle fluid dynamics method to discrete a fluid control equation to realize numerical simulation of hydrodynamic characteristics of the netting in a complex marine environment, and can be widely applied to the technical field of marine engineering.

Inventors

Sun Pengnan
XU YANG
LIU NIANNIAN
PENG YUXIANG
Lv Hongguan
GUAN XIANGSHAN
HUANG XIAOTING
ZHONG SHIYUN
ZHANG XIANG

Assignees

中山大学

Dates

Publication Date: 20260512
Application Date: 20230926

Claims (7)

1. A three-dimensional meshless numerical simulation method of hydrodynamic characteristics of a netting, the method comprising: acquiring a netting to be numerically simulated; Constructing a fluid motion control equation according to a continuity equation and a momentum equation, performing discrete processing on the fluid motion control equation based on a smooth particle fluid dynamics method, and constructing a gridless numerical pool by combining a wave-making function; Performing Lagrange type particle discrete treatment on the netting according to the shape of the netting, and establishing a Lagrange type netting particle model by combining a screen model; reading the Lagrangian type netting particle model into the gridless numerical water tank, and carrying out gridless coupling calculation on the netting and fluid in each time step to obtain the influence of the netting on the fluid and the fluid resistance of the netting; The fluid motion control equation is constructed according to the continuity equation and the momentum equation, the fluid motion control equation is subjected to discrete processing based on a smooth particle fluid dynamics method, and a gridless numerical pool is constructed by combining a wave-making function, and the method comprises the following steps: Carrying out numerical pool model construction treatment on the netting according to a right-hand Cartesian coordinate system to obtain a numerical pool model; performing fluid motion analysis processing on the numerical pool model according to a continuity equation and a momentum equation to obtain a fluid motion control equation; performing discrete solution on the fluid motion control equation through kernel function approximation and particle approximation according to a smooth particle fluid dynamics method to obtain a discrete fluid motion control equation; Simulating the numerical pool model by combining the discrete fluid motion control equation and the wave-making function to obtain a gridless numerical pool; performing lagrangian type particle discrete processing on the netting according to the shape of the netting, and establishing a lagrangian type netting particle model by combining a screen model, wherein the lagrangian type netting particle model comprises the following steps: Performing Lagrange type particle discrete treatment on the netting according to the shape of the netting to obtain a netting particle space; establishing an influence relationship between the netting particles and the fluid particles on the netting particle space according to a hydrodynamic formula of the screen model to obtain a Lagrangian type netting particle model; said mesh-free coupling calculation of said netting and fluid at each time step comprising: calculating attack angles between the plane of the Lagrangian type netting particle model and the incoming flow direction in the gridless numerical water tank to obtain a netting attack angle; Calculating to obtain a lift coefficient and a resistance coefficient of each piece of netting particles in the Lagrangian type netting particle model according to the angle of attack of the netting; Fluid particles in the fluid within the influence range of the netting are obtained, kernel function interpolation processing is carried out on the netting particles according to the speed of the fluid particles, and the flowing speed of the positions where the netting particles are located is obtained; Calculating the fluid resistance of the netting particles according to the flow speed of the netting particles and the resistance coefficient; And summing the fluid resistance of all the netting particles on the netting to obtain the fluid resistance of the netting.
2. The method of claim 1, wherein said simulating the numerical pool model by combining the discretized fluid motion control equation and the wave-making function to obtain a gridless numerical pool comprises: expanding the boundary condition of the free surface of the numerical pool model according to a perturbation method to obtain a push plate motion equation; Performing second-order harmonic elimination treatment on the push plate motion equation to obtain a wave-making function; and carrying out wave simulation treatment on the numerical pool model through the wave-making function, and carrying out fluid motion simulation treatment on the numerical pool model through the discrete fluid motion control equation to obtain the gridless numerical pool.
3. The method of claim 1, wherein the fluid motion analysis of the numerical pool model according to the continuity equation and the momentum equation yields a fluid motion control equation comprising: Setting a wave-cutting boundary for the numerical pool model, and adding a source term into the momentum equation to perform wave-cutting treatment to obtain a wave-cutting momentum equation; And carrying out fluid motion analysis treatment on the numerical pool model according to the continuity equation and the wave-eliminated momentum equation to obtain a fluid motion control equation.
4. The method of claim 1, wherein calculating the angle of attack between the plane of the lagrangian-type netting particle model and the direction of incoming flow in the meshfree numerical basin comprises: Selecting netting particles from the Lagrangian type netting particle model, and performing position vector calculation on the netting particles to obtain normal vectors of the netting particles; Performing pointing calculation on the normal vector according to a sign function to obtain a normal vector pointing to the fluid flow direction; And performing inverse cosine trigonometric function calculation on the normal vector pointing to the fluid flowing direction to obtain the attack angle of the netting.
5. The method of claim 1, wherein said calculating from said angle of attack of the netting to obtain a lift coefficient and a drag coefficient for each netting particle in said lagrangian-type netting particle model comprises: obtaining the compactness of the netting; And calculating to obtain the lift coefficient and the resistance coefficient of each piece of netting particles in the Lagrange type netting particle model according to the compactness of the netting and the attack angle of the netting.
6. The method according to claim 1, wherein the obtaining fluid particles in the fluid within the influence range of the netting, and performing kernel function interpolation processing on the netting particles according to the velocity of the fluid particles, to obtain the flow velocity of the netting particles, includes: calculating according to the type of the fluid particles to obtain a position vector between the net particles and the fluid particles, and obtaining the fluid particles in the fluid within the influence range of the net according to the position vector to obtain first fluid particles; Solving the fluid motion control equation based on a smooth particle fluid dynamics method, and updating the first fluid particles to obtain second fluid particles; And calculating the network coating particles near the second fluid particles according to a kernel function interpolation formula to obtain the flow speed of the positions of the network coating particles.
7. The method of claim 1, wherein said calculating the fluid resistance of the netting particles from the flow velocity at which the netting particles are located in combination with the resistance coefficient comprises: acquiring fluid density and the volume of the netting particles; and calculating the fluid density, the volume of the netting particles and the flow speed of the netting particles according to a netting fluid resistance formula to obtain the fluid resistance of the netting particles.

Description

Three-dimensional gridless numerical simulation method for hydrodynamic characteristics of netting Technical Field The invention relates to the technical field of ocean engineering, in particular to a three-dimensional gridless numerical simulation method for hydrodynamic characteristics of a netting. Background Ocean pasture is an important path for transformation and upgrading of traditional fishery industry, and deep-open sea cultivation equipment is core equipment for developing ocean pasture. The deep-open sea cultivation faces a complex wave flow environment, extreme waves occur, the netting is used as an important component of the cultivation net cage, a large part of hydrodynamic load is born while the cultivation functions of maintaining the cultivation space and preventing the cultivation objects from escaping are achieved, and an accurate and efficient hydrodynamic calculation method for the netting is established and is important for improving the safety of the whole deep-sea cultivation equipment. The method of applying the empirical formula in the related art has simplified the complexity of the practical problem to some extent, but the simplification may deviate the expected result from the practical situation to some extent. The traditional grid method has the condition of numerical dissipation and has low simulation precision on strong nonlinear waves, and the problems of hydrodynamic characteristics of the netting in the complex wave field under high sea conditions are difficult to solve. In view of the foregoing, there is a need for solving the technical problems in the related art. Disclosure of Invention In view of this, the embodiment of the invention provides a three-dimensional meshless numerical simulation method for hydrodynamic characteristics of a netting, so as to improve the numerical simulation precision of the hydrodynamic characteristics of the netting. In one aspect, the invention provides a three-dimensional meshless numerical simulation method for hydrodynamic characteristics of a netting, comprising the following steps: acquiring a netting to be numerically simulated; Constructing a fluid motion control equation according to a continuity equation and a momentum equation, performing discrete processing on the fluid motion control equation based on a smooth particle fluid dynamics method, and constructing a gridless numerical pool by combining a wave-making function; Performing Lagrange type particle discrete treatment on the netting according to the shape of the netting, and establishing a Lagrange type netting particle model by combining a screen model; And reading the Lagrangian type netting particle model into the gridless numerical water tank, and carrying out gridless coupling calculation on the netting and the fluid in each time step to obtain the influence of the netting on the fluid and the fluid resistance of the netting. Optionally, the constructing a fluid motion control equation according to a continuity equation and a momentum equation, performing discrete processing on the fluid motion control equation based on a smooth particle fluid dynamics method, and constructing a gridless numerical pool by combining a wave-making function, including: Carrying out numerical pool model construction treatment on the netting according to a right-hand Cartesian coordinate system to obtain a numerical pool model; performing fluid motion analysis processing on the numerical pool model according to a continuity equation and a momentum equation to obtain a fluid motion control equation; performing discrete solution on the fluid motion control equation through particle approximation according to a smooth particle fluid dynamics method to obtain a discrete fluid motion control equation; And carrying out simulation treatment on the numerical pool model by combining the discrete fluid motion control equation and the wave-making function to obtain the gridless numerical pool. Optionally, the simulating the numerical pool model by combining the discrete fluid motion control equation and the wave-making function to obtain a gridless numerical pool comprises: expanding the boundary condition of the free surface of the numerical pool model according to a perturbation method to obtain a push plate motion equation; Performing second-order harmonic elimination treatment on the push plate motion equation to obtain a wave-making function; and carrying out wave simulation treatment on the numerical pool model through the wave-making function, and carrying out fluid motion simulation treatment on the numerical pool model through the discrete fluid motion control equation to obtain the gridless numerical pool. Optionally, the fluid motion analysis processing is performed on the numerical pool model according to a continuity equation and a momentum equation to obtain a fluid motion control equation, including: Setting a wave-cutting boundary for the numerical pool model, and adding a source ter