Numerical Simulation Of The Flow Fields Around Fishing Nets Under The Water Flow

There are three methods, includes theoretical analysis, physical experiment and numerical simulation, to investigate the current flow through and around the fishing nets and cages. A numerical simulation of the flow fields around fishing nets under the water flow is performed in this paper, the two dimesional and threee dimensional model of fishing net are established in different angle and velocity, the model is numerically simulated by finite volume approach, which is completed through the commercial available computational fluid dynamics(CFD) software FLUNET.The validation are conducted through two experiments, the drag and lift force of the net and current reduction behind the net can be obtained by the finite volume method. A comparison between the numerical simulation and the experiment data is made, the results show this method is useful for the numerical model about the flow fields around the fishing nets.The numerical model which simulates the flow fields around fishing net is designed by GAMBIT, the numerical meshes are unstructured grids in the GAMBIT, the element choices to triangular in 2D or tetrahedral in 3D, the size of the elements can be controlled quite effectively by the use of size function. In the numerical model the net is simplified a porous panel, so easy to use the porous model in FLUENT, the drag and lift coefficient are got through the finite volume method, which is used to get the drag and lift force of the net through pressure integral, the current reduction is the absolute difference between the inlet velocity and the mean velocity divided by the inlet velocity.In order to confirm the accuracy of the numerical model, a comparison between numerical model and experiment shows that the numerical simulation agrees well with the experiment data for both current reduction behind the net and the drag and lift force on the net. The agreement between measured and modeled data is good with a mean error of 15% when the attack angle from 30°to 90°, we can use this method to get the drag and lift coefficient and the velocity reduction. Through the three dimensional numerical results and 2-d numerical results contrast, three-dimensional numerical simulation has more small error, in order to reduce the numerical calculation the channel can be reduced in the three dimensional numerical. So this numerical simulation has a very important reference value in the projects.