Dynamic simulation of mid-water trawl in fishing simulator
In order to simulate the dynamic behaviors of mid-water trawl in fishing simulator, a hydrodynamic model of mid-water trawl is established according to lumped mass model and researches on the numerical method for solving the model have also been done. In the modeling process, the mid-water trawl has been simplified by using an equivalent method, then the trawl is divided into finite mass points connected with springs without mass and fluid force of each mass point is calculated by simplifying the point to a spherical object or a rod-shaped object. To take a relative bigger step size for calculation, calculated positions of mass points instituting variables of position are used to calculate connected mass points' elastic force and every mass point's equations can be solely solved. Simulation researches of a mid-water trawl have been done, and simulated results are compared with that of flume experiments, which verifies model's rationality.
Introduction of mesh resistance to opening in a triangular element for calculation of nets by the finite element method
Nets made of thick and stiff twines are used in fishing industry. The meshes of these nets are resistant to opening. To be able to calculate the shape of such nets, a triangular element modelling of the net is modified to introduce the opening mesh stiffness. The basic hypothesis is that the twines remain straight, and that the opening stiffness is located in the knots connecting the twines. The forces exerted on the element due to the opening stiffness, are calculated using the principle of virtual work. The results of calculation are given. Copyright © 2001 John Wiley & Sons, Ltd.
Calculation of net shapes by the finite element method with triangular elements
The calculation of net shapes is performed using the finite element method. A triangular element is developed for the modelling of the net. The main hypothesis is that the strain in each triangular element is constant, the net has only two directions of twine and the twines are elastic. The forces due to the tension in twines are described and calculated by a direct method. Results of the model based on such triangular elements are given. The comparison with a model where each twine is described as an elastic bar is quite good. Copyright © 1999 John Wiley & Sons, Ltd.