Hydrodynamic modeling of fishing nets

Design of efficient fish nets by means of small scale hydrodynamic models is of fairly recent origin in the United States. While investigators have developed basic equations for modeling flow around fish nets by considering the inertia and gravity forces as primary forces, they assume that the elastic deformations of twines and ropes in the net are negligible. However, the shape of the fish net and therefore the forces acting on it are affected by the elongation of twines and ropes under load. In order to allow the correct numerical transfer of model observations to the prototype, it is necessary to establish special hydrodynamic model laws which take the stress-strain characteristics of the model and prototype net materials into consideration. This paper outlines the establishment of such laws and their verification by full scale ocean tests and by laboratory tests. It is also shown how distortion of mesh and twine size prevents a relatively too high influence of viscous forces in the models.