A new generation of tools for trawls Dynamic numerical simulation

IFREMER and ECN have been working together for almost ten years on problems related to the numerical simulation of trawls and more generally the numerical simulation of any kind of fishing gear. To develop such a simulation tool, we need to build (i) a software in which all the parameters of the fishing gear are taken into account; (ii) a software that computes the physical behaviour of the fishing gear (static or dynamic); (iii) a software to visualise the results of calculations. The most complex part of this work most of the time rests in the point (i), because of the huge amount of parameters and elements of an actual fishing net. We have already developed a tool (point (i), named Cachalot) to describe a trawl. However, this software was designed to build numerical meshes that are intended for the calculation software CATS. Thus, Cachalot software cannot take into account the most important actual building specifications of a trawl. The new method for calculating numerical meshes for trawls which we are presenting in this workshop, is in keeping with recent research results about dynamic simulation of nets: the previous limiting factors due to the hypothesis of CATS do not longer exist. It is now possible to compute a net with its actual parameters, like elasticity, symmetrical shape or not, strengthening rope, different kinds of meshes, hanging ratio, etc … We will present the operating mode and the possibilities of this new software. We will also show the different prospects of the simulation software : turning circle, obstruction, simulation of fish catch, etc … Finally, we will show some examples of application of these software : animation of pelagic and bottom trawls, twin trawls etc