Refined calculation model for NaLA, a fishing net shape simulator, applicable to gill nets

ABSTRACT:   The purpose of the present paper was to describe the dynamic behavior of gill nets using the computer-aided simulation NaLA (net shape and loading analysis), a system that was developed for determining net shape and load. The general calculation model of the system was refined after considering gill net construction and the environment during operation, such as wave motion and the boundary conditions of the water surface and bottom. This method models a gill net as a group of lumped masses interconnected by springs without mass, which are arranged as knots, mesh bars, netting lines, and other rigging components. Equations of motion are then derived for each lumped mass point. Net shape, mesh opening angle, and tension distribution are estimated at each time-step by using a PC to solve the system of equations. To examine the applicability of the refined calculation model of NaLA to gill nets, experiments were conducted with a gill net in a water channel. The experimental and calculated net shape, loading, and mesh opening angles were compared. The results agreed well, confirming that the refined calculation model of NaLA for gill nets is applicable to estimate the dynamic behavior of gill nets.