A simplified approach for fatigue life prediction of aquaculture nets under waves and currents

Abstract

With increasing trends to move fish farms to more exposed locations engineers need quick and accurate tools for creating initial design proposals. In this paper, a simplified analytical model for estimating the axial force in the ropes supporting the fish net is presented. Hydrodynamic loads acting on the net are calculated using a state of the art screen model. The simplified analytical model is a quasi-static solution based on the principle of virtual displacements. The assumed mode shape in the calculations is a simplification of the actual quasi-static displacement shape under combined wave and current loading in view of the high natural frequencies of pre-tensioned ropes compared to wave frequencies. The results from the simplified calculations are compared to numerical simulations performed in RIFLEX. The simplified method is extremely efficient with regard to computation time compared to the numerical simulations and is well suited for preliminary design of fish nets.