Analysis of drag force, deformation and stress distribution of biofouled flexible nets

Abstract

This research integrates laboratory experiments and numerical simulations to examine hydrodynamic behavior and structural responses of clean and biofouled flexible nylon nets under varying current velocities and attack angles. Experiments were conducted in a recirculating water channel, while fluid-structure interaction simulations coupled a large-deformation nonlinear structural model with large-eddy simulation. Results indicate that biofouling elevates drag forces by 35.5–41.4 % across tested velocities ranging from 0.3 m/s to 0.8 m/s. In addition, biofouling fundamentally alters deformation and stress patterns, increasing peak equivalent stresses and intensifying local stress concentrations at knots and attachment points. It follows that the stress distribution becomes more heterogeneous, thus increasing the risk of twine failure. Furthermore, net solidity, aperture size and twine diameter critically influence hydrodynamic loading and have been analyzed and assesed.