Modelling fishing nets as porous surfaces for understanding demersal trawling seabed impact

Bottom trawling is a globally practised fishing technique where the fishing gears are trawled close to the seabed. It is often associated with large amounts of by-catch, poor fuel efficiency and the alteration of the seabed. This study computationally simulates the flow through fishing nets by modelling them as surfaces for applying porous media models to understand the effect of different parameters associated with bottom trawling.
The netting surface of a demersal fishing gear is complex in shape. However, usually, there are several types of netting panels joined in a single gear making it easy to simulate if modelled as triangulated surfaces. In this study, simulations were carried out of a rigid net panel being trawled close to the seabed. The resulting wall shear stress on the bottom boundary was investigated to provide a better understanding of sediment entrainment in the panels wake.
Results show that the faster and closer we tow the netting to the seabed, the higher the wall shear stress peak experienced on the seabed, the magnitude of which is large enough to mobilise fine sand sediments.