Towing cylindrical fishing gear components on cohesive soils

The analysis of penetration into cohesive soils of truncated rigid cylindrical objects that are associated with demersal trawl fishing is presented. Numerical simulations of three-dimensional models were performed using the finite element software ABAQUS to assess the influence that the dimensions, the weight, the cross-sectional geometry and the soil material properties have on penetration and drag. In general, over the parameter ranges examined; there is a non-linear increase in penetration and drag as the weight increases; there is a decrease in penetration and an associated reduction of drag as the Yield stress and Young's modulus increase; and the drag and penetration of aerofoil shaped cylinders are less than those of circular ones of similar weights and dimensions.

The non-dimensional form of the problem is examined and it is demonstrated that the penetration and drag values reduce respectively to expressions that are dependent solely, at least to a first order of approximation, on the non-dimensional weight, suggesting that the problem is essentially two-dimensional in nature and that three-dimensional effects at the edges of the clumps do not play a significant role.

We illustrate how these expressions can be used to evaluate the physical impact of towed gears and ultimately contribute to the development of fishing gears/techniques of reduced impact.