A Lagrangian approach for the coupled simulation of fixed net structures in a Eulerian fluid model

Abstract

A Lagrangian approach for the coupled numerical simulation of fixed net structures and fluid flow is derived. The model is based on solving the Reynolds-averaged Navier–Stokes equations in a Eulerian fluid domain. The equations include disturbances to account for the presence of the net. For this purpose, forces on the net are calculated using a screen force model and are distributed on Lagrangian points to represent the geometry of the net. In comparison to previous approaches based on porous media representations, the new model includes a more physical derivation and simplifies the necessary numerical procedure. Hence, it is also suitable for arbitrary geometries and large scale simulations. An extensive validation section provides insight into the performance of the new model. It includes the simulation of steady currents through single and multiple fixed net panels and cages, and wave propagation through a net panel. Different solidities, inflow velocities and angles of attack are considered. The comparison of loads on and velocity reductions behind the net with available measurements indicates superior performance of the proposed model over existing approaches for a wide range of applications.