Towards modelling wave-induced forces on an armour layer unit of rubble mound coastal revetments

Abstract

Wave-induced forces on an armour layer unit are key parameters for assessing the stability of rubble mound coastal revetment, but how to predict them accurately and efficiently remains an open question. This study explores the feasibility of using the Morison-type equation to convert numerically simulated porous media flow in an armour layer into the forces on a single armour unit. Wave flume tests are conducted, in which the forces on a cuboid placed in the armour layer of a sloped revetment were measured. In conjunction, numerical simulations were performed using an OpenFOAM solver, which treats the revetment as a porous media. The validated flow simulation was synchronized with the force measurement to illustrate the correlations between the predicted porous media flow and the impact force. Based on these correlations, a Morison-type predictor, which consists of inertial force, drag force, pressure gradient force and lift force, is proposed. The calibrated model can reasonably approximate the temporal variation of wave-induced force. However, it is found that the inertial coefficients vary significantly with the dynamic stability number and the initial submergence of the armour unit. Additional research is required to give a sufficiently large dataset for calibrating empirical formulae.