Numerical modelling of wave-induced currents in the presence of coastal structures

Abstract

The hydrodynamic aspects of the general methodology of calculation of nearshore processes by means of numerical models are described. The paper focuses on the method implemented for calculating combined wave refraction-diffraction and reflection due to coastal structures and the associated radiation stresses. Results of numerical modelling are compared with experimental data obtained by Gourlay in the case of a shore-connected breakwater with periodic waves. A good agreement is found between both methods of investigation as concerns the spatial distribution of wave height and mean water level (wave-induced set-up). A good similarity of the wave-induced eddies in the lee of the structure is observed. A less satisfactory agreement is obtained between the velocity distributions in several profiles normal to the shore, although the overall order of magnitude is the same. A critical review of several wave-breaking criteria and sensitivity tests of the numerical model lead to advocate the use of the CERC criterion, particularly with steep beach slopes.