Numerical Investigation of the Effects of the Cross-Shore and Groyne-Wall Slopes on Flow Pattern Around an Impermeable Groyne

The groynes which are typical of shore protective structures can provide several aims. Although these structures may partly help to shoreline protection, they would also create some major problems in adjacent regions. Therefore the real performance of these structures needs to be considered carefully before going to construction. In this research, the effects of the cross shore and groyne wall slopes on flow pattern around an impermeable groyne were considered using a three-dimensional numerical CFD model (i.e., FLUENT). The widely accepted eddy viscosity concept and k-ε turbulence model were used to evaluate the Reynolds stresses and eddy viscosity coefficients, respectively. The finite volume method used in the software makes attractive flexibility to use any shape of grids to cover the cross and structural slopes in the computational domain. The model was first applied to a vertical groyne on a flat bed and the numerical model results were compared with experimental data. The model results of this numerical test showed a very good agreement with the corresponding experimental measurements, in terms of water elevation and velocity magnitudes. The model was then applied to a series of structures with different lateral slopes on various cross sectional bed slope. It was found that the flow pattern around the groyne was not changed significantly when the slopes of the structure and bed were slightly changed. The numerical model results, however, showed that by increasing the cross shore slope in any case of the lateral slope of the structure, the magnitude of the maximum velocity was decreased. The bed shear stresses were also decreased when the cross shore slope was increased. Moreover, these values were further decreased when the groyne-wall slope was reduced.