Studies on hydrodynamic characterisation and optimisation of vertical cellular breakwater

Abstract

Permeable and slender coastal protection systems are gaining ground in the field since newlinethese are relatively economical and easy to construct especially in cases where newlinetraditional breakwaters are not feasible. In this study, a vertical cellular breakwater newlineconsisting of prefabricated rectangular cells with two vertical permeable walls newlinesupported by two rows of vertical circular piles is proposed. The vertical wall consists newlineof a perforated upper part and a lower part with horizontal slots. The numbers of cells newlineare varied depending upon the water depth. The wave transmission, reflection and newlineenergy dissipation characteristics of the breakwater under regular waves for a normal newlineangle of incidence are studied experimentally and theoretically. An empirical formula newlinefor determining the friction coefficient of a double walled permeable vertical newlinebreakwater is proposed in terms of variables such as the porosities of the seaward side newlineand the shoreward side vertical walls, the gap between the walls and the depth of newlinewater. The values of friction coefficient in the permeability parameter of a vertical newlinepermeable breakwater are estimated on the basis of the best-fit between the predicted newlineand experimental values of hydrodynamic coefficients such as transmission, reflection newlineand energy dissipation coefficients. A theoretical model based on the eigenfunction newlineexpansion method is used to predict the hydrodynamic coefficients of the breakwater. newlineThe validity of the proposed formula is evaluated by conducting experiments and by newlinecomparing with published results. A methodology based on multi-objective newlineoptimisation is proposed for the optimal design of a vertical cellular breakwater. newlineMaximisation of wave energy dissipation coefficient and minimisation of the volume newlineof material used in the breakwater are the two objectives considered. The newlinemethodology employed in this study uses a theoretical model to determine the wave newlineenergy dissipation coefficient and material volume in the vertical cellular breakwater.