SCOUR AT THE HEAD OF A VERTICAL-WALL BREAKWATER

This paper presents the results of an experimental investigation on th e near-bed flow patterns, the bed shear stress amplification and scour around the head of a vertical-wall breakwater, using regular waves. T he Keulegan-Carpenter number (KC), based on the diameter of the breakw ater head, is found to be the major parameter that governs the flow an d the equilibrium scour depth. Basic flow structures are identified as function of KC. The scour depth is found to increase with increasing the Keulegan-Carpenter number. The necessary extent of the conventiona l stone protection is studied. An empirical formula is worked out for the width of the protection layer as function of KC. Also, the effects of head shape, the angle of attack and the presence of a co-direction al current are investigated. The results indicate that the scour depth is increased considerably in the presence of a current. Likewise, the scour depth is increased when the head shape is changed from a round shape to a sharp-edged one. It is found that the angle of attack is al so an influencing factor as regards the scour depth.