Large-Eddy Simulation of Local Flows around the Head of a Breakwater

In this study, three-dimensional fluid motion in waves around the head of a semi-infinite vertical breakwater was investigated using large-eddy simulation (LES). Wave deformation, separation, and evolution of vortices were investigated to obtain basic data in order to develop a reliable model for predicting local scouring and for estimating local fluid forces acting on the structure. Moreover, the processes by which separated eddies are generated and evolved were discussed in detail in order to determine the mechanisms by which the separated vortices cause local failures of armor blocks and the mound of a breakwater. Two significant vertical separations appeared around both edges of the breakwater head, especially when the wave front passed each edge. The velocity field around the head of the breakwater became significantly three-dimensional because secondary horizontal and helical eddies arose due to the vertical gradient of shear associated with the vertical separation. Furthermore, during interactions among these eddies, a complex three-dimensional eddy structure was formed around the head of the breakwater. It is possible that the vertical velocity caused by the three-dimensional eddy structure is associated with the suspension of sediment around the structure.