Topographically controlled, breaking-wave-induced macrovortices. Part 2. Changing geometries

This is the second part of a series examining the behaviour of breaking-waveinduced macrovortices. The first part examined theoretically general behaviours during startup conditions, and gave computational results for macrovortex generation and their evolution on widely spaced breakwaters. In this paper, we extend and test qualitatively and quantitatively some of the basic results of Part 1, in particular the initial longshore vortex transport for a wide range of geometries ranging from narrow rip current topographies to isolated breakwaters. Accounting for the presence of a shoreline is found to be necessary for the representation of longshore vortex transport. Results show vortex motion ranging from strongly offshore in the case of a narrow rip current, to strongly longshore in the case of an isolated breakwater. Even with the significant approximations inherent in the analytical predictions, numerical computations using time-domain Boussinesq-type equations and laboratory experiments confirm the trends. Part 3 examines the horizontal mixing features of wave-induced flows over isolated (single-breakwater configuration) or multiple (ripcurrent configuration) submerged structures.