Oscillatory Flow Across an irregular boundary
Oscillatory flow past a rough boundary is a prevalent feature in a number of oceanographic situations from estuarine environments to continental slopes. These flows include tidal flows past headlands and across undersea canyons and ridges as well as in wave boundary layers over bedforms. At the core of the problem of flow over rough topography is the issue of flow separation. Separation introduces vorticity into larger scales, which can, in turn, generate residual flows, particularly in cases where eddies are created systematically and may linger near the generation site. A fundamental aspect in the ability of this periodic eddy field to generate mean currents is the persistence of this field over a tidal cycle. The longevity of coherent eddies is, in turn, determined by the dissipation due to bottom and surface stresses, turbulence and internal wave generation.
Laboratory experiments, conducted at the University of Washington in collaboration with Parker MacCready, examined oscillatory flow along a coastline with a series of headlands or ridges and revealed a mechanism for the transfer of momentum and mass from the boundary to the interior flow through the establishment of organized residual flow patterns. The experiments examine the homogeneous density case with two-dimensional roughness.
Mean vorticity field and velocity vectors
for oscillatory flow past a single ridge
