Mixing and Across-Boundary Layer Transport in Colliding Internal Solitary Waves

Abstract:

Internal solitary waves are a well documented occurrence throughout the coastal oceans. Over the past two decades a variety of mechanisms have been identified through which these waves induce mixing and hydrodynamic instabilities throughout the water column. Near the bottom boundary, these waves have been associated with increased sediment resuspension. In this study, we considered the head on collisions of internal solitary waves. Mathematically, these collisions have been classified as “weak” and hence seemed a reasonable place to begin a systematic study of internal solitary wave collisions. Using well-resolved numerical simulations, we will demonstrate that head on collisions can, in fact, be far from weak. They induce significant overturning (and hence mixing) at the back of the wave after the collision has occurred, and induce instability near the bottom that can effectively transport tracer that is initially found in the bottom boundary layer. Unlike past studies in the literature, the near bottom instability does not manifest itself as a bursting separation bubble.