June 07, 2012: FB1-Seminar

10:30, Großer Konferenzraum WEST, Düsternbrooker Weg 20


Abstract:
The traditional approach to assessing shear-driven instability and mixing in density-stratified geophysical flows is to appeal to the Kelvin-Helmholtz (KH) mode of instability. This involves the generation of turbulence and mixing when the destabilizing shear overwhelms the stabilizing influence of the density stratification. This is also a common conceptual basis for turbulence and mixing parameterizations. However, this is a simplified view that does not consider alternate modes of instability and mixing in which the density stratification acts as a destabilizing influence on the flow. One such mode - the Holmboe mode - leads to the generation of internal waves that may cause turbulence and mixing through a fundamentally different process. The unique mixing behaviour, evolution of the wave field, and identification of Holmboe waves in a highly-stratified estuary are all described through the combined use of numerical simulations, laboratory experiments, field observations and analytical methods.