Fundamental boundary layer and turbulence research

The simulations of turbulent atmospheric and oceanic boundary layers are exposing the importance of coherent structures in turbulent transport, mixing under stably stratified conditions, and the key role of turbulence in boundary-layer frontogenesis and frontal arrest.   Ocean boundary layer simulations driven by time-evolving observed surface forcing are yielding essential information on the interaction of surface waves and buoyancy on vertical mixing.  A novel technique to determine stationarity within in-situ turbulence observations is yielding critical insight into the relationship between an observed mean wind and canopy drag.

BLT figure

Results from large eddy simulation (LES) of turbulent flow over steep laboratory waves. The upper left panel shows colored contours of the instantaneous streamwise velocity in an $x-z$ plane. Streamtraces of the vector $(u, w)$ depict flow separation from the wave crest. The lower panel shows the corresponding contours of static pressure fluctuation. The right panel compares the pressure form drag from the LES with measurements obtained in wind-wave tanks as function of the root-mean-square waveslope. The LES estimates, the colored symbols, are in very good agreement with the measurements, further details are described in Sullivan et al (2017).

Reference: Sullivan, P.P., M. L. Banner, R. P. Morisson, W. L. Peirson, 2017:Turbulent flow over steep steady and unsteady waves under strong wind forcing. Journal of Physical Oceanography, accepted.