Date: 04/09/09

Speaker: Dr. K. Hendrickson

Title: The study of breaking waves through numerical simulation

Abstract:
This talk is an update on ongoing work in the study of breaking waves
through numerical simulation.  The first part focuses on the study of
the mechanisms of energy transfer at the air-water interface during
wave breaking.  Understanding the effect wave breaking has on this
mechanism is important for understanding the coupled air-sea boundary
layer and its role on ocean and climate modeling.  An inviscid and
viscous mechanism for interfacial energy transfer is identified that
is based on the presence of a surface normal velocity component.  The
viscous and inviscid components of this term are computed directly for
a range of non-breaking and breaking Stokes waves.  For the
non-breaking waves, we show that there is no net transfer of energy at
the air-water interface within its wavelength.  As the intensity of
the breaking increases, the amount of net energy transfered from the
water to the air increases.  This finding is in opposition to what
conventional wisdom dictates as the process during wave breaking.  We
show that for some waves this energy transfer from the water to the
air can be a significant portion of the energy lost to the wave in
wave breaking.

The second part of this talk focuses on the simulation of breaking
waves using Large Eddy Simulation (LES).  The use of LES for breaking
waves allows us to simulate waves at a scale (wavelength) much larger
than that achieved by Direct Numerical Simulation.  We develop a
formulation and its associated closure models and show the performance
of these models in a priori and a posteriori testing.  The a
posteriori simulations of the breaking waves report the same amount of
kinetic energy lost to breaking waves as the DNS simulations.