PHYSICAL MATHEMATICS SEMINAR


TOPIC:		WAVE-DRIVEN CURRENTS AND VORTEX DYNAMICS
		ON BARRED BEACHES


SPEAKER:	OLIVER BUHLER
		Department of Mathematics and Statistics
		University of St Andrews
		Scotland, United Kingdom.

ABSTRACT:

Theoretical and numerical results are presented on longshore
currents driven by breaking waves on beaches, especially barred beaches.
The wave envelope is allowed to vary in the alongshore direction, which
leads to the generation of strong dipolar vortex structures where the
waves are breaking.  The nonlinear evolution of these vortex structures is
studied using a simple analytical model of the effects due to a sloping
beach.  Among other things, a robust mechanism is found through which the
location of the longshore current can move shorewards from the location of
wave breaking.  Such current dislocation is an often-observed (but poorly
understood) phenomenon on real barred beaches.

These results are underpinned by developing the relevant wave-mean
interaction theory for a sloping shallow-water beach, incorporating
effects due to wave transience, inhomogeneity, and dissipation.
Nonlinear numerical simulations are then presented of both waves and
vortices using the full shallow-water equations with bottom topography, in
which wave breaking occurs through shock formation of the shallow-water
waves.  The results are discussed and related physical problems are
pointed out.


DATE:		TUESDAY, OCTOBER 23, 2001

TIME:		2:30 PM

LOCATION:	Building 2, Room 338


Refreshments will be served at 3:30 PM in Room 2-349


Massachusetts Institute of Technology
Department of Mathematics
Cambridge, MA  02139