PHYSICAL MATHEMATICS SEMINAR


TOPIC:		A PARTICLE METHOD AND ADAPTIVE TREECODE
		FOR VORTEX SHEET MOTION IN 3-D FLOW


SPEAKER:	ROBERT KRASNY
		University of Michigan


ABSTRACT:

A Lagrangian particle method will be presented for computing vortex sheet
motion in 3-D flow. The particles representing the sheet are advected by a
regularized Biot-Savart integral. New particles are inserted to maintain
resolution as the sheet rolls up.  The particle velocities are evaluated
efficiently using an adaptive treecode algorithm based on Taylor
approximation in Cartesian coordinates.  The Taylor coefficients are
computed to high order using a recurrence relation.  The adaptive features
include a divide-and-conquer evaluation strategy, nonuniform rectangular
clusters, variable order approximation, and a run-time choice between
Taylor approximation and direct summation.  The method has been applied to
simulate the roll-up of a circular-disk vortex sheet into a vortex ring.
Two examples will be presented, the growth of azimuthal waves on a vortex
ring and the merger of two vortex rings.  (This is joint work with Keith
Lindsay, NCAR).


DATE:		TUESDAY, APRIL 30, 2002

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