PHYSICAL MATHEMATICS SEMINAR


TOPIC:		Internal Hydraulic Jumps and Mixing in
		Two-Layer Flows

SPEAKER:	DAN STEFANICA
		Department of Mathematics
		Massachusetts Institute of Technology

ABSTRACT:

Internal hydraulic jumps (shocks) are ubiquitous occurrences in the
atmosphere and the ocean. In the ocean, internal hydraulic jumps might
develop in dense overflows downstream of a sill, as in the cases of the
overflow of Mediterranean Waters over the strait of Gibraltar, or of the
overflow of Arctic Waters over the Denmark Strait.

In this talk, we discuss internal hydraulic jumps in two--layer flows with
particular emphasis on their role in entrainment and mixing.  For highly
entraining internal jumps, we propose a new closure for the jump
conditions, based on two main assumptions:

(i)   	most of the energy dissipated at the jump goes into
	turbulence, and

(ii)  	the amount of turbulent energy that a stably stratified flow may
	contain without immediately mixing further, is bounded in terms of
	the stratification.

As a consequence of this closure, surprising bounds emerge.  For example:
on the amount of entrainment that may take place at the location of the
jump.  The bounds predicted by our model are in good agreement with the
existing observations of the oceanic downslope currents (which play a
crucial role in the formation of abyssal and intermediate waters in the
global ocean).

This is joint work with David Holland, Rodolfo Rosales, and Esteban Tabak.


DATE:		TUESDAY, APRIL 9, 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