Jet dynamics in stratified media

Friday, April 16, 2010 - 10:00am - 10:45am
EE/CS 3-180
Juan Restrepo (University of Arizona)
Keywords: jet, buoyancy, stratified flow,

Abstract: I discuss the flow structure and stability of a planar saline jet
descending into a stable, density-stratified fluid.
The jet retains its slender shape, largely due to the low salt
diffusion. As the jet descends it entrains fresher water due to the
relatively high mechanical viscous effects, when these are compared to
inertial effects. This fresher water forms a recirculation cell.
The jet exhibits a
rapid acceleration on release, then deceleration, as it encounters the more
dense surrounding fluid, and stops at a location much higher than the
neutral buoyancy point.

I will recount preliminary work aimed at explaining the fluid dynamics of the jet:
Stratification, mechanical diffusion and nonlinear inertial effects, as well as salt diffusion
are all found to be crucial to the dynamics. I will also summarize our work on characterizing the basic instability
modes of the jet by numerical means. We successfully captured the inception of the
most salient symmetric and anti-symmetric instabilities and their dependence on
the Reynolds number and the non-dimensional stratification gradient number.

This jet, though deceptively simple, is far from well understood. I will enumerate key dynamic
aspects that are beyond our present understanding and worthy of further study due to
their relevance to other important physical phenomena.

This is joint work with Sam Schofield, Los Alamos National Laboratory, with contributions
from Adriana Pesci and Raymond Goldstein, Cambridge University.