The images show
internal gravity waves
being generated when a
stratified.
flow passes over a thin vertical barrier.
The fluid near the top of the barrier is weakly stratified, and the fluid beneath is
strongly stratified.
The internal waves are visualised
using a recently developed
"synthetic schlieren''
technique.
The left image is a measure of the displacement of the waves from their initial
positions, and
the right image is a measure of the rate of change of the displacement.
Note, the latter filters out long time-scale motions.
To illustrate the effect of large amplitude internal gravity wave generation
on the shear flow numerical simulations have been performed:
The left image, showing contours of vorticity,
demonstrates that negligible internal gravity wave excitation occurs if the
flow is uniformly stratified.
If the deep fluid is more strongly stratified (right-hand image), then
large amplitude waves are
generated and the evolution of the mixing region changes dramatically.
A
reprint-style paper
discussing the excitation of internal waves in shear flow is also available.
Department of Earth and Atmospheric Sciences
For more information on internal wave excitation and synthetic schlieren
visualisation, see a recent
reprint-style paper.
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