GALCIT Home Page
| 2003-2004 Fluids Seminar Page |
Abstract-
Langmuir circulation forms in the surface layers of oceans, lakes and ponds when
winds of moderate strength blow over them, and manifest as a parallel series of
counter rotating vortices that more-or-less align with the wind. Since they act
at the surface to concentrate flotsam, seaweed and air bubbles into streaks,
they are clearly visible; satellite photographs suggest they are present over
about 20% of the ocean at any time. Their spacings range from millimeters to
hundreds of meters. Physically, Langmuir circulations are thought responsible
for the transport of heat, mass and momentum in the section of the upper ocean
termed the mixed layer, a layer that absorbs not just atmospheric gases but also
plays a key role in determining the weather. In view of the importance of the
mixed layer and the transport processes therein, a credible model of Langmuir
cells should be included in future global change models. Langmuir circulation
cells are thought to arise through an inviscid instabilty owing to the nonlinear
interaction of surface gravity waves and wind-induced shear. This seminar uses
generalized Lagrangian mean theory to describe the wave mean flow interaction
and instability theory to describe the formation of Langmuir circulation.
|
GALCIT Home Page
|
|