[GTP] Seminar--Keith Julien, CU Boulder

[Silvia Gentile]

The Nonhydrostatic Balanced-Geostrophic Equations

by Keith Julien
   Department of Applied Mathematics
   University of Colorado

Monday, October 26
Location: University of Colorado Duane Physics
Room: E126
Lecture: 4:00 pm


Convection under the influence rotation has been the subject of a great 
deal of
theoretical and experimental research. This problem is relevant to 
convectively
driven fluid flows in the Earth's atmosphere, ocean and interior and also in
the Sun and other stars, where the influence of rotation is generally
important.  In general numerical simulations of rotationally constrained 
flows
are unable to reach realistic parameter values, e.g., Reynolds $Re$ and
Richardson $Ri$ numbers.  In particular, low values of  Rossby number
$Ro$, defining the
extent of rotational constraint,  compound the already prohibitive 
temporal and
spatial restrictions present for high-$Re$ simulations by engendering high
frequency inertial waves and the development of thin (Ekman) boundary 
layers.

Recent work in the development of reduced partial differential equations
(pde's) that filter fast waves and relax the need to resolve boundary layers
has been extended to construct a hierarchy of balanced equations that 
span the
stably- and unstably-stratified limits.  By varying the aspect ratio for
spatial anisotropy characterizing horizontal and vertical scales, rapidly
rotating convection and stably-stratified quasi-geostrophic motions can be
described within the same framework.

In this talk, the asymptotic pde's relevant for rotating
convection are explored.  Special classes of fully nonlinear exact solutions
are identified and discussed. Direct numerical solutions that correctly 
capture
the regular vortex columnar and irregular geostrophic turbulence regime of
recent laboratory experiments are also presented and discussed.

For more info please contact Baylor Fox-Kemper <Bfk at colorado.edu>

Thanks,

Silvia Gentile
NCAR iMAGe