"Characterizing Stratified Turbulence in Estuaries
and Assessing Turbulence Closure"
Dr. Malcolm Scully
CCPO
Monday, March 30, 2009
3:30 PM
Room 3200, Research Innovations Building I
Abstract
Measurements made using the Mobile Array for Sensing Turbulence (MAST)
are used to examine the turbulent characteristics of the Merrimack River
-- a salt wedge estuary located north of Boston, MA. The MAST provides a
unique platform to measure the dissipation rate of turbulent kinetic
energy and scalar variance, the turbulent fluxes of momentum and buoyancy,
as well as estimates of the turbulent length scale. These measurements
demonstrate that for gradient Richardson numbers (Ri) less than 0.25 both
the velocity auto-spectra and the flux co-spectra are consistent with
theoretical predictions when properly normalized. Fitting the data with
theoretical spectra provides estimates of the turbulent fluxes and
turbulent kinetic energy and an estimate of the turbulent length scale.
Estimates of the turbulent length scale are consistent with boundary layer
scaling under unstratified conditions with Ozmidov scaling under
stratified conditions. The observations demonstrate that as Ri approaches
0.25, there is a dramatic increase in anisotropy and a decrease in the
correlation between the vertical and horizontal velocities, suggesting
the transition from turbulence to internal waves. While most turbulence
closure models do not physically represent this transition, they
empirically capture the shut down of turbulence as Ri approaches a
critical value and reduce the correlation coefficient for turbulence that
is not in local equilibrium (i.e. production = dissipation), consistent
with the MAST observations.
Biography
Malcolm Scully received a Ph.D. in Marine Science from the College of
William & Mary. After a post-doctoral position at Woods Hole Oceanographic
Institution, he joined the faculty at Old Dominion University in 2008 as an
Assistant Professor. Dr. Scully's research interests are in the areas of
physical processes that control mixing, circulation and transport in
estuaries, numerical modeling of coastal and estuarine systems, and boundary
layer turbulence.
Reception before seminar at 3:00 PM
Research Innovations Building I
Old Dominion University
Norfolk, VA 23529
757-683-5548
Last updated 03/12/2009.
This page is maintained by
Julie Morgan
Copyright Info: Old Dominion University 2009
