HR: 1330h
AN: A42B-0757    [PDF]
TI: High Resolution Simulation of Gravity Currents and Internal Bores on the Continental Shelf
AU: * Piacsek, S
EM: piacsek@nrlssc.navy.mil
AF: Naval Research Laboratory, Code 7300, NRL-SSC, Stennis Space Center, MS 39529 United States
AU: Gallacher, P
EM: gallacher@nrlssc.navy.mil
AF: Naval Research Laboratory, Code 7300, NRL-SSC, Stennis Space Center, MS 39529 United States
AU: Dietrich, D
EM: dietrich@nmia.com
AF: Acu-Systems, Inc, 1421 Monte Largo Dr, Albuquerque, NM 87112 United States
AB: The propagation of gravity currents and internal bores was investigated over the flat and sloping portions of the continental shelf. The generation of the bores was effected by the collapse of a lock-exchange configuration, with the heavier fluid initially in the shallow region. Interest was focused on the 5-50 km coastal dynamic scales, as many motions on these scales exhibited nonhydrostatic effects. Model resolutions ranged from 1-5 m in the vertical and 1 to 50 m in the horizontal. Besides the standard shallow ocean (H) and standard nonhydrostatic (NH) deep convection models, we also examined a type of so-called quasi-hydrostatic (QH) model in which the vertical pressure gradient is balanced by a sum of the buoyancy and inertial terms. The final vertical velocity and pressure are determined by an iteration procedure. The simulated Froude numbers and Richardson numbers agreed within 10 % of those found in applicable laboratory experiments. In general, the NH models tended to exhibit the full spectrum and amplitude of the Kelvin-Helmholtz (K-H) instabilities that grow on the plume- ambient fluid interface, and treated the advancing bore front and the rotor situated behind it correctly. The QH model developed K-H instabilities for smaller diffusivities and further back behind the front, with little rotor action behind the bore edge. Both the NH and QH models were found to be sensitive to the grid ratio r = dx/dz and behaved like hydrostatic models for r $>$ 5. In addition, all three classes of models have exhibited strong sensitivity to the size of the time step and diffusivity.
DE: 4219 Continental shelf processes
DE: 4255 Numerical modeling
DE: 4546 Nearshore processes
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting