Hydrostatic and Nonhydrostatic Simulations of Buoyantly Driven Coastal Jets
by Patrick C. Gallacher, Steven Piacsek, and David Dietrich
pp. 204-214, (doi 10.1061/40628(268)13)
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| Document type: |
Conference Proceeding Paper |
| Part of: |
Estuarine and Coastal Modeling 2001 |
| Abstract: |
The coastal ocean includes dynamics and phenomena that have inherently three dimensional circulations. When the vertical accelerations are large the physics is nonhydrostatic. Most coastal ocean models are hydrostatic. Are fully nonhydrostatic models required for coastal ocean forecast systems? We begin to address this question by looking at one of the features of the coastal ocean, the buoyant jet. Buoyantly driven jets are ubiquitous in estuaries and in the coastal ocean. These jets are forced by fresh water outflows, by the tides and by differential surface heating and cooling. They are modulated by the earth’s rotation. We have conducted two dimensional quasi-hydrostatic and nonhydrostatic simulations of idealized buoyant jets. We used the ’Lock Exchange’ problem in which two fluids of different density are separated by a lock. When the lock is removed two jets form traveling in opposite directions. We simulated the lock with a front. The width of the front was varied reduce the vertical velocity and reduce the nonhydrostatic nature of the flow. The nonhydrostatic model correctly simulated the structure of the front of a rotor followed by an overturning region. The speed of propagation of the front was slightly too slow. The quasi-hydrostatic model produced a front that was too smooth and too sharp with no rotor or overturning region. The propagation speed of the front in the quasi-hydrostatic simulations was too fast. In both models the propagation speed increased with decreasing frontal width. |
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