Characteristic features of many geophysical flows, on a wide variety of length and time scales, are sloping interfaces that separate zones of less dense and more dense fluid. Because long waves on stable layers of fluid tend to travel faster the deeper the layer, it means that fluid far from the deep part of the zone tends to move towards the shallower, leading edge of the zone. This process tends to increase or maintain high gradients of density near the boundary, which becomes a sharply defined interface. The higher hydrostatic pressure at the base of the zone of dense fluid forces it to move into the lower part of the zone of less dense fluid, producing the well-known phenomena of gravity currents.
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 Axisymmetric gravity current with rotation: g=48 cm/s2, f=3s-1 |
Axisymmetric gravity current with slope and rotation: g=24 cm/s2, f=1.5s-1 |