Effects of rotation on fronts of density currents

The effects of background rotation with angular velocity fr2 are studied for buoyancy driven currents of initial height h0 whose density exceeds by Dr the ambient value of r . Our aim is to find how viscous density currents adjust in time under 0 effects of background rotation focusing on time evolution of fronts of density currents. Rotation reduces the front velocity, f Ž . 0 0 Ž . U sF ft U , of the density current which is compared to a non-rotating case, U , by the function F ft where FTM1 as F F F ftTM0 and FTM0 as ftTM`. When the parameter ms ft becomes of order one, there is a transition to the geostrophic asymptotic regime. We present numerical results for the transition curve for the density current front radial position for axisymmetric density currents on a rigid surface in a rotating frame. The transition is from a non-rotating power law to a long-time solution. The results of laboratory experiments are found to agree with the results of numerical simulations. q 2000 Published by Elsevier Science B.V. All rights reserved.