Finite volume release non-Boussinesq gravity flows on slopes
Résumé
Finite volume release gravity currents of large density contrasts on steep slopes are simulated numerically using a dynamic mesh adaptation technique. This technique allows to treat large Reynolds numbers and large density differences but it is (presently) restricted to two dimensions. Comparison of numerical results with experiments in the Boussinesq limit shows that these simulations capture the essential dynamics. Large density contrast simulations are then presented, allowing to analyse the behaviour of dense clouds on steep slopes. It is shown that large density clouds accelerate over much larger distances and that their spatial growth in height decreases substantially. The maximum velocity inside the cloud, relative to the front velocity, decreases from about a factor of 2 in the Boussinesq limit to about 1.3 when the density ratio is 20. Non-Boussinesq clouds are found to consist of a relatively dense layer near the bottom and a dilute layer above.
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