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Entrainment and mixing in unsteady gravity currents

Author(s): Luisa Ottolenghi; Claudia Adduce; Roberto Inghilesi; Vincenzo Armenio; Federico Roman

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Keywords: Buoyancy-driven flows; density currents; entrainment; laboratory studies; large eddysimulations; lock-release; mixing

Abstract: Entrainment and mixing in lock-exchange gravity currents are investigated by large eddy simulations. Nine cases are analysed, varying the initial excess density driving the motion and the aspect ratio r of the initial water depth to the lock length. Laboratory experiments are also performed and a fair agreement between numerical simulations and measurements is found. Mixing between the gravity current and the ambient fluid, in both the slumping and self-similar phases, is studied for a range of entrainment parameters, gravity current fractional area and using an energy budget method. The entrainment is found to increase as r decreases. The occurrence of irreversible mixing is detected during the entire development of the flow, i.e. both in the slumping and self-similar phases. A higher amount of mixing is observed as r decreases and the initial excess density increases.


Year: 2016

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