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LES of Gravity Current Propagation at the Base of a Linearly Stratified Ambient

Author(s): Angelos Kokkinos; Panagiotis Prinos

Linked Author(s): Panagiotis Prinos

Keywords: Gravity currents; Stratification; Lock-Exchange; Large-Eddy Simulation

Abstract: LES results are presented on a partial-depth lock-release propagating gravity current (GC) at the base of a linearly stratified ambient. Stratification is determined through the parameter S = (ρb – ρ0) / (ρc -ρ0) which varies from 0 up to 1 (ρb, ρ0 and ρc are the density at the bottom of the ambient, at the top of the tank of depth H and of the heavy fluid in the lock respectively). The dynamics of the propagation depend on the Froude number and are different for subcritical GC (Fr 1/π). The Froude number is defined as Fr=Uf / NH where N is the buoyancy frequency of the ambient fluid and Uf is the current front velocity. The focus of the study is to investigate the effect of S on GC motion. Numerical experiments are carried out for 0 ≤ S ≤ 1 covering both the subcritical and the supercritical regimes. Emphasis is given to both the constantvelocity and the deceleration phases determining the front velocity and the transition distance (travelled distance at the end of the constant-velocity phase). For the subcritical GCs the transition distance increases with increasing Fr, while it decreases for the supercritical GC. For the subcritical GC the flow is dominated by the evolved internal waves (IWs), while the supercritical GC propagation does not generate IWs in the ambient fluid.


Year: 2023

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