Investigation of asymmetric gravity current collision with LES

Abstract

This study presents LES results of two colliding gravity currents, with different densities and/or heights, in a half-depth lock-exchange set-up. The dynamical features of collision for gravity currents with different densities and heights, the post-collision motion and the mixing are examined for the first time. It is found that the maximum height of the displaced fluid depends on the gravity currents heights difference, while it is not affected by their density difference. Maximum vertical velocity during collision depends on both height and density difference and decreases with increasing asymmetry. Post-collision phase consists of two counterflowing bores with almost constant velocities and heights with time. When the collided gravity currents have considerably different densities or heights only one bore emerges after collision. Bore velocities agree relatively well with the hydraulic theory of gravity currents collision with different heights. Mixing is enhanced during collision consuming approximately 20% of the total consumed system energy.