Author(s): Angelos Kokkinos; Panagiotis Prinos

Linked Author(s): Panagiotis Prinos

Keywords: Collision; Gravity Currents; Stratification; Lock-exchange; Large Eddy Simulation

Abstract: This study presents LES results of the collision of two counterflowing gravity currents (GCs) in a linearly stratified environment. GC collision is important in many physical conditions and especially in atmospheric flows such as sea breezes, thunderstorm outflows, etc., where stratification effects often evolve. The lock-exchange configuration is considered using a half-depth setup since it is considered as a better approximation of the collision in the deep air column of the atmosphere or the deep depth of the oceans. The effect of stratification is considered through the parameter S = (ρb – ρ0) / (ρc – ρ0), where ρb and ρ0 are the densities at the bottom and the top of the tank respectively, and ρc is the initial density of the left-lock fluid. The effect of S on the height, the vertical velocity of the collided fluid and the mixing during collision are investigated. Numerical experiments are conducted for the symmetric collision (GCs with same densities and heights) with varying S, 0 ≤ S ≤ 1, covering both the subcritical and supercritical GC propagation before collision. It is found that the collision of supercritical GCs is similar to the GCs collision in a uniform environment. For the subcritical GCs collision, the motion of the collided fluid is affected by the Internal Waves (IWs), generated in the ambient fluid during the propagation of the two GCs. For the supercritical GCs collision, both the maximum height and the vertical velocity of the collided fluid decreases with increasing S, while mixing is increased for weaker stratification. The collided fluid of subcritical GCs collision does not have neither significant height nor vertical velocity during collision.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0986-cd

Year: 2023