Mixing in lock-release gravity currents propagating up a slope

Abstract

Lock-exchange gravity currents propagating up a slope are investigated by large eddy simulations, focusing on the entrainment and mixing processes occurring between the dense current and the ambient fluid. Relevant parameters, such as the aspect ratio of the initial volume of dense fluid in the lock R, the angle between the bottom boundary and the horizontal direction θ and the depth aspect ratio φ, are varied. The numerical results are compared with laboratory experiments and a good agreement is found. Entrainment and mixing in a lock-release gravity current are studied using different entrainment parameters and an energy budget method. The entrainment is found to depend on both Froude, Fr, and Reynolds, Re, numbers. In addition, the dependence of both entrainment and mixing on the parameters varied is discussed. The entrainment decreases with increasing steepness of the bottom and R. Irreversible mixing is not affected by the varied parameters during the slumping phase, while during the successive phases of motion, it is found to decrease with the increase of θ and R. Low entrainment and mixing occur for φ < 1

Large-eddy-simulation approach in understanding flow structures of 2D turbulent density currents over sloping surfaces

“…The results obtained in sections 3.1 and 3.2 compare qualitatively with those obtained by Ottolenghi et al (2016aOttolenghi et al ( , 2016bOttolenghi et al ( , 2017a. A one-to-one comparison cannot be made on account of disparate definitions of Re used as well as the orientation of the slope.…”

Investigations of dynamic behaviors of lock-exchange turbidity currents down a slope based on direct numerical simulation

“…where Qbulk,n and Qinst,n are the effective bulk and instantaneous water entrainment discharge and Sn and Sn-1 are the area of the upper interface at t = tn and t = tn-1. A first-order relation proposed by Ottolenghi et al [17,53] is used to compute the area , ( ) 1 n f n S h l X     , where Xf,n is the front position at t = tn. The parameters Qbulk,…”

Small-scale entrainment in inclined gravity currents

“…Many authors have since tried to validate and extend the determination of E either empirically or based on theoretical modelling (e.g. [2][3][4][5][6][7][8]; see also [9] and references therein). However, there is still significant uncertainty in the accurate quantification and correct parametrization of E [5].…”