Axisymmetric three-dimensional gravity currents generated by lock exchange

Abstract

Unconfined three-dimensional gravity currents generated by lock exchange using a small dividing gate in a sufficiently large tank are investigated by means of large eddy simulations under the Boussinesq approximation, with Grashof numbers varying over five orders of magnitudes. The study shows that, after an initial transient, the flow can be separated into an axisymmetric expansion and a globally translating motion. In particular, the circular frontline spreads like a constant-flow-rate, axially symmetric gravity current about a virtual source translating along the symmetry axis. The flow is characterised by the presence of lobe and cleft instabilities and hydrodynamic shocks. Depending on the Grashof number, the shocks can either be isolated or produced continuously. In the latter case a typical ring structure is visible in the density and velocity fields. The analysis of the frontal spreading of the axisymmetric part of the current indicates the presence of three regimes, namely, a slumping phase, an inertial-buoyancy equilibrium regime and a viscous-buoyancy equilibrium regime. The viscous-buoyancy phase is in good agreement with the model of Huppert (J.

Prediction of particles deposition in a dilute quasi-steady gravity current by Lagrangian markers: effect of shear-induced lift force

“…1 and 2. The dimensions of the channel and obstacle are presented in Tables 1 and 2, respectively. Based on Boussinesq approximation a set of equations can be simplified by assuming a constant density equal to the reference density ρ 0 , except in the gravity-buoyancy term of the momentum equations, if the difference of the current density with the ambient fluid is sufficiently low 34,35,[43][44][45][46] .…”

Statistical characterisation of turbulence for an unsteady gravity current

“…Unsteady gravity currents have been the focus of much research, and are commonly reproduced in a laboratory by the sudden release of a fixed volume of fluid into a channel using the lock-exchange technique (Rottman & Simpson 1983; Härtel, Meiburg & Necker 2000; Cantero et al 2008; Fragoso, Patterson & Wettlaufer 2013; Nogueira et al 2014; Inghilesi et al 2018; Kyrousi et al 2018; Lombardi, Adduce & La Rocca 2018; Ottolenghi et al 2018; Pelmard, Norris & Friedrich 2018; Pérez-Díaz et al 2018 a , b ; Wilson, Friedrich & Stevens 2018 b ; Zhao et al 2018). The structure of gravity currents can be divided into three parts: an active dense frontal head, followed by a long body akin to a stratified shear layer and a decayed tail (Middleton 1966; Komar 1972; Kneller, Bennett & McCaffrey 1999) (see figure 1).…”

Large eddy simulation of turbidity currents in a narrow channel with different obstacle configurations

“…Release of a dense fluid into a lighter ambient fluid from a non-continues source (e.g., the lock-exchange technique) or a continuous source (e.g., a dense jet) has been studied in several experimental investigations [6][7][8][9][10][11][12][13][14][15][16][17][18] . Experimental investigations also assessed the interactions between turbidity currents of different densities and velocities with an obstacle of varying geometrical features including height and width 19-27 .…”