Small-scale entrainment in inclined gravity currents

M. van Reeuwijk*, D. Krug, M. Holzner

*Corresponding author for this work

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4 Citations (Scopus)
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Abstract

We investigate the effect of buoyancy on the small-scale aspects of turbulent entrainment by performing direct numerical simulation of a gravity current and a wall jet. In both flows, we detect the turbulent/nonturbulent interface separating turbulent from irrotational ambient flow regions using a range of enstrophy iso-levels spanning many orders of magnitude. Conform to expectation, the relative enstrophy isosurface velocity vnvn in the viscous superlayer scales with the Kolmogorov velocity for both flow cases. We connect the integral entrainment coefficient E to the small-scale entrainment and observe excellent agreement between the two estimates throughout the viscous superlayer. The contribution of baroclinic torque to vnvn is negligible, and we show that the primary reason for reduced entrainment in the gravity current as compared to the wall-jet are 1) the reduction of vnvn relative to the integral velocity scale uTuT; and 2) the reduction in the surface area of the isosurfaces.
Original languageEnglish
Pages (from-to)225-239
JournalEnvironmental fluid mechanics
Volume18
Early online date7 Mar 2017
DOIs
Publication statusPublished - 2018
Externally publishedYes

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