Turbulent entrainment in a gravity current

M. Holzner, M. van Reeuwijk, H. Jonker

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

Abstract

We revisit the classical entrainment experiments for gravity currents on inclined slopes (Ellison and Turner, J. Fluid Mech. 6, 423-448, 1959). We derive an entrainment relation that couples the entrainment rate E to the production of turbulence kinetic energy, the net effect of buoyancy and inner layer. Using direct numerical simulations that are run for durations long enough for the flow to reach universal self-similarity, we show that the net effect of inner layer processes on entrainment is very small and that buoyancy has an almost negligible effect on E. It is demonstrated that the dominant process causing entrainment is turbulence production due to shear. Second, we observe that for all simulations the eddy diffusivity and dissipation rate can be parameterised using the turbulence kinetic energy and shear parameter. This information can be used to derive an entrainment law which is in good agreement with the Direct Numerical Simulation (DNS) results. We discuss the potential reasons for why this result is significantly different from experiments and the classical entrainment law introduced by Ellison and Turner.

Original languageEnglish
Title of host publicationSustainable Hydraulics in the Era of Global Change - Proceedings of the 4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016
EditorsS. Erpicum, B. Dewals, P. Archambeau, M. Pirotton
PublisherCRC Press / Balkema - Taylor & Francis Group
Pages1025-1031
Number of pages7
ISBN (Print)978-113802977-4
DOIs
Publication statusPublished - 2016
Event4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016 - Liege, Belgium
Duration: 27 Jul 201629 Jul 2016

Conference

Conference4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016
CountryBelgium
CityLiege
Period27/07/1629/07/16

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