Understanding and modeling turbulent fluxes and entrainment in a gravity current

PHYSICA D-NONLINEAR PHENOMENA

卷:241

Article

Odier, P.¹  Chen, J.^2,3,4  Ecke, R. E.^2,3 

[1] Ecole Normale Super Lyon, Phys Lab, F-69364 Lyon 07, France

[2] Los Alamos Natl Lab, Condensed Matter & Thermal Phys Grp, Los Alamos, NM 87545 USA

[3] Los Alamos Natl Lab, Ctr Nonlinear Studies, Los Alamos, NM 87545 USA

[4] Purdue Univ, Sch Mech Engn, W Lafayette, IN 47907 USA

关键词: Mixing;    Gravity current;    Mixing length;    Entrainment;    Oceanic circulation;   

DOI  :  10.1016/j.physd.2011.07.010

来源: Elsevier

【 摘 要 】

We present an experimental study of the mixing processes in a gravity current flowing on an inclined plane. The turbulent transport of momentum and density can be described in a very direct and compact form by a Prandtl mixing length model: the turbulent vertical fluxes of momentum and density are found to scale quadratically with the vertical mean gradients of velocity and density. The scaling coefficient, the square of the mixing length, is approximately constant over the mixing zone of the stratified shear layer. We show how, in different flow configurations, this length can be related to the shear length of the flow (epsilon/partial derivative(z)u(3))(1/2). We also study the fluctuations of the momentum and density turbulent fluxes, showing how they relate to mixing and to the entrainment/detrainment balance. We suggest a quantitative measure of local entrainment and detrainment derived from observed conditional correlations of density flux and density or vertical velocity fluctuations. (C) 2011 Elsevier B.V. All rights reserved.

【 授权许可】

Free