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Transient evolution and high stratification scaling in horizontal mixing layers

  • C. ArratiaEmail author
  • S. Ortiz
  • J. M. Chomaz
Conference paper
Part of the Springer Proceedings in Physics book series (SPPHY, volume 132)

Abstract

Mixing layers (sheared flows in homogeneous or stratified fluid) are present in many geophysical contexts and may lead to turbulence and mixing. In several cases, mixing layers are known to exhibit the Kelvin-Helmholtz instability leading to the roll-up of spanwise vortices, the Kelvin-Helmholtz (KH) billows. This is an essentially two-dimensional (2D) process. In fact, in the homogeneous cases the Squire’s theorem implies that the most unstable mode is 2D. However, Squire’s theorem applies only for the exponentially growing perturbations that control the large time dynamics and is not valid for the transient dynamics at short time. Indeed, Iams et al.[1] have shown that, in the non-stratified case, the most amplified optimal perturbations for short times are three-dimensional (3D) and result from a cooperation between the lift-up and Orr mechanisms[2]. This provides a finite time mechanism for spanwise scale selection, scale that may persist at later times if nonlinearities are strong enough.

Keywords

Froude Number Unstable Mode Homogeneous Case Horizontal Shear Transient Growth 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  1. 1.Laboratoire d’Hydrodynamique (LadHyX)École Polytechnique-CNRSPalaiseau CedexFrance
  2. 2.UME/DFA, ENSTA, chemin de la HuniérePalaiseau CedexFrance

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