# Dynamic structuring and mixing efficiency in rapidly rotating shear layers

Bernard J. Geurts, Darryl D. Holm

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## Abstract

Flow evolution in a rotating mixing layer is investigated using direct and large-eddy simulation. The mixing layer rotates about a fixed vertical axis perpendicular to the plane of its mean initial shear. The rotating mixing layer forms oscillatory large-scale columnar structures and rapid horizontal flow-reversals. The frequency of these oscillations varies approximately inversely with the Rossby number, $Ro$. At low $Ro$ vertical mixing of a passive scalar is strongly reduced. This is quantified by investigating the evolution of level-sets of the scalar field. The surface-area of the level-sets remains virtually constant even at modest rotation rates. More localized motions are less affected by rotation and yield comparatively high levels of surface-wrinkling. Rotation effects are accurately predicted in large-eddy simulations that involve the dynamic eddy-viscosity model or the LANS-$\alpha$ or Leray regularization models. The small-scale variability is best preserved when using the LANS-$\alpha$ formulation.
Original language English Direct and Large-Eddy Simulation VI Eric Lamballais, Rainer Friedrich, Bernard J. Geurts, Olivier Métais Dordrecht Springer 249-256 8 978-1-4020-5152-4 978-1-4020-4909-5 https://doi.org/10.1007/978-1-4020-5152-2_29 Published - Oct 2006 6th ERCOFTAC Workshop on Direct and Large-Eddy Simulation VI, DLES 2005 - University of Poitiers, Poitiers, FranceDuration: 12 Sep 2005 → 14 Sep 2005Conference number: 6

### Publication series

Name ERCOFTAC series Springer 10 1382-4309 2215-1826

### Conference

Conference 6th ERCOFTAC Workshop on Direct and Large-Eddy Simulation VI, DLES 2005 DLES France Poitiers 12/09/05 → 14/09/05

## Keywords

• Direct numerical simulation
• Rotation rate
• Passive scalar
• Momentum thickness
• Rossby number