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Direct numerical simulations of turbulent flows over superhydrophobic surfaces

Published online by Cambridge University Press:  10 February 2009

MICHAEL B. MARTELL
Affiliation:
Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA 01003, USA
J. BLAIR PEROT*
Affiliation:
Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA 01003, USA
JONATHAN P. ROTHSTEIN
Affiliation:
Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA 01003, USA
*
Email address for correspondence: perot@ecs.umass.edu

Abstract

Direct numerical simulations (DNSs) are used to investigate the drag-reducing performance of superhydrophobic surfaces (SHSs) in turbulent channel flow. SHSs combine surface roughness with hydrophobicity and can, in some cases, support a shear-free air–water interface. Slip velocities, wall shear stresses and Reynolds stresses are considered for a variety of SHS microfeature geometry configurations at a friction Reynolds number of Reτ ≈ 180. For the largest microfeature spacing studied, an average slip velocity over 75% of the bulk velocity is obtained, and the wall shear stress reduction is found to be nearly 40%. The simulation results suggest that the mean velocity profile near the superhydrophobic wall continues to scale with the wall shear stress but is offset by a slip velocity that increases with increasing microfeature spacing.

Type
Papers
Copyright
Copyright © Cambridge University Press 2009

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