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Numerical simulation of turbulent drag reduction using rigid fibres

Published online by Cambridge University Press:  20 October 2004

J. S. PASCHKEWITZ ,
YVES DUBIEF ,
COSTAS D. DIMITROPOULOS ,
ERIC S. G. SHAQFEH  and
PARVIZ MOIN
J. S. PASCHKEWITZ
Affiliation:
Department of Chemical Engineering, Stanford University, CA 94305, USA
YVES DUBIEF
Affiliation:
Center for Turbulence Research, Stanford University, CA 94305, USA
COSTAS D. DIMITROPOULOS
Affiliation:
Department of Chemical Engineering, Stanford University, CA 94305, USA Center for Turbulence Research, Stanford University, CA 94305, USA
ERIC S. G. SHAQFEH
Affiliation:
Department of Chemical Engineering, Stanford University, CA 94305, USA Department of Mechanical Engineering, Stanford University, CA 94305, USA
PARVIZ MOIN
Affiliation:
Center for Turbulence Research, Stanford University, CA 94305, USA Department of Mechanical Engineering, Stanford University, CA 94305, USA
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Abstract

We present a study of the drag reduction induced by rigid fibres in a turbulent channel flow using direct numerical simulation. The extra stresses due to the fibres are calculated with the well-known constitutive equation involving the moments of the orientation vector. Drag reductions of up to 26% are calculated, with the largest drag reductions observed using non-Brownian fibres and semi-dilute concentrations. These findings suggest that elasticity is not necessary to achieve turbulent drag reduction. Flow statistics show trends similar to those observed in simulation of polymeric drag reduction: Reynolds stresses are reduced, velocity fluctuations in the wall-normal and spanwise directions are reduced while streamwise fluctuations are increased, and streamwise vorticity is reduced. We observe strong correlations between the fibre stresses and inter-vortex extensional flow regions. Based on these correlations and instantaneous visualizations of the flow field, we propose a mechanism for turbulent drag reduction by rigid fibre additives.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 518 , 10 November 2004 , pp. 281 - 317
Copyright
© 2004 Cambridge University Press

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