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On the coherent drag-reducing and turbulence-enhancing behaviour of polymers in wall flows

Published online by Cambridge University Press:  24 August 2004

YVES DUBIEF ,
CHRISTOPHER M. WHITE ,
VINCENT E. TERRAPON ,
ERIC S. G. SHAQFEH ,
PARVIZ MOIN  and
SANJIVA K. LELE
YVES DUBIEF
Affiliation:
Center for Turbulence Research, Stanford University, CA 94305, USA
CHRISTOPHER M. WHITE
Affiliation:
Mechanical Engineering Department, Stanford University, CA 94305, USA
VINCENT E. TERRAPON
Affiliation:
Mechanical Engineering Department, Stanford University, CA 94305, USA
ERIC S. G. SHAQFEH
Affiliation:
Mechanical Engineering Department, Stanford University, CA 94305, USA Department of Chemical Engineering, Stanford University, CA 94305, USA
PARVIZ MOIN
Affiliation:
Center for Turbulence Research, Stanford University, CA 94305, USA Mechanical Engineering Department, Stanford University, CA 94305, USA
SANJIVA K. LELE
Affiliation:
Mechanical Engineering Department, Stanford University, CA 94305, USA Department of Aeronautics and Astronautics, Stanford University, CA 94305, USA
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Abstract

Numerical simulations of turbulent polymer solutions using the FENE-P model are used to characterize the action of polymers on turbulence in drag-reduced flows. The energetics of turbulence is investigated by correlating the work done by polymers on the flow with turbulent structures. Polymers are found to store and to release energy to the flow in a well-organized manner. The storage of energy occurs around near-wall vortices as has been anticipated for a long time. Quite unexpectedly, coherent release of energy is observed in the very near-wall region. Large fluctuations of polymer work are shown to re-energize decaying streamwise velocity fluctuations in high-speed streaks just above the viscous sublayer. These distinct behaviours are used to propose an autonomous regeneration cycle of polymer wall turbulence, in the spirit of Jiménez & Pinelli (1999).

Type
Papers
Information
Journal of Fluid Mechanics , Volume 514 , 10 September 2004 , pp. 271 - 280
Copyright
© 2004 Cambridge University Press

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