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ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

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Year 2006

• 1Turbulence, Heat and Mass Transfer 5
Proceeding of The International Symposium on Turbulence, Heat and Mass Transfer - Dubrovnik, Croatia, September 25-29, 2006

806 pages

Volume price - $246.00

Entropy generation in the viscous layer of a turbulent channel flow

Donald M. McEligot
Aero. Mech. Engr. Dept., Univ. Arizona, Tucson, Ariz. 85721; Idaho National Laboratory, Idaho Falls, Ida. 83415-3885 USA; and Inst. für Kernenergetik u. Energiesysteme (IKE), Uni. Stuttgart, D-70550 Stuttgart, Germany

Edmond J. Walsh
Mech. Aero. Engr. Dept., Univ. Limerick, Limerick, Ireland

Eckart Laurien
Inst. für Kernenergetik u. Energiesysteme (IKE), Uni. Stuttgart, D-70550 Stuttgart, Germany

ABSTRACT

The local (pointwise) entropy generation rate per unit volume S''' is a key to improving many energy processes and applications. Entropy generation due to friction occurs from viscous dissipation of mean-flow kinetic energy (called "direct dissipation") and dissipation of turbulent kinetic energy into thermal energy ("indirect" or turbulent dissipation). The objective of the present study is to compare two approaches for the prediction of S''' for the viscous layer in near asymptotic (high Reynolds number) turbulent flows. By employing available direct numerical simulations (DNS) it was found that about two-thirds of the entropy generation occurs in this layer. A popular approximate approach does not agree with the result from the more exact evaluation of S''' but its integral falls within about four per cent at the edge of the viscous layer.