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A NEW WALL FUNCTION STRATEGY FOR FORCED AND MIXED CONVECTION

Timothy J. Craft
Turbulence Mechanics Group, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, PO Box 88, Manchester M13 9PL, UK

Aleksey V. Gerasimov
Mechanical, Aerospace в Manufacturing Engineering Department, UMIST, Manchester, UK

Hector Iacovides
Turbulence Mechanics Group, School of Mechanical, Aerospace and Civil Engineering. The University of Manchester, Manchester M13 9PL, U.K.

Brian E. Launder
School of Mechanical, Aerospace & Civil Engineering, The University of Manchester, PO Box 88, Manchester M60 1QD, UK

C. Robinson
Department of Mechanical Engineering, UMIST P.O. Box 88, Manchester, UK

Аннотация

The paper describes progress in developing a wall function strategy to enable CFD predictions of turbulent convective heat transfer to be made without incurring the cost of a very fine near wall grid. Analytical expressions are obtained for the variation of velocity and temperature across the near-wall sublayer, allowing one to compute the effective "resistance" of the viscous sublayer to heat and momentum transport. The present work significantly extends the approach employed in conventional wall functions, by accounting for the effects of buoyancy, pressure gradients, convection and variations in molecular transport properties. The scheme is applied to the problems of forced and mixed convection in a vertical pipe, separated flow in an asymmetric diffuser, and to the opposed wall jet with encouraging results.