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ISSN 961-91393-0-5

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Year 2001

Volume 1 - CHT'01 - Advances in Computational Heat Transfer II
Proceedings of a Second Symposium - Palm Cove, Queensland, Australia, May 20 - 25, 2001

729 pages

EFFECT OF THE THERMAL WALL BOUNDARY CONDITIONS ON SCALAR TRANSPORT IN CLEAR AND PARTICLE LADEN TURBULENT BOUNDARY LAYER

Gad Hetsroni
Technion-Israel Institute of Technology

C. Li
Department of Mechanical Engineering, Technion - Israel Institute of Technology, 32000 Haifa, Israel

Albert Mosyak
Department of Mechanical Engineering, Technion - Israel Institute of Technology, 32000 Haifa, Israel

Iztok Tiselj
Reactor Engineering Division, Institute "Jozef Stefan", Jamova 39, 1000 Ljubljana, Slovenia

Elena Pogrebnyak
Department of Mechanical Engineering, Technion - Israel Institute of Technology, 32000 Haifa, Israel

ABSTRACT

Direct numerical simulation (DNS) of fully developed turbulent velocity and temperature fields in a flume was done. DNS was performed for Reynolds number, based on the wall shear velocity and the height of the flume Re = 171 and Prandtl numbers Pr = 1.0 and Pr = 5.4. Our focus in this study is the turbulent scalar transfer associated with the vortex-surface interactions and the condition on the solid wall. Two types of thermal wall boundary conditions (BC) for dimensionless temperature equation were studied: isothermal wall boundary conditions - H1, and isoflux wall boundary conditions - H2. For clear flow the profile of the mean temperature was not affected by the type of BC. However, the type of BC has a profound affect on the statistics the temperature fluctuations in the near-wall region y⁺ < 10. Comparison of near-wall statistics of temperature fluctuations shows that at Pr = 1 the buffer part of the turbulent boundary layer significantly influence the scalar transfer in the conductive sublayer, whereas at Pr = 5.4 the near-wall temperature field may be associated with predominant motion in the viscous sublayer. The DNS performed at Pr = 5.4 indicate the essential enhancement of heat transfer coefficient due to presence of the sphere attached to the bottom of the flume.