Effect of Wall Boundary Condition on Scalar Transfer in Turbulent Low-Prandtl-Number Convection

Abstract

One important issue in understanding and modeling of turbulent heat transfer is the behavior of the fluctuating temperature and velocity close to the wall. The usual approach assumes the temperature fluctuations to be zero on the wall. This assumption of ideal heat flux wall boundary condition may result in the ill-posedness of the energy equation as discussed by Sommer et al. 1994. In the present paper constant heat flux boundary condition was assumed, allowing nonzero wall temperature fluctuations and the effects of temperature fluctuations close to the wall are investigated using the LES simulation approach. The subgrid-scale (SGS) turbulence model for non-unity Prandtl numbers by Otic, 2010 is applied to analyze forced convection in a channel at friction velocitybased Reynolds numbers 390 and 599, for Prandtl numbers 0.701 and 0.022. A simple criteria for the contribution of turbulence models to the resolved scales in the entire computational domain is provided. Simulation data is statistically analyzed and compared with the DNS results from the literature.