Effect of Prandtl number on the turbulent thermal field in annular pipe flow

The effect of Prandtl number on the turbulent thermal statistics in fully developed annular pipe flow, with isoflux boundary conditions, is investigated by use of direct numerical simulation, for two values of Reynolds number. The Prandtl number has marked influence on the thermal field. With decreasing Pr, the conductive sublayer at both walls spreads from the walls to the core region, while the root mean square of temperature fluctuations and the turbulent heat fluxes are reduced near both walls. Asymptotic behaviours of these quantities are analyzed.