Progress in the Prediction of Non-Unity Prandtl Number Flows Using TransAT

Abstract

We report LES results of the flow and convective heat transfer in a heated channel at a wall shear Reynolds number of Re = 150 and 171. The results are compared with available DNS data for various Prandtl number fluids (Pr = 0.1-10). In order to deal with non-unity Pr fluid flows, we have extended the variant of the Dynamic sub-grid scale (SGS) model of Germano proposed by Lilly [1] to the thermal field, whereby the motion of the unresolved fluid flow and thermal structures is dictated by the resolved thermal-flow field. The base LES strategy as built in the code TransAT has been first validated for a practical case: the thermal-flow in a T junction, showing time-averaged results with excellent agreement with the experiment. The extended SGS model to the thermal field delivers results in line with the DNS data of a heated channel flow, and reveals that the turbulent Prandtl number cannot be fixed in an ad-hoc manner, and is clearly dependent on both the fluid and flow properties.