Large eddy simulation of turbulent heat transfer from a rotating disk subjected to a forced parallel air stream

Abstract

Nowadays, rotating disks are an important part of most industries such as turbo machines, heat exchangers, braking systems, rotating sawing machines, and computer disk drives. Working temperature and consequently heat transfer have a profound effect on performance and lifetime of rotating disks. There is a noticeable difference between numerical and experimental results in the studies of turbulent heat transfer from a rotating disk subjected to parallel air stream. The main objective of this study is numerical simulation of turbulent convective heat transfer from a rotating disk subjected to parallel air stream. In this study, the 2nd order finite volume scheme and large eddy simulation (LES) with the dynamic Smagorinsky procedure in sub-grid-scale is used. Two limit cases called rotating disk in still air (von Karman's swirling flow), stationary disk subjected to parallel air stream are investigated as well. The mean Nusselt number of the disk surface is obtained at statistical steady state for a wide range of rotational and cross flow Reynolds numbers. The influence of flow separation and finite disk thickness on heat transfer is investigated and followed by a detailed discussion. The effect of convection and diffusion on temperature field is illustrated. Comparison with experimental data shows that the LES dynamic Smagorinsky results are by far better than available numerical results. It is discussed in detail that there is a critical value for ratio of crossflow Reynolds number to rotational Reynolds number which above that the influence of disk rotation on mean Nusselt number is negligible.