LES of heat transfer in an asymmetric rib-roughened duct: influence of rotation

We report on an LES study of effects of destabilising rotation on heat transfer over a ribbed surface in a rectangular duct at Re = 15000. The duct bottom wall, ribbed by flow-normal, equally-spaced squaresectioned ribs, was uniformly heated (except for the ribs) by a constant heat flux. The duct was rotated with angular velocity corresponding to the rotation number of 0.3, around an axis parallel to the ribs in counterclockwise direction destabilising the ribbed-wall adjacent flow. These well-resolved LES gave some new insight into the rotation effects on flow and heat transfer providing information that are not easily accessible to experiments. An attempt was made to identify the heat transfer effects due to the rotation-induced modifications of the secondary motion, and the direct effects on the turbulence statistics, especially the budgets of the temperature variance and turbulent heat flux. It turned out that the former is predominant in the recirculation zone, whereas the latter prevails just after it.