Breakdown of similarity between momentum and energy transfer in a stagnation-region with free-stream turbulence

Abstract

A direct numerical simulation of turbulent stagnation-region heat transfer with free-stream turbulence is performed. The temperature field in the 'damping' regime is mildly disturbed and that in the 'attached amplifying' regime is organised. In the 'detached amplifying' regime, the temperature field becomes turbulent, The temperature field is stretched in the x direction near the wall. The surface contours reveal that the temperature field is influenced significantly by streamwise vorticity. The enhancement of wall heat transfer by free-stream turbulence is similar to that in the previous results of the organised inflow disturbances. This indicates that the effect of large-scale eddies on the enhancement of wall heat transfer is important in the turbulent stagnation-region heat transfer. The breakdown of similarity between momentum and energy transfers in the stagnation-region with free-stream turbulence is analysed. The wall blocking and the pressure fluctuations are found to be responsible for the dissimilarity.