Breakdown of the Reynolds analogy in a stagnation region under inflow disturbances

A systematic analysis is performed for the Reynolds analogy breakdown at st agnation-region flow and heat transfer in the presence of inflow disturbanc es. The Reynolds analogy breakdown between momentum and energy transfers in a stagnation region is scrutinized by varying the Reynolds number (5000 le ss than or equal to Re less than or equal to 20 000), the amplitude (0.0007 5 less than or equal to A less than or equal to 0.003) and the length scale (lambda/delta = 10.6). A spanwise sinusoidal variation is superimposed on the velocity component normal to the wall. Self-similarity solutions are ob tained with trigonometric series expansions. The Reynolds analogy criterion demonstrates that the rate of change of skin friction is different from th at of wall heat transfer. Different evolutions of the rates of skin frictio n and wall heat transfer are due to the difference between (s'v') and (v'T' ). An in-depth analysis on (s'v) and (v'T') is performed by analysis using disturbance correlations based on the fluctuating velocity transport equati ons in vorticity form. It is found that the pressure fluctuations, the wall blocking and the Lamb vectors are responsible for the breakdown of the Rey nolds analogy. A direct comparison is made between momentum and energy bala nces associated with the three responsible mechanisms. A common finding is that their profiles are changed significantly at a location where the evolu tion of the streamwise vortex is strong.