containing a heated rod. As the spacing δ between the rod and the duct wall decreased from
0.10 D (D is the rod diameter) to 0.03 D, coherent turbulent kinetic energy and temperature
fluctuations dramatically increased in the gap region, but, for δ= 0.01 D, coherent
fluctuations essentially disappeared. As δ/D→ 0, the frequency of coherent fluctuations
decreased and cross-gap mixing weakened, contrary to predictions based on extrapolated …