Direct numerical simulation of turbulent concentric annular pipe flow Part 2: Heat transfer

A direct numerical simulation is performed for turbulent heat transfer in a concentric annulus at ReDh=8900 and Pr=0.71 for two radius ratios (R1/R2=0.1 and 0.5) and wall heat flux ratio q*=1.0. Main emphasis is placed on the transverse curvature effect on near-wall turbulent thermal structures. Near-wall turbulent thermal structures close to the inner and outer walls are scrutinized by computing the lower-order statistics. The fluctuating temperature variance and turbulent heat flux budgets are illustrated to confirm the results of the lower-order statistics. Probability density functions of the splat/anti-splat process are investigated to analyze the transverse curvature effect on the strong relationship between sweep and splat events. The present numerical results show that the turbulent thermal structures near the outer wall are more activated than those near the inner wall, which may be attributed to the different vortex regeneration processes between the inner and outer walls