Direct Numerical Simulation of Forced Convection over Steps at Low Prandtl Number

Convective heat transfer in transitional and weakly turbulent conditions is investigated numerically for a Prandtl number Pr =0.025, representative of liquid lead-bismuth eutectic (LBE). The geometry selected is a periodic channel with cavities. Finitevolumesimulations are carried out on structured orthogonal curvilinear grids, for two different values of the Reynolds numberin the weakly turbulent range. The main features of the mean and instantaneous flow fields are described. The influence of flowseparation mechanisms and turbulent mixing on local and global heat transfer rates is also discussed, considering the effect ofdifferent thermal boundary conditions imposed at the channel walls