End-wall heat transfer of a rectangular bluff body at different heights: Temperature-sensitive paint measurement and computational fluid dynamics

Complementary methods - temperature sensitive paint measurement and computational fluid dynamics - are used to elucidate the end-wall heat transfer of a rectangular body in a turbulent channel flow. Four systems with bluff body-height-to-channel-height ratio Hb/H = 0.25, 0.5, 0.75, and 1.0 are compared. For Hb/H = 1.0, an extremely high heat transfer rate is observed in the upstream area, attributing to the highly unstable corner vortex; the absence of pair vortices entails a distinctly different flow pattern and heat transfer in the downstream region. For Hb/H = 0.75, the presence of the paired vortices together with Karman vortex shedding leads to the arch-shaped vortex and heat transfer augmentation. Ongoing from Hb/H = 0.75 to 0.25, the growth of the arch vortex is highly weakened. At Hb/H = 0.25, the heat transfer measurement reflects the absence of the Karman vortex in the wake region. Augmentation of the convective heat transfer pertinent to the shear layer's reattachment is shown to be sensitive to Hb/H. As Hb/H decreases, the reduced reattachment length results in attenuated heat transfer in the wake region; the strength of the horseshoe vortex structure, characterized by the heat transfer rate, is also progressively weakened.