CFD analysis of convective heat transfer at the surfaces of a cube immersed in a turbulent boundary layer

Steady RANS (Reynolds-Averaged Navier-Stokes) CFD is used to evaluate the forced convective heat transfer at the surfaces of a cube immersed in a turbulent boundary layer, for applications in atmospheric boundary layer (ABL) wind flow around surface-mounted obstacles such as buildings. Two specific configurations are analysed. First, a cube placed in turbulent channel flow at a Reynolds number of 4.6x103 is considered to validate the numerical predictions by comparison with wind-tunnel measurements. The results obtained with low-Reynolds number modelling (LRNM) show a satisfactory agreement with the experimental data for the windward surface. Secondly, a cube exposed to high-Reynolds number ABL flow is considered. The heat transfer in the boundary layer is analysed in detail. The dimensionless parameter y*, which takes into account turbulence, is found to be more appropriate for evaluating heat transfer than the commonly used y+ value. Standard wall functions, which are frequently used for high-Reynolds number flows, overestimate the convective heat transfer coefficient (CHTC) significantly (± 50 %) compared to LRNM. The distribution of the CHTC-U10 correlation over the windward surface is reported for Reynolds numbers of 3.5E4 to 3.5E6 based on the cube height and U10, where U10 is the wind speed in the undisturbed flow at a height of 10 m.