Turbulence modulation and heat transfer enhancement in channels roughened by cube-covered surface

Direct numerical simulations are carried out to study turbulence modification and heat transport augmentation in rough channels with minor cubes on one wall. To account for the effect of the cubes on momentum and heat transfer in wall-bounded turbulent flows, the lattice Boltzmann method which is based on a double-distribution-function and D3Q19 model is applied to perform the numerical computation. The present study focuses on the modulations of the temperature field and heat transfer process by rough wall with different cube heights. Some typical dynamic and thermal statistics, such as the mean velocities, mean temperature, velocity fluctuations, the Reynolds stresses, and turbulent heat flux are analyzed. The similar trend of temperature and velocity roughness functions illustrates there is strong correlation between the heat transfer augmentation and a drag increase in rough channel flows. A significant heat transfer enhancement (26%, by taking into account the drag consumption) is obtained with the medium-height cubes. (C) 2018 Elsevier Ltd. All rights reserved.