Direct Numerical Simulation of Thermal Turbulent Boundary Layer Flow over Multiple V-Shaped Ribs at Different Angles

Direct numerical simulations (DNSs) of spatially developing thermal turbulent boundary layers over angle-ribbed walls were performed. Four rib angles (γ=90°,60°,45° and 30°) examined. It was found that the 45° ribs produced highest drag coefficient, whereas 30° most improved Stanton number. In comparison to transverse case, streamwise velocity dimensionless temperature in V-shaped cases significantly increased near wall region attenuated by secondary flows further away from ribs, which suggested a break outer-layer similarity scenario presented. The surprising improvement heat transfer performance case mainly due its large dispersive flux, while stress reached peak value emphasizing dissimilarity transporting momentum turbulence ribbed surface. Additionally, calculating global local Reynolds analogy factors, we concluded enhancement efficiency attributed an increasing factor intermediate as angle decreased.