Numerical simulation of manipulated flow and heat transfer over surface-mounted rib

A numerical study of the manipulated air flow and heat transfer over a surface-mounted rib is performed using Large-Eddy Simulation (LES). The Reynolds number is set as Re = 3000 (based on the rib height, h, and the inflow velocity, U0) and the frequency of zero mass-flux jet is chosen as Str = fh/U0 = 0.08. The purpose of this study is to elucidate the effect of perturbation on the flow and thermal fields and the dissimilarity of transportation between momentum and heat transfer. Due to perturbation, the mean reattachment length shows a reduction of 13%, while the maximum mean Nusselt number on the heated wall has an augment of 10%. The effect of perturbation on heat transfer disappears after 10h, which is shorter than 15h for the friction coefficient. The Stanton number and the coefficient of friction are applied to study the dissimilarity of heat and momentum transport. Detailed instantaneous flow structures and spectral analysis suppose that spanwise vortices (large turbulent coherent structures) shed behind the rib contribute to the dissimilarity by transporting the hot fluid to the center flow and carrying the cold fluid to the bottom wall. The phase-averaged iso-surface of Q-criteria confirms above dissimilarity mechanism.