Turbulence heat transport by Prandtl's secondary flows and Kelvin-Helmholtz instabilities

Prandtl's secondary flow of the second kind, also known as stress-induced secondary flow, arises from the anisotropy of Reynolds stress terms. This phenomenon is typically generated by spanwise heterogeneous surfaces, resulting in secondary flow in the form of counter rotating streamwise vortices. Extensive research has analyzed this type of secondary flow under various roughness types, spacings, and widths. Recently, a few studies have investigated the effect of anisotropic buoyancy on secondary flow using streamwise-aligned, alternately heated smooth patches. However, the combined effect of heterogeneous spanwise roughness and anisotropic buoyancy remains largely unexplored. In this study, Large Eddy Simulations (LES) of streamwise-aligned, heated bluff objects will be conducted to investigate how secondary flow of the second kind influences heat transfer. The results will be compared with heat transfer induced by Kelvin-Helmholtz instability-triggered spanwise rollers, generated by spanwise-aligned heated bluff objects.