Tuning heat transport via boundary layer topographies

A primary objective in turbulent thermal convection research is to understand and control the heat transport scaling behaviour. Previous studies have shown that the heat transport can be tuned by manipulating the boundary layer topographies with monoscale roughness elements. Now, Zhu et al. (J. Fluid Mech., vol. 869, 2019, R4) have demonstrated that with multiscale wall roughness, the heat transport law with an exponent of can be achieved for an extended range of the Rayleigh number, providing a new way to manipulate heat transport by tuning boundary topographies in turbulent flows.