Wall Roughness Effects

Surface roughness is known to have a large impact on the global heat transfer. Therefore we study numerically the effect of the roughness introduced by a set of distinct obstacles attached to the heating and cooling plates, for different Rayleigh and Prandtl numbers, and configurations of the cell geometry.

2D/3D roughness
Time-averaged temperature distributions with superposed velocity vectors for different roughness configurations:
(a,c) two-dimensional DNS for Ra=108, Pr=1;
(b,d) three-dimensional DNS for Ra=107, Pr=0.786 in the vertical slice at half-depth.

Further reading

Sebastian Wagner and Olga Shishkina. Heat flux enhancement by regular surface roughness in turbulent thermal convection J. Fluid Mech. 763 (2015), 109–135.