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.
In our recent work Emran, et al., J. Fluid Mech. 882 (2020), A3, we investigate the
influence of the regular roughness of the heated and cooled plates on the mean heat
transport in a cylindrical Rayleigh–Bénard convection (RBC) cell of the aspect ratio
one. The roughness is introduced by a set of isothermal obstacles, which are attached to
the plates and have a form of concentric rings of the same width. The considered Prandtl
number Pr equals 1, the Rayleigh number Ra varies from 106 to 108, the number of the
rings on each plate is 1, 2, 4, 8 or 10, the height of the rings is varied from 1.5% to 49%
of the cylinder height and the gap between the rings is varied from 1.5% to 18.8% of the
cell diameter.
Temperature iso-surface and streamlines for Ra=107, a/H=0.25 and n=4 (notations are illustrated below).