Buoyancy-assisted mixed convection in a vertical channel with spatially periodic wall temperature

► Mixed convection in upward channel flow with periodic temperature on the colder wall is numerically studied. ► The effects of Gr, Re, channel length, and wavelength of the periodic wall temperature are examined. ► A multi-cellular flow regime is observed, with features that match the periodicity of the boundary temperature distribution. ► The recirculations are enlarged with increasing Gr/Re and wavelength of wall temperature. ► Larger wall heat fluxes can be obtained than those in the case with uniform temperature at both walls.