Amplification of boundary layer instability by hot wall thermal oscillation in a side heated cavity

A numerical study has been conducted to investigate the amplification of boundary layer instability in a side-heated enclosure with a thermal oscillation of vertical hot wall. The impetus of the present study is to elucidate the influence of wall thermal oscillation, in which the imposing frequency is one order of magnitude higher than that of the internal gravity wave on the fluctuation characteristics of boundary layer flow and internal flow in an enclosure. The numerical results show that the intensity of fluctuation of boundary layer flow is augmented and the internal flow in the cavity core is substantially influenced when the wall thermal oscillation is in tune with the characteristic frequency of boundary layer instability. For the wall thermal oscillation with a specific frequency, the modulated frequency fluctuation appears in the corner region due to the flow interaction between the vertical boundary layer flow and the wall jet along the horizontal walls. The amplified fluctuation of boundary layer flow affects the time-averaged heat transfer. The maximum enhancement of Nusselt number is obtained for the wall thermal oscillation in tune with the boundary layer instability frequency. The effect of wall thermal oscillation on heat transfer is more pronounced when the forcing amplitude is the average value of nondimensional temperature difference between the hot and cold walls.