Numerical study on the enhanced wall-to-fluid heat transfer caused by the bubble wake

This numerical study investigated the wall-to-fluid heat transfer enhancement caused by an air bubble rising with an oscillatory trajectory. The geometric volume of fluid method, isoAdvector, is used to simulate a bubble rising near a heated wall in a static fluid, considering different bubble–wall distances (S), Galilei (Ga) number, and Eötvös (Eo) number. The results indicate that when the distance between the bubble walls is relatively small, the repulsive force from the walls predominates, causing the bubble to move away from the wall and thereafter spiral upwards initially. As the distance increases, the bubble movement approaches a stable periodic spiral trajectory, and the influence of wall disturbances diminishes. The rise in the quantity of Eo exacerbates bubble deformation, resulting in increased resistance and a decrease in ascent velocity. Simultaneously, the shedding frequency of the vortex increases, further disrupting the thermal boundary layer. An increase in the Ga number accelerates the shedding frequency of the tail vortex and significantly amplifies the disturbance intensity of the flow field. Compared to the case of S = 4D, the mean maximum Nusselt number on the wall surface increases by 27.07% and 11.70% for S = 2D and S = D, respectively. Compared to Ga = 50, the mean maximum Nusselt number at the wall increases by 187.58% and 238.71% for Ga = 279.58 and 559.17, respectively. Compared to Eo = 0.54, the average maximum Nusselt number of the wall for Eo = 1 and Eo = 5 increases by 2.69% and 17.16%, respectively.