This study numerically investigates the influence of square-wave inlet velocity pulsations on flow structure and heat transfer around a transverse circular cylinder, with particular emphasis on wall condensation behavior. The evolution of wake vortices and the distribution of the convective heat transfer coefficient on the cylinder surface are analyzed under both single-phase and two-phase flow conditions over a range of pulsation frequencies. The results indicate that inlet pulsations significantly modify the wake dynamics, leading to reduced vortex size and enhanced momentum and turbulence dissipation in single-phase flow, which in turn improves convective heat transfer downstream of the separation point. Under two-phase condensation conditions, similar wake modifications are observed, while additional small-scale vortical structures are generated within the condensate film due to interfacial shear, further enhancing local heat transfer. Overall, the findings demonstrate that appropriately tuned inlet pulsations can effectively enhance heat transfer performance for both single-phase and condensing flows around a circular cylinder.
Cheng et al. (Sun,) studied this question.