Wind-driven pumping flow ventilation of highrise buildings: Effects of upstream building arrangements and opening area ratios.

Periodic vortex shedding around a building could play an important role in wind-driven single-sided ventilation especially when two free openings are mounted on the leeward wall, in which case "pumping" flow dominates the natural ventilation. In this paper, we investigated the characteristics of vortex shedding and "pumping" flow affected by the arrangements of upstream buildings and opening area ratio of ports on the downstream target building. Computational fluid dynamics (CFD) simulations have been used to predict the instantaneous and mean flow fields. Numerical results indicate that the strength of "pumping" flow could be intensively weakened by two upstream buildings. Vortex shedding from the inner shear layers dominates the vortex shedding from the target building and constrains that from both upstream buildings except at W/B = 0.5, in which case the gap flow is weak and the St is close to that of a single building. The increase of upstream building length leads to decrease of the vortex shedding frequency at the wake of all buildings and ventilation rate of the downstream building. An increase of opening area ratio on the rear wall of the downstream building will raise the Strouhal number but have no positive correlation with ventilation rate. "Pumping" flow oscillating frequency does not have clear correlation with the ventilation rate. Our study on the wake vortex shedding flow across building clusters could benefit the future green design of urban buildings.