Investigation of local severe suction on the side walls of a high-rise building by standard, spectral and conditional POD

Abstract

Local severe suction greatly determines the safe and economic wind-resistant design of cladding system in the façade of buildings. This study focuses on two localized regions with severe suction of a building, i.e., the lower windward corner of side wall and the region immediately upstream of trailing edge. The aspect ratio of building is 3. The characteristics and mechanism of wind peak pressures are investigated by standard, spectral and conditional proper orthogonal decomposition (POD). Spectral POD extracts the space–time modes which oscillate at the single frequency of the anti-symmetric vortex shedding, where the pressure distributions have the shape of ‘dragonfly’ wing and opposite signs on two side walls. Conditional POD is demonstrated to be a powerful tool to study the average evolution of peak pressures. By inspection of conditional POD modes, high positive fluctuating pressure is observed in the trailing portion of the lower side wall, accompanied by the minimum pressure in the windward corner. The identified pressure behaviors provide the statistical evidences for flow reattachment and shear-layer roll-up which were observed by instantaneous flow visualization in the literature. The trailing-edge peak pressure in the middle-height region is induced by trailing-edge vortex of great vorticity concentration. The flow mechanism and occurrence phase of trailing-edge peak pressures are similar to those of infinite-length cylinders.