Peak suction on a wall-mounted square cylinder by conditional POD: Effects of incident angles

Abstract

The wind incident angle (α) is one of the crucial factors that dominates the peak suction on wall-mounted square cylinders (e.g., high-rise buildings). With a focus on the incident angle effects, this study applies the conditional space–time proper orthogonal decomposition (conPOD) to investigate the temporal evolution of peak suction in a statistical sense. Local regions of peak suction are typically classified as the lower windward corner, upper windward corner, trailing-edge region, and lower central side wall, which occur at different ranges of incident angle. The results show that the occurrence of peak pressures at the upper and lower windward corners on the wall of flow separation bubble is not synchronized on average when the incident angle is smaller than the critical angle (α≈15°). However, at a greater angle, a strong correlation is observed between the two regions of peak pressures at α=15–35°. The peak suction on the lower central side wall observed when α=5–15° is verified to have the same flow mechanism (i.e., inverted conical vortex) as the lower windward corner. The location, time of occurrence, and the flow mechanism of the trailing-edge peak suction are systematically clarified at different incident angles by the conPOD method.