Storm-Driven Trajectories of Rain near Balconies on Tall Building

This investigation is a computation of the trajectories of raindrops of various sizes in an irrotational, two-dimensional (2D) wind that flows to the side of a building sized horizontal cylinder. Vertical surface winds, as derived from a published survey of pressures on a model of a high-rise building, are used to modify the “cylinder wind” trajectories near the balconies to determine their ability to shelter ceiling-height, unsealed windows against impact and intrusion of rain there. It is determined that in a severe open country storm wind, portions of all drops with sizes smaller than about 2.3 mm in diameter will be driven upward to impact on unsealed window tops on the three floors above the stagnation point. Other drops sized from 4.5 mm down to the very smallest (0.1 mm) will fall below the stagnation point on the building. All window tops on the lower 10 floors will be well sheltered. Some favorable estimates of the accuracy of the calculations and some physical observations of vortex wind on the balconies of the building are provided. A scale effect was determined for a higher building and for one particular drop size.