Spectator comfort in sports stadiums: on the impact of roof geometry on wind-driven rain shelter

The main aspect for spectator comfort in outdoor stadiums is protection from wind and rain. This paper presents an investigation of the impact of roof geometry on rain shelter. CFD simulations and Lagrangian particle tracking are performed to analyse the wind flow pattern and rainfall distribution in seven generic stadium configurations and to assess the performance of each roof type. Although most existing stadium roofs are built with a light to medium upward slope towards the field, the analysis indicates that roofs with a downward slope of 13° provide significantly better rain shelter. The reason is not only the well-known trigonometric shielding effect. In addition, this roof type – as opposed to its counterparts – restricts the extent of the primary vortex in the stadium and generates a sufficiently strong counter-rotating secondary vortex below the roof that sweeps the rain away from the stands.