Effect of Wind Direction on the Ventilation Dynamics of a Model Sports Stadium

Dispersion around open-air structures is complicated by the interaction between external and internal flow dynamics. Variations of wind direction alter the relative position between openings in the structure and the pressure field around it, affecting ventilation rates. This work experimentally investigates passive scalar dispersion around a model sports stadium as a prototypical open-air structure. Realistic ventilation features are included, such as an asymmetric roof opening, roof slits, and entrance tunnels. The effect of free-stream wind direction is reproduced by rotating the test model embedded at the bottom wall of a water channel at fully turbulent Reynolds numbers. Novel medical imaging techniques are combined with laser-based diagnostics to obtain a comprehensive set of flow velocity and concentration fields. External and internal three-dimensional velocity fields are measured using magnetic resonance velocimetry, while time-resolved concentration fields at a central plane and outside the stadium are obtained using planar laser induced fluorescence. Results show the strong dependence of the internal-external flow exchange with wind angle, with large variations in flow rates through openings which affect the surrounding concentration fields. The unique combination of experimental techniques provides detailed flow and scalar dispersion insights key to improved indoor-outdoor air exchange strategies.