Full-scale measurements of indoor environmental conditions and natural ventilation in a large semi-enclosed stadium : possibilities and limitations for CFD validation

The use of Computational Fluid Dynamics (CFD) to study complex physical processes in the built environment requires model validation by means of reduced-scale or full-scale experimental data. CFD studies of natural ventilation of buildings in urban areas should be validated concerning both the wind flow pattern around the buildings and the indoor airflow driven by wind and buoyancy. Reduced-scale wind tunnel measurements and full-scale on-site measurements both have particular advantages and disadvantages. A main disadvantage of reduced-scale experiments is the difficulty to fulfill the similarity requirements, especially when wind flow and buoyancy effects are combined. This paper presents the results of unique full-scale measurements for a situation in which accurate wind tunnel experiments are not possible: natural ventilation and thermal, humidity and CO2 concentration conditions inside a large semi-enclosed multifunctional stadium with relatively small ventilation openings. The emphasis is on three consecutive evenings on which concerts took place in the stadium. Although the repeatability of full-scale on-site measurements is in general quite low, nearly identical meteorological and indoor environmental conditions were present on the three concert evenings. Furthermore, the calculated air exchange rate based on CO2 concentration decay measurements shows that also the natural ventilation on the three evenings was almost equal. The paper addresses the possibilities and limitations of this type of experimental data for the validation of CFD simulations. The data will be used in future studies for validation of CFD models for wind flow, natural ventilation and indoor environmental conditions in buildings