Wind effects on mechanically depressurized indoor containment zones: Impact of uncertainties in computational fluid dynamics wind pressure on ventilation network model output

Hazardous pollutant containment zones should be maintained at a pressure lower than the outdoor atmospheric pressure to prevent pollutants from escaping to the outdoor environment. However, atmospheric wind conditions can cause breaching of the containment zone that is established through mechanical ventilation. This paper combines external wind pressure (Pe) time series on an internally depressurized building with a carefully designed ventilation network to analyze indoor pressure (Pi) and containment breach duration. The Pe data are obtained by wind-tunnel (WT) tests and computational fluid dynamics (CFD) simulations of large-eddy simulation (LES) and scale-adaptive simulation (SAS). The objectives of the paper are (1) comparing Pe results by WT and CFD; (2) assessing the impact of Pe uncertainties in CFD on the resulting Pi and breach duration; and (3) estimating Pi and breach duration for an initial case study with indoor depressurization of -40 Pa and reference wind speed (Uref) of 12.65 m/s at building height. The results are discussed in terms of dimensionless pressure coefficients (Cpe and Cpi). It is shown that LES and especially SAS Cpe data deviate substantially from the WT values but that the impact of these CFD uncertainties on Cpi and breach duration remains fairly limited. Deviations for Cpi statistics fall within the experimental uncertainty, and the CFD breach duration deviates generally less than 10% from the WT result. Estimated breach durations for Uref = 12.65 m/s, however, can go up to 80% in spite of the −40 Pa depressurization, stressing the importance of this type of studies.