Scaling effects on experimentally obtained pressures on an idealized building: Possible implications towards asbestos containment

Abstract

Atmospheric wind may affect mechanically-induced depressurization in asbestos containment zones set to prevent escape of hazardous fibers. The associated health risks necessitate investigation of wind effects on internal depressurization. This can be achieved by experiments in atmospheric boundary layer wind tunnels utilizing relatively large geometrical scaling ratios (e.g., 1:40), suitable for accommodating all components of the reduced-scale mechanical ventilation system. However, physical constraints in the wind-tunnel cross-section limit replicating large-scale turbulent structures, thus mispredicting exceedances of pressures responsible of containment breaches. Investigating the latter is the innovative goal of present study, for which external pressure characteristics and duration of a certain threshold pressure exceedance have been analyzed for an idealized low-rise cubic building with two geometrical scaling ratios (1:40 and 1:300). The 1:300 scaling ratio allows to represent turbulent structures of almost all relevant sizes of the ABL; whereas, with the 1:40, large-scale turbulent structures are missing. Overall, findings suggest that a larger scaling ratio of 1:40 can be effectively used for mechanical ventilation studies in scenarios where ventilation inlets or outlets are not installed on the roof. However, with the caution that the containment breach probability can be underpredicted at regions of flow reattachment and recirculation.