Development of PIV techniques to measure airflow patterns in ventilated airspaces

A measurement technique based on particle image velocimetry (PIV) to measure quantitatively airflow patterns and distribution in ventilated airspaces is presented. Air laden with helium-filled bubbles was illuminated by a two-dimensional light sheet in a full-scale ventilated room. Images of bubbles visualized in the light sheet were recorded using a photographic camera. Relatively long camera exposure time makes it possible to record the bubble path in the designed time period. Image-shift techniques remove the directional ambiguity. The photographic images were scanned into a computer, and the digitized images were processed automatically using an image-processing program to extract flow-field velocity information. The configuration, working principles, sample results, accuracy, capability, and limitations of the technique are discussed in this paper. This measurement method is part of a larger study of aerosol spatial distribution, ventilation effectiveness, and aerial contaminant control strategies.