Experimental and numerical investigation of aerosol sampling in calm air.

Abstract

Aerosol sampling in calm air may be highly relevant to many indoor air measurements, including in workplaces. However, it has not been studied widely, and the physics of the sampling mechanism is not yet fully understood. This research sets out to provide a body of experimental work to investigate the nature of calm air sampling by using a new version of the trajectory method. In the application of this method, measurements of aspiration efficiency were carried out for two types of samplers. One set is thin-walled cylindrical sampling probes with several sampling inlet diameters and different sampling orientations. The other set is blunt spherical samplers with two sampler body diameters and two sampling orientations. The experimental results were found to be satisfactory and provided a great deal of new information for calm air sampling. In addition, a Computational Fluid Dynamics (CFD) model, FLUENT, was used for numerical simulation of calm air sampling with thin-walled cylindrical probes in order to visually investigate the sampling mechanism and acquire numerical data. The numerical results showed a good match with the experimental data acquired from this research. Based on the combined experimental and numerical results, semi-empirical models were developed for various sampling scenarios to describe the physics of calm air sampling. Overall, it was shown that the successful implementation of these very difficult experiments, numerical simulations and semi-empirical model development fills a longstanding gap in the aerosol sampling science literature, providing a rich body of new experimental data and information for aerosol sampling in calm air.