Local experimental methodology for the study of microparticles resuspension in ventilated duct during fan acceleration
Résumé
The purpose of this study is to develop an experimental methodology with relevant space and time resolutions to track the velocity properties responsible for the resuspension of microparticles during the acceleration stage of a fan start. Microparticles release is investigated over a time period of several seconds, i.e. at short time. This methodology involves velocity signal measurements thanks to Hot Wire Anemometry, and an optical counting method to build resuspension kinetics curves. During the fan acceleration the velocity evolution is characterized by two stages: a first increase without fluctuations, and then the acceleration with fluctuations. The same behavior is observed whatever the distance to the wall at which velocity is considered. The resuspension phenomenon seems to be initiated by a threshold turbulent kinetic energy, i.e. by turbulent events powerful enough to release microparticles having the lowest adhesion forces. For the studied particles properties/wall properties/aeraulic conditions, a significant fraction of particles remains on the duct wall at the end of experiments, despite the fact that the remaining fraction is stabilized. This may reveal that the highest energy levels of flow events seen by microparticles were not powerful enough to release particles having the highest adhesion forces.
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