Entrainment of fine particles from surfaces by gas jets impinging at oblique incidence

This paper describes an experimental study of the removal of fine (12 μm) polystyrene particles from a glass substrate, using a gas jet that impinges obliquely onto a particle-laden surface. In order to avoid transient affects associated with jet start-up, the sample was slowly translated under a steady jet. The translating gas jet produces a long, clean path that provides very good statistics for exploring the effect of jet parameters. This study focuses on the dependence of the spatial distribution of removal on the jet pressure ratio and impingement angle. The jet is translated over the sample both longitudinally and transversely to determine both the width and the length of the particle removal footprint. The width of the removal footprint increases and the length decreases as the impingement angle is increased. Previous researchers have reported seemingly contradictory results regarding the dependence of removal efficiency on impingement angle; this paper seeks to resolve these differences. For the steady jet, the threshold jet pressure ratio required for 50% particle removal increases with decreasing impingement angle. In addition, studies of the entrainment of well-characterized particles from well-characterized substrates provide insight into the surface shear stress imposed by the oblique jet. Received: 15 December 1998/Accepted: 15 March 2000