Aerosol Science 35 (2004) 1189–1204 www.elsevier.com/locate/jaerosci Microparticle detachment from surfaces exposed to turbulent air ow: microparticle motion after detachment A.H. Ibrahim, R.M. Brach, P.F. Dunn ∗ Particle Dynamics Laboratory, Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA Received 7 January 2004; received in revised form 7 May 2004; accepted 17 May 2004 Abstract The motion of heavy microspheres after their detachment from at surfaces is considered. The microspheres initially are in static contact equilibrium, embedded fully in the viscous sublayer and subjected to a slowly ac- celerating fully developed turbulent ow. The equations of motion of the microspheres are presented, including surface roughness eects. The equations are solved numerically for detachment with and without consideration of a burst–sweep event initiating detachment. The microsphere velocity along the surface after detachment is measured using a strobed laser-light sheet and compared to the numerical solutions. Results indicate that the microspheres undergo pure rolling along the surface before possible entrainment and that the sweep plays a role in the detachment process. A model for predicting the microsphere velocity along the surface after detachment is presented. ? 2004 Elsevier Ltd. All rights reserved. Keywords: Microsphere; Detachment; Rolling; Turbulent ow 1. Introduction The detachment of heavy microparticles due to air ow in the presence of surface contact adhesion is involved in many applications. This work is a further study made by the authors on the subject of microsphere detachment from surfaces. The authors presented experiments and a model for the free-stream ow velocity at which 50% of the microspheres detach by the uid ow, U th , under con- trolled experimental conditions (Ibrahim, Dunn, & Brach, 2003). This work presents measurements and a model for the microsphere velocity after detachment. * Corresponding author. Tel.: +1-5746316089; fax: +1-5746318355. E-mail address: pdunn@nd.edu (P.F. Dunn). 0021-8502/$ - see front matter ? 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaerosci.2004.05.003