Particle penetration through inclined and L-shaped cracks

This paper presents a particle penetration model predicting particle penetration coefficient ([P.sub.p]) through a narrow crack of arbitrary incline angles ([theta]). The objective was to simulate [P.sub.p] for outdoor-to-indoor particle penetration for residential infiltration conditions. This model assumes laminar infiltration flow and considers particle deposition from both gravitational sedimentation and Brownian diffusion. For micron-sized particles, modeling results indicate that gravitational sedimentation is the major deposition mechanism. [P.sub.p] increases monotonically with [theta] because effective particle sedimentation velocity ([[upsilon].sub.s] cos[theta]) decreases monotonically with [theta]. For submicron-sized particles (0.1 [micro]m), Brownian diffusion is the major particle deposition mechanism. Because Brownian diffusion is a nondirectional deposition mechanism, crack inclination did not affect [P.sub.p]. This study applied this model to estimate [P.sub.p] for L-shaped cracks, and validated modeling results with experiments. Experimental results indicated that inertial impaction and crack entrance cutoff effects were not significant particle deposition mechanisms for the test micron-sized particles. Gravitational sedimentation was the major deposition mechanism. An L-shaped crack can be simulated as the combination of horizontal and vertical sections. This model agreed reasonably with experimental results. DOI: 10.106 I/(ASCE)0733-9372(2007)133:3(331) CE Database subject headings: Particles; Penetration; Indoor air pollution; Infiltration; Cracking.