Particle Penetration through Inclined and $L$ -Shaped Cracks

This paper presents a particle penetration model predicting particle penetration coefficient $\left(P_p\right)$ through a narrow crack of arbitrary incline angles $\left(\theta \right)$ . The objective was to simulate $P_p$ 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. $P_p$ increases monotonically with $\mid \theta \mid$ because effective particle sedimentation velocity $\left(v_s\cos \theta \right)$ decreases monotonically with $\mid \theta \mid$ . For submicron-sized particles $\left(0.1\mathrm{\mu }\mathrm{m}\right)$ , Brownian diffusion is the major particle deposition mechanism. Because Brownian diffusion is a nondirectional deposition mechanism, crack inclination did not affect $P_p$ . This study applied this model to estimate $P_p$ 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.