Particle Deposition in a Two-Dimensional Slot from a Transverse Stream

ABSTRACT

This paper addresses the problem of coarse mode particle deposition in a two-dimensional slot from a transverse flow. A dimensional analysis enables us to identify five independent dimensionless groups: the leak Reynolds number, Re, the dimensionless velocity gradient of the approaching flow, α, the Stokes number, Stk, the slot aspect-ratio, e/h, and the interception parameter, d_p/h.. A sticky aerosol (MMD ≊3–7 μm; GSD ≊ 2–3) was injected into a 15 cm diameter duct and blown out through a rectangular opening (3 × 40 mm; e = 0.6 mm) drilled in a direction perpendicular to the flow. A video camera was set up to continuously monitor the leak behavior in time. The image then was digitized, enabling us to assess the slot-width as a function of time. It appeared that the slot could be sealed in less than 20 minutes. These results were compared with a simplified model based on a scale analysis of the deposition velocity on the slot thickness. Agreement between predicted and measured leak-widths is very good when the pressure differential across the opening does not exceed 60 Pascals. Deposition on the upstream edge is observed only when its surface is not smooth.