Particle Deposition in Cyclic Bifurcating Tube Flow

Deposition efficiency (DE) of aerosol particles in a bifurcating tube was determined experimentally with cyclic flow conditions at a frequency of 16, 30, and 50 cycles/min. Two bifurcation tube models with identical dimensions but different branching angles (θ = 30° and 45°) were used. Monodispersed oleic acid droplets (3, 5, and 7 μm in diameter) tagged with uranine were used as test aerosols and sampled through the model tube at a mean Reynolds number (Re) of 679–5548. Stokes number (Stk) ranged between 0.028 and 0.25. The model tube was washed section by section with deionized water and the fluorescence content in the washed solution was used to determine deposition efficiency. DE increased monotonically with increasing Stk at Re < ～ 2000. However, at higher values of Re, Stk failed to unify DE. There was no significant difference in DE between θ = 30° and 45° and among different cyclic frequencies used. However, DE with cyclic flows was 80–200% higher than those obtained with constant flows. The implications of the results were also discussed.