NUMERICAL PREDICTION OF THE PERFORMANCE OF A MANIFOLD SAMPLER WITH A CIRCULAR SLIT INLET IN TURBULENT FLOW

The performance of a bioaerosol manifold sampler with a circular slit inlet in a turbulent flow field was modeled using a 3-D numerical approach. The standard κ–ε turbulence model was used for simulating the mean turbulent flow, and the Lagrangian approach was used for predicting the particle trajectories. The ratios of wind velocities to sampler inlet velocities were from 0.5 to 3.5. Calculations were conducted for particle sizes of 2, 8, 15,and26 μm. The agreement between numerical and empirical sampling efficiencies was good. It was found that lower sampling efficiencies at high R values were associated with increased positive pitch of the velocity vectors generated at the inlet slit. Unbalanced sampling velocities between the upstream and downstream arcs were found only at high R values. At an inlet velocity of 0.8 m/s, sampling efficiencies for 15 μm particles decreased about 24% as R was increased from 0.5 to 3.5. A similar effect was observed at an inlet velocity of 0.4 m/s. Turbulence decreased sampling efficiency and was related to the sum of the magnitudes of the wind and sampling velocity vectors.