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 Bow field was modeled using a 3-D numerical approach. The s tandard kappa-epsilon turbulence model was used for simulating the mean tur bulent Bow, and the Lagrangian approach was used for predicting the particl e trajectories. The ratios of wind velocities to sampler inlet velocities w ere from 0.5 to 3.5. Calculations were conducted for particle sizes of 2, 8 , 15, and 26 mu m. The agreement between numerical and empirical sampling e fficiencies was good. It was found that lower sampling efficiencies at high R values were associated with increased positive pitch of the velocity vec tors generated at the inlet slit. Unbalanced sampling velocities between th e upstream and downstream arcs were found only at high R values. At an inle t velocity of 0.8 m/s, sampling efficiencies for 15 mu m particles decrease d about 24% as R was increased from 0.5 to 3.5. A similar effect was observ ed at an inlet velocity of 0.4 m/s. Turbulence decreased sampling efficienc y and was related to the sum of the magnitudes of the wind and sampling vel ocity vectors. (C) 1999 Elsevier Science Ltd. All rights reserved.