Effects of separated flow on cotton dust sampling with a vertical elutriator.

The vertical elutriator used for cotton dust sampling was examined theoretically and experimentally to determine airflow patterns and particle transport. The theory of diverging channel flow predicts that a separated eddying flow will occur in the elutriator. This calculation disagrees with the laminar flow assumptions used to predict the size sampling characteristic or cutoff of the elutriator. Smoke injection tests verified random local velocity components and clearly showed that the flow is not uniformly upward and laminar. Particle transport tests indicated that unit density spheres as large as 27 micron can reach the sample on the elutriator filter.