Equation Describing Granular Flow Through Circular Orifices

PHYSICAL relationships affecting granular flow were used to derive an equation to predict flow through orifices. The equation was derived by balancing downward and upward forces in the system. Laminar flow conditions were assumed and verified which simplified the derivation. Extremely large orifices coupled with high bulk density could violate this assumption. Laboratory experiments using various grains and food products for circular orifices verified the equation with R2 values in excess of 0.999 and were significant at an alpha level of 0.001. Data reported in the literature were also tested with resulting R2 values in excess of 0.98 and were highly significant. Finally, it was found that flow became irregular for orifice diameters less than four times the largest particle dimension compared to values of 10 to 20 previously reported.