2.23. Rate of Flow. Leva16 reviewed a number of investigations of the flow rate. The depth of the solids and solids carrying duct diameter had very little effect on the flow rate. If the diameter of the granular particles is greater than 0.04 the diameter of the orifice, a flow rate reduction may be experienced. The angle of approach of the floor to the orifice and the coefficient of friction of the granular material on the floor may, in combination, affect the flow rate. The flow rate varied as nearly the cube of the orifice diameter, the exponent range being from 2.50 to 2.96, with 2.75 seeming to be the average