A second topic discussed in this chapter is the flow of particulate solids through orifices and their flow pattern during emptying of bins and enclosures. Internal friction among particles influences the flow pattern. Many granular materials are metered through orifices during handling. Therefore, it is often necessary to estimate the flow rate of the material. The manner in which particulate materials flow from a bin is affected by both particle interaction and the angle which the bottom of the bin makes with the horizontal.