The analysis of the flow of granular material in a silo using particle-in-cell method is presented. The behavior of granular material is modeled using elasto-plastic material with Drucker- Prager yield condition and the non-associative flow rule. The PIC method uses computational grids which can be chosen arbitrarily and material points which are followed throughout the deformation of a body. Therefore it if efficient for the large strain problem. The Columb model of friction is considered between the granular material and silo walls. The comparison of results obtained by the PIC method with those acquired by the updated Lagrangian formulation of the FEM is made. The flow pattern is similar but the boundary traction near the silo outlet is more reasonable in the case of PIC simulation. The results from the PIC analysis and those from the Beverloo's experimental formula. There are some discrepancies between the calculated mass flow rates from the PIC analysis and those from the Beverloo's experimental formula. But, the tendencies of the mass flow rates due to the changes of the silo outlet diameter are similar in both cases.
