I am doing some fluid flow simulations in hydrocyclone for incompressible flow using Fluent. The geometry is a 3D geometry. I have given velocity inlet as the B.C for the inlet and Pressure outlet as the B.C for the two outlets. At the inlet i have specified the velocity and turbulent intensity and hydrulic dia. In the other two outlets also i have mentioned the TI and the hydraulic dia.when i check the massflow rates inbetween the iterations the mass flow rate at the inlet is much less than the actual value, and this doesn't change.I have checked the fluid property, the units in which the grid was made. everything is alright. I don't why there is a discrepency in the mass flow rate? alternatively can i use the mass-flow inlet B.C at the inlet?

You may be knowing that Fluent calculates mass flow rate from Velocity Inlet condition by multiplying Velocity with Cross-sectional area of inlet region and Density of fluid. You double check the velocity value which you are giving as input and check the density. Good Luck satheeskannan