Radial Force calculation

sans

Hi,

I would like to calculate the radial force on an impeller using CFX POST. I have obtained the values of Fx, Fy,Fz using the function calculator.But the radial forces are way of target. Moreover a small change in the volute (with the same impeller and position) causes a large change in the values of Fx and Fy. But both the simulations gives me almost the same pump performance. Can someone explain this difference or someone let me know the exact procedure to calculate the radial force?

Thanks,

Sans