Mass flux looks ok. if you see the attached pictures, you will find mass of mixture is 0.785 kg/s, and that for the particle phase 0.075. When I translate theses value into volumetric flowrate, if found that mixture and particles have flowrates of 7.8e-3 and 2.96e-5 m3/s, which equals a volume fraction of 0.0376. However, I still don't understand why I got similar volume flowrate from surface integral report as shown in the above picturenn