Calculating flow rate through a cut surface

[mejahandar]

Dear CFX Experts,

I am trying to use the following equation to calculate the mass inflow though a cut surface in my domain. It is a steady state simulation.

(areaInt_y( Velocity v* (if (Velocity v < 0[m/s] , 1, 0 )) )@ Plane1)+

(areaInt_x( Velocity u* (if (Velocity v < 0[m/s] , 1, 0 )) )@Plane1 ) +

(areaInt_z( Velocity w* (if (Velocity v < 0[m/s] , 1, 0 )) )@Plane1 )

“if (Velocity v < 0[m/s] , 1, 0 )” is to filter the flow entering the surface since I have reverse flow as well. And Plane1 is on the x-z plane.

It works with < 0.3% error at the inlet, however, it is showing me a flow rate larger than the inlet at this cut surface.

If no filter is used, then the total flow rate though this surface is zero.

Please see the attached image.

Any thoughts?

Thanks,  

[Surya Deb]

Hello,
You can try to create an iso-clip on the x-z Plane that you have now. The iso clip will be based on negative values of Velocity v.
Then you can calculate the mass flow rate using this iso-clip.
Regards SD