Mass flow rate
Hello All,
I have a mass flow rate (0.0468 kg/s) outlet result for a 2D model and need to apply this to a 3D model for inlet mass flow rate boundary. What does this mass flow rate means in term of 3D? How can I use this result and apply to the 3D model? Thank you 
Re: Mass flow rate
Was your 2D model axisymmetric? If yes then the mass flow rate is real. Apply directly to the 3D model.

contrast case
hello~ everyone
I have a another question about this post What if I have mass flow rate for 3d and i want to apply that flow rate to 2d axisymmetric casek for reducing computational cost? 
Same date for axisymmetric and 3d.
But you can also use velocity inlet, and check the massflow rate (report/) 
Dear All, I have simulated a combustion flow in CFX some time ago. It was possible to define a surface which was a wall, but from which some reacting species were inserted into the domain.
This boundary was a wall+source, so that I was able to specify both mass fractions of the various species and the mass flow rate coming in; it was also possible to have a certain heat flux at that boundary. It was one of the parameters calculated during the simulation. Is there a similar condition in Fluent? 'cause i saw just traditional walls and mass flow inlet boundaries. If not, is there any other way to make Fluent do what i need? (which is basically introducing a certain amount of mass from the boundary, with specified mass fractions and calculating the heat flux without imposing it at the beginning). Thanks a lot Marta 
Negative mass flow rate in everywhere except inlet
Hi all,
In my 2D model, I found negative mass flow rate in everywhere except in the inlet. What does it mean? Please enlighten me . Thanks in advance. 
It means that the flow exits the computational domain.

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Boundary faces like an inlet have an orientation, indicated by the normal vector of the face.
For example the normal vector of the inlet face points towards the computational domain. If the flux vector is pointing in the same direction, the mass flow rate is positive (the flow enters the computational domain). For faces where the normal vector and the flux vector are pointing in opposite directions, the mass flow rate is negative. For an outlet this indicates that the flow is leaving the domain. 
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negative mass flow rate at outlet
I am facing the same problem of negative mass flow rate & I don't quite understand what's meant by the fluid's leaving the domain.
Isn't the direction of my flow supposed to be the same at all positions? and that's what I'm getting when I display the velocity vectors, then how come my mass flow rate is negative? Please help me understand this. 
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Thanks a lot Pakk, that was really helpful :)

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