# Air-blast-atomizer azimuthal angle reference system and mass flow rate

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• Last Post 24 September 2018
Cybex posted this 21 September 2018

ANSYS Fluent 18.2. I have to simulate a spray through a semicircular inlet (whose normal vector is axis -X) with a given flow rate of 1 kg/s on the whole circle (it's a symmetry-plane system). I guess I have to set start azimuthal angle to 0° but I don't know whether the stop azimuthal angle would be 180° or -180°. In other words, I don't know what is the reference system for rotation used by Fluent. The inlet half which will be crossed by the spray is the superior one.

Furthermore, which mass flow rate do I have to put in injection point properties? 1 kg/s or halved?

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mli posted this 21 September 2018

If you simulate half of the atomizer with a symmetric plane, then use half of the total mass flow rate.

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Cybex posted this 23 September 2018

Thank you for your reply. Yes, it a symmetric-plane problem. Now I'm wondering whether I have to specify an azimuthal angle less than 360° or it is accounted automatically given the symmetry. As you can see, the spray is directed along the -X axis

rwoolhou posted this 24 September 2018

If you only have half of the domain then any particles that are created outside of the mesh won't be processed. So try 0-180 and 180-360 and see which puts particles into the domain.

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Cybex posted this 24 September 2018

Ok, thank you. Which flow rate should I have to choose if I set 0-180 (or 180-360)? 1 kg/s or half?

abenhadj posted this 24 September 2018

The flow rate is the one of 360 degrees. Fluent will use for the effective mass flow through the nozzle your input divided by the azimuthal angle difference multiplied with 2*PI. Regarding the angles: keep in mind that we rely on right hand rule and that counterclockwise is always positive. Just stick to rwoolhou suggestion to get the right range.

Best regards,

Amine