Axisymmetric volume conversions: is pressure affected?
 

Hi, I'm using a 2D axisymmetric model with a mass flow inlet and examining pressure between two different sized pipes. and the guide says that the axisymetric model works by assuming the volume is swept around the axis by 1 radian, and that reported quantities need to be multiplied by 2pi to get the values for the full 360 degrees volume.

So if I have a mass flow for the inlet divided by 2pi for the swept volume of 1 radian, for example 0.2kg/s --> 0.0318 kg/s, does this mean that the reported pressure should be multiplied by 2pi? So 600kpa becomes 3,769.9kpa? It seems a bit too much, I'm not sure how to do this. Or does the conversion not affect pressure? What values are and aren't affected?

Thankyou for your advice.

Dear Andrew,

for 2D axisymmetric case only quanities which are dependent from the circumferencial direction need to be converted, such as volume flow and mass flow.
However, hydraulic pressure is a unidirectional quantity of the fluid. It is not changing in a circumferencial direction for an axisymmetric case. On the contrary, the force (in axial direction) on a surface exerted by pressure is dependent by the circumferencial direction.

You might check out the fluid flow formulation for axisymmetric models in the tutorial manual.

Best regards,
Sebastian