[celebre17]

I am working on water free jet evolving into a quite air ambiance (vertical free jet)

I use VOF (volume of fluid) model to represent both water and air mixture. The goal of this study is to reproduce the jet break-up for instance the Rayleigh regime.

The domain of the calculation is a rectangular form to represent an axisymmetric form of a jet issuing into a domain.

The boundary condition of the test is as follow: inlet velocity at the jet injection. Three sides of the rectangular domain are used as pressure outlet condition and the forth side near the jet exit is used as axisymmetric axis.

I------------------------pressure-outlet------------------------I

I I

I I

pressure-outlet pressure-outlet I I

I I

I I

inlet velosity I

---------------------------------------------axisymmetric----------------------------------------------------- I

The problem is: when I want to check the accuracy of the results I try to calculate the mass flow rate over the boundaries (inlet mass flow rate + outlet masse flow rate) which should be very small (vanishes in case of perfect calculation).

The results converge well (residue =10-6)

The result seems very realistic while the sum of (inlet mass flow rate + outlet masse flow rate) is very important

I guess that inlet mass flow rate must be in same order of outlet masse flow rate ( isn’t it???)

Please help me to explain this anomaly (is it an anomaly?)

Is there any other method to check the accuracy of the results using VOF.