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Old   June 2, 2010, 02:24
Default Vof for spray simulation
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Hi every body!

i am doing a simulation project in which i have to model (3D) a two phase spray. the two phase (water and air bubbles) enter the orifice at high pressure and leave the orifice in to atmosphere (STP). due to pressure difference, the air bubble expands and explode and break up the water stream into liquid jets and drop lets.

Unstdeay-pressure based implicit- vof implicit - laminar / rke - comp - BC (press I/L & O/L)

1) i am using vof to model this problem? is it the correct approach?
2) as a practice, While doing an axi-symmetric case, some of the droplets appear in the atmosphere but the simulation diverges at this instant (x-mom diverge, temp diverge etc) . What could be the problem for divergence?

regards and hope for an early answer
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Old   June 6, 2010, 08:28
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I will give u my opinion, but as i am not a specialist in sprays, so i hope what i am saying will be true:
1-VOF+Laminar for a spray flow is a suicide mission.
If u use VOF so u must have a mesh with cells that are at least two time smaller then ure droplets (to not violate shannon_nyquist). If not, u will have artificial coalescence.
Laminar: ure cells must be at least two time smaller then ure flow structures (droplets and vortices....)
2-Ure flow is horizontal or vertical? are u including gravity??
if u are including gravity for an horizontal flow, the axisymetric solver will diverge i think. u must use purely 3D solver.
Hope that it was helpful.
(Maybe eulerian-eulerian model can perform much better)
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