Learning Forum

[jiangtao.lu]

Dear all, I am using Eulerian multiphase model to simulate a liquid-gas1-gas2 stirred tank system. Clearly, in the headspace, there is no liquid, and the sum  of the volume fraction of gas1 and gas2 should be 1. I tried to initialize such, say first initialize liquid_vof=1.0 to full domain, and then patch gas1_vof=0.8 and gas2_vof=0.2 in the headspace, but Fluent gives such warning

patching single gas vof to 1.0 is fine, so I guess it is due to the smoothing that both gases are at the +side at some cells. How can we avoid it? Or it has no influence on simulation?

Thanks. 

[Vishesh Aggarwal]

Hi,

Lets assume vof1 is the volume fraction of primary phase, and vof2, vof3 are the volume fraction of the secondary phases. The primary phase volume fraction will first be picked up based on initial conditions provided as = 1 - (vof2 + vof3). As the warning suggests, when the patching of secondary phase volume fractions end up being such that vof1 + vof2 + vof3 > 1 in some cells, it shows up.

The solver will anyways 'normalize' the volume fractions. So, it is best to verify through contour plots, after initialization and patching, if the phasic volume fractions represent the desired condition.

Lastly, I assume liquid is your primary phase. Initialize the case with gas1 and gas2 volume fractions as zero. Have a cell register for the top headspace and patch gas1 and gas2 volume fractions in this register.

Regards,
Vishesh

[jiangtao.lu]

Thanks Vishesh. I did exactly the same as you described. Good to know this warning is not a problem, as vof is always normalized.