[Zhanyuan Wang]

The equation is shown in attached picture, which is a transport equation solving mass fraction Y, and alphal is liquid phase fraction defined in VOF solvers. Problem is that there are always many cells where 1 - alpha1 = 0, so if i simply write equation like:
(1 - alphal)*fvm::ddt(rhovg, Y) + (1 - alphal)*fvm:rhophi, Y).....
solver will break at the first time step because the value of (1 - alphal) is somewhere zero.
Anyone know how to write the right equation? I will be VERY appreciated for any help offered

[Cyp]

what if you divide your equation by (1-alphal) and that you have m/(1-alphal+SMALL) instead?

[Zhanyuan Wang]

Thank you Cyprien!

I changed (1 - alphal) to (1 - alphal + SMALL) and then the solver will not break down, but regretfully i also didn't get the result i want.
This equation aims to solver Y only in regions where alphal = 0, but result showed Y was still solved in regions where alphal = 1 and its value was unnormally big. I add a picture in my thread and you can see the result here. A droplet was put in the calculating area where alphal = 1 inside the droplet.
So could you give me any suggestion on how to achieve my goal? Sorry to bother you so much time, but I m truly desperate for help...
BTW, The equation can be find in following article, where the writter applied such equation in OpenFoam.

http://scihub.bban.top/10.1615/atomizspr.2019027077

[Cyp]

Why not using the Continuous Species Transfer formulation instead? It is fully compatible with the VOF approach (single-field equations instead of two-fields equations)


https://www.sciencedirect.com/scienc...21999119307302

[Zhanyuan Wang]

Thank you Cyprien for your kind advise!
I will read this article and hope it can help me solve my problem!

[clarkent]

Originally Posted by Zhanyuan Wang

The equation is shown in attached picture, which is a transport equation solving mass fraction Y, and alphal is liquid phase fraction defined in VOF solvers. Problem is that there are always many cells where 1 - alpha1 = 0, so if i simply write equation like:
(1 - alphal)*fvm::ddt(rhovg, Y) + (1 - alphal)*fvm:rhophi, Y).....
solver will break at the first time step because the value of (1 - alphal) is somewhere zero.
Anyone know how to write the right equation? I will be VERY appreciated for any help offered

Hi Zhanyuan,


Have you found a solution to your problem?