Hello Mohammad,

I did not understand the term static or rolling geometry. which geometry you are talking about?

besides, the following are my suggestions for your questions.

1. For the VOF model, a single set of momentum equations is solved while simulating any problem. So, the source terms that you add to the momentum equation, they are always added to the mixture phase. It depends on your problem whether the source terms are hooked to a particular phase or to the mixture

2. You can access the volume fraction of secondary phases through the use of different macros such as "DEFINE_ADJUST". I am not aware of the volume fraction multiplication that you mentioned.

3. For better convergence, first make sure that your mesh quality is good. Start with a smaller timestep size or you could use a variable time-stepping method. Try playing around with URFs for pressure and momentum and discretization schemes.

Hope this helps,

Shivam

Shivam Salokhe

hi shivam

the rolling condition is one of 6DOF motions and it means the geometry have a sinusidal movement . static mode means the geometry is fixed in his place and we havent any movement or motion.

about question number 2: when we add a force to momentum eq, we should consider we have two phase(water and vapor).then we should multiply single phase momentum eq by alfa term. alfa is vof of each phase. for define adjust macro i should define the phases??

about queston 3: what is URFs?

Alfa is the volume fraction of the secondary phase (correct me if I am wrong). Hence, when you speak about accessing the volume fraction while using UDF with the VOF model, it will always return to the volume fraction of the secondary phase. I am not sure about the multiplication of alpha in source terms unless your formula for source tells you to do so. As I mentioned earlier, when you add source terms while using the VOF model, they are always hooked to the mixture, not to any particular phase. URF means (Under relaxation factors)

Shivam Salokhe

look at this pic.

it can shown during rolling the alfa should be multiply in external force.

Thanks for the picture Mohammad, it is clear now.

As I mentioned earlier, if your formula for source includes alpha term then you should use it. According to the picture, the effect of rolling motion is added via UDF then you should use two different macros. The first is to access and store the volume fraction of the secondary phase and the second is to add source term based on the formula. I am sure that there are a couple of examples given in the ANSYS UDF manual you just need to modify it.

Hope this helps,

Shivam