Hello,

I'm studying the oscillations of a column of liquid in a U-tube using the VOF model. I'm wondering what is the difference between the VOF solver every time step and every iteration. Because by default (Solve VOF every time step) my simulations fit with some experimental data for the big oscillations but the damping is under-estimated. And when I use the VOF solver every iteration, on the contrary, I have too much damping so that the big oscillations are under-estimated but the small oscillations are well approximated. Thus I managed to fit the experimental data by computing in 2 steps (every time step then every iteration) and I'd like to know if this method is common or valid. I hope someone can help me.

Best regards, Jean-Philippe

What do you mean "Every iteration", do you mean you use steady solver ?

No, I use an unsteady solver. But since I have a two-phase flow, I also use the Volume Of Fluid (VOF) multiphase model. This solver offers several options, and I can choose between "solve VOF every time step" (the volume fraction is then updated once for each time step), or "solve VOF every iteration" (the volume fraction is updated once for each iteration within each time step).