[MDinc]

Hello Everyone,
I am modeling a 2D single droplet impingement to a liquid film thickness using VOF. I defined the model BCs as: Rectangular domain; bottom (ground) surface is Wall, left&right surfaces are also Wall and top surface is Pressure Outlet.

I have some questions about the model choice and also solution procedure:
1.) I started simulation of the model and once I started transient simulation, I got this error message:
Divergence detected in AMG solver: pressure coupled -> Decreasing coarsening group size!
# Divergence detected in AMG solver: pressure coupled -> Increasing relaxation sweeps!
# Divergence detected in AMG solver: pressure coupled -> Changing to W-cycle!

Then, I tried different solution method and parameters. This time I got this error message:
Error: Global courant number is greater than 250.00 The
velocity field is probably diverging. Please check the solution
and reduce the time-step if necessary.

I also tried DPM (single droplet particle tracking) + VOF (Hot liquid film thickness). I got same error messages during iterations. Thus, how can I solve these problems?

2.) For future simulations, I also want to include droplet collisions and particle-wall collisions. Thus, can I use eulerian based DDPM+VOF models instead of DPM+VOF in order to simulate single and/or multiple droplets impinging on a thin liquid film?

3.) Maybe, I should have asked this question before: Which model is the best for the following situations?

-Single Droplet impinging on thin liquid film (With/without heat transfer and phase change mechanisms, and bubble dynamics)

-Multiple (train) droplets in a single and multiple lanes impinging on thin liquid film (with/without heat transfer and phase change mechanisms and bubble dynamics)

-Spray modeling to include droplets leaving a nozzle then impinging on thin liquid film (heat transfer and phase change mechanisms included)

Regards.