Hi @YB128, really sorry for the delay, only noticed this when it was bumped by @Kai_himself. I think most multiphase simulation projects on the public projects have subdomain based initialisation for phase fraction. The general workflow is to make a geometry primitive in the simulation setup, and then enable subdomain initialisation from the drop-down box, then assign your second fluid in the region and set the default fraction to the primary fluid.
The error about CFL is detailed in the log where it says it was in the order of e34, this is unrealistic and so you have likely diverged for another reason, try the above subdomain based initialisation and see if this goes away otherwise I will look into the simulation for you.
Hope this helps and isn’t too late,