I would like to know if it is possible to simulate aa buble of water mooving in a flow of oil with a mesh refinement very fine in the neighbouurhood of the buble and coarse mesh elsewhere(so as to save time) Or even a mesh refinement that depends on the gradiant of vof(volume of fluid )?(and like that the fine meshing follows for each time step the buble) That means that I need a fine mesh that mooves inside a coarse mesh this depending on the gradient of VOF (free surface) thanks it is urgent please respond

What you are talking about is dynamic grid adaptation and the answer is no, not currently although I heard a rumour that STAR-CCM+ is getting it in the near future.

Yep, that is true, but don't expect it to come out soon. Star CD infact demonstrated dynamic grid adaptation during their previous European User Conference. I have to say it looked really impressive.