Graph of RMS residue not converging
 

Hi, I have a problem regarding my transient model. While running the model, it seems that the RMS residue graph is not converging, instead it is fluctuating. Is this problem relates to inaccurate mesh or boundary conditions? Really need a help as soon as possible. Thank you.

This FAQ is written for steady state runs but many of the comments are applicable to transient runs as well:
http://www.cfd-online.com/Wiki/Ansys...gence_criteria