I have a problem with using baffle. I run a problem with a baffle put in nearly half of the path. It was keeping diverged in less than 200 iteration no matter what a relaxation I selected, such as R for press < 0.05. Once I switch the fluid adjecent to baffle to solid, calculation converged to -3 order of magnitude in mass. Does anyone have similar problem before or any suggestion, I will feel very grateful.

Is your flow domain completely separated by the baffles? That would imply that they are permeable baffles. In that case: Start with a low pressure loss over the baffles and restart with higher ones, until you reach your desired value.
Hope that helps, Marc

thank you for your response. my case is not that complicated as you guessed, with only mesh seems complex. it is a problem with flow bifurcated for a distance and merged again at downstream. once a baffle works as a door shut off one side path, diverge happens. mesh quality is not good but works well as i mentioned in first post.

If your baffle door shuts off a side path, and the fluid in that path becomes completely separated from the rest of the flow, it becomes a two-stream problem. In other words, you have two completely separate flow domains. This is numerically unstable, and requires some special treatment.

See Tutorial 13 for how to handle that - Tut 13 is a moving mesh case, but you should get the idea.