Using an unsteady solver for unstable simulations
 

A few days ago, I posted a message regarding what I could do to converge a laminar sim which would not converge otherwise. An answer I was given was to try an unsteady solver-- to eliminate the instability caused by transient phenomena. I have tried this, but my unsteady solver keeps diverging. Perhaps my setup is wrong.

What settings should I be using on my unsteady solver?

My sim involves a simulation of larynx flow- average Re # between 1000 and 20000. There is a couple species transport, and on average, any given particle will stay within the geometry of my simulation for t = 0.03 s or less.