Reference Velocity Calculation & Convergence Problem
 

Hi all,

I am trying to simulate pitching/plunging motion cases in hover (no free-stream velocity, all BC's are pressure outlet, laminar case) Yet, I have some problems as:

1) I confused a little on reference velocity value to be used in force coefficient's calculations in pure pitch motion case (pure pitch motion is defined as alpha=30*pi/180*sin(w*t)). Since in my simulations there is no free-stream velocity, i assume that V=2*pi*freq*(c/4) where c/4 is my rotation location. Is it a good idea to use this assumption? Or there is a better definition for this velocity?

2) Nearly all of my cases do not convergence still after 10 periods of simulation. Can it be because I simulate in water using laminar (Re~1000 in my simulations) solver? Is there a tricky way to get converged solution cases as using bla bla model, using bigger domain, etc..?