I am trying to modelate a Savonius VAWT with Flowsimulation. I am looking for the idle speed of the rotor so I am calculating the Torque given by different rotational speeds and with this I calculate the Power (P=angularvelocity x Torque) The problem is that I get unexpected oscilations in the results that it makes it totally unlogical. If somebody has an idea I would be really greatful.

The initial conditions are the following:

Inlet velocity in the wind channel : 7,5 m/s

Outlet of the wind channel: environmental pressure

Rotational speed: 0 - 100-200-300......1000 rpm

Local mesh: Level 8 near the turbine

Initial mesh: Level 4

Convergence criterion: Torque 5e-3