Modelling the damping system

Hello everybody,

I am now modelling a free bearing system which oscillate quite a bit.  I want to reduce the oscillation by adding a damper on the bearing system.  The algorithm as simple as M=k*Ω where M is the damping torque, k is the damping coefficient and Ω is the rotation speed of the system.  Of course if I increase the damping coefficient k, the effect of damping becomes more significant which is preferred.  However, accompanying the increased stability, the simulation takes much longer time.  Does anyone know if there is a more proper way to model the damper instead of the simple equation M=k*Ω which introduces a lot of fluctuation of torque due to the fluctuation in the rotation speed?

Regards,

Pomelo