Hello, I’m modelling the IEA 15MW turbine using OpenFAST 3.5.3. To simplify things, I’ve fixed the platform and made the blades rigid by disabling these degrees of freedom. I am applying a steady wind of 25m/s with no vertical wind shear. So I am expecting the rotor to reach steady state conditions. Rotor speed, blade pitch and generator torque all look constant as expected. However I am seeing a variation in rotor thrust of about +/- 4% above and below the mean value. See plots below. Just wondering if anyone else had the same issue and could explain why this is happening? Kind regards
Dear @Oisin.Conway,
I would guess that this small oscillation in thrust results from the skewed inflow with respect to the rotor, with the skew resulting from shaft tilt and tower deflection.
Best regards,
Thank you for the response @Jason.Jonkman