# OpenFAST initial conditions

Hello everybody,

I hope my question is not too silly and I hope that it has not yet been answered in another post and I have not found it.

I have problems with the initial conditions for the simulation of the NREL 5 MW wind turbine, which are given in “Definition of a 5 MW Reference Wind Turbine for Offshore System Development” on page 32 for wind speeds from 3 to 25 m*(s^-1). For speeds below the rated wind speed, my results look realistic to me (for example for 7 m*(s^-1), 1_7_Flp_Edg_Pitch.jpg).

However, for wind speeds above the rated wind speed, the blade moments oscillate and, in my opinion, do not look realistic (for example for 13 m*(s^-1), 1_13_Flp_Edg_Pitch.jpg).

I suspect that this is somehow related to the control for the blade pitch angle, since they seem to differ greatly for speeds above the rated wind speed. Are initial conditions for wind speeds from 3 to 25 m*(s^-1) suggested elsewhere? I have little experience with this because I am still a student. The simulations were carried out under calm sea conditions.

Best regards,

Malte Frieling

Dear Malte,

What stands out to me in 1_13_Flp_Edg_Pitch.jpg is the pitch angle, which oscillates heavily between 0 and 90 degrees. But it is hard for me to understand why the pitch is doing this. Are you using the baseline controller for the NREL 5-MW turbine (DISCON.dll)? What initial conditions in terms of rotor speed and pitch angle did you set?

Best regards,

Hi Dr. Jonkmann,

Yes, I use the basic controller for the NREL 5 MW turbine and the initial conditions that I used are from the document “Definition of a 5 MW Reference Wind Turbine for Offshore System Development” (page 32).
For the simulation with a wind speed of 13 m *(s^-1) I used the following values:
OoPDefl1: 3.8
IPDefl1: -0.8
BlPitch: 10
Rotspeed: 12.4
TTDspFA: 0.2

Best regards.

Dear Malte,

My guess is the problem is the initial rotor speed of 12.4 rpm, which is above the expected value of 12.1 rpm at above rated wind speeds for the baseline NREL 5-MW turbine / controller. I would guess this higher than expected rotor speed is confusing the baseline controller, which does not appear to recover. Does changing RotSpeed to 12.1 rpm solve the problem?

Best regards,

Hi Dr Jonkmann,
that was the mistake. I mixed the values for the rated wind speed and the rated rotor speed.
Many thanks for your help.

Best regards,

Malte Frieling