How to correctly set the initial conditions in Elastodyn？

[cross-max]

I am currently using OpenFast for simulation, with version 4.1.2. The wind turbine model is IEA-15-240-RWT, the controller is ROSCO 2.10.1, and the wind field is generated by Turbsim (with the IEAKAI turbulence model) with a reference wind speed of 10 m/s. During the OpenFast simulation process, the problem as shown in the figure occurred.

I don't know if this will cause distortion in the simulation data. I have learned that setting the correct initial pitch angle and initial rotational speed can effectively prevent this situation from occurring. However, I referred to the documentation of the 15MW wind turbine and repeatedly set various combinations of initial pitch angles and initial rotational speeds. The problem still persisted. In the future, I will need to conduct simulations under different wind speed conditions.
Could this be a problem with the initial condition settings?
How can we find the correct initial conditions corresponding to a specific wind speed to avoid this situation from happening?

[jjonkman]

Dear @cross-max,

I gather you are setting the initial rotor speed to 7.2 rpm and the initial pitch angle to 1.0deg based on your ROSCO message, which is close to what I expect for the IEA 15-MW RWT at 10 m/s, but from Figure 3-1 of the IEA Wind 15-MW RWT specifications report (https://docs.nrel.gov/docs/fy20osti/75698.pdf) I would expect the pitch angle to be closer to 0.0deg. Does reducing the initial pitch to 0.0deg solve your issue?

I see a warning about time-varying tau1, which suggests your simulation has other issues. Switching from DBEMT_Mod = 2 in AeroDyn to a DBEMT model with constant tau1, such as DBEMT_Mod = 1 or 3 would eliminate this specific warning, although I'm not yet sure if that is the fundamental issue.

Best regards,

[cross-max]

Dear @jjonkman ,

Set DBEMT_Mod to 3 and assign tau1_const to 25. The alarm regarding tau1 has been successfully eliminated.

According to Figure 3-1, I have set the initial pitch angle to 0° and adjusted the initial rotational speed around 7 rpm.

However, the problem still persists.Will the current alert affect the accuracy of the simulation results?

I changed the UAStartRad parameter in the aerodyn input file from 0.1 to 0.2. The alarm was successfully eliminated, but I'm not sure what impact this will have on the results.

Sincerely,

[jjonkman]

Dear @cross-max,

I'm glad switching to DBEMT_Mod = 3 eliminated the first warning.

By "alert", presumably you are referring to the warning about "temporarily turning off UA". This may not be an issue if high angle of attack or low relative velocity are expected under the conditions you are simulating. But you'd have to provide more information on the results you are obtaining and whether they are expected or not to comment more.

Best regards,