jjonkman
commented
6 months ago Dear @sffgd,
My guess is that you are running into the blade-edgewise physical instability that would be expected when simulating a parked or idling rotor under high wind speeds at high yaw error (IEC load case 6.2). Once the model is physically unstable, the solution may blow up (leading to warning about large deflection warning, an error about tower strike, an error about aerodynamic analysis nodes leaving the wind domain, and/or excessive limit-cycle oscillations). This case has been discussed before on our forum, e.g., see:
https://forums.nrel.gov/t/designing-for-yaw-errors-using-fast/1051 https://forums.nrel.gov/t/wind-veer-parameter/2103 https://forums.nrel.gov/t/natural-frequencies-and-mode-shapes/2545 https://forums.nrel.gov/t/tower-strike-with-latest-versions-of-openfast-and-iea-15mw/3024
Best regards,
sffgd
hello everyone， I am simulating the idle shutdown state with normal turbulent wind files with wind speeds of 40m/s and 45m/s, grid size (X=284, Y=284), which can be calculated when PropagationDir=0° and PropagationDir=270°. However, when the wind field is deflected counterclockwise by 30° (PropagationDir=330°), it warns of "violation of the small angle assumption" and then reports the error "GF wind array boundary violated: grid is too small, Y direction." Y=142.03;Y boundary=[-142,142]. When the wind field is deflected 60° counterclockwise (PropagationDir=300°), an error is reported that”TwrInfl:Tower strike“. Is there any solution? Thank you very much！