Dear @Jason.Jonkman ,
At present, I want to understand the flapwise and edgewise response of blade with the change of inflow wind speed. I am using the IEA-15MW wind turbine model and ROSCO controller. There have been many studies that have presented relevant results (such as the figure below), but the author seems to have not clearly described why such changes occur. For researchers, this seems like common sense and does not require special explanation, but I may lack relevant knowledge reserves.
The above results are from this paper（Qu X, Li Y, Tang Y, et al. Comparative study of short-term extreme responses and fatigue damages of a floating wind turbine using two different blade models[J]. Applied Ocean Research, 2020,97）
As shown in Figure (a), the wind speed gradually increases over time. For the flapwise response results (as shown in Figures (f) and (h)), with the increase of inflow wind speed, the response results show a trend of first increasing and then decreasing, which seems reasonable because pitch control occurs at high wind speeds. However, for the edgewise response (as shown in Figure (e) and Figure (g)), the response results also show a similar pattern, and when the wind speed is high enough (close to the cut-out wind speed), the response results seem to show a increase again (the phenomenon in the figure is not obvious). I don’t quite understand this phenomenon. In my opinion, the edgewise response should be more affected by non wind speed conditions such as gravity and centrifugal force. Could you please describe the flapwise and edgewise response of blade with the change of inflow wind speed and why this change occurs?
Thanks a lot!
Dear @Xiang.Wang,
I generally agree with your comments. The flapwise blade-root moment is impacted by the rotor thrust, which is heavily impacted by the pitch controller, which is why the response decreases with increasing wind speed above rated. The edgewise blade-root moment is generally impacted by gravity and torque, which is also impacted by the pitch controller. However, being flapwise and edgewise signals, the coordinate system of these signals rotates with the blade as it pitches, so, the impact of thrust, torque, and gravity are a bit mixed as the blade pitches, hence the somewhat odd looking edgewise signal. The response is often clearer to interpret when looking at out-of-plane and in-plane blade-root bending moments rather than flapwise and edgewise moments.
Best regards,
Dear @Jason.Jonkman ,
Thank you for your patient guidance and clarification. I understand this issue now.
Dear @Jason.Jonkman ,
Sorry to bother you again. I am currently studying the response of 15MW wind turbine blade under low-level-jet(LLJ)conditions. I constructed many cases by setting 5 jet heights (ZJetMax=90,150,210,270,and based on ZJetMax=270, deducing ZJetMax=30) and many jet wind speeds (setting RefHt to ZJetMax, URef ranging from 8 to 24, with intervals of 2) in Turbsim. For example, the following graph shows the wind profiles corresponding to five different jet heights with jet speed of 12m/s (different numbers in the legend represent different jet heights, for example, 90 represents ZJetMax=90)
When studying the response of blade tip and root under different LLJ cases, I obtained the following results.
The horizontal axis Jet WindSpeed in two of the graphs represents the wind speed at the jet height. I refer to TipTDyr as the blade tip edgewise displacement and RootMxr as the blade root edgewise moment, I am not sure if this is a reasonable term for them. According to the description of OutListParameters, parameters ending in the letter r are obtained under the IEC blade (b) coordinate system, which is shown below:
My understanding of coordinate systems may be shallow, but I believe that pitch angle does not seem to affect the edgewise direction. Why does the edgewise response seem strange when the direction and influencing factors (torque, gravity) seem to be constant at large wind speed(for example, for the 270 cases, there is monotonic positive shear in the rotor disk, which should be similar to the conventional situation, so the response pattern does not seem to be caused by negative shear).Or rather, even if the edgewise direction does not change, the response result in that direction is still affected by the pitch angle?
Dear @Xiang.Wang,
Actually, the “r” system in BeamDyn is fixed to the root of the blade, which spins with the rotor and rotates with the blade as it pitches. So, as the blade-pitch increases with increasing wind speed above rated, the “r” system will pitch with it. This is consistent with the IEC blade “b” coordinate system definition.
Best regards,
Dear @Jason.Jonkman ,
Thank you for your guidance.
