Why do we observe instabilities at certain yaw misalignment angles during parked or idling conditions?
Bladed versions affected: all Bladed versions supporting dynamic stall calculations.
Date of last article update: 13 March 2023
The following article might explain your issue:
https://renewableenergysoftwareportal.dnv.com/KnowledgeBase/Details?productID=1&knowledgeBaseID=131
In addition, more detailed analysis of this phenomenon is discussed in the aerodynamics verification report that can be downloaded from the Bladed portal.
This is a long-standing issue that affects aeroelastic simulation tools and is related to the amount of aerodynamic damping/structural damping included in the simulation. In addition, the dynamic stall models are simplified 1st order engineering models designed to capture delays in aerodynamic response. These models are generally validated in 2D test cases. However, the real question is accuracy of the modelling in 3D. In reality, the phenomenon is more complicated where for instance vortex induced vibration may occur that is not captured by these 1st order models typically used in aeroelastic software.
We are pleased to discuss with you case by case if you have this issue as the causes may vary from different blades. Please email renewables.support@dnv.com