DLC 6.2 Assumptions for Typhoon-Prone Offshore Wind Turbines and Large Yaw Misalignment Conditions

Wind & Water Structural Analysis
1

Hello,

I have a question regarding the application of DLC 6.2 to offshore wind turbines in typhoon-prone regions.

For some projects in Korea, DLC 6.2 appears to be one of the governing load cases for the support structure because extreme wind conditions combined with large yaw misalignment can generate very high tower-base and foundation loads.

My first question concerns the yaw system assumptions. Modern turbines may include backup power systems (e.g., batteries or UPS systems) that could maintain some yaw capability following a grid-loss event. In industry practice, is emergency yaw functionality ever considered in the definition or assessment of DLC 6.2, or is complete loss of yaw capability generally assumed regardless of such systems?

My second question concerns the aerodynamic modeling of cases with very large yaw misalignment angles (for example, around 150°), where some governing loads may occur. Under these conditions, the flow around the rotor, nacelle, and tower may become highly separated and complex. Are there any recommended references, validation studies, or industry experiences regarding the reliability of aeroelastic load predictions for DLC 6.2 at such large yaw misalignment angles?

Thank you for any insights or references.

2

Dear @SaangBum.Kim,

I can’t speak for other countries, but in the USA it is common practice to require a battery back-up system, rendering DLC 6.2 obsolete.

DLC 6.2 can lead to an blade-edgewise instability, which has been discussed several times on this forum, e.g., as summarized in the following forum post: Yaw Dependent Instability.

Best regards,

3

Thank you, Jason. This is very helpful and provides useful perspective. Have a great day.