Kaimal Spectrum vs. Improved von Karman Spectrum

Hi everybody,

I’ve got a question about Kaimal and improved von Karman spectra.
The last IEC 61400-3 edition is recommending to model wind turbulence by means of either the Kaimal model (with Sandia approach) or the Mann model. No mention anymore about the standard von Karman model, which does not well fit measured data and has loss of variance in the high frequency region.

To overcome this breakdown, ESDU proposes to discard the standard von Karman model in favor of the improved one, and actually some commercial tools (Bladed) afford the usage of this kinda model.

From my little understanding, the von Karman model should have a smaller impact on loads if compared to Kaimal, so that I would expect the same happens with the improved von Karman compared to Kaimal. Furthermore, there would be some reason if IEC completely abandoned the von Karman approach.

Do you believe it makes any sense to certificate offshore WEC using the improved von Karman spectrum or it would be better switching towards Kaimal and Mann models?

I thank you all in advance.

I think this is a very interesting question worth looking into. I have been thinking about the problem recently and try to find out the answer also.