Metocean data

Wind & Water NWTC Wind Data
1

Sorry to post here, but there is no specific forum for Metocean data, and I think this matches enough.
In nwtc.nrel.gov/metocean there are data for 3 standard sites, but the excel lacks description of parameters; furthermore, there is no indication of the height above sea level of wind speed .

I think all this information should be in the mentioned paper “Stewart, G. M., Robertson, A., Jonkman, J., and Lackner, M. A. “The creation of a comprehensive metocean data set for offshore wind turbine simulations.” Wind Energy, 19 (2016): 1151–1159. doi: 10.1002/we.1881.” but there is no download link for it.

Is it possible to have a copy of it?
Any help will be appreciated
Sesto

2

Dear Sesto,

The link to Stewart et al’s paper is provided on that site and is repeated here: onlinelibrary.wiley.com/doi/abs/10.1002/we.1881.

Best regards,

3

Thanks Jason, I saw it, but only the summary is freely available.
For the full paper looks like I’ll have to buy it.
Sesto

4

Yes, that’s true.

5

Dear Jason,

Is the data referenced in the above paper still being made available? [url]https://www.nrel.gov/wind/nwtc/metocean-data.html[/url] only provides a link to the paper abstract, I haven’t been able to find the datasets anywhere else on the NREL website.

Thanks,

Brendan

6

Dear Brendan,

The new site (drive.google.com/drive/folders/ … sp=sharing.

Best regards,

7

Dear Jason,

I am using the spreadsheet of metocean data you provided and am attempting to form the Von Mises CDFs in MATLAB. Am I correct in saying the “Parameter 1” is mu the mean and “Parameter 2” is k the dispersion?
Also do you know of any pre existing Von Mises CDF functions for MATLAB as exists with both the gamma and Weibull distributions?
Alternatively, is the square root of k a standard deviation that can be used as part of a normal distribution?

Kind regards,
Breen Elliott

8

Hi Breen,

When I did this work, I used the Circular Statistics Toolbox for Matlab which is available on the MathWorks File Exchange (mathworks.com/matlabcentral … statistics)

Yes, Parameter 1 in the Excel sheet is mu, the mean, and Parameter 2 is k. Sorry that wasn’t made more clear.

I don’t think I quite understand your third question (it has been quite awhile since I worked with circular statistics), but from a quick search, the k constant is analogous to the reciprocal of variance. K=0 is a uniform distribution (undefined variance), and as k gets larger, the distribution approaches a standard normal distribution with a small variance.

I tried many different non-circular distributions for the wave direction parameter, but none came close to the Von Mise distribution in terms of goodness of fit. This makes sense as the wave direction is a circular input.

Hope that helps, and I will try to monitor this thread in case you have other questions.
-Gordon Stewart

9

Hi Gordon,

I was using a besselj function from MATLAB for my von Mises CDF function. The besselj functuon is a “Bessel function of first kind” but the one that should be used is “Modified Bessel function of first kind”. This was made evident from the MathWorks File Exchange you linked.

Thank you so much for your help.

Kind regards,
Breen