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How do I interpret the SDR wind rose report?


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See the example PDF above...


The extension of each bar in the wind rose from ?inner
circle? towards ?outer circle? represents the percentage of the time the wind
blew from those various directions. 


The outer circle percentage indicates
the amount of relative uniformity of the wind direction.  For example, if
there was a very strange site where the wind only blew from one direction all
the time, and never from any other direction, there would be a single bar going
out from 0 to 100%.  Most sites, however, have more scatter with wind
directions distributed among numerous directions. 


All of the bars
extending out will of course add up to 100% of the time period that was
measured.  The ?outer circle? value is intended to provide some context
for the graph so that at a quick glance, you can tell that at the site below,
almost 30% of the time, the wind direction was southwest, another 25% or so was
north, and then the rest of the directions are distributed among the other
directions to add up to the remaining 45%.




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  • 8 months later...

Hi -

The outer numbers are the Turbulence Intensity (TI) for each sector.  Higher values represent more turbulent winds while lower values represent less turbulent winds. 

I've included a definition of TI from our knowledgebase...


Calculation of Turbulence Intensity on SDR wind rose report

Turbulence intensity (Ti)is defined as the windspeed interval standard
deviation (SD) divided by the windspeed interval average (AVG)...


the windrose, the samples are first sorted by direction into sectors.
In each sector, there will be "n" samples. A Ti is calculated for each
sample and an average Ti is then created for the sector...

WindRose Ti for each sector = (SD/AVG + SD/AVG + SD/AVG...n)/n

Note that SDR defaults to 16 sectors for a standard windrose.





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  • 4 years later...


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