Wind rose data

In the simscale article below it refers to P_dir, which is the probability of a specific wind direction…

image

The bit I’m not clear on is the k_dir and c_dir, which are the Weibull distribution constants for a particular wind direction, so (in the wind data below) does this mean literally the distribution of the blue highlighted data, where the peak value is 3.9% ? …or does that line of data first have to be normalised (so that the total probability of that line equals 100%)

(Atmospheric boundary layer | Pedestrian Wind Comfort | SimScale)

Hello,

You can understand the construction of a stat file as taking a series of wind data, “labeling” each one of the data points with respect to velocity and direction, and then placing each one of these into “buckets”.

For example, say that you have a total of 1000 data points for wind direction and velocity. Out of the 1000 data points, only 2 of them show a velocity less than or equal to 0.5 m/s with a north direction. This “bucket” (north and V <= 0.5) is the very first entry of the table, where you see a 0.2% probability.

For the second “bucket” of the first row, the wind velocity is now going to be less than or equal to 2, but greater than 0.5. This gives you a 0.7% occurrence.

By following the same logic, you can fill the rest of the entries from the table. So yes, the data that you see there has already been normalized.

Cheers
Ricardo

Hi @garcfd ,
for getting the c_dir and k_dir parameters for a specific direction you indeed have to normalize the data and then compute the Weibull Distribution parameters using a parameter fitting algorithm.

Best,
Richard

Hi Richard, thanks very much for confirming that! (its what I thought)
Regards Giles