Dear all,

in the last weeks I’ve been developing an alternative turbulent generator to TurbSim. For the time being, let’s assume that the time series are generated correctly. The goal would now be saving the 4D velocity matrix as a FAST-compatible .bts file. Threfore, I’ve been writing the following Matlab function:

[code]

fwrite(fid, 7, ‘int16’); % TurbSim format identifier (should = 7, just 'cause I like that number), INT(2)

fwrite(fid, WindFileStruct.Nz, ‘int32’); % the number of grid points vertically, INT(4)

fwrite(fid, WindFileStruct.Ny, ‘int32’); % the number of grid points laterally, INT(4)

fwrite(fid, 0, ‘int32’); % the number of tower points, INT(4)

fwrite(fid, WindFileStruct.N, ‘int32’); % the number of time steps, INT(4)

fwrite(fid, WindFileStruct.dz, ‘float32’); % grid spacing in vertical direction, REAL(4), in m

fwrite(fid, WindFileStruct.dy, ‘float32’); % grid spacing in lateral direction, REAL(4), in m

fwrite(fid, WindFileStruct.dt, ‘float32’); % grid spacing in delta time, REAL(4), in m/s

fwrite(fid, WindFileStruct.U0, ‘float32’); % the mean wind speed at hub height, REAL(4), in m/s

fwrite(fid, WindFileStruct.HubHt, ‘float32’); % height of the hub, REAL(4), in m

fwrite(fid, WindFileStruct.Zbottom, ‘float32’); % height of the bottom of the grid, REAL(4), in m

fwrite(fid, 1000, ‘float32’); % the U-component slope for scaling, REAL(4)

fwrite(fid, 0, ‘float32’); % the U-component offset for scaling, REAL(4)

fwrite(fid, 1000, ‘float32’); % the V-component slope for scaling, REAL(4)

fwrite(fid, 0, ‘float32’); % the V-component offset for scaling, REAL(4)

fwrite(fid, 1000, ‘float32’); % the W-component slope for scaling, REAL(4)

fwrite(fid, 0, ‘float32’); % the W-component offset for scaling, REAL(4)

fwrite(fid, l, ‘int32’); % the number of characters in the description string, max 200, INT(4)

for ii = 1:l

fwrite(fid, Version(ii), ‘int8’); % the ASCII integer representation of the character string

end

v = zeros(1,3);

cnt = 0;

for it = 1:WindFileStruct.N

for iz = 1:WindFileStruct.Nz

for iy = 1:WindFileStruct.Ny

for ii = 1:3

cnt = cnt + 1;

v(ii) = WindFileStruct.WF(it,iy,iz,ii)*1000;

end

fwrite(fid, v, ‘int16’);

end

end

end[/code]

What I’d like to undestand is the following: is the chunk related to time-series saving correct? If not, could you please point out how to successfully save the time series?

At the state of writing, I have performed to sets of simulations: the one set with standard TurbSim wind, the second set with my turbulent generator. When running a fatigue post-process, the damage equivalent loads stemming from my turbulent generator are always lower than those with TurbSim windfiles. Wind speed power spectra overlap perfectly though.

I’ve done something similar with Bladed, and equivalent loads were within a +/- 2% range.

I thank you for the support you will be showing me.

Best regards from Germany,

Francesco Perrone