open a .bts file from OpenFast wind turbine simulation

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Matt Thomas on 3 Jul 2023

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https://in.mathworks.com/matlabcentral/answers/1991333-open-a-bts-file-from-openfast-wind-turbine-simulation

Commented: Shushant on 10 Aug 2023

I am using an open source wind turbine simulation program.

The issue i am running into is trying to read a .bts file. The dev of the openfast program wrote some matlab code to read (and hopefully allows me to edit the file since i need to change windspeed) the .bts file. Here is the code, but when i run it, by hitting run, it has alot of errors. I know 0.0000% of matlab or programing. But i think maybe im supposed to "call" the code somehow like i had to for reading a .outb file?

function [velocity, twrVelocity, y, z, zTwr, nz, ny, dz, dy, dt, zHub, z1,mffws] = readfile_BTS(FileName,fileFmt)

%[velocity, twrVelocity, y, z, zTwr, nz, ny, dz, dy, dt, zHub, z1,mffws] = readfile_BTS(FileName,fileFmt)

% Author: Bonnie Jonkman, National Renewable Energy Laboratory

%

% Input:

% FileName - string: contains file name (.bts extension) to open

% fileFmt - string: optional, contains format of grid points.

%

% Output:

% velocity - 4-D array: time, velocity component (1=U, 2=V, 3=W), iy, iz

% twrVelocity - 3-D array: time, velocity component, iz

% y - 1-D array: horizontal locations y(iy)

% z - 1-D array: vertical locations z(iz)

% zTwr - 1-D array: vertical locations of tower points zTwr(iz)

% nz, ny - scalars: number of points in the vertical and horizontal

% directions of the grid

% dz, dy, dt - scalars: distance between two points in the vertical

% [m], horizontal [m], and time [s] dimensions

% zHub - scalar: hub height [m]

% z1 - scalar: vertical location of bottom of grid [m above ground level]

% mffws - scalar: mean hub-height wind speed

if ( nargin < 2 )

fileFmt = 'int16';

end

nffc = 3;

fid = fopen( FileName );

if fid > 0

%----------------------------

% get the header information

%----------------------------

tmp = fread( fid, 1, 'int16'); % TurbSim format identifier (should = 7 or 8 if periodic), INT(2)

nz = fread( fid, 1, 'int32'); % the number of grid points vertically, INT(4)

ny = fread( fid, 1, 'int32'); % the number of grid points laterally, INT(4)

ntwr = fread( fid, 1, 'int32'); % the number of tower points, INT(4)

nt = fread( fid, 1, 'int32'); % the number of time steps, INT(4)

dz = fread( fid, 1, 'float32'); % grid spacing in vertical direction, REAL(4), in m

dy = fread( fid, 1, 'float32'); % grid spacing in lateral direction, REAL(4), in m

dt = fread( fid, 1, 'float32'); % grid spacing in delta time, REAL(4), in m/s

mffws = fread( fid, 1, 'float32'); % the mean wind speed at hub height, REAL(4), in m/s

zHub = fread( fid, 1, 'float32'); % height of the hub, REAL(4), in m

z1 = fread( fid, 1, 'float32'); % height of the bottom of the grid, REAL(4), in m

Vslope(1) = fread( fid, 1, 'float32'); % the U-component slope for scaling, REAL(4)

Voffset(1) = fread( fid, 1, 'float32'); % the U-component offset for scaling, REAL(4)

Vslope(2) = fread( fid, 1, 'float32'); % the V-component slope for scaling, REAL(4)

Voffset(2) = fread( fid, 1, 'float32'); % the V-component offset for scaling, REAL(4)

Vslope(3) = fread( fid, 1, 'float32'); % the W-component slope for scaling, REAL(4)

Voffset(3) = fread( fid, 1, 'float32'); % the W-component offset for scaling, REAL(4)

% Read the description string: "Generated by TurbSim (vx.xx, dd-mmm-yyyy) on dd-mmm-yyyy at hh:mm:ss."

nchar = fread( fid, 1, 'int32'); % the number of characters in the description string, max 200, INT(4)

asciiINT = fread( fid, nchar, 'int8' ); % the ASCII integer representation of the character string

asciiSTR = char( asciiINT' );

disp( ['Reading from the file ' FileName ' with heading: ' ] );

disp( [' "' asciiSTR '".' ] ) ;

%-------------------------

% get the grid information

%-------------------------

nPts = ny*nz;

nv = nffc*nPts; % the size of one time step

nvTwr = nffc*ntwr;

% velocity = zeros(nt,nffc,nPts);

velocity = zeros(nt,nffc,ny,nz);

twrVelocity = zeros(nt,nffc,ntwr);

if strcmpi(fileFmt,'float32')

Voffset = 0.0*Voffset;

Vslope = ones(size(Vslope));

end

for it = 1:nt

%--------------------

%get the grid points

%--------------------

[v, cnt] = fread( fid, nv, fileFmt ); % read the velocity components for one time step

if ( cnt < nv )

disp([ it nt ny nz nffc nv cnt])

fclose(fid);

error(['Could not read entire file: at grid record ' num2str( (it-1)*(nv+nvTwr)+cnt ) ' of ' num2str(nt*(nv+nvTwr))]);

end

ip = 1;

for iz = 1:nz

for iy = 1:ny

for k=1:nffc

velocity(it,k,iy,iz) = ( v(ip) - Voffset(k))/Vslope(k) ;

ip = ip + 1;

end %k

end %iy

end % iz

%---------------------

%get the tower points

%---------------------

if nvTwr > 0

[v, cnt] = fread( fid, nvTwr, fileFmt ); % read the velocity components for the tower

if ( cnt < nvTwr )

error(['Could not read entire file: at tower record ' num2str( (it-1)*(nv+nvTwr)+nv+cnt ) ' of ' num2str(nt*(nv+nvTwr))]);

end

for k=1:nffc % scale the data

twrVelocity(it,k,:) = (v(k:3:nvTwr) - Voffset(k))/Vslope(k);

end

end %it

fclose(fid);

else

error(['Could not open the wind file: ' FileName]) ;

end

y = [0:ny-1]*dy - dy*(ny-1)/2;

z = [0:nz-1]*dz + z1;

zTwr = z1 - [0:ntwr-1]*dz;

return;

i think i am supposed to run something in the command window to get this script writen by the dev to work?? but i have no idea and there is no documentation on this.

in order to read a simular block of code for .outb files i had to paste this code in the matlab command window:

%% Run this command first

%% Read a binary output file

% Read file

outbfile = '5MW_Land_DLL_WTurb.outb';

[Channels, ChanName, ChanUnit, FileID, DescStr] = ReadFASTbinary(outbfile);

time = Channels(:,1);

which then generated some matrix with useful information that i used the plot command to make pretty pictures haha. The issue is, i dont have the code to paste in the command window, like above, to read the .bts file like i could with the .outb file. Since i do not know programming, i have no idea what to even write. the above code was an example i found hidden in the github repo. I have searched for 2 days for the other code to read the .bts file with no luck. So i assume its going to be simular as above to geerate the data?

im guessing i need to write something simular??? bu ti am just writing things that mean nothing to me. windfile is a word i made up

windfile = '90m_12mps_twr.bts';

[velocity, twrVelocity, y, z, zTwr, nz, ny, dz, dy, dt, zHub, z1,mffws] = readfile_BTS(windfile);

any help would be great.

tahnk you very much:)

To recap, im looking for the small block of code to run in the command window of matlab that will run the big chunk of code pasted above so it will read the .bts file and then i need to somehow EDIT the .bts file so i can change the stupid windspeed from 12m/s to 15m/s or whatever i want haha

thanks

2 Comments
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Amiya on 7 Aug 2023

Hi Thomas,

You need to insert the bold text, I modified it here. I hope it helps.

function [velocity, twrVelocity, y, z, zTwr, nz, ny, dz, dy, dt, zHub, z1,mffws] = readfile_BTS, ('90m_12mps_twr.bts')

% [velocity, twrVelocity, y, z, zTwr, nz, ny, dz, dy, dt, zHub, z1,mffws] = readfile_BTS,('90m_12mps_twr.bts')