write2bts.m

function write2bts(filename,u,v,w,t,y,z,zHub,uHub,ntower)
% This function is a first attempt to write output from windSimFast into
% bts file. The function write2bts is based on the function readTSgrid.m by
% Bonnie Jonkman, National Renewable Energy Laboratory
% Author: E. Cheynet  - UiB - Last modified 28/11/2022

nffc = 3; % number of velocity components
nt = size(u,1);
ny = numel(y);
nz = numel(z);
dt = median(diff(t));
fid  = fopen(filename,'wb');

dz = abs(median(diff(z)));
dy = abs(median(diff(y)));

if fid > 0
    
    % Headers
    fwrite( fid, 8, 'int16');        % TurbSim format identifier (E.C.: should = 8 to work on fast.Farm), INT(2)
    fwrite( fid, nz, 'int32');        % the number of grid points vertically, INT(4)
    fwrite( fid, ny, 'int32');        % the number of grid points laterally, INT(4)
    fwrite( fid, ntower, 'int32');        % the number of tower points, INT(4)
    fwrite( fid, nt, 'int32');        % the number of time steps, INT(4)
    fwrite( fid, dz, 'float32');      % grid spacing in vertical direction, REAL(4), in m
    fwrite( fid, dy, 'float32');      % grid spacing in lateral direction, REAL(4), in m
    fwrite( fid, dt, 'float32');      % grid spacing in delta time, REAL(4), in m/s
    fwrite( fid, uHub, 'float32');      % the mean wind speed at hub height, REAL(4), in m/s
    fwrite( fid, zHub, 'float32');      % height of the hub, REAL(4), in m
    fwrite( fid, min(z), 'float32');      % height of the bottom of the grid, REAL(4), in m
    

    coeff = 1000;
    
    fwrite(fid, coeff, 'float32'); % the U-component slope for scaling, REAL(4)
    fwrite(fid, 0, 'float32'); % the U-component offset for scaling, REAL(4)
    fwrite(fid, coeff, 'float32'); % the V-component slope for scaling, REAL(4)
    fwrite(fid, 0, 'float32'); % the V-component offset for scaling, REAL(4)
    fwrite(fid, coeff, 'float32'); % the W-component slope for scaling, REAL(4)
    fwrite(fid, 0, '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."
    asciiSTR = double('This full-field file was generated by windSimFast');
    fwrite(fid, numel(asciiSTR), 'int32');     % the number of characters in the description string, max 200, INT(4)
    fwrite(fid, asciiSTR, 'int8' ); % the ASCII integer representation of the character string
    disp( ['Reading from the file ' filename ' with heading: ' ] );
    disp( ['   "' asciiSTR '".' ] ) ;
    
    WF(:,:,:,1)=u;
    WF(:,:,:,2)=v;
    WF(:,:,:,3)=w;
    
    val = zeros(1,nffc);
    for it = 1:nt
        for iz = 1:nz
            for iy = 1:ny
                for ii = 1:nffc
                    val(ii) = WF(it,iz,iy,ii)*coeff;
                end
                fwrite(fid, val, 'int16');
            end
        end
    end
    
    
    
    fclose(fid);
    
end