I have a problem with "At line 85 of file ../src/userio.f (unit = 5, file = 'stdin') Fortran runtime error: End of file" when attempting to run xfoil using matlab

The script that calls the xfoil script is something like this

Options=optimset('Display','iter','DiffMinChange',0.01,'TolCon',0.01)
[rootWeightsSQP,rootDragSQP]=fmincon(@drag,goodrootweights,[],[],[],[],zeros(1,14),ones(1,14),@thicknessconstraint,Options);
meanError=getstartweights(rootWeightsSQP,1);
[cd,cl,rootAlpha]=drag(rootWeightsSQP);

and the script whichs opens xfoil is

    function [cd,cl,alpha]=drag(w)
    global wingParameters constants
    % control points
    p0=[1 0]';  
    p1=[0.8 w(1)*0.2-0.05]';
    %p1=[0.8 w(1)*0.2-0.1]';
    p2=[0.3 w(2)*0.15]';
    %p2=[0.3 w(2)*0.2-0.05]';
    p3=[0 -0.1]';
    q1=[0 0.1]';
    q2=[0.4 w(3)*0.2+0.1]';
    q3=[0.8 w(4)*0.2-0.05]';
    q4=[1 0]';

    if length(w)<5
        w=[w wingParameters.bezierw];
    end

    % weights
    zp=[w(5)*1.9+0.1 w(6)*1.9+0.1 w(7)*1.9+0.1 w(8)*1.9+0.1 w(9)*1.9+0.1];
    zq=[w(10)*1.9+0.1 w(11)*1.9+0.1 w(12)*1.9+0.1 w(13)*1.9+0.1 w(14)*1.9+0.1];

    % calculate connection point
    p4=(4/(4+4))*p3+(4/(4+4))*q1;
    q0=p4;

    % calculate rational cubic Bezier for t[0,1]

    lower=bezier([p0 p1 p2 p3 p4]',zp);
    upper=bezier([q0 q1 q2 q3 q4]',zq);

    fid=fopen('aerofoil.dat','w');
    for i=1:101
       fprintf(fid,'%20.18f %20.18f\n',lower(i,1),lower(i,2));
    end
    for i=2:101
       fprintf(fid,'%20.18f %20.18f\n',upper(i,1),upper(i,2));
    end
    fclose(fid);

    a=340.3;                                    %speed of sound
    v=constants.V;                              %velocity
    M=v/a;                                      %Mach number
    nu=0.00001461;                              %kinematic viscosity
    L=wingParameters.localChord;                %local chord length of wing section airfoil
    Re=v*L/nu;                                  %local Reynold's number

    fid=fopen('commands.in','w');
    fprintf(fid,'load %saerofoil.dat\n',constants.file_path);
    fprintf(fid,'GuyMartin\n');
    fprintf(fid,'panel\n');
    fprintf(fid,'plop\nG\n\n');
    fprintf(fid,'oper\n');
    fprintf(fid,'visc %f\n',Re);
    fprintf(fid,'M %f\n',M);
    fprintf(fid,'type 1\n');
    fprintf(fid,'pacc\n');
    fprintf(fid,'%spolar.dat\n',constants.file_path);
    fprintf(fid,'\n');
    fprintf(fid,'iter\n250\n');
    fprintf(fid,'cl %f\n',wingParameters.CL2d);
    fprintf(fid,'\n');
    fprintf(fid,'\n');
    fprintf(fid,'quit\n');
    fclose(fid);

    run_xfoil_command=[constants.xfoil_path 'xfoil < ' constants.file_path 'commands.in > dump.out' ];
    setenv('GFORTRAN_STDIN_UNIT','5');     %only for matlab on mac
    setenv('GFORTRAN_STDOUT_UNIT','6');    %only for matlab on mac
    setenv('GFORTRAN_STDERR_UNIT','0');    %only for matlab on mac
    try
      system(run_xfoil_command)
      fid=fopen('polar.dat');
            for i=1:13
                tline = fgetl(fid);
                disp(tline);
            end
      fclose(fid);
          cl=str2num(tline(12:17));
          cd=str2num(tline(20:28));
          alpha=str2num(tline(3:8));
    catch me
      cl=777;
      cd=777;
      alpha=777;
    end    
    setenv('GFORTRAN_STDIN_UNIT','-1');      %only for matlab on mac
    setenv('GFORTRAN_STDOUT_UNIT','-1');     %only for matlab on mac
    setenv('GFORTRAN_STDERR_UNIT','-1');     %only for matlab on mac
    delete polar.dat

I am running this script on a windows 10 machine and I am using Xfoil 6.99. Do let me know if you have any idea what could have gone wrong because I have spent ages rectifying it and the error seems intermittent

[Diogo Nascimento]

Hey, have you been able to solve this? I'm having the same error and dont know why!

thanks

[Kai Mommsen]

Its the same with me,

trying to figure out what might be the issue, but i did not find anything about it.

Using matlab 2018b on Win 10 with Xfoil6.99 and an airfoil of Airfoiltools

Thanks

Answer 1

[Jan]

Are you creating the control file in the correct folder? This is safer:

fid = fopen(fullfile(constants.file_path, 'aerofoil.dat'),'w')
...
fid=fopen(fullfile(constants.file_path, 'commands.in'),'w');

[benho]

Thank you, I've tried your suggestion but I am still getting those intermittent runtime errors from Xfoil.

There is another thing which I would like to ask, I get matlab stopping suddenly while its iterating (opening, running and closing xfoil) where the computation seems to become terribly slow which last for hours/days. I have no idea what is wrong.

As shown, right before it stops, it shows the Iteration, F-Counts, Feasibility, F(x), Feasibility, First Order Optimality and Step.

Ben

[Oscar]

I noticed that this happens when you are trying to run xfoil in the background. I'm using Python, but I have the same issue..

Answer 2

[Haris Hameed]

Anyone got this error solved