Undefined function 'mtimes' in line 56

Line 56 (M = (m/-dt)-(qdot/(dens*dx*cp))*dx-(h*dx/(dens*dx*cp))*Tinf;) creates a 'mtimes' error and evrything I can find says this has to do with multiplying function handles, but I don't have any function handles anywhere in the code.

cp = 1007;
dens = 1.18;
k = 60;
h = 100;
dx = 0.01;
dt = 0.1;
endTime = 50;
qdot = 1000;
alpha = 3.243*10^-5;
F = alpha * dt / dx^2;
C = 0.05;
Bi = (h*C)/k;
Tinf = 27;
T2 = 20;

T = zeros(4, 5);

Z = dens*dx*cp;
Y = (1+2*F*(2+Bi));
Coef = 2*Bi*F*Tinf;
CoefBottom = 2*Bi*F*T2;
Y2 = 1+4*F;
Q = 1-4*k*Z;
Q2 = 2*qdot*Z*dx;
U = ((-h*dx/Z)-(2*k/Z)-(1/dt));
R = (1+4*F*(1+Bi));

numTimeSteps = ceil(endTime / dt);
for t = 1:numTimeSteps
    Tnew = T;
    A = [U k/Z 0 0 0 k/Z 0 0 0 0 0 0 0 0 0 0 0 0 0 0,%1
        k*Z Q k*Z 0 0 0 2*k*Z 0 0 0 0 0 0 0 0 0 0 0 0 0,%2
        0 k*Z Q k*Z 0 0 0 2*k*Z 0 0 0 0 0 0 0 0 0 0 0 0,%3
        0 0 k*Z Q k*Z 0 0 0 2*k*Z 0 0 0 0 0 0 0 0 0 0 0,%4
        0 0 0 k/Z U 0 0 0 0 k/Z 0 0 0 0 0 0 0 0 0 0,%5
        -F 0 0 0 0 Y -2*F 0 0 0 0 -F 0 0 0 0 0 0 0 0,%6
        0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0 0 0 0 0 0,%7
        0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0 0 0 0 0,%8
        0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0 0 0 0,%9
        0 0 0 0 -F 0 0 0 -2*F Y 0 0 0 0 -F 0 0 0 0 0,%10
        0 0 0 0 0 -F 0 0 0 0 Y -2*F 0 0 0 0 -F 0 0 0,%11
        0 0 0 0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0,%12
        0 0 0 0 0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0,%13
        0 0 0 0 0 0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0,%14
        0 0 0 0 0 0 0 0 0 -F 0 0 0 -2*F Y 0 0 0 0 -F,%15
        0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 0 R -2*F 0 0 0,%16
        0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -F Y -F 0 0,%17
        0 0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -F Y -F 0,%18
        0 0 0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -F Y -F,%19
        0 0 0 0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -2*F R];%20

    m = T(1,1);
    n = T(1,5);
    M = (m/-dt)-(qdot/(dens*dx*cp))*dx-(h*dx/(dens*dx*cp))*Tinf;
    N = (n/-dt)-(qdot/(dens*dx*cp))*dx-(h*dx/(dens*dx*cp))*Tinf;

    B = [M,
        -T(1,2)-Q2,
        -T(1,3)-Q2,
        -T(1,4)-Q2,
        N,
        Coef+T(2,1),
        T(2,2),
        T(2,3),
        T(2,4),
        Coef+T(2,5),
        Coef+T(1,3),
        T(3,2),
        T(3,3),
        T(3,4),
        Coef+T(3,5),
        2*CoefBottom+T(1,4),
        CoefBottom+T(4,2),
        CoefBottom+T(4,3),
        CoefBottom+T(4,4),
        2*CoefBottom+T(4,5)];
    
    C = A^-1 * B;

    Tnew = [C(1) C(2) C(3) C(4) C(5),
            C(6) C(7) C(8) C(9) C(10),
            C(11) C(12) C(13) C(14) C(15),
            C(16) C(17) C(18) C(19) C(20)];
    T = Tnew;
    h = imagesc(T);
    title(['Time = ' num2str(t*dt) ' ']);
    colorbar;
    axis equal;
    xlabel('X-axis');
    ylabel('Y-axis');
    drawnow;

end

Operator '*' is not supported for operands of type 'matlab.graphics.primitive.Image'.

Answer 1

[Walter Roberson]

h = 100;

h is numeric.

    M = (m/-dt)-(qdot/(dens*dx*cp))*dx-(h*dx/(dens*dx*cp))*Tinf;

You do calculations with h inside the loop.

   h = imagesc(T);

But now h is the handle to the image() object that is created by imagesc().

Next iteration will try to multiply the handle to the image object, by numeric values... but that is going to fail.

Answer 2

[atharva]

Hey teag,

I understand that you are facing the error "Operator '*' is not supported for operands of type 'matlab.graphics.primitive.Image'."

The error you are encountering is due to the fact that while looping you are trying to add a value to the handle h, which is already an image object created by the imagesc function. To fix this, you should use a different variable for the temperature distribution plot and avoid overwriting it with the image handle.

Here is the code you can try

cp = 1007;
dens = 1.18;
k = 60;
h = 100;
dx = 0.01;
dt = 0.1;
endTime = 50;
qdot = 1000;
alpha = 3.243*10^-5;
F = alpha * dt / dx^2;
C = 0.05;
Bi = (h*C)/k;
Ttinf = 27;
T2 = 20;

T = zeros(4, 5);

Z = dens*dx*cp;
Y = (1+2*F*(2+Bi));
Coef = 2*Bi*F*Ttinf;
CoefBottom = 2*Bi*F*T2;
Y2 = 1+4*F;
Q = 1-4*k*Z;
Q2 = 2*qdot*Z*dx;
U = ((-h*dx/Z)-(2*k/Z)-(1/dt));
R = (1+4*F*(1+Bi));

numTimeSteps = ceil(endTime / dt);
for t = 1:numTimeSteps
    Tnew = T;
    A = [U k/Z 0 0 0 k/Z 0 0 0 0 0 0 0 0 0 0 0 0 0 0,%1
        k*Z Q k*Z 0 0 0 2*k*Z 0 0 0 0 0 0 0 0 0 0 0 0 0,%2
        0 k*Z Q k*Z 0 0 0 2*k*Z 0 0 0 0 0 0 0 0 0 0 0 0,%3
        0 0 k*Z Q k*Z 0 0 0 2*k*Z 0 0 0 0 0 0 0 0 0 0 0,%4
        0 0 0 k/Z U 0 0 0 0 k/Z 0 0 0 0 0 0 0 0 0 0,%5
        -F 0 0 0 0 Y -2*F 0 0 0 0 -F 0 0 0 0 0 0 0 0,%6
        0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0 0 0 0 0 0,%7
        0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0 0 0 0 0,%8
        0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0 0 0 0,%9
        0 0 0 0 -F 0 0 0 -2*F Y 0 0 0 0 -F 0 0 0 0 0,%10
        0 0 0 0 0 -F 0 0 0 0 Y -2*F 0 0 0 0 -F 0 0 0,%11
        0 0 0 0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0 0,%12
        0 0 0 0 0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0 0,%13
        0 0 0 0 0 0 0 0 -F 0 0 0 -F Y2 -F 0 0 0 -F 0,%14
        0 0 0 0 0 0 0 0 0 -F 0 0 0 -2*F Y 0 0 0 0 -F,%15
        0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 0 R -2*F 0 0 0,%16
        0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -F Y -F 0 0,%17
        0 0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -F Y -F 0,%18
        0 0 0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -F Y -F,%19
        0 0 0 0 0 0 0 0 0 0 0 0 0 0 -2*F 0 0 0 -2*F R];%20

    m = T(1,1);
    n = T(1,5);
    M = ((m/-dt)-(qdot/(dens*dx*cp))*dx-(h*dx/(dens*dx*cp)))*Ttinf;
    N = ((n/-dt)-(qdot/(dens*dx*cp))*dx-(h*dx/(dens*dx*cp)))*Ttinf;

    B = [M,
        -T(1,2)-Q2,
        -T(1,3)-Q2,
        -T(1,4)-Q2,
        N,
        Coef+T(2,1),
        T(2,2),
        T(2,3),
        T(2,4),
        Coef+T(2,5),
        Coef+T(1,3),
        T(3,2),
        T(3,3),
        T(3,4),
        Coef+T(3,5),
        2*CoefBottom+T(1,4),
        CoefBottom+T(4,2),
        CoefBottom+T(4,3),
        CoefBottom+T(4,4),
        2*CoefBottom+T(4,5)];
    
    C = A^-1 * B;

    Tnew = [C(1) C(2) C(3) C(4) C(5),
            C(6) C(7) C(8) C(9) C(10),
            C(11) C(12) C(13) C(14) C(15),
            C(16) C(17) C(18) C(19) C(20)];
    T = Tnew;
    temp = imagesc(T);
    title(['Time = ' num2str(t*dt) ' ']);
    colorbar;
    axis equal;
    xlabel('X-axis');
    ylabel('Y-axis');
    drawnow;

end

I hope this helps!

[Walter Roberson]

there is no obvious reason to store the handle at all.