Diffusion in a 2D box - animation in Matlab

diffusion-2D.m

clc; clear all;

domain = -0.5:0.005:0.5;
[X,Y] = meshgrid(domain,domain);
Z = zeros(length(domain), length(domain));
cmap = hot;
cmap = flipud(cmap(:, [3 2 1]));
outfile = 'aaa.gif';
set(gcf,'renderer','zbuffer');
t_vals = [0:4:200];
D = 10^-3;

for t=1:length(t_vals)
    
    for i=1:length(domain)
        for j=1:length(domain)
            x = domain(i);
            y = domain(j);
            Z(i,j) = C_analytical(x,y,t_vals(t));
        end
    end

    hp = pcolor(X,Y,Z);
    set(hp, 'edgecolor', 'none');
    axis square;
    colormap(cmap);
    caxis manual;
    caxis([0.0 2.0]);
    hc = colorbar;
    set(get(hc,'ylabel'), 'string', 'Concentration (kg/m^3)');
    xlabel('X (m)');
    ylabel('Y (m)');
    title(['Diffusion of Point Source in a Box (t=' num2str(t_vals(t)) 's)']);
    hold on;
    xlim([-1 1]);
    ylim([-1 1]);
    
    for m = -20:20
      for n = -20:20
          hcirc = circle(n,m,3*sqrt(2*D*t_vals(t)));
          set(hcirc, 'color', 0.75*ones(1,3));
      end
    end
    
    % gif utilities
    set(gcf,'color','w');
    drawnow;
    frame = getframe(1);
    im = frame2im(frame);
    [imind,cm] = rgb2ind(im,256);
    
    if t==1
        imwrite(imind,cm,outfile,'gif','DelayTime',0,'loopcount',inf);
    else
        imwrite(imind,cm,outfile,'gif','DelayTime',0,'writemode','append');
    end
    
    clf;
end