writing mesh file and loading for further use

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RS 2015-8-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/232824-writing-mesh-file-and-loading-for-further-use

Hi..

I have a simple square geometry (1x1) which i created in matlab and meshed using meshgrid command with 20 points. I write the x and y coordinates of this geometry to file (consider it as mesh or grid file). Now when i load this file and run the usual code on it but i am unable to.

For simplicity i have considered a simple 2D lid-driven cavity code (taken from net). The script cavity.m is the actual working code shown below.

CODE:

cavity.m

 clear; close all; clc;
n = 20;  
xx = linspace(-1,1,n);
yy = xx;
[x,y] = meshgrid(xx,yy);
dx = xx(2)-xx(1);
dy = dx;
T = zeros(n,n);
T(1,1:n) = 0; 
T(n,1:n) = 100;  
T(1:n,1) = 0;  
T(1:n,n) = 0;  
dt = dx^2/4; error = 1; TOL = 1e-2; k = 0;
    while (error > TOL )
        k = k+1
          Told = T;
          for i = 2:n-1
          for j = 2:n-1
          T(i,j) = Told(i,j) + dt*((Told(i+1,j)-2*Told(i,j)+Told(i-1,j))/dx^2 ... 
                                 + (Told(i,j+1)-2*Told(i,j)+Told(i,j-1))/dy^2);
          end
          end
          error = max(max(abs(Told-T)));
          pcolor(x,y,T)
          contour(x,y,T,20)
          pause(0.001)
    end
    end

Now i split this code in two part: cavity_part1.m and cavity_part2.m

The first code cavity_part1.m creates a mesh using the meshgrid command and the data is written to dat file (mesh.dat) as shown.

Part1: cavity_part1.m

    clc;
n = 20;  
xx = linspace(0,1,n);
yy = xx;
[x,y] = meshgrid(xx,yy);
Data   = [x; y];
fileID = fopen(['mesh.dat'],'w');
fprintf(fileID,'%12.8f  %12.8f \n',Data);
fclose(fileID);
  end

In the second part cavity_part2.m, this mesh file is loaded and the usual cavity code is runned over it. There is a problem the way geometry is being loaded.

Part1: cavity_part2.m

 load('mesh.dat'); 
dx = x(2)-x(1); 
dy = dx;
TOL = 1e-2; 
T = zeros(n,n);
T(1,1:n) = 0; %bottom
T(n,1:n) = 100;  %top
T(1:n,1) = 0;  %LEFT
T(1:n,n) = 0;  %RIGHT
dt = dx^2/4;
error = 1; 
k = 0;
    while (error > TOL )
        k = k+1
          Told = T;          
          for i = 2:n-1
          for j = 2:n-1
          T(i,j) = Told(i,j) + dt*((Told(i+1,j)-2*Told(i,j)+Told(i-1,j))/dx^2 ... 
                                 + (Told(i,j+1)-2*Told(i,j)+Told(i,j-1))/dy^2);
          end
          end          
          error = max(max(abs(Told-T)));                    
          pcolor(x,y,T)
          contour(x,y,T,20)
          pause(0.001)
    end
  end