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Stability issues of ODE solutions using Matlab

  1. Apr 4, 2013 #1
    Hello, guys


    I am struggling with attaining stability values for u in solving the diffusion equation. The stability of u depends on the value of r from :

    Code (Text):
    D=1000;
    r0=1000;
    std=1.0;
    tau=1.0;

    IP=2500;  %initial pressure
    %
    % Radial grid and inhomogeneous term
    nr=51;
    dr=r0/(nr-1);
    dr=50;
    for i=1:nr
    r(i)=(i-1)*dr+200;
    end
    Values of u doesn't oscillate and follow stable path from r at i=1 i.e. at r=200 as can be seen from the code above. Ideally u should vary with time and r exponentially as you will see from the graph in the code attached. However, when I replace 200 from the above equation with 1 to obtain u at r=1, the results become unstable and oscillates. So I would like to obtain variation of u from r=1 not from r=200 without osciallation

    Can you please help me to fix that problem.

    All necessary codes are attached.
     

    Attached Files:

  2. jcsd
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