Solving a strong form differential equation (FEM) using MATLAB












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$begingroup$


I need some diagnosis on how I'm solving my differential equation. This was a template given to me by my professor and I manipulated it to the best of my ability.



The governing equations are here:



enter image description here



And here is my code:



    clear;
clc;
close all;

% u,,xx=-(f/ea) on [0,L]
% u,x(L)= R
% u(0)=0

% Parameters
L= 1;
% Parameters in force function
A= .0001;
E= 70e9;
R= 1000;
a= 1000;
g= R/E*A;
f= @(x) ((((-1)*(a)*(x))/E*A));

% solve analytical solution

u1 = dsolve(['D2y = ' char(sym(f))], ['Dy(1) = ' num2str(g)], ['y(0) ='
num2str(0)] ,'x');


% change symbolic function to anonymous matlab function for easier
computing

u = matlabFunction(u1);

% plot the analytical solution
n= 20;
x = linspace(0, 1, n);
plot(x, u(x), '-ro', 'LineWidth', 4)
title('Analytical Solution u')
axis([0, 1, 0, 3])
xlabel('x')
ylabel('u')


I come across issues when I try to plot my values. The analytical solution should be around in the .21428 range or something. I figured that it has to be an issue with my differential solver or the way that I am plotting it but I definitely think its the ODE solving that's got me messed up.



I'm pretty much stuck at this point. I checked my equations to be sure they were right but alas no issues there so I could definitely use another brain.



If you need to see the question prompt let me know. I was wary of posting it because of my professor so I didn't think it'd be too necessary.



Note: u,xx is a second order and u,x is a first order.










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    0












    $begingroup$


    I need some diagnosis on how I'm solving my differential equation. This was a template given to me by my professor and I manipulated it to the best of my ability.



    The governing equations are here:



    enter image description here



    And here is my code:



        clear;
    clc;
    close all;

    % u,,xx=-(f/ea) on [0,L]
    % u,x(L)= R
    % u(0)=0

    % Parameters
    L= 1;
    % Parameters in force function
    A= .0001;
    E= 70e9;
    R= 1000;
    a= 1000;
    g= R/E*A;
    f= @(x) ((((-1)*(a)*(x))/E*A));

    % solve analytical solution

    u1 = dsolve(['D2y = ' char(sym(f))], ['Dy(1) = ' num2str(g)], ['y(0) ='
    num2str(0)] ,'x');


    % change symbolic function to anonymous matlab function for easier
    computing

    u = matlabFunction(u1);

    % plot the analytical solution
    n= 20;
    x = linspace(0, 1, n);
    plot(x, u(x), '-ro', 'LineWidth', 4)
    title('Analytical Solution u')
    axis([0, 1, 0, 3])
    xlabel('x')
    ylabel('u')


    I come across issues when I try to plot my values. The analytical solution should be around in the .21428 range or something. I figured that it has to be an issue with my differential solver or the way that I am plotting it but I definitely think its the ODE solving that's got me messed up.



    I'm pretty much stuck at this point. I checked my equations to be sure they were right but alas no issues there so I could definitely use another brain.



    If you need to see the question prompt let me know. I was wary of posting it because of my professor so I didn't think it'd be too necessary.



    Note: u,xx is a second order and u,x is a first order.










    share|improve this question







    New contributor




    Lil_TEE is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.







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      0








      0





      $begingroup$


      I need some diagnosis on how I'm solving my differential equation. This was a template given to me by my professor and I manipulated it to the best of my ability.



      The governing equations are here:



      enter image description here



      And here is my code:



          clear;
      clc;
      close all;

      % u,,xx=-(f/ea) on [0,L]
      % u,x(L)= R
      % u(0)=0

      % Parameters
      L= 1;
      % Parameters in force function
      A= .0001;
      E= 70e9;
      R= 1000;
      a= 1000;
      g= R/E*A;
      f= @(x) ((((-1)*(a)*(x))/E*A));

      % solve analytical solution

      u1 = dsolve(['D2y = ' char(sym(f))], ['Dy(1) = ' num2str(g)], ['y(0) ='
      num2str(0)] ,'x');


      % change symbolic function to anonymous matlab function for easier
      computing

      u = matlabFunction(u1);

      % plot the analytical solution
      n= 20;
      x = linspace(0, 1, n);
      plot(x, u(x), '-ro', 'LineWidth', 4)
      title('Analytical Solution u')
      axis([0, 1, 0, 3])
      xlabel('x')
      ylabel('u')


      I come across issues when I try to plot my values. The analytical solution should be around in the .21428 range or something. I figured that it has to be an issue with my differential solver or the way that I am plotting it but I definitely think its the ODE solving that's got me messed up.



      I'm pretty much stuck at this point. I checked my equations to be sure they were right but alas no issues there so I could definitely use another brain.



      If you need to see the question prompt let me know. I was wary of posting it because of my professor so I didn't think it'd be too necessary.



      Note: u,xx is a second order and u,x is a first order.










      share|improve this question







      New contributor




      Lil_TEE is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.







      $endgroup$




      I need some diagnosis on how I'm solving my differential equation. This was a template given to me by my professor and I manipulated it to the best of my ability.



      The governing equations are here:



      enter image description here



      And here is my code:



          clear;
      clc;
      close all;

      % u,,xx=-(f/ea) on [0,L]
      % u,x(L)= R
      % u(0)=0

      % Parameters
      L= 1;
      % Parameters in force function
      A= .0001;
      E= 70e9;
      R= 1000;
      a= 1000;
      g= R/E*A;
      f= @(x) ((((-1)*(a)*(x))/E*A));

      % solve analytical solution

      u1 = dsolve(['D2y = ' char(sym(f))], ['Dy(1) = ' num2str(g)], ['y(0) ='
      num2str(0)] ,'x');


      % change symbolic function to anonymous matlab function for easier
      computing

      u = matlabFunction(u1);

      % plot the analytical solution
      n= 20;
      x = linspace(0, 1, n);
      plot(x, u(x), '-ro', 'LineWidth', 4)
      title('Analytical Solution u')
      axis([0, 1, 0, 3])
      xlabel('x')
      ylabel('u')


      I come across issues when I try to plot my values. The analytical solution should be around in the .21428 range or something. I figured that it has to be an issue with my differential solver or the way that I am plotting it but I definitely think its the ODE solving that's got me messed up.



      I'm pretty much stuck at this point. I checked my equations to be sure they were right but alas no issues there so I could definitely use another brain.



      If you need to see the question prompt let me know. I was wary of posting it because of my professor so I didn't think it'd be too necessary.



      Note: u,xx is a second order and u,x is a first order.







      matlab






      share|improve this question







      New contributor




      Lil_TEE is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question







      New contributor




      Lil_TEE is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this question




      share|improve this question






      New contributor




      Lil_TEE is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      asked 46 mins ago









      Lil_TEELil_TEE

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      Check out our Code of Conduct.






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      Check out our Code of Conduct.






















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