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ptc-67242811-Visitor
1-Visitor
October 29, 2014
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Problem solving system of ODE

  • October 29, 2014
  • 2 replies
  • 4365 views

Hello everyone, i hope all are having a great day.

I started this discussion because im having a little problem solving a system of 2 ordinary diff eqs.
Im not defining a function for t or x because theres not a way to put this in function of w.Also I dont know if i define w with a random numer and t and x with random functions would affect the final result. I just want to solve the differential eqs. I defined r(w) for example for simplicity.

The problem im trying to solve is for chemical engineering. Its about solving the mass and heat differnetial eq simultaneously. Heres the document.

Thanks for your time

Best answer by Werner_E

Here is one possible solution. Other approaches would either copy the expressions of your function Ca, k and r directly in the solveblock equations or include those functions in the solve block (using the boolean 😃 and solve for all five functions.

BTW, the last (optional) argument of odesolve() is the number of iteration steps (not the step width) and has to be a positive integer (default is 1000).

1.png

2.png

2 replies

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Werner_E25-Diamond IAnswer
25-Diamond I
October 29, 2014

Here is one possible solution. Other approaches would either copy the expressions of your function Ca, k and r directly in the solveblock equations or include those functions in the solve block (using the boolean 😃 and solve for all five functions.

BTW, the last (optional) argument of odesolve() is the number of iteration steps (not the step width) and has to be a positive integer (default is 1000).

1.png

2.png

    F
    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    October 29, 2014

    Werner,

    Is there a reason you inverted the RHS of the second ODE? Alexander had Fao/-r.

      W
      Werner_E25-Diamond I
      25-Diamond I
      October 29, 2014

      Fred Kohlhepp wrote:

      Werner,

      Is there a reason you inverted the RHS of the second ODE? Alexander had Fao/-r.

      ??? As far as I see I haven't changed anything.

      This is what I see when I open his original sheet:

      4.png

      BTW, attached is a second approach using five functions to solve for.

      EDIT: Just noticed that in my first file those three functions (r,Ca and k) won't need w as argument. It doesn't hurt but its obsolete.

        A
        AlanStevens19-Tanzanite
        19-Tanzanite
        October 30, 2014

        As Alexander sent me a private message asking me to look at his file I've attached my response here, though I see Fred and Werner have already tackled it.

        Alan

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          ptc-67242811-VisitorAuthor
          1-Visitor
          October 30, 2014

          Hello Alan, thanks for taking your time to reply my message. It was really helpful those notes you put in the worksheet. As you can see im starting to learn on how to use this progam. Thanks a lot, I hope you have an awesome day!

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