Problem in NDSolve in mathematica

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  • Thread starter yashar
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In summary, The user is having trouble with a large system of coupled differential equations and is getting an error message. They attach the notebook in zip format and ask for help with the problem. The expert suggests searching for specific variables and provides a link to a method for finding user-defined variables and functions in Mathematica. The expert also encourages the user to develop their ability to find explanations for Mathematica behavior on their own.
  • #1
yashar
31
0
i want to solve a large system of coupled differential equations but i get this error

NDSolve::nlnum:

i attach the notebook in zip format.

what is the problem?

thanks
 

Attachments

  • NDSolvev4.zip
    21.8 KB · Views: 270
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  • #2
Search your notebook for
ro24 and ro44
and see if you really meant
rod24 and rod44

Just a guess
 
  • #3
thanks
that was amazing!
how you guess that?
 
  • #4
Actually I did not just guess that. If I had guessed that it would have been amazing. Now you have to think about how I was able to find those two in the 400+ equations that you have there. And how you might more likely avoid problems similar to this in the future.
 
Last edited:
  • #5
i can not understand how did you do that.
please tell me how?
 
  • #6
http://stackoverflow.com/questions/...iables-functions-in-a-notebook-in-mathematica

is one method to do this particular task.

Developing the ability to find explanations for puzzling Mathematica behavior is extremely important for every Mathematica user. I really suggest that you try to figure out how you could have found this yourself. Then see if you can generalize that method to help you be able to find the answer to the next question you find.
 

1. What is NDSolve in Mathematica and what does it do?

NDSolve is a built-in function in Mathematica that is used to numerically solve differential equations. It allows users to input a differential equation and obtain a numerical solution, making it a powerful tool for solving complex mathematical problems.

2. Why am I getting an error message when using NDSolve in Mathematica?

There are a few reasons why you may be getting an error message when using NDSolve in Mathematica. Some common reasons include incorrect syntax in the input, incompatible boundary or initial conditions, or the equation may not have a unique solution. Double-checking your input and making sure all necessary conditions are included can help resolve these errors.

3. How do I specify boundary or initial conditions in NDSolve?

To specify boundary or initial conditions in NDSolve, you can use the syntax "y[x0] == y0" for initial conditions or "y[a] == ya" and "y[b] == yb" for two boundary conditions at points "x=a" and "x=b". You can also use the function "WhenEvent" to specify conditions that change over time.

4. Can NDSolve handle systems of differential equations?

Yes, NDSolve is capable of solving systems of differential equations. You can input multiple equations and corresponding initial or boundary conditions, and NDSolve will provide a numerical solution for each equation.

5. Are there any limitations to NDSolve in Mathematica?

While NDSolve is a powerful tool, it does have some limitations. It may struggle with very stiff or highly nonlinear systems of equations, and may not always provide the most accurate solution. Additionally, it may take a long time to compute solutions for complex systems. It is always recommended to double-check your results and consider alternative methods if necessary.

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