Numerical methods for a system of coupled ODE

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Discussion Overview

The discussion revolves around solving a system of coupled ordinary differential equations (ODEs) with arbitrary initial values. Participants explore numerical methods, specifically addressing the challenges posed by the initial conditions and the implications for discretization and iteration schemes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a system of coupled first-order ODEs and notes the challenge of having initial conditions specified at different points in the domain.
  • Another participant suggests the Runge-Kutta method as a potential numerical approach but does not elaborate on its application to the boundary conditions.
  • A third participant inquires about the domain of the variable z, seeking clarification on the problem's constraints.
  • A later reply confirms the domain of z as {0, 10} and suggests that combining the Runge-Kutta method with the Shooting method could address the boundary condition issue.

Areas of Agreement / Disagreement

Participants express differing views on how to handle the boundary conditions in the context of numerical methods, indicating that the discussion remains unresolved regarding the best approach to take.

Contextual Notes

Participants have not fully explored the implications of using different initial conditions or the specific details of the proposed numerical methods, leaving some assumptions and mathematical steps unaddressed.

Telemachus
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Hi there. I have to solve a system of coupled ordinary differential equations. I have some initial values, but in different points of the domain. The equations are all first order. Let's suppose the system looks like this:

##\displaystyle\frac{dy_1}{dz}=y_1+y_2+0.01##
##\displaystyle\frac{dy_2}{dz}=y_1+y_2+0.01##

with initial conditions: ##y_1(0)=0, y_2(10)=0##

So, I use some discretization in z, and get some iteration scheme that looks like

##y_{1,n+1}=f_1(y_{1,n},y_{2,n})##
##y_{2,n+1}=f_2(y_{1,n},y_{2,n})##

I don't give exactly the recursion formula I've arrivesd I just simplified it to discuss the important aspects, ##f_1## and ##f_2## are just some functions. The thing is, that as you can see, the forward value depends in the current one for both solutions. So, the only way I can get a formula which I can solve is by setting the initial condition at the same point (lets say ##y_1(0)=0## and ##y_2(0)=0##), otherwise, I lack the information necessary to update the values in both solutions.

Does anyone know where I can find some examples on how to solve coupled differential equations with arbitrary initial values?

Best regards.
 
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What is the domain of z?
 
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Hi, thank you both for your feedback, ##z\in \{0,10\}##

Regarding runge kutta, I could use that, but how would it solve the issue with the boundary conditions?
 
Telemachus said:
Hi, thank you both for your feedback, ##z\in \{0,10\}##

Regarding runge kutta, I could use that, but how would it solve the issue with the boundary conditions?

We can combine it with the Shooting method.
 
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