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Numerically solving coupled DEs?

  1. Sep 20, 2006 #1
    Hi folks!

    I'm trying to (numerically) find a steady-state solution for [tex]N_b[/tex] and [tex]N_w[/tex] in the following set of coupled DEs using the software package Matlab:

    \frac{\delta N_b}{\delta t} = P_b(N_b) - N_b \cdot \left( \frac{1}{\tau_b} - \frac{1}{\tau_c}D \right)\\
    \frac{\delta N_w}{\delta t} = \frac{N_b}{\tau_c} - \frac{N_w}{\tau_w(N_w)} - P_w(N_w)

    where [tex]\tau_b[/tex], [tex]\tau_c[/tex] and [tex]D[/tex] are constants. Which way would be the right one to go?
    Last edited: Sep 20, 2006
  2. jcsd
  3. Sep 20, 2006 #2
    Remove the dimensions and write a program to do RK4 unless this is just for a class in which case RK2 or Euler's with really small step is easier.
  4. Sep 20, 2006 #3


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    I'm don't know MatLab but I'd run two Runge Kutta 4th order (RK4) algorithms simultaneously, using the current values for Nb and Nw in each formula.
  5. Sep 22, 2006 #4


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    What form do [tex]P_b[/tex] and [tex]\tau_w[/tex] take?
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