# Math Help - Numerical solution of partial differential equation

1. ## Numerical solution of partial differential equation

I need to solve the following system of equations for $n=0,1,2$ subject to the given initial and boundary conditions. Please give me some idea which numerical scheme I should use for better accuracy and how should I proceed for the numerical solution of this equation. The coupled boundary conditions are challenging for me. Please help.

$\frac{\partial C_n}{\partial t}-\frac{\partial^2 C_n}{\partial r^2}-\frac{1}{r}\frac{\partial C_n}{\partial r}=\beta n\, f(r,t)C_{n}$
$\frac{\partial \zeta_n}{\partial t}-\frac{\partial^2\zeta_n}{\partial r^2}-\frac{1}{r}\frac{\partial \zeta_n}{\partial r}=\beta n \,g(r,t)\zeta_{n}$

$C_n(0,r)=1$

$\zeta_n(0,r)=1$

$\frac{\partial C_n}{\partial r}+\gamma C_n=0 \quad\mbox{at}\quad r=a$
$\frac{\partial C_n}{\partial r}=\kappa \frac{\partial \zeta_n}{\partial r} \quad\mbox{at}\quad r=b$
$C_n=\lambda\zeta_n \quad\mbox{at}\quad r=b$
$\frac{\partial \zeta_n}{\partial r}=0 \quad\mbox{at}\quad r=0$

By using Crank Nicholson method and Thomas algorithm I can solve the following, but the above one gives trouble for me.
$\frac{\partial C_n}{\partial t}-\frac{\partial^2 C_n}{\partial r^2}-\frac{1}{r}\frac{\partial C_n}{\partial r}=\beta n\, f(r,t)C_{n}$
$C_n(0,r)=1$
$\frac{\partial C_n}{\partial r}+\gamma C_n=0 \quad\mbox{at}\quad r=a$
$\frac{\partial C_n}{\partial r}=0 \quad\mbox{at}\quad r=0$

2. ## Re: Numerical solution of partial differential equation

What exactly bothers You?