Dear all,

I'm trying to solve the diffusion PDE for my system, shown below:

$\displaystyle \frac{\partial C}{\partial t} = D (\frac{\partial^2 C}{\partial r^2} + \frac{1}{r} \frac{\partial C}{\partial r})$

where C is the concentration, changing with time t and radius r. D is the diffusion coefficient.

I'm solving this using seperation of variables, giving me two ODE.

One of the ODE is:

$\displaystyle \frac{d^2R}{dr^2} + \frac{1}{r} \frac{dR}{dr} + lamda^2 R = 0$

where lamba is a constant.

Does any one have any ideas on how to solve this ODE tro obtain a general solution? I tried using a change in variables.

Any help would be appreciated. Thanks in advance!

Regards,

Billy