Matlab pdepe homogeneous surface diffusion

Hi guys. I'm trying to model the diffusion equation below using matlab pdepe function.

dq/dt=D/r2 *d[r2(dq/dt)/dr

Initial condition: at t=0, q=0

BC1: at r=0, dq/dr=0

BC2: at r=R, Ddq/dr = kf(C-Cf)

kf, C, and Cf are unknown, so we need this equation:

dC/dt = -3kf*Vm/RV*(C-Cf) , subject to t=0, C=C0 vs*dq/dt = vl*dC/dt

How should I write the boundary condition then?

I used, Ddq/dr - vs*RV/(3*vl*Vm)* dq/dt = 0

so in the matlab file, I wrote:

sol = pdepe (m,@pdex1pde,@pdex1ic,@pdex1bc,x,t); surf (x,t,sol) ---- function [pl,ql,pr,qr] = pdex1bc(xl,ul,xr,ur,t) global sol

pr= vs*RV/(3*vl*Vm)*sol;

end

but I just got a linear plane in the plot of x vs t for sol. Could you please point out where/what is wrong with my coding?

Thanks a lot.

[Mathischan Maheswaran]

Hello,

I cannot help you but i am also stuck with the resolution of intraparticle diffusion in pdepe. Did you solve it at the end ?

If yes can you show me?

Thank you

Math