[ConvDiff]

I am currently trying to solve the convection diffusion problem for Phip(centre of node) utilising the power law scheme but have come unstuck in determining the co-efficients(ae, aw, Su, Sp) at the boundaries i.e the first and last nodes. The form utilised is following the Versteeg CFD Textbook 1995, and the co-efficients are given for only the central nodes:

ap*Phip=ae*Phie+aw*Phiw+Su

ap=aw+ae-Sp

For instance for the central differencing scheme at the 1st node:

aw=0, ae=D-F/2, Sp=-(2D+F), Su=(2D+F)*Phi0.
Where D=DiffusionCoeff/dx and F=rho*u

I have written a TDMA solver in matlab that is currently working for the central differencing, upwind and hybrid schemes, this is the last one and I'm losing my mind!

Any help would be greatly appreciated! Regards Rastaman