[cliffoi]

Hi all,
I am trying to implement a new boundary condition for the solution of the neutron diffusion equation. For this problem we have what is commonly called an extrapolated length boundary condition, i.e. the neutron density goes to zero at some distance past the boundary.
I have derived the necessary expressions to be implemented in my extrapolatedLengthFvPatchField class functions (evaluate, gradientInternalCoeffs, etc.) but I'm having problems coding them. I keep getting errors when compiling because the necessary operators aren't found.
This is clearly because I don't know how to code the expressions in such a way that they apply to all the templated types (The sphericalTensor class is in particular giving me problems).
If anybody could help me, I'd really appreciate it.
The gradient at the boundary dF/dx|_B = -1/(deltaX+extrLen)*F_P
The value at the boundary F_B = deltaX/(deltaX+extrLen)*F_P

where
F_P is the cell value (this->internalField())
deltaX is the distance to the boundary (1/deltaCoeffs())
extrLen is the extrapolated length value specified by the user.

Any help would be appreciated.
Thanks in advance