2nd order derivative calculation at the boundaries

Vishal

Hello, I am trying to calculate the second order derivatives in a simple computational domain for which I know the analytical value. I am somewhat successfull also, in the sense that I get correct second order derivative in the core of the simple domain, but difficulty arises at the wall boundaries, where there is a lot of variation in the 2nd order derivative value. Can anybody please help? Also can anybody please tell how are the gradients calculated in fluent near the boundary? (I mean how is the Gauss divergence theorem used at the boundary) Thanks for reading! Regards, Vishal