turbulent dissipation rate of e B.C.
 

Hi all,

I'm trying implement a low-Re turbulence model using an UDF in Fluent. I know that I can turn on the low-Re turbulence model in Fluent, but the main objective is modify one of the models by changing the damping functions.
The model that i'm using have a boundary condition for epsilon as:
http://www.cfd-online.com/Forums/dat...BJRU5ErkJggg==\epsilon_wall=dynamicviscosity*∂^{2}k/∂^{2}y (expression in attached file)
but there is no command for the second derivative of k.
Anyone can help me... How can I implement this boundary condition in a UDF?

Another question: what is the better way to change the boundary condition at wall for epsilon (expression as a function of second derivative of k)? It is going to Boundary Conditions->Wall.1->Edit->UDS Boundary condition and in User-Defined Scalar Boundary Value changhe for the variable name defined in the UDF?