[Ricardo]

I would like use boundary condition (sufraceGradient=k*(A-Ainf)), where k is constant, A is value at surface of solid and Ainf is value of air. I used groovyBC, it works, but are here other posibilities?

I would like calculate surface value A from other fields, and groovyBC uses only average values of other field.

Thanks
Richard

[Ricardo]

Hello, if i understood correctly fixedGradient is gradient between surface and central point.

code from "fixedGradientFvPatchField.H"

       
 
          x_p = x_c + \frac{\nabla(x)}{\Delta}
 
where
 
x_p      | patch values
x_c      | internal field values
\nabla(x)| gradient (user-specified)
\Delta   | inverse distance from patch face centre to cell centre

Is any possibility how to set gradient between surface and ambient?
Thanks
Richard

[Ricardo]

Hello,
I used explicit scheme to calculate boundary values and then implicit scheme to calculate field centre values. It is conditionaly stable, but it works...

Does not exist easier method?
Something like using only half element on boundary, center point will be on boundary and will be solved with field values in matrix?
Thanks
Richard