Applying several BC to a boundary

General Discussion
1

Hi there;

I wonder if anyone can help me find out how I can apply several derivatives in a boundary; in a 1D problem
\frac{\partial \phi}{\partial x}=\alpha
\frac{\partial^2 \phi}{\partial x^2}=\beta
\frac{\partial^3 \phi}{\partial x^3}=\gamma
How can I impose them to a single boundary?
And does it make sense? If so, is there any consideration on the element type that should be used?

2

You have to write the correct variationnal form of you problem, I thing it is a Tri-Laplacien , this imply C^2 conformity and we do not have is regularity on FreeFEM++ finite element.