[Getdp] Neummann boundary condition

[Christophe Geuzaine]

Lin Ji wrote:
> 
> Hi, Christophe,
>     I am still using getdp to solve 2-D accoustic wave equation in bounded
> half space with Neummann boundary condition on all four sides. Recently, I
> noticed that the way I specify the Neumman boundary condition in getdp should
> be examined more carefully. I know that when we write out the wave equation
> in weak form, the Neummann boundary function would appear in the equation as
> an integral with test function on the boundary. I thought it is equivalent to
> specifying Neumman boundary condition explicitly. But now, I doute it.
>     I checked the reference. It seems to me there is no example for
> specifying such boundary condition in the Constaint object. The Assign type
> in the Constraint object seems only apply to Dirichlet boundary condition.
> So, can you let me know how to specify Neummann boundary condition explicitly
> in getdp in the way as specifying Dirichlet boundary condition? Thanks in
> advance.
> 

Neumann boundary conditions _are_ defined in a weak sense (through a
surface integral with test functions). There is no way to explicitely
fix beforehand the associated coefficients in a function space.

Christophe

-- 
Christophe Geuzaine

Tel: 32 (0) 4 366 37 10    http://geuz.org
Fax: 32 (0) 4 366 29 10    mailto:Christophe.Geuzaine at ulg.ac.be