On 11 Jul 2020, at 13:16, zhangtengfei@sjtu.edu.cn wrote:

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Dear all,

I am using the robin boundary condition in Nektar+ but have some problems understanding how it works.

The b.c. I want to impose is 

  D* gradient {u} + 0.5 * u = 0

in which D is the diffusion constant (same as the D value used in the adjacent element), u is the unknown field.

To do this I normalize the b.c. into the form of  

gradient {u} + 0.5 / D * u = 0,

and specify the robin boundary condition as 

<R VAR="u"  PRIMCOEFF="0.5/D" />

This setting does not yield the correct answer, unless the special case that D = 1.0. Could anyone please tell me what is wrong here?

Thanks,

Tengfei Zhang

 

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