[Nek5000-users] Open Boundary condition in NEK user Documentation

[nek5000-users at lists.mcs.anl.gov]

Dear Neks,


I am trying to understand what is actually meant by an "open boundary" in Nek.

Un the user documentation, eqn (4.5) sais that, for the temperature, it is


grad(T) dot n = 0, where n is the normal to the boundary.


Since the heat flux is q = - grad(T), I would rather interpret this as a zero flux boundary condition.


And indeed, the insulated boundary described by equation (4.6) is identical to the open boundary condition.


Is equation (4.5) a type-O or is the open boundary for the temperature actually the same as an insulated boundary?


Also: Should not the open boundary condition for the "no-stress forumlation" also be given by the same expression as for the "stress-formulation" eqn (4.2)?


Best Regards,


Johan
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