[Nek5000-users] Variable density flows

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

Thanks Ammar for the help. My channel is quite long so I can use the 'ON'
boundary condition at outlet for the passive scalar. I have a scalar
equation

c_t + u.grad(c) = div(D*grad(c))

with

c = 1 as initial condition

I want to use inlet bc

c = 0 at x=0 (inlet)

but this leads to a discontinuous initial condition. Is it ok to use such
bc ?

To avoid specifying such dirichlet bc, I tried to use zero flux bc for c at
inlet but then c did not change with time at all.

Thanks
praveen

On Sun, Oct 13, 2013 at 12:34 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

> If you are to use outflow BCs' at the channel exit plane it should be
> located sufficiently far from the inlet (i.e. the channel length long
> enough) to allow the flow and scalars to be fully developed d phi /dx =0
> Insulation is usually used at solid walls where there is no gradient in
> the wall normal direction (no heat or mass flow across the boundary) so it
> works for temperature and scalars.
>
> try to at least check on mass conservation in an integral sense..
>
> Ammar
>
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