[Nek5000-users] Outflow bc and pressure

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

Hi Praveen,

For Pn-Pn-2, it uses the natural bc, which is the one you showed.

For Pn-Pn, it is p=0 at outflow, du/dn=0 at outflow.

Paul

________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Tuesday, May 27, 2014 9:01 AM
To: nek5000
Subject: [Nek5000-users] Outflow bc and pressure

Dear neks
When we specify a boundary as outflow "O", I thought we take the normal stress to be zero

-p*n + mu*(grad(u) + grad(u)^T)*n = 0

which is a natural boundary condition and where n = normal vector. But it seems that nek sets p=0 on the outflow boundary. So does this mean we on outflow boundary we take both normal stress to be zero and pressure to be zero ?

Is it possible to use the normal stress condition without specifying a pressure ?

Thanks
praveen
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