[Nek5000-users] Nek5000-users Digest, Vol 108, Issue 2

Fri Feb 2 22:33:35 CST 2018

Thank you Paul and Phillip for such a quick reply. I will run the jet case
attached. So why was there no such problem when the first vortex from the
wake of a circular cylinder was leaving the domain?

On Sat, Feb 3, 2018 at 1:49 AM, <nek5000-users-request at lists.mcs.anl.gov>
wrote:

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> Today's Topics:
>
>    1. Outflow Boundary Condition Clarification
>       (nek5000-users at lists.mcs.anl.gov)
>    2. Re: Outflow Boundary Condition Clarification
>       (nek5000-users at lists.mcs.anl.gov)
>    3. Re: Outflow Boundary Condition Clarification
>       (nek5000-users at lists.mcs.anl.gov)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 3 Feb 2018 00:40:32 +0530
> From: nek5000-users at lists.mcs.anl.gov
> To: nek5000-users at lists.mcs.anl.gov
> Subject: [Nek5000-users] Outflow Boundary Condition Clarification
> Message-ID:
>         <mailman.7741.1517598636.19102.nek5000-users at lists.mcs.anl.gov>
> Content-Type: text/plain; charset="utf-8"
>
> Im trying to simulate the formation of shear layer when a jet exits a
> nozzle and enters the flow domain. As the FIRST vortex leaves the outlet (
> at which I have provided 'O' boundary condition using genbox) the solution
> diverges. I tried to implement the 'turbulent outflow' subroutine as
> suggested in the forum but now the vortex affects the upstream flow. But
> when I run the flow past circular cylinder example, the vortices leave the
> domain without any issue even though only 'O' boundary condition is used'.
> What is the difference between the two cases and what can i do to prevent
> the issue?
>
> --
> Nitish Kovalam
> Aerospace Engineering
> Indian Institute of Space Science and Technology
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> Message: 2
> Date: Fri, 2 Feb 2018 20:27:50 +0100
> From: nek5000-users at lists.mcs.anl.gov
> To: nek5000-users at lists.mcs.anl.gov
> Subject: Re: [Nek5000-users] Outflow Boundary Condition Clarification
> Message-ID:
>         <mailman.7745.1517601585.19102.nek5000-users at lists.mcs.anl.gov>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I think you should try the stabilised O condition, as described in a
> paper by Dong (2014). We have an implementation of that, we should
> probably provide it as a module in the repository.
>
> best regards,
> Philipp
>
> On 2018-02-02 20:10, nek5000-users at lists.mcs.anl.gov wrote:
> > Im trying to simulate the formation of shear layer when a jet exits a
> > nozzle and enters the flow domain. As the FIRST vortex leaves the outlet
> > ( at which I have provided 'O' boundary condition using genbox) the
> > solution diverges. I tried to implement the 'turbulent outflow'
> > subroutine as suggested in the forum but now the vortex affects the
> > upstream flow. But when I run the flow past circular cylinder example,
> > the vortices leave the domain without any issue even though only 'O'
> > boundary condition is used'. What is the difference between the two
> > cases and what can i do to prevent the issue?
> >
> > --
> > Nitish Kovalam
> > Aerospace Engineering
> > Indian Institute of Space Science and Technology
> >
> >
> > _______________________________________________
> > Nek5000-users mailing list
> > Nek5000-users at lists.mcs.anl.gov
> > https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
> >
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 2 Feb 2018 20:19:54 +0000
> From: nek5000-users at lists.mcs.anl.gov
> To: "nek5000-users at lists.mcs.anl.gov"
>         <nek5000-users at lists.mcs.anl.gov>
> Subject: Re: [Nek5000-users] Outflow Boundary Condition Clarification
> Message-ID:
>         <mailman.7749.1517602797.19102.nek5000-users at lists.mcs.anl.gov>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Attached is a .usr with turb_outflow that works for this case---there is
>
> no difficulty if you use the prescribed input values, as shown in the
> attached
>
> files.
>
>
> Here is a movie of the result - you can see that turb_outflow is turned on
> prior to the jet reaching the top of the domain.
>
>
> http://mcs.anl.gov/~obabko/jet_vm.mpeg
>
>
> This mesh is a bit under-resolved in the z-direction.
>
> The files for a new case, with more axial resolution, are posted here
>
>
> www.mcs.anl.gov/~fischer/jet2.tgz<http://www.mcs.anl.gov/~fischer/jet2.tgz
> >
>
>
> I'll be posting an example with a script on how to build this geometry to
> nekexamples soon.
>
>
> Paul
>
>
> ________________________________
> From: Nek5000-users <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: Friday, February 2, 2018 1:10:32 PM
> To: nek5000-users at lists.mcs.anl.gov
> Subject: [Nek5000-users] Outflow Boundary Condition Clarification
>
> Im trying to simulate the formation of shear layer when a jet exits a
> nozzle and enters the flow domain. As the FIRST vortex leaves the outlet (
> at which I have provided 'O' boundary condition using genbox) the solution
> diverges. I tried to implement the 'turbulent outflow' subroutine as
> suggested in the forum but now the vortex affects the upstream flow. But
> when I run the flow past circular cylinder example, the vortices leave the
> domain without any issue even though only 'O' boundary condition is used'.
> What is the difference between the two cases and what can i do to prevent
> the issue?
>
> --
> Nitish Kovalam
> Aerospace Engineering
> Indian Institute of Space Science and Technology
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> End of Nek5000-users Digest, Vol 108, Issue 2
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>

-- 
Nitish Kovalam
Aerospace Engineering
Indian Institute of Space Science and Technology
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