[Nek5000-users] New Recycling BC based on interpolation

Fri Jul 16 17:32:17 CDT 2010

Hi Michael,

As a follow-up --- if you need me to code up a more sophisticated
discriminator, I'm happy to do so.

Paul

On Fri, 16 Jul 2010, nek5000-users at lists.mcs.anl.gov wrote:

>
>
> Hi Michael,
>
> Thanks for the suggestion --- I think it's a good one, but we're
> not quite there yet.   I have a couple of comments -
>
> Technically "R  " is the same as "v  " --- because it is a time-space
> varying prescribed Dirichlet condition.
>
> Why not simply populate bc(4,f,e,1) with 1,2,3,...  to indicate that it is a 
> Recycle bc of type 1,2,3,... ?   For every cbc, there
> are 6 bc() entries (i.e, bc(k,f,e,1) for k=1 to 6).  For "v  ", the first one 
> of these (k=1) is reserved.
>
> That being said, genmap doesn't care about any bc other than "O  " and
> "P  " (in fact, only "P  " at this point), so you could in fact do what
> you propose right now, as long as you replace in usrdat or usrdat2 with
> the functionally correct "v  " bc.
>
> At present I'm a bit reluctant to make a change to the repo that is
> still in flux w.r.t. development -- There are a few issues to resolve.
> Presumably what one wants to be able to specify is the translation
> distance -- with respect to what? -- and the scale factor as a function
> of time.  We have selected w.r.t. to the unit normal on the R face.  In
> exact arithmetic there's no difficulty - but in some tricky situations
> there will be problems.  Rather than try to engineer a solution for all
> possible scenarios I think it's best to handle this on a case-by-case
> basis until we get a handle on what works and what doesn't.
>
> There are also performance issues to be investigated, particularly at
> high processor counts.
>
> In a few months I expect we'll have a consolidated code team such
> that we can implement changes (at least the mechanics of them)
> without much difficulty.  Right now (through the summer) we're
> a bit saturated.
>
> Paul
>
>
> On Fri, 16 Jul 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Oh ok.
>> 
>> Let's say that I leave one inlet as 'v ', but then change the other
>> inlet to some other variable 'v1 ' or 'X ' or whatever. Would this be
>> ok, without interfering with other routines?
>> 
>> I suppose where this discussion is heading is: What is the possibility
>> of adding a recycling boundary condition explicity in Nek, such that
>> you can apply it like any other boundary condition, say R for example.
>> So, in the routine you now search for this recycling flag 'R', and
>> then run through the setup, rescale etc...?
>> 
>> -Michael
>> 
>> ----- Original Message -----
>> From: nek5000-users at lists.mcs.anl.gov
>> To: nek5000-users at lists.mcs.anl.gov
>> Sent: Friday, July 16, 2010 4:47:11 PM GMT -06:00 US/Canada Central
>> Subject: Re: [Nek5000-users] New Recycling BC based on interpolation
>> 
>> 
>> Hi Michael,
>> 
>> Use whatever discrimination you like --- I would not suggest
>> modifying the character bcs, however, save that you can enter
>> values in bc(k,f,e,1) for k > 1, for any cbc(f,e,1) = 'v '
>> 
>> The reason for this is that nek checks explicitly for cbc='v '
>> (v, followed by two spaces) in many locations.
>> 
>> The correct place for discriminating parameters is in the
>> arracy bc().
>> 
>> Normally I discriminate by geometry --- e.g., x < x0, or
>> something similar, occasionally involving the unit normals on
>> the face in question - as that can be a stronger discriminator.
>> 
>> Paul
>> 
>> 
>> On Fri, 16 Jul 2010, nek5000-users at lists.mcs.anl.gov wrote:
>> 
>>> Hi Aleks,
>>> 
>>> Thank you very much for looking into this. I already have a question; I 
>>> noticed that you marked several notes dealing with "RBC single inlet -- 
>>> modify for other cases". I am assuming this means that you have one inlet 
>>> that you want to recycle, but another inlet that you do not want to 
>>> recycle, which just happens to be my case.
>>> 
>>> Can I distinguish in the rea between the two by "v1 " and "v2 " without 
>>> giving genmap any problems, and then modify the checks in the usr file 
>>> accordingly? Also, the subroutine rescale_inflow mentions to modify for 
>>> multiple inlets as well but I do not see where any modification 
>>> could/needs to be done for it.
>>> 
>>> - Michael
>>> 
>>> ----- Original Message -----
>>> From: nek5000-users at lists.mcs.anl.gov
>>> To: nek5000-users at lists.mcs.anl.gov
>>> Sent: Friday, July 16, 2010 3:03:52 PM GMT -06:00 US/Canada Central
>>> Subject: [Nek5000-users] New Recycling BC based on interpolation
>>> 
>>> Hi Michael and Markus,
>>> 
>>> Here is a test case for an unsteady pipe flow with Michael's 
>>> GambitPipe.rea file which sets inlet Recycling BCs based on interpolation 
>>> from a cross-section downstream that you specify by a multiple of the 
>>> inlet normal:
>>> 
>>> http://www.mcs.anl.gov/~obabko/z4.tgz
>>> 
>>> 
>>> Let me know if you have any questions.
>>> Best,
>>> Aleks
>>> 
>>> 
>>> 
>>> 
>>> ----- Original Message -----
>>> From: nek5000-users at lists.mcs.anl.gov
>>> To: nek5000-users at lists.mcs.anl.gov
>>> Sent: Thursday, July 8, 2010 5:06:48 PM GMT -06:00 US/Canada Central
>>> Subject: Re: [Nek5000-users] New Recycling BC method?
>>> 
>>> 
>>> 
>>> 
>>> 
>>> No worries, just checkin in to see how it was going, thanks for the 
>>> update! Look forward to trying it out!
>>> 
>>> 
>>> 
>>> - Michael
>>> 
>>> _______________________________________________
>>> Nek5000-users mailing list
>>> Nek5000-users at lists.mcs.anl.gov
>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>>> 
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