[Nek5000-users] New Recycling BC based on interpolation

Fri Jul 16 18:06:35 CDT 2010

Hi Michael,

Just to be clear - in order for the RBC to work properly inside
nek, cbc must be "v   ".

Paul

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

> Hi Paul,
>
> Thanks for the emails. At present, it seems easier and more straight forward to use a discriminator for RBC so long as it doesn't effect any other routine (like you mentioned other routines that use 'v '). I think, but could be wrong, that the recycling routine negates using the 'v ' boundary condition for that particular inlet?
>
> I think that as long as the discriminator change doesn't effect anything and at the same time, not calling it 'v ' doesn't cause any issues that the discriminator would be easier.
>
> In the mean time I can try creating the bc() based on cbc and geometry location and use that.
>
> - Michael
>
>
> ----- Original Message -----
> From: nek5000-users at lists.mcs.anl.gov
> To: nek5000-users at lists.mcs.anl.gov
> Sent: Friday, July 16, 2010 5:32:17 PM GMT -06:00 US/Canada Central
> Subject: Re: [Nek5000-users] New Recycling BC based on interpolation
>
>
> 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
>>>>
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