[Nek5000-users] Lagrangian particle tracking
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Fri Dec 13 12:01:28 CST 2013
Yes - it could matter.
The question is, how would you assess this, because
the trajectories are chaotic...
Probably it won't hurt to crank the tolerance down.
With the projection schemes that we have the impact
on pressure iteration is generally minimal.
Paul
On Fri, 13 Dec 2013, nek5000-users at lists.mcs.anl.gov wrote:
> Hi Paul,
> It helped a lot. But let me insist on the question of accuracy. If the
> problem is well resolved (and spectrally accurate) then the divergence
> error could matter. No?
> I am interested to simulate turbulent flows so, this is the reason why
> I am concerning about this issue.
> Thanks again and have a nice weekend.
> Barak
>
> Quoting nek5000-users at lists.mcs.anl.gov:
>> Hi Barak,
>>
>> I have just a bit of time but will try to give you some quick answers to
>> start.
>>
>> Interpolation is spectral.
>>
>> Decreasing div error simply sets the iteration tolerance tighter ---
>> meaning that the _discrete_ system is solved to a tighter tolerance
>> (i.e., closer to machine precision).  However, it does not mean that
>> the divergence is necessarily smaller, since there is also a
>> discretization
>> error associated with the fact that you are solving the discretized
>> problem
>> and not the continuous one.  Discretization error can be reduced by
>> increasing lx1 or the number of elements.
>>
>> If your problem is nondimensionalized in terms of convective timescales,
>> I find div=1.e-6 is generally adequate (except, say, for certain
>> stability problems, which tend to be very sensitive). If you are working
>> in physical units, I would suggest set div=0 and tolrel = 0.01 ---- this
>> will automatically choose tolerances for you. (It tends to be a bit more
>> conservative than the 1.e-6 value that I suggest above.)
>>
>> There is a moving boundary example in the peristaltic flow example
>> (/peris)
>> At present, I don't have any falling body examples. Such a case is
>> either
>> easy or very hard, depending on the flow domain.
>>
>> hth,
>>
>> Paul
>>
>>
>> ----- Original Message -----
>> From: nek5000-users at lists.mcs.anl.gov
>> To: nek5000-users at lists.mcs.anl.gov
>> Sent: Friday, December 13, 2013 3:44:49 AM
>> Subject: Re: [Nek5000-users] Lagrangian particle tracking
>>
>> Hi Katherine,
>>
>> I reinstalled the new version (981) and indeed the code is running. I am
>> going to check now the results.
>>
>> In previous messages I asked:
>> 1. Is the used interpolation spectral?
>> 2. When I decrease the desired divergence error, how does it increase
>> the computation time?
>> 3. Are there examples for moving solid bodies or boundaries?
>>
>> Many thanks.
>> Barak
>>
>> On 12/12/2013 10:14 PM, nek5000-users at lists.mcs.anl.gov wrote: > Hi
>> Barak,
>>>
>>> I believe your error is a result of a compiler specific update. I have
>>> updated the Nek source code to hopefully address this issue. Please
>>> update your code and let me know if the problem is not resolved.
>>>
>>> Thanks
>>> Katherine
>>>
>>>
>>> On Thu, Dec 12, 2013 at 12:06 PM, <nek5000-users at lists.mcs.anl.gov
>>> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>>>
>>> Â Â Hei Paul,
>>> Â Â I tried your example and I get just at the beginning an error. See
>>> Â Â the attached file.
>>>
>>> Â Â Thanks,
>>> Â Â Barak
>>>
>>> Â Â On 12/11/2013 02:51 AM, nek5000-users at lists.mcs.anl.__gov
>>> Â Â <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>>
>>>
>>> Â Â Â Â Hi,
>>>
>>> Â Â Â Â I've added a Lagrangian particle tracking example ---
>>>
>>> Â Â Â Â Â Â examples/hemi
>>>
>>> Â Â Â Â look at hemi.usr.
>>>
>>> Â Â Â Â It produces a sequence of files with particle positions and
>>>     a matlab script is provided for viewing. As soon as I have
>>> Â Â Â Â a chance I'll also develop a script for visit.
>>>
>>> Â Â Â Â Paul
>>>
>>>
>>> Â Â Â Â ----- Original Message -----
>>> Â Â Â Â From: nek5000-users at lists.mcs.anl.__gov
>>> Â Â Â Â <mailto:nek5000-users at lists.mcs.anl.gov>
>>> Â Â Â Â To: nek5000-users at lists.mcs.anl.__gov
>>> Â Â Â Â <mailto:nek5000-users at lists.mcs.anl.gov>
>>> Â Â Â Â Sent: Tuesday, December 10, 2013 4:25:19 PM
>>> Â Â Â Â Subject: Re: [Nek5000-users] Lagrangian particle tracking
>>>
>>> Â Â Â Â On 12/10/2013 03:27 PM, nek5000-users at lists.mcs.anl.__gov
>>> Â Â Â Â <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>>
>>> Â Â Â Â Â Â Le 10/12/2013 13:00, nek5000-users at lists.mcs.anl.__gov
>>>       <mailto:nek5000-users at lists.mcs.anl.gov> a écrit
>>>
>>>
>>>
>>> Â Â Â Â Â Â Hello,
>>>
>>> Â Â Â Â Â Â Â Â What do you want to known about Lagrangian
>>> Particle
>>> Â Â Â Â Â Â Tracking ?
>>>
>>>
>>>
>>> Â Â Â Â Hi Anne,
>>> Â Â Â Â I would like to perform some Lagrangian particle simulation
>>> to to
>>> Â Â Â Â compute the component of the velocity field or vorticity at
>>> the
>>> Â Â Â Â particle. Do you have example for such computation as
>>> described
>>> Â Â Â Â in the
>>> Â Â Â Â webpage:
>>> Â Â Â Â
>>> http://nek5000.mcs.anl.gov/__index.php/Data_processing___example
>>> Â Â Â Â
>>> <http://nek5000.mcs.anl.gov/index.php/Data_processing_example>
>>> Â Â Â Â Thanks,
>>>
>>> Â Â Â Â Barak
>>>
>>>
>>>       Anne Tanière
>>>
>>>
>>> Â Â Â Â Â Â Â Â Hi
>>> Â Â Â Â Â Â Â Â I am interested to know if there is an example
>>> for the
>>> Â Â Â Â Â Â Â Â Lagrangian
>>> Â Â Â Â Â Â Â Â particle tracking
>>> Â Â Â Â Â Â Â Â as described in
>>> Â Â Â Â Â Â Â Â
>>> http://nek5000.mcs.anl.gov/__index.php/Data_processing___example
>>> Â Â Â Â Â Â Â Â
>>> <http://nek5000.mcs.anl.gov/index.php/Data_processing_example>
>>> Â Â Â Â Â Â Â Â .
>>>
>>> Â Â Â Â Â Â Â Â Thanks,
>>> Â Â Â Â Â Â Â Â Barak Galanti
>>>
>>>
>>>
>>> Â Â Â Â Â Â Â Â
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>>> Â Â Â Â Â Â --
>>>       Pr. Anne Tanière, Lorraine University
>>> Â Â Â Â Â Â Nouvel email:anne.taniere at univ-__lorraine.fr
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>>> Â Â Â Â Â Â Responsable des stages 5A, MFE ESSTIN
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