[Nek5000-users] Lagrangian particle tracking
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Fri Dec 13 11:09:04 CST 2013
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:
>>
>> Hei Paul,
>> I tried your example and I get just at the beginning an error. See
>> the attached file.
>>
>> Thanks,
>> Barak
>>
>> On 12/11/2013 02:51 AM, nek5000-users at lists.mcs.anl.__gov
>> <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>
>>
>> Hi,
>>
>> I've added a Lagrangian particle tracking example ---
>>
>> examples/hemi
>>
>> look at hemi.usr.
>>
>> It produces a sequence of files with particle positions and
>> a matlab script is provided for viewing. As soon as I have
>> a chance I'll also develop a script for visit.
>>
>> Paul
>>
>>
>> ----- Original Message -----
>> From: nek5000-users at lists.mcs.anl.__gov
>> <mailto:nek5000-users at lists.mcs.anl.gov>
>> To: nek5000-users at lists.mcs.anl.__gov
>> <mailto:nek5000-users at lists.mcs.anl.gov>
>> Sent: Tuesday, December 10, 2013 4:25:19 PM
>> Subject: Re: [Nek5000-users] Lagrangian particle tracking
>>
>> On 12/10/2013 03:27 PM, nek5000-users at lists.mcs.anl.__gov
>> <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>
>> Le 10/12/2013 13:00, nek5000-users at lists.mcs.anl.__gov
>> <mailto:nek5000-users at lists.mcs.anl.gov> a écrit
>>
>>
>>
>> Hello,
>>
>> What do you want to known about Lagrangian Particle
>> Tracking ?
>>
>>
>>
>> Hi Anne,
>> I would like to perform some Lagrangian particle simulation to to
>> compute the component of the velocity field or vorticity at the
>> particle. Do you have example for such computation as described
>> in the
>> webpage:
>> http://nek5000.mcs.anl.gov/__index.php/Data_processing___example
>> <http://nek5000.mcs.anl.gov/index.php/Data_processing_example>
>> Thanks,
>>
>> Barak
>>
>>
>> Anne Tanière
>>
>>
>> Hi
>> I am interested to know if there is an example for the
>> Lagrangian
>> particle tracking
>> as described in
>>
>> http://nek5000.mcs.anl.gov/__index.php/Data_processing___example
>>
>> <http://nek5000.mcs.anl.gov/index.php/Data_processing_example>
>> .
>>
>> Thanks,
>> Barak Galanti
>>
>>
>>
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>>
>> --
>> Pr. Anne Tanière, Lorraine University
>> Nouvel email:anne.taniere at univ-__lorraine.fr
>> <mailto:email%3Aanne.taniere at univ-lorraine.fr>
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