[Nek5000-users] Lagrangian Particle Tracking

[nek5000-users at lists.mcs.anl.gov]

Hi Alireza,

I've attached an example that uses the particle tracking to create timelines
that track the flow past a hemisphere.  It is the same as this case:
http://www.mcs.anl.gov/~fischer/cfd/cfd.html.  Also, there is a video that
shows the particles (from the exact setup that I'm sending you) here:
http://www.mcs.anl.gov/~fischer/mov.mp4.

The particle routines are all called from userchk.  They are:
particle_init - initiates particles, can be as complex or simple as you need
particle_advect_std - advects particles by interpolating velocity values at
the current location and using history velocity values for AB3
particle_out - outputs particle data...sometimes using poorly coded MPI ;)

The main arrays are:
pts - keeps particle data
vel - keeps velocity history for AB3 and for output if you're interested
npart - the local number of particles
partpt - array of global particle numbers, for tracking

The only parameter that you need to adjust in SIZE is lpart for the maximum
number of particles.  If it's too small, Nek should tell you.

Justin

On Wed, Jun 29, 2011 at 2:42 PM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi Alireza,
>
> Let me check what is a current status of development for a complete set of
> Lagrangian particle tracking routines.
>
> My understanding that the subroutine particle_advect is written for the old
> interpolation w/ parameter mr -- we need to update it.  This subroutine has
> to be used in the timestep loop called from usrchk after one interpolates
> (w/ intpts) velocity field (to vvel) at coordinates of the most recent
> particle location rtl -- hmm, I do not see how this array vvel with
> interpolated velocity data is then passed to the subroutine
> particle_advect...
>
> Let me look further and get back to you later.
> Aleks
>
>
>
>
> On Wed, 29 Jun 2011, nek5000-users at lists.mcs.anl.**gov<nek5000-users at lists.mcs.anl.gov>wrote:
>
>  Hi,
>>
>> I have couple of questions regarding the subroutine given for Lagrangian
>> particle tracking at the following wiki page and I wonder if there are any
>> hints.
>>
>> http://nek5000.mcs.anl.gov/**index.php/Data_processing_**example<http://nek5000.mcs.anl.gov/index.php/Data_processing_example>
>>
>> - Where should this subroutine be inserted?
>> - What are the variables "rtl" and "mr" representing?
>> - How to set the initial positions of the particles?
>> - Should the constant parameters "npart" and "dt_p" be inserted in SIZE
>> file?
>>
>>
>> Thanks in advance,
>>
>>
>> Regards,
>> Alireza Karimi
>>
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