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, <[email protected]> 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, [email protected].**gov<[email protected]>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

______________________________**_________________ Nek5000-users mailing list [email protected].**gov <[email protected]> https://lists.mcs.anl.gov/**mailman/listinfo/nek5000-users<https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users>

______________________________**_________________ Nek5000-users mailing list [email protected].**gov <[email protected]> https://lists.mcs.anl.gov/**mailman/listinfo/nek5000-users<https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users>