[FLASH-USERS] potential issue on map particle to grid at periodic boundary

[Suoqing Ji]

Hi,

I’m mapping a few particle properties to grid variables, say, mapping from particle MASS_PART_PROP to grid PDEN with CIC method. I initialized uniformly distributed particles with sufficient large number, and set all the boundary conditions to be periodic. I tested three setups with UG and AMR:

Test 1: nxb=nyb=32, iProcs=2, jProcs=1
Test 2: nxb=nyb=16, iProcs=4, jProcs=2
Test 3: nxb=nyb=32, nblockx=2, nblocky=1, lrefine_max=1

All the tests have the same effective resolution, and should generate the same mapping to PDEN. However, both Test 2 and Test 3 produce single value PDEN as expected, while Test 1 produces artifacts at y-low and y-high boundaries (see attached figure).

I think this issue is related with the boundaries along which there’s only one block/processor with UG. Say, if I change set iProcs=1 in Test 1, the same artifacts also begin to appear at x-low and x-high boundaries. In addition, I did some additional tests with randomly distributed particles, and can still see the artifacts (but less obvious).

Although I can avoid this issue by setting Procs > 1 when using UG, or switching to AMR, I’m not very sure whether this issue is related to FLASH code itself or my own code.

Thanks in advance for any input!

Best wishes,
—
Suoqing JI
Ph.D Candidate
Department of Physics
University of California, Santa Barbara
http://physics.ucsb.edu/~suoqing <http://physics.ucsb.edu/~suoqing>
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