[FLASH-USERS] [Flash] ray tracing issue

[Don Lamb]

Dear Po-Yu,

The features in the laser ray trace image you attached to your email 
message may be a Moire pattern caused by using a uniform distribution of 
rays per unit distance, and choosing for the total number of rays a 
number that is incommensurate with the number of cells in the 
y-direction.  If this is the problem, you can solve it either by making 
the number of rays per cell in the y-direction an integer or by using a 
random distribution of rays.  If you choose to do the latter, you will 
need to use a large number of rays.

With warm regards, Don


On 7/27/15 6:44 PM, pchang wrote:
> Hi all,
> I am using flash to simulate the implosion of a cylindrical target 
> using lasers. Please see the attached file. I am using the cubic 
> interpolation with Runge Kutta Integration ray tracing in most recent 
> version, FLASH4.3, but similar issue was observed in Kaiser ray 
> tracing in FLASH4.2. The issue is I have more than 20 beams passing 
> through each grid (I have tried the case with about 50 beams/grid) in 
> my simulation. I should expect a smooth energy deposition. However, I 
> always see "ray traces" in the energy deposition plot. The separation 
> of those ray traces are much bigger than the grid size. It doesn't 
> make sense to me since I have so many rays passing through each grid, 
> how come I still have non-uniform energy deposition.
> Does anyone encounter similar issues?
> Thank you,
>
> Po-Yu

-- 
************************************************************************
*  Don Q. Lamb                                                         *
*  Robert A. Millikan Distinguished Service Professor                  *
*  Director, Flash Center for Computational Science                    *
*  Department of Astronomy and Astrophysics                            *
*    and the Enrico Fermi Institute                                    *
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