[yt-dev] SPH Smoothing Formulation?

[Cameron Hummels]

Thanks, Matt and Molly.  Very excited to see the kd-tree formulation that
Meagan has implemented.  A couple additional questions:

 * Using the chosen SPH kernel (thanks to Bili Dong, we now have cubic,
> quartic, quintic, wendland2, wendland4, and wendland6), the smoothing is
> conducted on each cell by looking at all the nearest particles.  This is
> implemented in the process function on the class VolumeWeightedSmooth in
> yt/geometry/particle_smooth.pyx
>
> What is the default SPH kernel that is used for deposition?  Is it
frontend specific (and if so, where is it defined for each frontend), or do
we just use a cubic spline as default?

Also, what value is used for the smoothing length of the particle
deposition?  I believe most codes already have a smoothing_length field
defined by the simulation.  Looking in VolumeWeightedSmooth, it seems to
accept a smoothing_length field for the particles but I don't know if this
is the simulation-defined field.  I may be wrong, but it seems to me that
using the simulation-defined smoothing_length field is only applicable for
the "scatter" deposition method.  I thought "gather" recalculates new
smoothing lengths to address the fact that you may try to sample the fluid
quantities a large distance away from the nearest particles, who all may
have small smoothing lengths because of their proximity to each other.  But
I may be mixed up here.

Cameron

-- 
Cameron Hummels
NSF Postdoctoral Fellow
Department of Astronomy
California Institute of Technology
http://chummels.org
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