[aspect-devel] How to grab the radius of every interior sphere made up from cell faces in the domain and some MPI questions

Wolfgang Bangerth bangerth at tamu.edu
Sun Oct 25 09:53:25 PDT 2015


On 10/25/2015 11:49 AM, Ian Rose wrote:
>
>     r_{lmi} =
>          \int \int \int  drho(r,phi,theta) Y_{lm} R_i(r) dtheta dphi dr
>
>     where R_i(r) are the basis functions in radial direction.
>
> ‚Äč Ah, but this is the beauty of the multipole expansion. As long as all the
> mass sources are completely external or completely internal to our
> circumscribing sphere, then the radial functions are entirely determi‚Äčned, and
> are just powers of r (where the power is related to the order of the multipole
> and whether it is external or internal).

Exactly, i.e.,
   R_i(r) = r^i
if I see it correctly, for some set of exponents i. Or do I misunderstand and 
you want to imply that it should be
   R_l = r^{-l}
or similar, and that we don't need another index 'i' at all?

Best
  W.

-- 
------------------------------------------------------------------------
Wolfgang Bangerth               email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/



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