[FLASH-BUGS] cylindrical coordinates, avisco

[Sean Matt]

Thanks again, Tomek.  It now seems to work just fine.  I understand that
the rotational symmetry axis is special, and that one possibly wants the
artificial viscosity to scale with cylindrical r. But I still don't
understand why the artificial viscosity should depend on my choice of
domain normalization.  For example, why should the artificial viscosity be
different if I choose xmin=0.0 ,xmax=1.0 as opposed to xmin=0.0,
xmax=100.0?

	-Sean

On Fri, 26 Sep 2003, Tomasz Plewa wrote:

> On Fri, Sep 26, 2003 at 03:47:23PM -0400, Sean Matt wrote:
> [snip]
> 
> > 	This actually raises the issue of whether the quantity (x(i)**2 -
> > x(i-1)**2) is the right formulation for the calculation of the
> > artificially viscocity.  We're not sure why the actual numerical value of
> > the x coordinate should be relevant, since it is arbitrarily set by the
> > user (e.g., 201**2-200**2 does not equal 2**2-1**2).  Perhaps what is
> > needed is something like the square of the difference, (x(i) - x(i-1))**2,
> > but since this is a different quantity, this should be looked at with
> > care, and we don't know the correct formulation.
> 
> There should be no flow across the symmetry axis at r=0 (the area
> vanishes there). The viscous flux (coefficient) should be set to zero.
> 
> Tomek
> 

-- 

_______________________________________________________________________
Sean P. Matt				     CITA National Fellow
phone: (905) 525-9140 x 23189		     Physics & Astronomy Dept.
http://www.physics.mcmaster.ca/~matt	     McMaster University
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