[Users] Error in GRHydro_SlopeLimiter.F90
jafsma at rit.edu
Tue Jan 10 11:17:08 CST 2012
Hi Ian, I completely agree with you about slope limiters. I'd keep minmod
and MC2, code in superbee just for historical reasons (it's in the sample
code I sent along), but eliminate all the others as obsolete. That way,
there would be two commonly used options,and one more for comparison, but
everything in one subroutine and much more condensed than before.
On Tue, Jan 10, 2012 at 6:05 AM, Ian Hawke <I.Hawke at soton.ac.uk> wrote:
> On 09/01/12 20:47, Joshua Faber wrote:
> > Hi everyone,
> > I believe the routines in GRHydro_SlopeLimiter.F90 are all either
> > mislabelled or simply the wrong formulae. As a quick reminder, for
> > the upwind slope ("dupw") and downwind slope ("dloc"), we expect to
> > get the following results:
> > On the rather nice wikipedia page,
> > http://en.wikipedia.org/wiki/Flux_limiter
> > they take variables r = dupw/dloc and phi = delta / dloc, but the
> > results are the same.
> Assuming the ET files follow Whisky, then I would note:
> 1) The Whisky results follow from my thesis, which follow from Toro (1st
> 2) Toro gives a formula to convert Flux limiters to Slope limiters; they
> are _not_ the same thing in his notation. The flux limiters are the
> canonical values, but the slope limiters "corresponding" to the flux
> limiters use different formulas.
> 3) I didn't revisit them after implementation, and it should be noted
> that Toro fixed a large number of typos between 1st and 2nd edition, so
> it wouldn't surprise me if some followed through.
> Saying all that, is there really a great call for the slope limiters? I
> would have thought that minmod and MC (the correct version is MC2) would
> be enough for basic testing. I've had similar thoughts with the Roe
> solver in the past; only inertia and not wanting to redo testsuites
> stopped me from taking them out of Whisky ages ago. Why not just remove
> them? Less to maintain, especially if they're not used.
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> Users at einsteintoolkit.org
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