question about stepgrid.f dans AMRCLAW

[Eva Tuholi]

Hi,
in amrclaw, in stepgrid.f or step2.f, why fm(i+1) and fp(i) are
differents?

in stepgrid.f when q is update, is writen:

q(i,j,m) = q(i,j,m)
& - dtdx * (fm(i+1,j,m) - fp(i,j,m))
& - dtdy * (gm(i,j+1,m) - gp(i,j,m))

c # fm, fp are fluxes to left and right of single cell edge

[Randall John LeVeque]

fm(i+1) would be the left flux at interface i+1/2 (and hence the flux
affecting cell i),
while fp(i) is the right flux at interface i-1/2 (also affecting cell
i). The notation is confusing since we can't use half-indices in
Fortran. The AMR version is different from standard Clawpack, where
interface fluxes are not used, because maintaining conservation at
grid interfaces requires knowing these. But to also work for problems
not in conservation form there is no longer necessarily a unique
interface flux, so fm and fp were introduced.

- Randy

[Eva Kardhashi]

I understand, thank you!

---

From: Randall John LeVeque <r...@uw.edu>
To: claw-...@googlegroups.com
Sent: Friday, September 2, 2011 4:02 PM
Subject: Re: question about stepgrid.f dans AMRCLAW

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