amrita-ebook Google Group

Re: restart using previously computed fields and different BC and domains

j...@galcit.caltech.edu (James Quirk) — Thu, 19 Nov 2009 20:51:06 UT

Matei,

It is possible, but not with AMR_SOL's existing idioms.
What you would need to do is use AMRITA's replace mechanism
on the keyword flowin providing a back-end that
does what you want. The back-end would basically lift
grids {G1,..,Glmax} from the target input and
and add them to the current G0. It would probably

restart using previously computed fields and different BC and domains

ma...@uottawa.ca (matei) — Thu, 19 Nov 2009 20:31:10 UT

Does anybody know if it is possible to combine computation results
from one run to the next.

For example, suppose I want to use a fully established 2D cellular
detonation profile as initial condition for subsequent studies where
the boundary conditions (e.g, diffraction, pertubations, etc...) would

Re: Grid adaption on curved surface

j...@galcit.caltech.edu (James Quirk) — Thu, 19 Nov 2009 17:04:57 UT

Chris,

AMR_SOL's body-fitted machinery is not actively supported,
mainly for the reasons you've run into which are quite hard
to solve and package for general use. The alternative,
which works well for stylized shapes, like your cylinder,
is to employ a level-set approach that allows internal

RE: Grid adaption on curved surface

ma...@uottawa.ca (Matei Radulescu) — Thu, 19 Nov 2009 17:07:46 UT

Christian,
I have used the embedded boundary technique to represent the surface of
a cylinder in problems of interaction with shocks or detonation waves.
It behaved well and permitted to use a rectangular grid. If you want to
go that route, there are examples posted on the AMRITA e-book about how

Grid adaption on curved surface

christian.heb...@usherbrooke.ca (chris) — Thu, 19 Nov 2009 15:47:53 UT

I have a curvilinear grid geometry with a curved surface in it
(circular). The flow currently shows artefacts on the wall due to the
N-sided nature of the surface. I could use a very fine mesh structure
for that wall but ideally, for the mesh adaption process, the elements
on the curved wall would need to be fitted to the exact computed wall

Re: Porous Wall Boundary Condition

j...@galcit.caltech.edu (James Quirk) — Wed, 04 Nov 2009 12:58:36 UT

Gary,

I wasn't suggesting you lift a far-field bc verbatim, it was more a case
of suggesting you look at the associated characteristic analysis for some
insight as what to do.

At a practical level, the first thing you should do is to implement
your own reflecting wall bc using the template from the bdy manpage.

Re: Multiple inert gas EquationSet

men...@leeds.ac.uk (Gary Sharpe) — Wed, 04 Nov 2009 09:51:24 UT

Christian, if you are just looking at having two ideal gas EoS's with
different gammas, there is a very simple, but robust method in
A Simple Method for Compressible Multifluid Flows
SIAM J. Sci. Comput. Volume 21, Issue 3, pp. 1115-1145 (1999)
by Saurel and Abgrall. This is also non-conserative but tests show

Re: Porous Wall Boundary Condition

men...@leeds.ac.uk (Gary Sharpe) — Wed, 04 Nov 2009 09:42:49 UT

James,
hmmm...I'm no sure the 'far-field' bc is appropriate here
a) if you run a znd wave parallel to wall, the wave would
remain 1D so wouldn't have the desired the effect.
b) there would be no way to control the "porosity"
i.e. degree of absorbtion.
We are currently looking at specifing the normal velocity

Re: Multiple inert gas EquationSet

j...@galcit.caltech.edu (James Quirk) — Tue, 03 Nov 2009 20:42:51 UT

Chris,

The attached script shows how a clue-in AMRITA user could
run a simulation with two inert gases; it nominally reproduces
the results of Quirk & Karni (1994). If you take a look
at the script using amrgi, you'll see it contains the
following procedures:

(i) BubbleEquations which defines a two-component EquationSet.

Multiple inert gas EquationSet

christian.heb...@usherbrooke.ca (chris) — Tue, 03 Nov 2009 19:05:21 UT

I have a shock tube model which I'd like to convert to use two
distinct inert gases (driver/driven). Looking in stdlib/equations, I
found ShockBubbleEquations which looked promising. However, the
machinery required by BCG doesn't seem to be present, so the latter
chokes on its call with a 'BCG under construction' message. (ie, no

Re: Porous Wall Boundary Condition

j...@galcit.caltech.edu (James Quirk) — Sun, 01 Nov 2009 20:22:04 UT

Gary,

So you really want an absorbing boundary condition.
These are often used in the aero community for far-field
boundary conditions, and you'll find a slew of references
in the literature.

If you think of Roe's schem, applied in the transverse
wave directon, then all you're doing is filling in a

Re: Porous Wall Boundary Condition

men...@leeds.ac.uk (Gary Sharpe) — Sun, 01 Nov 2009 17:23:33 UT

Hi James,
in the experiments, a cellular detonation in a channel runs over a
section of "porous wall"
- in the experiments the "wall" consists of a network of criss-
crossing wires with
a given "pore density" I believe. Its role is to partially absorb or
destroy transverse waves
which impact on it. We want a boundary condition which mimics

Re: Porous Wall Boundary Condition

j...@galcit.caltech.edu (James Quirk) — Sun, 01 Nov 2009 15:50:45 UT

Gary,

It's not difficult to add a transpiration boundary condition,
but without knowing the details of Matei's experimental setup
it's hard to advise on what formulation the transpiration
should take.

James

Porous Wall Boundary Condition

men...@leeds.ac.uk (Gary Sharpe) — Fri, 30 Oct 2009 17:34:54 UT

Hi all,
Matei and I wanting to simulate his porous wall detonation
experiments.
Does anyone know of or have any ideas for a boundary condition which
mimics
the "loss" effects or non-perfect reflectivity of a porous wall?
My idea was to include a non-reactive layer of complient (i.e. a gas
of some non-infinite density)

Re: time integration at a fixed grid location

j...@galcit.caltech.edu (James Quirk) — Wed, 28 Oct 2009 13:20:40 UT

Matei,
Yes. You have to ask yourself what are AMR_SOL's prolongation and
restriction operators doing to your NEW quantity. The prolongation
is the interpolation done when putting down a new fine patch that
can't lift its solution from a previous fine patch. The restriction
is the averaging done on a fine patch when projecting its solution