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
folder by the name plugin/amr_sol/BCG/equations/
ShockBubbleEquations...)

Keeping the question very wide: how would one go about modeling two
inert gases? Is it even possible using what's currently implemented?
(I'm running v3.04...)

Thanks for the help

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.

(ii) LoadBubbleCode which produces a two-component solver
without relying on BCG.

The solver used is probably not going to be good for your application,
as it is only reliable for weak shocks. This is because it uses
a primitive variable formulation, rather than a conservative one.
Thus it will not get the correct strengths for moderately
strong shocks. Nevertheless, the attached stands in that it
shows the plumbing needed to add a custom EquationSet and Solver
to AMRITA's plugin amr_sol.

I do have a conservative, multi-material setup which allows for
arbitrary numbers of materials with arbitrary EOS's, but for
contractual reasons I am not allowed to give it out to third-parties.
But it's construction follows that of the attached, there is just
a lot more of it.

Now to pick up on the analogy I made to you offline, AMRITA is not
a package like OpenFOAM, as in here it is please use it. The
TA in the name stands for teaching-aid. And the system essentially
exists to train "viloin-makers" and "violin-players." Here a
"violin-maker" is someone who can craft a specialist CFD component
that will benefit third-parties. While a "violin-player" is someone
who takes the time to learn how to use the specialist components
so as to make beautiful "CFD music" i.e. fluid simulations that
stand-up to hard-nosed, scientific scrutiny.

As a case in point, consider the recent requests by Gary and Matei
for a specialist boundary condition. If they looked at the manual
page for "bdy" using amrhelp, they would get a feel for the
constraints that come into play.

In your case, it's difficult to advise a path forward as I don't
know how much time you've allotted to the exercise. But the attached,
for all it's faults, should help convince you that AMRITA is
an open-ended system.

James  

run_hs 40K Download

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
it works very well for strong shocks too. The implementation would
involve
a) defining an advecting scalar, alpha say, initially 1 in one
material
and 0 in the other - the ReactiveEulerEquations
could be used for this by making the reaction rate of the reaction
progress
variable zero
b) modifying the roe solve scheme to solve a non-conservative eqn
for the evolution of alpha as described in the paper.
Cheers
GAry

On Nov 3, 7:05 pm, chris <christian.heb...@usherbrooke.ca> wrote:A
Simple Method for Compressible Multifluid Flows
SIAM J. Sci. Comput. Volume 21, Issue 3, pp. 1115-1145 (1999)