amrita-ebook Google Group

Re: Porous Wall Boundary Condition

2009-11-04T12:58:36Z

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

2009-11-04T09:51:24Z

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

2009-11-04T09:42:49Z

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

2009-11-03T20:42:51Z

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

2009-11-03T19:05:21Z

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

2009-11-01T20:22:04Z

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

2009-11-01T17:23:33Z

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

2009-11-01T15:50:45Z

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

2009-10-30T17:34:54Z

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

2009-10-28T13:20:40Z

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

time integration at a fixed grid location

2009-10-28T12:05:11Z

I would like to know how one can do a time-integration at a fixed
location on the grid, in a multi-grid situation.

For example, right now I have a piece of auxiliary code where i
compute a new field variable NEW at each time step, from which I want
its time integral W[7]. For a time integration, I simply cumulate the

RE: recording data along an internal boundary defined by a levelset

2009-10-20T16:29:43Z

James,
Thanks, I will try that.
matei

-----Original Message-----
[mailto:amrita-ebook@googlegro ups.com] On Behalf Of James Quirk
Sent: Tuesday, October 20, 2009 12:13 AM
To: Matei Radulescu
Cc: amrita-ebook
levelset

Matei,

There's no really clean way to do what you ask with
the existing functionality. But you might be

Re: recording data along an internal boundary defined by a levelset

2009-10-20T04:12:58Z

Matei,

There's no really clean way to do what you ask with
the existing functionality. But you might be
able to get away with the following.

Suppose that your line of constant PSI was predominantly

do x=$x1,$x2,$dc
along x=$x locate Y[] when PSI[]==$PSItarget -> y
probe MYFUNC[] at $x,$y -> v

recording data along an internal boundary defined by a levelset

2009-10-20T02:16:29Z

I hope someone can help me with this one.

In a simulation with an internally defined boundary, defined using the
levelset function PSI, I would like to record some variables along a
line of constant PSI.

Is there any direct way I can do that? So far, I have used the
"probe" command, while manually parametrizing a sequence of (x,y)

Re: Trouble to startup a supersonic flow over a triangle

2009-09-11T01:15:44Z

Jimmy,
You're using a linearized Riemann solver that cannot preserve
positive pressures in the strong expansion you get at sharp
corners. The script:
amrcp bcg/axs.3
will generate 108 alternative solvers for the ReactiveEulerEquations.
Most of them will suffer from the same numerical weakness
but those that use the lax-friedrichs flux should prove