Directory:
    ${PENCIL_HOME}/samples/2d-tests/Rayleigh-Taylor
SVN Id:
    $Id$
Maintainer:
    Michiel Lambrechts  <michiel/astro.lu.se>
Added:
    x/Aug/2012 
Status:
    succeeds # One of [succeeds|failing since <date>|obsolete| ...]
Recommended resolution:
    300*900 in order to see secondary Kelvin-Helmholtz instabilities develop.
Comments:
    Classical test for hydro codes. I tried to stay close to the standard test
    problem as described in 
    - Comparison of several difference schemes on 1d and 2d test problems for
    the euler equations - by Richard Liska and Burton Wendroff
    http://www-troja.fjfi.cvut.cz/~liska/ps.gz/compare_euler_SISC_03.pdf 
    The Rayleigh-Taylor instability occurs when a denser fluid (rho_2) is
    placed on top of a lighter fluid (rho_1) in a gravitational field.
    Although both fluids can be maintained in hydrostatic equilibrium, a small
    perturbation at the interface between the 2 fluids will lead to turbulent
    mixing.
    In the linear phase the growth rate is given by
    \omega = \pm \sqrt{gk \frac{\rho_1-\rho_2}{\rho_2 + \rho_1}} .
    This growth rate can be clearly seen between times t=4 to t=8, at 300*900
    resolution.
    WARNING: In the current implementation higher resolution runs (300*900)
    break the symmetry around the vertical ($x=0$)-axis, at late times
    (t>11).  This is unexpected since the equations solved by the Pencil Code
    are symmetric.
    NOTE: This sample makes use of the initial condition module.
References:
    None