claw/applications/euler/2d/shockbubble

A shock wave hits a sperical bubble of low-density gas (with constant
pressure and zero velocity near the bubble originally). The 2d Euler
equations with source terms for spherical symmetry are used, so the results
seen should be rotated about the x-axis. The bubble turns into a "smoke ring". 

The initial data consists of a spherical bubble of low density gas 
and constant pressure p=1.   A shock wave approaching from the left hits the
bubble and results in compression and distortion into a vortex ring.

The density inside the bubble and the pressure behind the shock wave are
specified in setprob.data.  (Try making the density inside greater than that
outside to see a different set of dynamics.)

The Riemann solvers rpn2eu5.f and rpt2eu5.f are used (located in
claw/applications/euler/2d/rp), which include a fifth equation for
a passive tracer advected with the fluid velocity.  This tracer is
initialized to be 1 inside the bubble and 0 outside and traces the
location of the gas initially inside the bubble.

The cylindrical source term is implemented in src2.f (and for amrclaw, also
in src1d.f) using Runge-Kutta with the fractional step method.   The
y-coordinate of each cell center is stored in aux(i,j,1) for use in the 
source term.