This test is commonly performed in one-dimension, but here we
extend this to consider two three-dimensional set-ups; the first of
these has the fluid membrane at 90 degrees to the x-axis of the box
([1,0,0] plane), causing the shock to propogate parallel to this axis.
The second set-up aligns the membrane at 45 agrees to each of the x, y
and z axes ([1,1,1] plane).
In both cases, the intial density and pressure jump either side of
the membrane are:
and we used a polytropic index of 5/3. In 2D, the projected initial
conditions look like the image below, with black and white regions
representing fluids of different densities. The left-hand image shows the
shock face oriented along the [1,0,0] plane, while the right-hand
image shows it oriented along the [1,1,0] plane. In actuality, this second one
needs to be oriented in the [1,1,1] plane i.e. oblique to all the
axes.