Advection on a quadrilateral grid.

The advection equation q_t + u*q_x + v*q_y = 0 is solved with u=1, v=0,
on a quarter anulus in polar coordinates.  The initial data is q=0
and q=1 is specified along a portion of the inflow boundary.

The velocity is specified using a stream function in stream.f,
called in setaux.f.  

The grid is specified by mapc2p.f.   To plot the results using plotclaw2
in matlab, MappedGrid=1 is set in setplot2.m so that mapc2p.m is used, which
should be consistent with mapc2p.m.

Setting MappedGrid=0 shows the results in the rectangular computational
domain.


WARNING: This example was modified February, 2006 to use
Version 4.3 of clawpack and the associated matlab scripts.