  Viscous fingers in the lifting Hele-Shaw cell form a hierarchical pattern due
to competition between growing fingers in a converging geometry. If the
defending fluid is visco-plastic, a permanent three-dimensional pattern is
formed, which is usually approximated as quasi-two-dimensional. We present here
a Monte-Carlo simulation which attempts to reproduce the real 3-dimensional
pattern in rectangular geometry using a very simple algorithm. We study the
finger length distribution, the rate of increase of coverage of the invading
fluid, the height profile of the final pattern and observe how these change
with characteristics of the fluids.
