  This is a computational study of gravity-driven fingering instabilities in
unsaturated porous media. The governing equations and corresponding numerical
scheme are based on the work of Nieber et al. [Ch. 23 in Soil Water Repellency,
eds. C. J. Ritsema and L. W. Dekker, Elsevier, 2003] in which non-monotonic
saturation profiles are obtained by supplementing the Richards equation with a
non-equilibrium capillary pressure-saturation relationship, as well as
including hysteretic effects. The first part of the study takes an extensive
look at the sensitivity of the finger solutions to certain key parameters in
the model such as capillary shape parameter, initial saturation, and capillary
relaxation coefficient. The second part is a comparison to published
experimental results that demonstrates the ability of the model to capture
realistic fingering behaviour.
