  We consider free surface instabilities of films flowing on inverted
substrates within the framework of lubrication approximation. We allow for the
presence of fronts and related contact lines, and explore the role which they
play in instability development. It is found that a contact line, modeled by a
commonly used precursor film model, leads to free surface instabilities without
any additional natural or excited perturbations. A single parameter
D=(3Ca)^{1/3}\cot\alpha$, where $Ca$ is the capillary number and $\alpha$ is
the inclination angle, is identified as a governing parameter in the problem.
This parameter may be interpreted to reflect the combined effect of inclination
angle, film thickness, Reynolds number and the fluid flux. Variation of $D$
leads to change of the wave-like properties of the instabilities, allowing us
to observe traveling wave behavior, mixed waves, and the waves resembling
solitary ones.

Fluid Dynamics