  The flow of thin liquid films on inclined or vertical surfaces is one of
immense importance, with applications spanning many types of process
industries, due to the increased mass and heat transfer brought about by the
presence of waves on film surfaces. While extensive research has been carried
out in this area, many outstanding questions remain due to the complexity of
the problem - a result of the extremely large aspect ratio and the
three-dimensional nature. In this study, the evolution process of both
naturally forming and forced waves on these thin liquid films is numerically
studied using a hybrid front-tracking/level-set hybrid method which has the
advantage of a distinct and accurate capture of the interface topology without
being affected by the issues of mass conservation, numerical diffusion or
spurious interface profiles. The simulation is conducted on an infinite domain
specification through the imposition of periodic boundary conditions at the
film outlet. The obtained results show the growth, step-wise progression, and
eventual transition of natural waves from the two-dimensional state to
three-dimensional disordered structures. Finally, three-dimensional simulations
of artificially forced waves are carried out while different
parameters/features of these waves are compared with the existing
two-dimensional benchmark cases in the literature with excellent agreement
found.
  Keywords: falling films, thin films, solitary waves, three-dimension,
forcing, interface tracking
