Nonlinear stability analysis of film flow with small weber number

Nonlinear-kinematic equation for the film thickness with small surface tension at the interface is used to investigate the nonlinear stability of film flow down an inclined plane. The analysis shows that both supercritical stability and subcritical instability are possible for film flow system. It is also found that if the magnitude of Reynolds number is larger than a critical value, the nonlinear effects make the film flow system unstable in the region near the upper neutral stability curve.