Nonlinear Stability of Plane Liquid Films in a Stationary Air Medium

Nonlinear stability analysis is an important method of studying on liquid jet disintegrated process. This paper reports a nonlinear stability analysis of viscous liquid sheet moving in a surrounding gas medium. Both dimensionless sinuous and varicose dispersion relations have been derived from both liquid and gas phases by nonlinear Navier-Stokes equations, and appropriate boundary conditions. An experimental investigation that a water jet was discharged from a planar slot nozzle into a stationary air medium has been conducted for water wave shapes and breakup processes by photographic technique. The results show that numerical simulations according to the varicose dispersion relation, and wave number vs displacement figures have a good agreement through comparison between theoretical results and experimental data in studying wave shapes and breakup lengths. The precision of predicted wave breakup lengths can be controlled within just one wave length. It is presented that liquid jet breakup length is prolonged with base flow velocity increase of liquid jet in lower aspect ratio and flow velocities. This indicates that liquid velocity is a stable factor of liquid jet in present conditions. Both the wave shapes and breakup lengths have no direct concern with injected pressure. Initial liquid film in thickness is a primary influencing factor on wave number comparing with the effects of Reynolds number, Weber number, and Euler number.