(469f) Influence of Topography and a Surfactant Monolayer On the Dynamics and Stability of a Thin Liquid Film Flowing Over a Locally Heated Surface

Thin liquid films flowing over surfaces with localized heating can become unstable and evolve into an array of rivulets or time-periodic waves. A long-wave analysis is used to investigate the effect of topographical features on the stability of the film. Basic step-down and mound features in the streamwise direction can stabilize the film with respect to rivulet formation, as seen from a significant increase of the critical Marangoni parameter at the instability threshold determined from a numerical linear stability analysis. Features that vary in the transverse direction are destabilizing. The presence of a surfactant monolayer significantly modifies the dynamics, as the surface tension and velocity field depend on both the imposed temperature profile and local surfactant concentration. An energy analysis is used to provide insight into the primary mechanisms of stabilization and destabilization.