Active control of thin liquid film flows: beyond reduced-order models

A thin liquid film flowing down an inclined plane is a canonical setup in fluid mechanics and pertains to a wide range of industrial applications. In some cases it is desirable to maintain the liquid-gas interface flat (e.g. coating problems), whereas other contexts (e.g. heat transfer) benefit from increased interfacial area. Ultimately, there is a strong need to reliably manipulate the flow in this mathematically rich system. Control theory has recently been applied successfully by A.B. Thompson et al. (Physics of Fluids 28, 012107, 2016) for an extended range of long-wave models such as the Benney and weighted residual equations, forming a hierarchy of complexity in which the effect of the control is well understood. The subject of this talk relates to the transition from controls on reduced dimensional systems to full Navier-Stokes solutions of this setup. A state-of-the-art volume-of-fluid methodology is used for the direct numerical simulation of the target flow, with control techniques informed by the modelling framework. We study both distributed and localised controls and analyse the robustness of these strategies, bringing us closer to their integration into real-life engineering designs.