Tomas Fullana : Bouncing and sloshing: from numerical simulations to reduced order models скачать в хорошем качестве

Tomas Fullana : Bouncing and sloshing: from numerical simulations to reduced order models

Numerical simulations can help us bridge the gap between complex phenomena and reduced order models. In the first part, we will explore the resonant behavior of a liquid drop bouncing on an atomically smooth mica surface at room temperature — extending the time to wet from less than a second to several minutes. Experiments and numerical simulations reveal two distinct hovering modes; at low forcing frequencies, drops bounce with a clear air gap, while at higher frequencies they become dynamically bound to the vibrating substrate via a thin air film. The excitation of the drop’s second spherical harmonic mode controls this transition and we develop a coupled linear spring model that accurately predicts drop trajectories without fitting parameters. In the second part, we will investigate the wave-induced mean flow generated by a partially filled container subject to an orbital shaking motion. Experimentally, it has been shown that the toroidal mean flow is co-directed with the wave and that poloidal structures appear close to the contact line, where the fluid-fluid interface meets the solid boundary. The total (Lagrangian) mean flow can be decomposed into a Eulerian component, representing the response of the flow to the time-averaged nonlinear Reynolds stress, and a Stokes drift component, accounting for the slight variation, or drift, of fluid particles. Using direct numerical simulations, we are able to characterize the two mean flow contributions, which confirms the predictions of the weakly non-linear analysis, and allows us to study the effect of both viscosity variations and contact line models.