A simple model for arbitrary pollution effects on swirling free-surface flows

Abstract

International audienceAmbient pollution acts like surfactants on free-surface flows and can hence strongly affect their nonlinear dynamics. A cylindrical free-surface flow driven by a slow rotating bottom is considered here as a generic example for such effects and is investigated both experimentally and numerically. We suggest here a simple numerical model without superficial transport of the surfactants, adaptable into any code for single-phase flows. The model does not possess any free parameter and is independent on the closure model for surfactants. For the stationary axisymmetric base flow, the radial velocity at the interface is set to zero whereas the usual stress-free boundary conditions are retained for the perturbations. For a geometrical aspect ratio of 1/4, known to display ambiguous behaviour regarding stability thresholds, the modal selection as well as a nonlinear stability island found in the experiments are well reproduced by the model, both qualitatively and quantitatively