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

In an experimental context, the contamination of air–liquid interface by ambient pollutants can strongly affect dynamics and stability a given flow. some configurations, interfacial flow even be blocked surface tension effects. A cylindrical free-surface driven slow rotating disc is considered here as generic example such effects investigated both experimentally numerically. We suggest simple numerical model, without any superficial transport pollutants, adaptable into code for single-phase flows. For stationary axisymmetric base flow, radial velocity at set to zero whereas usual stress-free boundary conditions are retained perturbations. The model does not feature free parameter. geometrical aspect ratio 1/4, known display ambiguous behaviour regarding thresholds, modal selection well nonlinear island found in experiments reproduced qualitatively quantitatively. robustness has also been validated replacing profile more accurate fit, with very little influence on results.