En las fronteras de la Materia Condensada

We carried out experiments of flow with newtonianos and viscoelastics fluids in a plane-cylinder system where at a determined Ca number (proportional to velocity), a type of instability denominated ribbing instability is unchained. With an original system of measurement (5% error) it was possible to determine the local pressure on the interface. The measurements were taken just before the instability began. The results show the influence of the gap and the flow and we could correlate the Ca number with the measured pressures We are interested in the relationship of obtained results with the rheologia of the non Newtonian fluid, particularly with the elastic effects. Additionally, the final thickness of the film was measured over the cylinder. In this case, the influence of the interfacial tension, the viscosity and the gravity could be analysed. The obtained results, agree with the predictions of classical models.