Etude expérimentale de la stabilité de l'écoulement de films de fluide non Newtonien sur plan incliné

We study the stability of shear-thinning (pseudoplastic) fluid films flow down an inclined plane. We focus on fluids obeying the Carreau law. An optical technique called electrocapillarity has been implemented in order to determine the surface tension and viscosity, at values of the shear rate as small as 10 -3 s -1 , by studying the damping of propagating capillary waves. The main objective of this work is to experimentally study the linear stability of shear-thinning fluid films flow. For a fixed inclination angle, the experimental study essentially consists in measuring the cutoff frequency and wavelength of primary waves, and then determining the critical Reynolds number. The experimental results presented in the (Re, f) and (Re, k) planes are in good agreement with the numerical results, and confirm the destabilizing effect of the shear-thinning properties in comparison with the Newtonian case. Mots clefs : Stabilite ; Rheologie ; Films minces ; Surface libre. 22 eme Congres Francais de Mecanique Lyon, 24 au 28 Aout 2015