Instability of the contact line and thickness profiles in vertical oil spreadings

J. GOMBA; A. G. GONZÁLEZ; J. DIEZ; R. GRATTON; L. KONDIC

Anales AFA

Asociación Física Argentina

Año: 2002 vol. 14 p. 86 - 90

0327-358X

We study the instability of the contact line of the spreading of a constant volume silicon oil (PDMS) on vertical glass substrates. The initial condition is generated from a horizontal filament of typical diameter of several tenths of mm and viscosity 10 Stokes. Two optical diagnostic methods are used. The first one gives the film thickness profile along a prescribed line. The second one produces the bidimensional pattern of the spreading. We use these techniques to determine the cross sectional area of the filament, the approximate shape of the profile, the evolution of fingers and troughs in function of time, and the Fourier spectra of the corrugations of the frontline. The experimental results are compared with numerical simulations and a model based on linear perturbations analysis. This simple model yields a Fourier spectrum in good agreement with experiments, and gives a good estimate of the wavelength corresponding to the maximum growth rate.