Contact line instability: Comparison between experiments and numerical simulations

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

New Jersey, EE.UU

Conferencia; 56th Annual Meeting Division of Fluid Dynamics, APS; 2003

American Physical Society

We report results of experiments and numerical simulations of the spreading of fixed volumes of silicon oil on vertical substrates. The initial condition is generated from a filament of diameter 0.4~mm and cross section of 10^-4 cm^2. By means of two optical techniques, the Schlieren method and the use of an anamorphic lens, we performed a systematic study for a range of cross sections. In particular, we measure the thickness during the early stable stage of the spreading, and analyze the spatial Fourier spectra of the shape of the contact line in the unstable stage, which leads to a finger shaped pattern. The experimental results are compared with numerical simulations within the framework of lubrication approximation. The good agreement found between experiments and simulations strongly supports the hypotheses of the theory and the methods employed in the numerical calculations. This comparison is essential to determine the realistic thickness of the precursor film that must be used in the simulations. Its value (approx 40 nm) is consistent with measurements in the literature.