Experimental study and modeling of the spreading of a two-dimensional strip of fluid flowing down a vertical plane

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

Banff, Canadá

Workshop; BIRS Workshop: Nonlinear Dynamics of Thin Films and Fluid Interfaces,; 2003

We report experimental results on the spreading of a constant volume of silicon oil (PDMS) down a vertical glass plate. The initial conditionhas the shape of a long strip and is  generated from a horizontal fluidfilament with typical cross sections between $3~10^{-4}~cm^2$ and$15~10^{-4}~cm^2$. To characterize the early stages of the spreading we employ an optical technique based on the use of an anamorphic lens. By comparing these  measurements with one dimensional numerical simulations, we are able to estimate the thickness of the precursor film needed in the calculations. For later stages, we use another technique based on the schlieren method that captures the  bidimensional pattern of the transversal film instability. By means of these techniques we determine the film thickness profiles,  and the evolution of the moving contact line, including its shape and  Fourier spectra. We also develop a linear model for the instability based on an adiabatic approximation, which extends the results of the stability analysis of the constant flux problem to the constant volume case.