Biomedical subjects

R Chebbi

Publications and source records attributed to R Chebbi.

3 recordsLinked to original sources

PubMed2000

Dynamics of Wetting.

We consider the dynamics of spreading of a small drop over a smooth solid surface. The analysis is concerned with complete wetting and accounts for capillary, viscous, and van der Waals effects, with two spreading geometries considered: cylindrical and axisymmetric. A complete description of the drop thickness, slope, and curvature profiles is provided. The model is not based on any fitting parameter, and the spreading laws are found to be in good agreement with published data obtained by different experimental techniques. The study evaluates the relative magnitudes of capillary, viscous, and disjoining-pressure effects and discusses the asymptotic form of the film profile and the existence of a singularity at the three-phase contact line. The model allows determination of the complete distribution of viscous dissipation in the whole drop, and the rate of viscous dissipation is related to the losses of the liquid drop free energy. Copyright 2000 Academic Press.

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PubMed1999

Capillary Spreading of Liquid Drops on Prewetted Solid Surfaces.

A description of the entire configuration of liquid drops spreading over a previously wetted solid surface is given in the case of negligible evaporation and small Bond and Weber numbers. Two solutions are developed: an outer one which is valid in the bulk of the drop and an inner solution which applies in the vicinity of the macroscopic boundary of the drop. The model accounts for deviations from the constant-curvature profile for the outer solution and, in addition, for deviations of the inner solution from the asymptotic approximation of V. V. Kalinin and V. M. Starov (1986, Colloid J. USSR (English tr.) 48, 907). Both solutions are shown to present an inflexion point. Its location is shown to be very sensitive to one parameter which fully determines the inner solution. The value of this parameter, and the spreading laws for the drop radius, the apex height, and the dynamic contact angle are determined by matching the inner and outer solutions. Results show deviations from the power laws used in the literature. These deviations are discussed in relation to the results obtained by V. M. Starov et al. (1994, Adv. Colloid Interface Sci. 50, 187), and R. Chebbi and M. S. Selim (1997, J. Colloid Interface Sci. 195, 66), compared with the experimental data presented by V. M. Starov et al. for spreading over dry smooth solid surfaces. Moreover, the present analysis allows description of the entire drop configuration and slope and curvature variations. Copyright 1999 Academic Press.

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PubMed1997

Capillary Spreading of Liquid Drops on Solid Surfaces

Spreading of a liquid over a dry smooth solid surface is analyzed in the case of complete wetting, negligible evaporation, and small Bond and Weber numbers. In the inner region, the approach of V. M. Starov et al. (Adv. Colloid Interface Sci. 50, 187 (1994)) is used and disjoining pressure effects are included. In the core region of the drop, both capillary and viscous effects are included to account for deviations from the constant-curvature profile near the inflexion point. The spreading laws for the drop radius, the apex height, and the dynamic contact angle are determined by matching the inner and outer solutions at the inflexion point. The results are compared with the model of Starov et al. (1994) and the experimental results of J. D. Chen (J. Colloid Interface Sci. 122, 60 (1988)). The model is not based on any fitting parameter. Copyright 1997 Academic Press. Copyright 1997Academic Press

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