| Abstract: | The motion of the contact line in gas-liquid-solid systems is theoretically investigated for small values of the capillary number and Reynolds number. The possible existence on the solid substrate of a residual microscopic film formed by adsorbed liquid molecules is taken into account and the spreading characteristics of the liquid on dry and wet substrates are compared. It is shown that, in accordance with the experimental data, in the model employed the motion of the liquid during wetting is  rolling motion, and that the increase in the dynamic contact angle is slower for a wet than for a dry substrate. The maximum dynamic contact angle is much less than 180°. The flow structure in the neighborhood of the moving contact line is analyzed and it is shown that under certain conditions regions with closed streamlines may be formed. The reason for this is the self-induced Marangoni effect — the reaction of the surface tension gradient on the liquid-solid boundary caused by the liquid flow on the flow that caused it.Based on a paper read at the Seventh Congress on Theoretical and Applied Mechanics, Moscow, August 1991. Presented by R. I. Nigmatulin.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 81–89, November–December, 1992. |
