A study of the advancing interface. I. Interface shape in liquid—gas systems

Abstract The shape of the advancing liquid—air interface has been studied in a glass capillary over the range in which viscous and interfacial forces are the dominant factors controlling the system. Plotting the apparent contact angle versus the capillary number plus a shift factor, one obtains a curve which correlates all the data. In the systems examined experimentally in this study, the shift factor is determined solely by the static contact angle between the liquid and the solid substrate. To generate the curve, data were first obtained over the full range of apparent contact angles from 0 to 180° with liquids having shift factors which were equal to zero or negligible. Then the validity of the correlation was tested with data on liquids requiring large shift factors and the results were found to agree with the data obtained on the other liquids.