ABSTRACT
At higher flow rates, the intersection of the continuation of the linear part of the graph with the pressure axis (shown by dotted lines in the insertion) gives a negative wetting tension equal to −0.36 mN/m, which results in dynamic advancing angle of the solution θA=93°. This means that at high flow rates, tetradecane wet better, as compared with the solution, the capillary surface covered with adsorbed layer of surfactant molecules. Deviation of interface tension from the adopted bulk value may influence the magnitude of the contact angle, but not the sign of the wetting tension. For instance, when γ12 of the moving meniscus is assumed to be 20 mN/m due to some loss of surfactant as a result of adsorption on tetradecane film interface, the calculated advancing angle decreases only slightly to 91°.
