Capillary wave disintegration

Fig. 1 illustrates the two mechanisms proposed for the processes of liquid disintegration and aerosol generation within ultrasonic nebulizers. The capillary-wave theory relates to the production of capillary waves in the bulk liquid. These waves constructively interfere to form peaks and a central geyser. When the amplitude of the applied energy is sufficiently high, the crests of the capillary waves break off, and droplets are formed. The rate of generation of capillary waves is dependent on both the physicochemical properties of the nebulized fluid and the intensity of the ultrasonic vibration. Mercer used Eq. (1) to calculate the threshold amplitude for the generation of capillary waves ... 

The influence of micellisation on the propagation of capillary waves has been discovered only for solutions of the nonionic surfactant - DePO. The determined values of Z2 are comparable with the results for solutions of DePB but they decrease monotonously with concentration. Therefore, the obtained results evidence that relations (5.284) and (5.285) describe the concentration dependence of the dynamic surface elasticity well. Hence, the method of transverse capillary waves can be used for studies of micellisation kinetics of surfactants with relatively low surface activity. For surfactants with higher surface activity where the formation and disintegration of micelles proceed slower the method of longitudinal surface waves can be used [102, 103]. The characteristics of longitudinal waves are more sensitive to the dynamic surface elasticity, and this allows one to study the micellisation kinetics under the condition... 

If the main factor causing the occurrence of waves is surface tension, then such waves are called capillary waves. In the case of predominance of gravitational forces we can talk about gravitational waves. An illustration of the first case is the outflow of a liquid jet from a nozzle into the air. At some distance from the nozzle, the surface of the liquid jet gets covered by waves, and then the jet disintegrates into drops (the process of jet breakage takes place). The second case is exemplified by ordinary waves on the surface of the water. 

Mehring C, Sirignano WA, Nonlinear capillary wave distortion and disintegration of thin planar liquid sheets, J. Fluid Mech. 388, 69-113, 1999. 

The disintegration of liquid sheets as studied by many authors [40-42] is generally a two-step process. First, liquid threads and/or ligaments disintegrate from the sheet, which secondly break into droplets due to capillary instabilities. This can be induced either through perforations or destabilising waves in the liquid sheet [40]. 

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