Nonlinear analysis and experimental investigation of liquid sheet breakup

• Main Author: Jazayeri, Seyed Ali
• Other Authors: Li, Xianguo
• Language: English; en
• Published: 2017
• Subjects: Thermodynamics; Nonlinear mechanics; Liquids
• Online Access: http://hdl.handle.net/1828/8296

A nonlinear stability analysis of a liquid sheet moving in an incompressible gas medium at rest subject to sinuous disturbances is presented. The first, second and third order governing equations have been derived along with appropriate initial and boundary conditions which describe the characteristics of the fundamental mode, and the first and second harmonics. It is found that the thinning of the sheet is caused by the growth of harmonic waves, and subsequent liquid sheet rupture occurs at every half wavelength interval. The amplitude growth rates of the disturbances are calculated at the dominant wavenumber for different initial amplitudes and are then compared with the predictions from the linear theory. The analysis also allows the determination of the breakup time and breakup length, and the effect of the flow parameters on the breakup time is also investigated. The present experimental study on the liquid sheet breakup explores the growth of liquid sheet instabilities and subsequent spray formation. Flow visualization reveals different flow regimes. Liquid sheet surface displacements, wavelengths and breakup lengths are measured using a photographic technique, and the drop sizes and velocities are measured simultaneously by the Phase Doppler Particle Analyzer (PDPA). The result of acoustic excitation for different regimes of liquid disintegration shows that for certain frequencies resonance and enhanced instability occur. However, in the spray regime where a fine spray is formed, although visually there are some effects of acoustic excitation on the wave development, the Phase Doppler Particle Analyzer (PDPA) measurements show no noticeable effect on the drop sizes and velocities. The theoretical predictions are compared with the experimental results for dominant wavelength and growth rate of the unstable waves on the liquid sheet surface. === Graduate