Surface Waves and Jet Breakup

It has been postulated that jet breakup is the result of aerodynamic interaction between the Hquid and the ambient gas. Such theory considers a column of Hquid emerging from a circular orifice into a surrounding gas. The instabiHty on the Hquid surface is examined by using first-order linear theory. A small perturbation is imposed on the initially steady Hquid motion to simulate the growth of waves. The displacement of the surface waves can be obtained by the real component of a Fourier expression ... 

In the breakup regime, spray characteristics include film angle, film velocity and thickness, breakup length, breakup rate, surface wave frequency, wavelength, growth rate, and penetration distance. These quantities, however, are extremely difficult to measure on account of the very small size and rapidly changing features of disintegrating Hquid jets or films. 

III. Second Wind-Induced Breakup. Further increasing jet velocity, the dynamic pressure of the surrounding air becomes predominant. The breakup of the jetis caused by the unstable growth of short-wavelength surface waves due to the relative motion between thejet and the surrounding air. The maximum growth rate occurs at... 

Factors influencing jet breakup may include (a) flow rates, velocities and turbulence of liquid jet and co-flowing gas, (b) nozzle design features, (c) physical properties and thermodynamic states of both liquid and gas, (d) transverse gas flow,[239] (e) dynamic change of surface tension, 1151[2401 (f) swirlj241 242 (g) vaporization and gas compressibility,[243] (h) shock waves,[244] etc. 

This breakup mechanism is similar to that of a jet breakup in still gases. In the presence of a relatively strong crossflow, however, additional instabilities and waves form on the surface of the jet. These instabilities grow larger as the jet deflects and deforms and contribute to the final jet breakup at Xb- We refer to Xb as the column breakup location (CBL). At this location, the jet disintegrates into a number of relatively large droplets, which themselves undergo secondary breakup processes and become smaller as a part of the atomization process. 

Amorphous ribbons are formed by directing a stream of liquid alloy onto a water-cooled drum. In the production of metallic ribbons by the melt spinning process some melts have been found to give serrated edges. It has been proposed that these serrations are due to instabilities which eventually lead to jet breakup. Serrated edges were found to occur [12] in metals with high levels of S and O, i.e. melts with low surface tension and Marangoni Numbers. This is consistent these are a result of the break-up of surface waves. 

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