Rayleigh jet breakup

Rayleigh Jet Breakup (Varicose Breakup) Surface Tension Force We <0.4 or We <1.2 + 3.41Oh0... 

Figure 3.2. Breakup regimes of round liquid jets in quiescent air. I Rayleigh Jet Breakup (Varicose Breakup) II First Wind-Induced Breakup (Sinuous Wave Breakup) III Second Wind-Induced Breakup (Wave-like Breakup with Air Friction) IV Atomization.

To account for the effect of liquid viscosity on liquid jet breakup, Weber extended Rayleigh s theory to a more general theory for low-velocity j et breakup. In Weber s theory it is assumed that... 

Figure 33. (a) Axisymmetric and (b) Non-axisymmetric Rayleigh-type breakup mode of round liquid jets in coaxial air flow. (Reprinted with permission from Ref. 210.)... 

The mechanical breakup mode occurs around the rims of the sheet where the air-liquid relative velocity is low, forming relatively large droplets. At low relative velocities, aerodynamic forces are much smaller than surface tension and inertia forces. Thus, the breakup of the liquid rims is purely mechanical and follows the Rayleigh mechanism for liquid column/jet breakup. For the same air pressure, the droplets detached from the rims become smaller as the liquid flow rate is increased. 

Experimental methods presented in the literature may prove of value in combustion studies of both solid and liquid suspensions. Such suspensions include the common liquid spray. Uniform droplets can be produced by aerosol generators, spinning disks, vibrating capillary tubes, and other techniques. Mechanical, physicochemical, optical, and electrical means are available for determination of droplet size and distribution. The size distribution, aggregation, and electrical properties of suspended particles are discussed as well as their flow and metering characteristics. The study of continuous fuel sprays includes both analytical and experimental procedures. Rayleigh s work on liquid jet breakup is reviewed and its subsequent verification and limitations are shown. 

Secondary atomization, the breakup of the drops first formed, has been studied by Littaye (11C), who assumes a necessary criterion that the drag forces exceed the inertia forces. Ohnesorge (17C) makes use of the principles of mechanical similarity by introducing dimensionless coefficients to help explain jet breakup. Above certain well defined numbers, the jet completely atomizes at the nozzle. Lower values indicate the formation of a jet which disintegrates, owing to helical vibrations which later change into Rayleigh vibrations. 

Rayleigh then postulated that this fastest-growing mode would dominate the instability and lead to the jet breakup. Drazin and Reid (1981) note this may not necessarily be correct because all disturbances might not have the same initial amplitude and because nonlinear effects may be important, though they do observe that it is a good working rule. ... 

For a 5-mm-diameter water jet the characteristic capillary time (pa Ia) is 4.14 X 10 s, so we may expect such a slow-moving jet to break up very quickly, in distances on the order of a centimeter for speeds approximately 0.1 ms The jet breakup length is predicted remarkably well by Rayleigh s linear result over a wide range of disturbance amplitudes even though the breakup process may be strongly nonlinear. 

FIGURE 20.7 The physical mechanism of Rayleigh-Plateau instability the undeformed jet (a) start to deform due to external pressure oscillations (b) surface deformations are amplified by Laplace pressure effects (c) until a jet breakup occurs (d). The new drops eventually recover their spherical shape (e). 

If the charge of the jet is low enough, the breakup of the initial drops takes place by the same Rayleigh jet instability mechanism as for a neutral jet as shown in Fig. 32.10 [17]. The droplet diameter can be related to the jet diameter in this case by the following relation [17] ... 

Fig. 5.7 Breakup modes (e = Eg = 0). Blue symbols. Rayleigh-type jet breakup. Red symbols. Non-Rayleigh-type jet breakup...

Theoretical and experimental studies on three-dimensional path and Rayleigh-type breakup of laminar particle-laden liquid jets were presented. The investigation focused on spiraling jets emerging from rotary atomizers which were additionally... 

Normal Pulsating Axisymmetric Rayleigh-type Sheet forms a round jet No breakup WfN <15... 

As described previously, in the atomization sub-model, 232 droplet parcels are injected with a size equal to the nozzle exit diameter. The subsequent breakups of the parcels and the resultant droplets are calculated with a breakup model that assumes that droplet breakup times and sizes are proportional to wave growth rates and wavelengths obtained from the liquid jet stability analysis. Other breakup mechanisms considered in the sub-model include the Kelvin-Helmholtz instability, Rayleigh-Taylor instability, 206 and boundary layer stripping mechanisms. The TAB model 310 is also included for modeling liquid breakup. 

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