Ligament regime

MMD = — CO l Y/2 J) For atomization in both Direct Droplet and Ligament regimes Yule Dunkley [5]... 

In both the Direct Droplet and Ligament regimes, the mean droplet size is inversely proportional to the rotational speed co and the square root of the electrode or disk diameter dp ... 

This approximate relationship is similar to those for centrifugal atomization of normal liquids in both Direct Droplet and Ligament regimes. However, it is uncertain how accurately the model for K developed for normal liquid atomization could be applied to the estimation of droplet sizes of liquid metals Tombergl486 derived a semi-empirical correlation for rotating disk atomization or REP of liquid metals with the proportionality between the mean droplet size, rotational speed, and electrode or disk diameter similar to the above equation. Tornberg also presented the values of the constants in the correlation for some given operation conditions and material properties. 

Figure 3.9. Regimes in rotary (centrifugal) atomization of liquids (a) Direct Droplet Formation, (b) Direct Droplet and Ligament Formation, (c) Ligament Formation, and (d) Film or Sheet Formation.

Table 4.11b. Correlations for Mean and Maximum Droplet Sizes Generated by Smooth Flat Vaneless Disks in Ligament Formation Regime...

Accordingly, for the transition from Direct Droplet to Ligament Formation regime and the reverse transition, the dimensionless transition flow rates are Q = 0.096 Re0,95/We115 and Q = 0.073 Re°-95/We115, respectively.[470]... 

For the transition from Ligament to Film/Sheet Formation regime or the reverse transition, the equation of Hinze and MilbornJ112 QX = 0.340 Re2/3/We° 883, may be used to predict the dimensionless transition flow rate for liquids of low viscosities (less than a few poises). For more viscous liquids, the equation derived by Tanasawa et al.,[48°l QX = 0.297 Re6/5/We, is applicable for the calculation of the dimensionless transition flow rate. 

Figure 4.3. Regimes in centrifugal atomization of melts Direct Droplet Formation, Ligament Disintegration, and Film/Sheet Disintegration.

Current breakup models need to be extended to encompass the effects of liquid distortion, ligament and membrane formation, and stretching on the atomization process. The effects of nozzle internal flows and shear stresses due to gas viscosity on liquid breakup processes need to be ascertained. Experimental measurements and theoretical analyses are required to explore the mechanisms of breakup of liquid jets and sheets in dense (thick) spray regime. 

It is commonly accepted that there are three disintegration regimes for liquids discharged from a rotating disk, namely direct drop, ligament, and sheet formation - (Figure 6.3). 

Senuma also reported that in the ligament formation regime, drop size resulting from the breakup of the ligaments in disk atomization is, according to Weber s theory, given by Equation 6.19... 

Another BEM modeling of a jet in the atomization regime was done by Park and Heister [24]. They simulated a swirling jet by using the superposition theory, which implements a complex potential containing a vortex. This potential vortex provides a vortical flow that acts as the circumferential pressure caused by the swirling. Annular ligaments pinched from the parent surface are presumed to break into the... 

F. 29.10 (a) Formation of drops from ligaments formed on the downstream side of the jet in the shear breakup regime (b) schematic top view of the cross section of a nonturbulent Jet at which a droplet (or ligament) is being formed similar to panel (a) (a From Herrmann [12]. Reprinted with permission. Copyright (2010) ASME)... 

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