Domain breakup

The solution of the gas flow and temperature fields in the nearnozzle region (as described in the previous subsection), along with process parameters, thermophysical properties, and atomizer geometry parameters, were used as inputs for this liquid metal breakup model to calculate the liquid film and sheet characteristics, primary and secondary breakup, as well as droplet dynamics and cooling. The trajectories and temperatures of droplets were calculated until the onset of secondary breakup, the onset of solidification, or the attainment of the computational domain boundary. This procedure was repeated for all droplet size classes. Finally, the droplets were numerically sieved and the droplet size distribution was determined. 

Oil and water do not mix, but on addition of a suitable surfaetant a microemulsion can be formed depending on the relative concentrations of the three components. Microemulsions (i.e. surfactant/water/oil mixtures) can also be used as reaction media see references [859-862] for reviews. Microemulsions are isotropic and optically clear, thermodynamically stable, macroscopically homogeneous, but microscopically heterogeneous dispersions of oil-in-water (O/W) or water-in-oil (W/O), where oil is usually a hydrocarbon. The name microemulsion, introduced by Schulman et al. in 1959 [863], derives from the fact that oil droplets in O/W systems or water droplets in W/O systems are very small (ca. 10... 100 nm nanodroplets). Unlike conventional emulsions, microemulsion domains fluctuate in size and shape with spontaneous coalescence and breakup. The oil/water interface is covered with surfactant molecules and this area can amount to as much as 10 m per litre ( ) of microemulsion. 

Abstract This chapter reviews atomization modeling works that utilize boundary element methods (BEMs) to compute the transient surface evolution in capillary flows. The BEM, or boundary integral method, represents a class of schemes that incorporate a mesh that is only located on the boundaries of the domain and hence are attractive for free surface problems. Because both primary and secondary atomization phenomena are considered in many free surface problems, BEM is suitable to describe their physical processes and fundamental instabilities. Basic formulations of the BEM are outlined and their application to both low- and highspeed plain jets is presented. Other applications include the aerodynamic breakup of a drop, the pinch-off of an electrified jet, and the breakup of a drop colliding into a wall. 

A faster mechanism of domain growth was proposed for the coarsening of interconnected domain structures [10], for d=3, when the volume fraction of the minority phase is sufficiently large to maintain such a percolating structure. The key mechanism then is the deformaricni and breakup of tubelike regions in the domain structure. The characteristic velocity field Vf around domains having linear dimensions i is... 

Yet another domain still in need of research is the history of the German chemical industry since 1945. The breakup of I.G. Farben, the impact of occupation policies, the East-West division, the role of the chemical industry in the rapid expansion of the West German economy, and the place of the industry in the international economic scene and especially in relation to the international chemical industry, all are in need of further exploration. 

Detailed analysis of microstructure development within the extruder showed that, in the process of microstructure formation of extmdates, the deformation, coalescence, breakup, and relaxation of the dispersed phase were all involved. The process of deformation ofLCP domains in the shear flow before the extmder die was controlled by the viscosity. The shear flow before the die could result in the deformation and fibrillation ofLCP droplets, if the viscosity ratio (0.01 or smaller) favored the fibrillation. The coalescence and further deformation of the LCP domains in the die entrance lead to the increase in volume and aspect ratio of the fibrils [20]. 

Figure 8.12 shows the total area of the individual particles of the SAN-rich region as a function of the shear rate calculated from the image analysis of the previous TEM images (Fig. 8.11). Obviously, the area of the dispersed domains remarkably decreased with the shear rate and leveled off at high shear rates. As mentioned above, this is due to a competition of particle breakup and coalescence which may occur at high shear rate values.

In the case of PS/PVME blends studied by Polis et al., the phase separation results initially in a large increase in the low-frequency complex moduli which is attributed to the highly interconnected PVME-rich and PS-rich phases, formed during the spinodal decomposition. The subsequent decrease is the result of the loss of interconnectivity between the two phases due to the breakup and coarsening of the phase-separated domains (Fig. 10.48) (Polios 1997). 

---