Static droplet test

The primary physical parameters, such as the fluid/fluid and fluid/solid interaction parameters, need a priori evaluation through model calibration using numerical experiments. The fluid/fluid interaction gives rise to the surface tension force, and the fluid/solid interaction manifests in the wall adhesion force. The fluid/fluid and fluid/solid interaction parameters are evaluated by designing two numerical experiments, the bubble test in the absence of a solid phase, and the static droplet test in the presence of solid wall, respectively. The details of these numerical experiments are detailed elsewhere. ... 

Two methods of capsule formation were employed static beaker tests and atomizer screenings. In the beaker tests, which comprised the first phase of the screening (Step 2 of Fig. 1), a small volume of inner polymer solution was extruded from a Pasteur pipette as a droplet (nominally 2-3 mm) into a receiv-... 

It would be extremely rare to have laboratory data of droplet coalescence for a given system. Qualitatively, we would expect droplet size to increase with retention time in the coalescing section and with heat input, which excites the system, leading to more collisions of small droplets. Droplet size could be expected to decrease with oil viscosity, which inhibits the movement of the particles and decreases the force of the collision. While it may be possible to predict the droplet size at the inlet to the treater, the shearing that occurs at the inlet nozzle and inlet diverter coupled with the coalescence that occurs at the oil-water interface cannot be determined. The treater represents a dynamic process, which cannot be adequately simulated by static laboratory tests. 

An AC corona discharge in the throat leads to a cloud of charged droplets whose large momentum allows very long travel distances. Multiple devices for eliminating static discharges in powder silos have been tested [41] but the tests did not address typical flow rates for large capacity, dense phase pneumatic transfer operations. 

After the static test mentioned above, the method is now tested for the impact and spreading of a glycerin droplet on a wax substrate and the computational results are compared with the experimental data of Sikalo et al. [32], The details of the experimental setup, material properties and computational model can be found in Refs. [33, 51]. The computed and experimental spread factor and contact line are plotted in Figs. 19a and b, respectively. These figures show that the present front-tracking method is a viable tool for simulation of interfacial flows involving moving contact lines. 

The data are used to give an indication of stability and the geometry of the droplets. Flocculation of the emulsion can be detected. In tests of flowing and static emulsions, it was shown that the flowing emulsions have lower static permittivities (52). This was interpreted as indicating flocculation in the static emulsions. 

However, to date, it is generally agreed, by both researchers and practitioners that bottle testing is still a good guide (257). The bottle test is static and does not model closely the dynamic effects of water droplets dispersed or coalescing in the actual equipment such as control valves, pipes, inlet delivery, baffles, water wash, ete. If the point of injection of chemicals is upstream of the settler, then the test approximates the situation better. It is, however, still crucial that the characteristies of the emulsion be understood before the treatment system is selected (273, 274). 

The present work investigates the static and dynamic behaviors of liquid droplets on 14 silicon wafers coated with one of two substrate materials with standard semiconductor industry processes. Wafers 1-10 were textured with an array of squares containing a nanopattem of linear grooves, and wafers 11-14 were unpattemed. Since the patterns were anisotropic, each test was conducted in two directions — parallel and perpendicular to the pattern. These directions could be easily tracked by their relation to the wafer notch. A schematic of the patterned wafers is shown in Fig. 1. 

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