Drop impingement and interaction with a solid surface

Experimental and theoretical studies on the impaction of a single drop on solid surfaces were conducted to provide a foundation for conducting further investigation on drop impingement onto textiles. Splashing phenomena, which are not relevant to ink jet printing, were therefore not included in this study. A fundamental understanding of the fluid dynamics associated with drop impingement is important for the overall process development and further advancement of understanding ink jet printing quality on textiles. The impacting and spreading of liquid drops on solid surfaces is also of significant scientific and practical importance in other applications such as spray coating, delivery of agricultural chemicals, and spray painting.; The experimental study showed the influence of kinetic energy, liquid-solid interaction and energy dissipation on the impact process. The results are reported for Reynolds number from 180 to 5513, Weber number from 0.2 to 176, four different liquids (distilled water, n-octane, n-tetradecane, and n-hexadecane), and four different surfaces (glass slide, uncoated silicon wafer, HMDS coated silicon wafer, and Teflon film).; A single drop impacting on a rough surface simulating a textile fabric was also investigated. For a smooth surface, the liquid flows radially outward from the impact point. In contrast, for the rough surface simulating a fabric, much of the liquid flows in the filament axial direction rather than in the transverse direction because of the roughness in the transverse direction. Also, the spreading and retracting shapes and maximum spreading ratios depend on the impact position.; The effect of reusing surfaces in consecutive impaction tests on spreading ratio and equilibrium contact angle on was studied. The results depend on the interaction of the liquid with the surface. For water drop on a hydrophilic surface, initial spreading ratio is not greatly affected, but maximum spreading ratio for surfaces rewetted twenty times is about 20% greater than for surfaces previously unused. For the rewetted surfaces, retraction rate from maximum spreading ratio is lower, and equilibrium spreading ratio is slightly greater. Once a surface is reused, the effect of further reusing is much smaller, and there is little difference in spreading ratio for the surfaces reused nine and twenty times. On the other hand, the results indicated that the effect of reusing hydrophobic surfaces with either hydrophilic (water) or hydrophobic (n-octane and n-hexadecane) liquids is extremely small. (Abstract shortened by UMI.)...