Experimental free coating flows at high capillary and Reynolds number

Experimental studies are carried out to enhance the fundamental understanding of coating processes over a broad parametric range. Experiments herein identify the phenomena leading to the formation of an asymptotic meniscus profile, which eventually develops a cusp at the interface. The non-dimensional parameters that describes these phenomena are identified. In addition, flow visualization is carried out to reveal the entire flow structure using a visible laser. Two phenomena of free coating are identified depending on a parameter called the property number (Po). When Po is larger than about 0.5, the non-dimensional final film thickness (T0) becomes constant beyond the capillary number (Ca) of about unity. When Po is less than about 0.1, T0 depends on Ca and the Reynolds number (Re) but it becomes constant beyond the Weber number (= Ca Re) of about 0.2. In both cases T0 becomes constant as the effect of surface tension on the meniscus becomes relatively unimportant. The cusp formation is due to the effect of inertia (Re). The effect of applicator dimensions on T0 is also investigated for large Re flows.