Shear-driven Film Separation

Dynamic thin liquid films driven by an adjacent gas flow have been subject to many investigations due to their presence in many engineering applications. More specifically though, the behavior of such films at a sharply expanding corner has received little attention, but can be observed in internal combustion engines, liquid atomizer systems, and refrigerant flows in evaporators. Efforts to validate computational models of the propagation and separation of films are limited by the lack of reliable non-intrusive techniques to measure and analyze dynamic film parameters. In this study, film propagation models and film separation models were validated separately using experimental measurements. For film thickness measurement, a laser focus displacement instrument was used following a theoretical and experimental qualification of the instrument. Thickness measurements with corresponding film velocities were then compared to the computational results of two numerical simulations. The experimental facility was also used to measure film separation at a sharp corner, and two film separation models were validated using these measurements.