Development of a digital image projection technique to measure wind-driven water film flows

Digital fringe projection (DFP) profilometry has been widely used to generate threedimensional (3D) surface information. In this work, a novel 3D shape measurement system based on DFP technique is proposed for accurate and quick thin film/rivulet flow measurement. The key concept of the technique is making use of digital image correlation (DIC) algorithm to direct calculate the projected grid points' displacements. In comparison to fourier transformation based DFP system, it gives more accurate measurement result without rigid image quality requirement. This technique was applied to characterization of wind-driven thin film/rivulet flows that were formed in an open circuit wind tunnel. The film thickness and surface wave frequency had been evaluated for variety of wind speeds and flow rates. The results show that this technique successfully revealed the dynamic motion features of thin film flows.