µPIV measurements of the phase-averaged velocity distribution within wavy films

Abstract Thin-film flows are frequently used in process engineering and therefore of great interest research. In most cases, waves occur which have a positive effect on the material heat transport significantly influence dynamics film flow. A combination µ-particle image velocimetry confocal chromatic distance measurement is to measure phase-averaged flow velocities naturally developed waves. trigger signal sent PIV system recording starts when wave reaches crest threshold. This makes it possible µPIV depending thickness. The focus this work triggering crest. functionality quality measurements depend correct positioning sensor, with light spot at level camera section. Simultaneously, minimum, average, maximum thickness, as well amplitude frequency, recorded. Film investigated glass plate various angles (5°, 10°, 15°) inclination, Reynolds numbers (30-200), positions. results compared theoretical solutions according Nusselt. addition, tilt angle measuring position explained. position, particular, has non-negligible since characteristics largely dependent streamwise position. Compared Nusselt, thicknesses greater due presence With increasing inclination measured mean increase. They almost double increases from 5° 15°. When comparing (300–500 mm), noticeable that increase between 5 15%, angle, development gravity.