Optical distortion correction of a liquid-gas interface and contact angle in cylindrical tubes

Abstract

Objects inside cylindrical tubes appear distorted as seen outside the tube due to the refraction of the light passing through different media. Such an optical distortion may cause significant errors in geometrical measurements using optical observations of objects (e.g., liquid-gas interfaces, solid particles, gas bubbles) inside the tubes. In this study, an analytical method using a point-by-point correction of the optical distortion was developed. For an experimental validation, the method was used to correct the apparent profiles of the water-air interfaces (menisci) in cylindrical glass tubes with different tube diameters and wall thicknesses. Then, the corrected meniscus profiles were used to calculate the corrected static contact angles. The corrected contact angle shows an excellent agreement with the reference contact angles as compared to the conventional contact angle measurement using apparent meniscus profiles.

3D/4D-printed bending-type soft pneumatic actuators: fabrication, modelling, and control

“…Feedforward and feedback controllers were applied for the control of 3D/4D-printed SPAs (George Thuruthel et al 2018). Providing feedback information required for closed-loop control of SPAs demand availability of sensory feedback instruments that could be realized either using external measurement devices, such as camera (Marchese, Katzschmann, and Rus 2014) electromagnetic sensor (Wang et al 2014), optical sensor (Zhuang et al 2018;Darzi and Park 2017) or integrated flexible sensors (Khosravani and Reinicke 2020a) that do not compromise the conformability of the SPAs (Low et al 2017) ).…”

Effect of Bend Wettability on Hydrodynamics of Liquid–Liquid Two-phase Flow in Serpentine Mini Geometry

“…The test sections are fixed in a rectangular box filled with glycerol to reduce optical distortion in a liquid–liquid interface in a capillary …”

Versatile analysis of closed-end capillary invasion of viscous fluids

“…During the measurement, optical distortion was observed when the refraction of the light passed into different media: gas, glass, and fluid. The distortion increased in the radial direction, i.e., the image of R′ taken by camera was larger than the actual radius of curvature, but there was no distortion in the invasion direction [26]. Therefore, the sagitta (h s ) from the circular arc did not change, and the dynamic contact angle could be calculated from the sagitta and the measured capillary radius (r c ) using the following equation:…”