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Proceedings of the 27th National and 5th International ISHMT-ASTFE Heat and Mass Transfer Conference December 14-17, 2023, IIT Patna, Patna-801106, Bihar, India
December, 14-17, 2023, Bihar, India

Experimental investigation of shape evolution and contact angle measurement of droplets over the vibrating liquid surface

Get access (open in a dialog) DOI: 10.1615/IHMTC-2023.1740
pages 1065-1070


The droplets over the vertically oscillating surface have a wide range of academic and industrial applications, as it is essential for several engineering applications, including spray cooling, inkjet printing, heat treatment, and fuel injection systems. Also, it is widely used in targeted drug delivery and lab-on-chip systems for diagnostics. This paper uses digital and analogue imaging techniques to determine the morphology of water, castor oil, and silicon oil droplets over the vibrating liquid surfaces of castor oil, water, and silicon oil, respectively. The droplets' shapes and an enlarged perspective of the contact zone are displayed in a series of images. The study reveals that small-size silicon oil droplets are spherical over the substrate surface, whereas castor oil droplets form circular patches over the water surface, irrespective of their size. The Bond number for water and silicon oil droplets varies between 0.24−1.13 and 0.08−1.51, respectively. Weber's number of droplets increases parabolically with the average velocity of the droplet. Furthermore, we found that the smaller droplets exhibit more propulsion velocity than larger droplets at the same frequency level. The average velocity of silicon and castor oil droplets lies in the range of 0 to 0.60 cm/s and 0 to 0.68 cm/s, respectively, when the vibration frequency increases from 20 Hz to 100 Hz in step 20. We also measured the contact angle of the droplets, and the result shows that the water droplet contact angle over the castor oil surface before they encapsulated in the substrate lies in the range of 16° to 26°. However, the contact angle of silicon oil droplets over the substrate is close to 90°.