Experimental study on shape and path of small bubbles using video-image analysis

This paper presents the results of an experimental study on the shape and path of small bubbles rising in stagnant water. Bubbles, generated at the bottom of the chamber holding water, rise through it. A high speed camera (1000 fps, Kodak, Model 1000 HRC) together with a 90 mm Macro lens is placed at a height of 60 cm from the bottom of the chamber. It is linked with a PC. The commercial software Sigma Scan Pro 5.0 and Adobe Photoshop are used for image capturing and processing. Bubbles (diameters 5.8, 16.2, 20.8 mm) were generated at the bottom of the chamber holding the water. We find that bubbles have two steady shapes, a sphere and an ellipsoid in this diameter range. The spherical bubble (5.8 mm) remains close to the vertical line of release, follows a zigzag path while rising though water. An ellipsoidal bubble (16.2, 20.8 mm) switches to spiral path.