Path instability of rising bubble in water

KUSUMASTUTI, Yuni, Prof. Ir. Suryo Purwono, M.A.Sc., Ph.D

2008 | Tesis | S2 Teknik Kimia

The hydrodynamic of single rising bubble under stagnant water, including both the shape deformation and its path instability, was investigated experimentally. The experiment conducted within a plexiglass column, was equipped with simultaneous of two high speed CCD camera recording at both sides. Using approximately 500 frames per second of the record rate, many experiments were focused on 2-4 mm of bubble diameter. Both the shape deformation and the motion of single rising bubble were recorded during its rising from the release point on the top of needle up to a certain distant above it. Knowing both position and the time elapsed between consecutive frames, the mean rise velocity was obtained, more or less 24.43 cm/s. From this measurement, it is indicated that the bubble behaves in impure water system, compare with that reported in the literature for the same region of ellipsoidal bubble. During the motion, the bubble change its shape from ellipsoidal shape with axis-symmetric to shape which is far away from ellipsoidal shape. The experimental result suggest the different forces acting on the bubble causing its shape to oscillate, thus the path instability occurs. As consequently, its velocity fluctuates even though after a certain time, the mean rise velocity of the bubble is statistically unchanged. In addition, from the captured picture, it showed that the produced bubble have a regular zig-zag rise path where the zigzagging motion path was confined with a new plane, among the horizontal and vertical planes.

Kata Kunci : Hidrodinamik, Naiknya bible dibawah stagnasi air