Rise characteristics of gas bubbles in a 2D rectangular column: VOF simulations vs experiments

Abstract

About five centuries ago, Leonardo da Vinci described the sinuous motion of gas bubbles rising in water. We have attempted to simulate the rise trajectories of bubbles of 4, 5, 7, 8, 9, 12 and 20 mm in diameter rising in a 2D rectangular column filled with water. The simulations were carried out using the volume-of-fluid (VOF) technique developed by Hirt and Nichols (J. Computational Physics., 39, 201-225 (1981)). To solve the Navier-Stokes equations of motion we used a commercial solver, CFX 4.1c of AEA Technology, UK. We developed our own bubble-tracking algorithm to capture "sinuous" bubble motions. The 4 and 5 mm bubbles show large lateral motions observed by Da Vinci. The 7,8 and 9 mm bubble behave like jellyfish. The 12 mm bubble flaps its wings like a bird. The extent of lateral motion of the bubbles decreases with increasing bubble size. Bubbles larger than 20 mm in size assume a spherical cap form and simulations of the rise characteristics match experiments exactly. VOF simulations are powerful tools for a priori determination of the morphology and rise characteristics of bubbles rising in a liquid. Bubble-bubble interactions are also properly modelled by the VOF technique.