Effect of frother on initial bubble shape and velocity

The effect of frother and NaCl salt on the shape and velocity of a ca. 2.4 mm diameter bubble close to the generation point at an orifice was studied using high-speed imaging. Bubbles accelerate to reach a maximum velocity at a given time depending on frother type and concentration, followed by deceleration and then oscillation about a mean velocity. A relationship between bubble shape and velocity is observed: the more spherical the bubble, the slower the rise, which is in agreement with recent literature. The findings support the argument that surfactants may affect bubble rise velocity through control of bubble shape. (C) 2010 Elsevier B.V. All rights reserved.