Wed September 15th 2010
Seminar On bubble motion and clustering of bubbles in a dilute surfactant solution
Yoshi Tagawa


A bubble motion is quite sensitive to contamination of water. In this seminar, experimental investigations of surfactant effects on a single bubble motion in quiescent water and upward bubbly flow in a rectangular channel will be presented.

A 2mm single bubble in quiescent purified water rises along zigzag or spiral path (The Leonardo paradox!). Here, a small amount of surfactant plays a great role. It changes surface boundary condition from free-slip to no-slip, which affects not only drag force but also lift force. An addition of surfactant can even expand the bubble horizontal motion though it decreases bubbleĀ¹s speed. For the experimental force calculation, two cameras follow a rising bubble to observe its shape and instantaneous acceleration preciously.
Holographic system for 3-D PTV measurement is also introduced.

Upward bubbly channel flow with surfactant is also investigated. Bubble clustering near a wall is observed when the local void fraction distribution is wall-peaking. A certain amount of surfactant changes it from wall-peaking to uniform. This is because shear-induced lift force on an 1mm spherical bubble decreases due to the change of the slip condition, and the tendency of the lateral migration toward the wall becomes weaker.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing