Surfactant effects on single bubble motion in quiescent water and upward bubbly flow in a rectangular channel are investigated. Generally, path instability of the single bubble and the bubble motion in inhomogeneous flow are sensitive to the contamination of water. Addition of surfactant in gas‐water system yields immobilization of the bubble surface due to Marangoni effect. Single bubble 3D trajectories in dilute surfactant solution are measured by two high‐speed cameras. All measured trajectories are plotted on two‐dimensional field of bubble Reynolds number Re and instantaneous boundary slip condition. In free‐slip and no‐slip condition, bubble motions are dependent on Re. However, in half‐slip condition, bubble motions are spiral and almost independent from Re. Bubbles in certain condition move along trajectories changing from spiral to zigzag. These interesting motions are caused by changing slip condition. Bubble motion in upward channel flow is also observed. The local void fraction distribution changes from wall‐peaking to uniform by stronger Marangoni effect. This is because that shear‐induced lift force on 1 mm spherical bubble decreases due to the change of the boundary condition of the bubble surface from free‐slip to no‐slip, and the tendency of the lateral migration toward the wall becomes weaker.

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