In the present study, we investigate the effect of contaminant to the motion of a rising bubble. As is well-known, a bubble in contaminated water rises much slower than that in pure water and the rising velocity in contaminated system can be less than a half of that in pure system. Further, Zhang & Finch recently reported very interesting phenomenon through experiment. They reported that transient distance to reach steady terminal velocity also strongly depends on the surfactant concentration in bulk liquid. Here, we conducted numerical simulations of rising bubble related to this phenomenon, taking "Marangoni effect" into account. We also conducted the experiment related to this phenomenon, using super-purified water with the addition of various amount of three kinds of surfactants (1-pentanol, 3-pentanol and Triton X-100). It is shown that the present numerical results represent the experimental results well and that the transient phenomenon largely depends on the surfactant characteristics.
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