Abstract
A cylindrical bath is strongly agitated by a swirl motion of a bubbling jet. This swirl motion is useful for wastewater treatment. Wastewater sometimes contains sludge in it. So far, the effect of sludge on the swirl motion has not been investigated. Air, silicone oil, and spherical particles are used in this study as the models for a mixture of ozone and air, wastewater, and sludge, respectively. The density of the particles is lower than that of silicone oil, and accordingly, they initially float on the bath surface. In the presence of the swirl motion, they are carried deep into the bath due to strong mixing ability of the swirl motion. The occurrence condition and basic characteristics of the swirl motion are investigated. An apparent kinematic viscosity is introduced for correlating the period, amplitude, starting time, and the damping time of the swirl motion. Empirical equations are proposed for these quantities.
