A plunging jet is a powerful tool for the agitation of a bath as well as the entrapment of fine powder into the bath. As a fundamental model study of the development of novel refining processes using a plunging jet, the mixing time in a cylindrical water bath agitated by the jet was measured with an electric conductivity meter. The measured values of the mixing time depended significantly on the aspect ratio of the bath. Two empirical equations of the mixing time were proposed for two aspect

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... io regimes; regime 1 (aspect ratioഡ 0.3ϳ1.0) and regime 2 (aspect ratioഡ1.0ϳ2.0). Uniform mixing was established in regime 1 just after the completion of plunging. The mixing time in regime 2 became much longer than that in regime 1. The relationship between the mixing time and the rate of dissipation of energy density was also discussed. In regime 1, a plunging jet had higher mixing ability than gas injection.