Mean Flow and Turbulence of Water in a Cylindrical Vessel Agitated by Bottom Air Injection

Abstract

Cold model experiments based upon aqueous systems were carried out to study the mean velocity and turbulence intensity in a cylindrical bath. The axial and radial velocity components in the cylindrical bath agitated by air injection through a centered single-hole bottom nozzle were measured using a two-dimensional laser Doppler velocimeter. The spatial mean kinetic energy for the time-averaged component k_{m, v} and that for the turbulence component k_{t, v} were obtained. It was found that k_{m, v} and k_{t, v} depended on 0.60 and 0.72 powers of the injected gas flow rate, respectively. The energy supplied by the injected gas into the bath therefore was more consumed to maintain turbulent motions than to do the mean flow, i.e., the circulating flow as the gas flow rate increased. Measured values of the spatial mean velocity V_{m, v}=(2k_{m, v})^1/2 were satisfactorily approximated by an empirical correlation proposed so far, but the dependence of the present V_{m, v} values on the bath depth H_w and bath diameter D was different from this correlation. The spatial mean turbulence intensity Tu_v=(k_{t, v}/k_{m, v})^1/2 was above unity under the present experimental conditions.