ESTABLISHMENT TIME OF LIQUID FLOW IN A BATH AGITATED BY BOTTOM GAS INJECTION

The establishment time of gas-liquid two-phase flows in a cylindrical bath agitated by bottom gas injection through a central single-hole bo ttom nozzle was investigated. Because the turbulence intensity in the bath was comparable to or larger than the unity, the conventional defi nition of the flow establishment time based on the history of mean vel ocity was not suitable for the present case. In fact, it was difficult to determine the flow establishment time based on the well-known 90 o r 99 pct criterion for the mean velocity. Accordingly, two methods of determining the flow establishment time by focusing on the turbulence components instead of the mean velocity components were proposed. Velo city measurements were made with a two-channel laser Doppler velocimet er. The flow establishment time was correlated as a function of gas fl ow rate. Close agreement was obtained by the two methods.