BEHAVIOR OF THE GAS-LIQUID INTERFACE IN A HORIZONTAL TUBE AFTER THE STEP CHANGE OF AIR FLOW.

We studied the behavior of the air-water interface in a horizontal tube caused by the step change of air flow above still water. As to the critical condition of wave generation, the experimental results are well explained by the theory of Kelvin-Helmholtz instability. This tendency holds true also in the case of different surface tension. The lower limit of air velocity for slugging in a short time (1. 75 sec) after commencement of the flow is about 3 m/s greater than the Wallis' results regarding the transition from the steady wavy flow.