液体中ガス吹き込みにおけるジェッティングの特性

抄録

The present study is concerned with jetting behavior of gas jets injected into water bath. Nitrogen gas (20010 000 cm³/s) was injected into the water bath through an orifice of 0.10.3 cm in diameter located at the bottom. The gas jet behavior was observed directly by using a high speed cinecamera. The frequency of the bubble knocking at the bottom was measured with a microphone.
It is found that the bubbling-jetting transition of gas jets injected into water begins to occur when the gas-flow velocity at the exit of an orifice exceeds the sonic velocity. This phenomenon is similar to the behavior of gas jets in mercury bath. In the sonic region the frequency of bubble knocking decreases with increasing gas-flow velocity. At the highest gas-flow velocity explored in the present study perfect jetting is found to occur. The injection pressure in this case is 30 kgf/cm². The initial expansion angle of jet increases with increasing gas-flow velocity and agrees well with theoretical calculation. From this, it is presumed that the speed of a gas jet which is equal to the sonic velocity at the exit of the orifice exceeds the sonic velocity just beyond the exit.