Study on mechanism of occurrence of carry-under by liquid jet

Bubble carry-under into the water pool was examined. In experiments, a water jet from a nozzle of 5 mm in diameter plunged into the water pool. The present experimental results showed that the water jet disintegrated into small drops on the way from the nozzle outlet to the pool surface when the flow rate of the water jet was small; the carry-under was observed. As flow rate of the water jet was increased, the surface of the water jet became smooth and no perturbation was observed; the carry-under was not observed in this situation. As the flow rate of the water jet was further increased, large waves came to appear on the water jet surface; the carry-under was observed again. From these observations, the criterion of the carry-under was obtained through energy balance: kinetic energy of liquid jet and surface energy of pool-surface. (author)