초록 열기/닫기 버튼
Self-entrainment of air occurs when water is supplied through a venturi nozzle with an air hole in its throat. To study the characteristics of air entrainment, the air flow rates and air volume ratio were measured. The flow inside the nozzle was visualized for various diverging angles and water flow rates. The results shows that air entrainment increases with the water flow rate; however, the air volume ratio remains almost constant. Furthermore, air entrainment is the highest at a diverging angle of 40°. As the water flows downstream, an annular, two-phase flow starts to form in the diverging section, changing the flow pattern to a churn flow. This sudden expansion in the diverging section induces a vortex separation that blocks the pathway of air entrainment when air bubbles are present in the vortex.
