NUMERICAL INVESTIGATION OF ELONGATED BUBBLE CHARACTERISTICS AND PRESSURE FLUCTUATIONS IN HORIZONTAL AIR–WATER TWO-PHASE SLUG FLOW

抄録

 Air entrainment phenomena often occur in hydraulic structures such as the head-tank spillway of hydro power plants and urban stormwater systems. When the air–water mixture flow is discharged to the submerged downstream tank, both shock and noise occur owing to the instantaneous release of elongated bubbles. In other words, the air hammer phenomenon occurs. This study considered two-phase air–water slug flow with air hammer phenomena in a horizontal circular pipe with an internal diameter of 100 mm, and investigated the influence of the computational grid size on the length and velocity of the elongated bubbles, the energy loss, and the pressure fluctuation to contribute to the quantitative evaluation of the air hammer phenomenon using computational fluid dynamics (CFD). The numerical results were validated by experimental results.