NUMERICAL STUDY ON LARGE BUBBLE CHARACTERISTICS AND PRESSURE FLUCTUATIONS IN HORIZONTAL AIR-WATER TWO-PHASE SLUG FLOW

Abstract

 Air entrained phenomenon can often occur in hydraulic structures, for example, head-tank spillway of hydro power plant, stormwater systems, and so on. When the air-water mixture flow is discharged to the submerged outlet tank, there is both shock and noise due to the instantaneous release of large bubbles; that is, the air hammer phenomenon occurs. In this study, in order to contribute to the quantitative evaluation of the air hammer phenomenon using computational fluid dynamics, the influence of the calculation grid on the size and velocity of the large bubble, the energy loss, and the pressure fluctuation was investigated. Furthermore, it was clarified that the calculation results on the two-phase air-water two-phase slug flow in a horizontal pipe, 100mm ID, was compared with the experimental results and that it could be reproduced accurately.