Algorithm to Measure Three-Dimensional Velocity of Individual Bubble Acquired with Wire-Mesh Sensors

A two-phase flow often exhibits a complicated three-dimensional structure by nature even in a simple vertical pipe. In order to model such a complicated flow structure and to validate multiphase flow CFD, experimental database for three dimensional velocity and void fraction distributions are crucial. The paper addresses an algorithm to measure three-dimensional velocity of individual bubble with a bubble paring scheme. The bubble paring scheme finds a pair of bubble in two sets of wire-mesh sensor data to determine the direction and magnitude of velocity vector for each bubble. The devised scheme was applied to the vertical upward air-water flow (jG=0.64m/s, jL=0.64m/s) in a large diameter pipe (i.d. 224mm). The bubble pairing scheme visualized the developing process of two-phase flow: large bubbles coalesced with each other to move toward the center, while the rest of bubbles broke up into smaller bubbles and decelerated.