Wake Flow of the Ventilation Cylinder

Injecting air into water serves as an effective measure of generating bubbles. The characteristics of the background water flow must exert a significant effect on the bubbles trapped. In this chapter, it is intended to reveal the bubbly flow pattern downstream of a cylinder. Therefore, a cylinder is installed in the horizontal transparent section of a water tunnel. Particle image velocimetry technique is used to measure flow velocity downstream of the cylinder under no-ventilation condition. Air is injected into water flows through a flow passage inside the cylinder. High-speed photography, in association with a LED light source, is utilized to capture consecutive images of moving bubbles downstream of the cylinder. With the research techniques, it is expected to obtain primary bubble parameters such as velocity, Sauter mean diameter and volume fraction. Furthermore, the relationship between carrier flow characteristics and bubbly flow pattern is expected to be established.