Whole-field velocity measurements of isothermal bubble plume using PTV

The current work focuses on obtaining bubble dynamics properties in a plume by the shadowgraphy technique. Bubble parameters such as the bubbles diameter and velocities were estimated using an in-house developed algorithm. Two gases were independently used in this study, namely Sulfur-Hexafluoride (SF6) and Air. Three separate cases were observed: small (0.01 L/min), medium (0.15 L/min), and large (0.30 L/min) flow rates. The bubble plume was created by injecting the gas from the bottom of a glass tank. The tank was illuminated with two halogen lamps. High speed cameras were situated in the front of the tank. The average axial velocity of Air bubbles was calculated to be 13.25 cm/s, 13.92 cm/s, 28.17 cm/s for small, medium, and large flow rates, respectively. The average axial velocity of SF6 bubbles was calculated to be 8.05 cm/s, 8.02 cm/s, and 24.64 cm/s for small, medium, and large flow rates, respectively. It was found that as the bubbles position increased vertically, they were more buoyant-driven than flow-driven. The present study constitutes part of a larger project devoted to the analysis of thermal-hydraulic characteristics of bubble plumes. Results from these series of experiments are intended to provide new and accurate information for the development and validation of correlations used in two phase flow models. (author)