Analytical studies of the penetration dynamics of starting forced plume

• Main Author: Toh, Vincent Woon Sen.
• Other Authors: Yu, Simon Ching Man
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/15427
• Institution: Nanyang Technological University

Plumes are a formed when a fluid discharges into another fluid of a different density. These are common phenomenon and can be seen as hot ashes being released during a volcanic eruption. The study of mixing and entrainment of plumes is therefore of environmental focus. While the far-field penetration of the plume has been properly documented, the near-field is yet to be understood. Therefore, near-field studies for the penetration dynamics of plumes will be the focus of this project study. A comprehensive analysis on the penetration dynamics that covers the entire development of the starting plume is proposed. This development encompasses the initial period to the transition and the final evolution of the plume. In particular, three separated stages are analyzed during the initial to the transition period, namely starting vortex formation, trailing stem appearance to vortex pinch-off, and vortex-stem reconnection. These stages have been formulated with the use of geometrical and fluid mechanics equations to explain the penetration dynamics. In the analytical results, a larger reduced gravity will generally give rise to a longer plume development time and a farther plume penetration. However, this phenomenon might not exist for a larger buoyancy-induced momentum plume as a buoyancy-induced dominated plume results in shorter time frame between pinch-off and reconnection. In general, the analytical results have shown to be in good agreement with the experimental results of Ai et al. [1] and Sangras et al. [7], especially in the far-field. As of now, the deficient in near-field experimental data is accredited to the inability of conventional methods to record plume penetration. Therefore, there is insufficient experiment data in this region of plume dynamics to validate the near-field accuracy of the analytical model. However, this model is sufficiently accurate when approximation for the far-field is concerned.