CFD simulation of bubbly flow in a vertical pipe

• Main Author: Adarsh Gouda
• Other Authors: Tang Hui
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/55148
• Institution: Nanyang Technological University

Bubbly flow is widely encountered in many engineering applications, such as those in chemical and nuclear systems, bubble column reactors and oil transportation pipes. The deformation of bubbles as well as their interactions has significant effect on the flow field. Therefore, the understanding of bubble dynamics is extremely important for two-phase flow systems. The objective of current project is to numerically study air-water bubbly flow in a vertical pipe. The motions of the bubbles are tracked using the discrete phase model which is embedded in ANSYSY FLUENT. The dynamics of both single bubble and multiple bubbles in a vertical pipe is investigated. For single bubble dynamics study, the bubble is injected from the center of the inlet surface in the simulation domain. The bubble trajectory is tracked from the inlet to the outlet of the domain using both two-way coupling and one-way coupling. The effects of the bubble diameter and bubble injection velocity on the bubble movement in the vertical pipe are investigated. Bubble terminal velocity under different conditions is compared. It is found that the bubble terminal velocity increases with the increase of bubble diameter, whereas the bubble injection velocity has no much effect on the bubble terminal velocity. An equation for the bubble terminal velocity is proposed based on the studied cases. For multiple bubble dynamics study, the dense discrete phase model is used to investigate the volume fraction of bubble phase in the flow filed. Bubbles are injected through the inlet surface of the simulation domain with a uniform distribution. Water flow field as well as the bubble volume fraction at different locations is studied. It was seen that, inclusion of bubbles varies the velocity gradient of water near the wall region and also an increase in volume fraction of the bubbles causes decrease in axial velocity of the water.