UNH Ocean Seminar

Bubble Plumes with Small Gas Inflow Rates—Physics and Modelling

Chris C.K. Lai
Assistant Professor

School of Civil and Environmental Engineering
Georgia Tech 

Friday, Mar. 12, 2021, 3:10pm

Two-phase plumes laden with gas bubbles or heavy particles are ubiquitous in geophysical flows, e.g., volcanic eruptions and natural gas seeps, and in engineering e.g., wastewater buoyant jets. From an environmental protection and management perspective, it is necessary to predict the trajectory and volume flux of these plumes as they mix with the surrounding fluid. Traditionally, the mean flow properties of these plumes are predicted by following (with appropriate modifications to account for the dispersed phase) the integral plume formulation by Morton, Taylor, and Turner (1956). This formulation has been proven to be simple, versatile, and effective. At its core, the approach hypothesizes that the increase in plume volume flux is due to entrainment which can be modeled by an entrainment coefficient α. This entrainment hypothesis implies that the plume width grows linearly with distance. In this talk, Dr. Lai will show that the hypothesis does not apply in air-water bubble plumes with low gas inflow rates. The plume growth instead follows a diffusion process with a width growing with the square-root of distance. Such plumes are called weak plumes to distinguish them from the classic, strong plumes. A unified scaling framework will be presented to bridge the weak and strong plumes.         


Chris Lai is an assistant professor in the School of Civil and Environmental Engineering at Georgia Tech (GT). Before joining GT in November 2019, he worked for three years as a postdoctoral research associate of the Extreme Fluids Team at the Los Alamos National Laboratory in New Mexico. He was awarded his PhD degree in 2015 from Texas A&M University, and his MPhil and BEng degrees in 2010 and 2007 from the University of Hong Kong, all in civil engineering. His research interests are in the broad areas of environmental fluid mechanics and experimental fluid mechanics. Currently, his group focuses on multiphase flow turbulence, and heat and mass transfer across a melting ice interface.