Research Summary - Christopher E. Brennen
Complex multiphase and multicomponent flows are a ubiquitous part of almost all existing and projected energy systems, and yet our understanding of these flows remains inadequate for many engineering purposes. In particular, our ability to predict the dynamic characteristics of multiphase flows or their behavior at high concentrations is very limited. Current research is focused on several of these fundamental issues. One such project is directed at improved understanding of the dynamics and acoustics of cavitation. Specific projects include: (1) studies of the interactions between cavitation bubbles and the flow and the implications for cavitation noise and damage (2) the population dynamics of cavitation nuclei of microbubbles and the relation to cavitation event rates (3) studies of the dynamics and acoustics of clouds of cavitation bubbles.
Another important research activity is our effort to understand the instabilities and unsteady flows that limit the design and operation of modern, high-speed turbomachines. Cavitation, which is inevitable in many pumps, provides one set of severe problems, and our laboratory was the first to measure the dynamic transfer function for a cavitating pump. More recent projects have included studies of the unsteady flows and forces due to rotor/stator interaction, and a substantial body of experimental work on rotordynamic flows and forces.
Other current research on multiphase flow includes studies of granular material flow and the behavior of other concentrated suspensions such as occur in fluidized beds. A particular focus is a study of the effects of imposed vibration on granular material flows and the potential use of such vibration in industry. In a related study in collaboration with Professor Melany Hunt we have made a extensive an detailed study of "booming dunes", the natural phenomenon in which high sand dunes produce a remarkable booming sound when wind-induced avalanches occur on their leeward slopes. In each of these granular flow projects there is a focus on developing instrumentation to make measurements of particle motions in dense media.
In more recent years, I have collaborated with colleagues at the University of Western Australia in studying various bubble and granular processes that occur in lakes, reservoirs and oceans. One such project has been the study of methane bubbles emerging from submerged granular beds. Another has been a study of the mechanisms of wave-induced mixing of solutes, nutrients and contaminants from granular beds into the overlying water.
Last updated 6/10/11.
Christopher E. Brennen, brennen@caltech.edu