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Special CEAFM Seminar : 2017

Speaker: Dr. Matthew J. Rau (Naval Research Lab)
Title:
"Marine Floc Breakup in Turbulent Flow"
Hosted By: Joseph Katz (ME)

Date: Friday, June 9, 2017 (Special Date)
Time: 11:00 a.m.
Location: Latrobe 106 (Special Location)


Abstract

Aggregation of marine particles is a key part of the ocean biological pump. Aggregation collects sub-micron- and micron-sized particles into larger flocs, which can then settle out of suspension from the ocean surface. It is through this process that carbon and other material is sequestered into the deep ocean. Turbulence in surface waters can act to break up these fragile flocs, lengthening their lifespan near the surface. Our current lack of understanding of floc breakup makes predicting the fate of marine particulate matter, and ultimately the uptake of carbon by the ocean, very challenging. As a step towards understanding the breakup processes, flocs of clay particles have been studied in controlled turbulent flow conditions in the laboratory. Flocs are grown in a large aggregation tank before being subjected to fully developed turbulent pipe flow at Reynolds numbers of up to 16,000. Particle size distributions are measured using in-situ sampling of the small-angle forward light scattering function and through direct microscopic imaging. Floc size is compared before and after exposure to both laminar and turbulent flow conditions and found to be a strong function of the dissipation rate of turbulent kinetic energy. Hydrodynamic conditions within the aggregation tank are found to have a large influence on overall floc strength. The feasibility of developing remote sensing techniques to quantify floc breakup in the ocean is also confirmed, as changes in spectral light attenuation measurements are shown to occur with changes in floc size during breakup.

Bio

Dr. Matthew J. Rau is currently a National Research Council Postdoctoral Fellow with the Remote Sensing Division at the U.S. Naval Research Lab and will be starting as an Assistant Professor of Mechanical Engineering at the Pennsylvania State University this August. He previously received his doctoral degree from Purdue University working with the Cooling Technologies Research Center. Dr. Rau’s current research focus is on the study of flocculated marine particulate matter and its interactions with turbulence in the ocean. In addition to marine particulate matter, he also has an extensive background in the study of boiling heat transfer, including the application of tomographic particle image velocimetry for the study of subcooled two-phase jet impingement. Dr. Rau’s research interests revolve around the experimental study of turbulent multiphase flows for heat and mass transfer applications relevant to energy sustainability and our understanding of the environment.



Upcoming Seminar

Speaker: Dr. Christin Murphy (Naval Undersea Warfare Center, DIVNPT)
Title: "Whiskers as Hydrodynamic Sensors: Structures, Signals, and Sensitivity"

Date: December 8, 2017
Time: 11:00 a.m.
Location: Hodson Hall 210

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