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Turbulent flows is topic of Director's Colloquium Jan. 26

Paul Dimotakis, the John K. Northrop Professor of Aeronautics and professor of applied physics at the California Institute of Technology, will address the theoretical justification and experimental evidence for turbulent flow transitions and discuss its consequences at a Director's Colloquium at 1:10 p.m., Monday (Jan. 26), in the Physics Building Auditorium at Technical Area 3. The talk is open to all Laboratory badgeholders.

The title of Dimotakis' talk is "The Mixing Transition: Experimental evidence, theory, and implications." The talk will review some of the experimental evidence that supports the notion that turbulent flows undergo a transition that takes place at values of approximately 100 Taylor (microscale) Reynolds numbers. This transition is observed in gas- and liquid-phase flows and is encountered in many geometries and configurations. Dimotakis will discuss how, in the context of mixing, this transition has been identified as a flow transition, in which a change/increase in mixing is only one of many manifestations.

Dimotakis' research at Caltech has focused on investigations of turbulent-flow phenomena, with an emphasis on turbulent transport and mixing in liquid- and gas-phase, chemically-reacting as well as non-reacting flows, and combustion. This research has yielded several important results on turbulent entrainment and mixing in compressible and incompressible free-shear flows.

Dimotakis has been responsible for the development of several experimental facilities, as well as diagnostic methods using lasers. He, along with members of his group, has introduced advances in signal processing, high-speed digital temporal- and image-data acquisition techniques, high-speed CCD imager design and image-data processing.

Dimotakis earned his undergraduate degree in physics, his master's degree in nuclear engineering and a doctorate in applied physics from the California Institute of Technology.

In some of his work as a consultant, Dimotakis has participated in the development of pilotless drones, high-power chemical lasers, the stealth fighter, contributed to the development of the Space Shuttle aerodynamics, assisted in the internal aerodynamics of sealed computer (Winchester) disks, helped with the fluid mechanics design of the "Leap-Frog fountain" at Disney's Epcot Center in Florida, and participated in experiments at the Lawrence Livermore Nova laser facility. He recently served on the National Academy of Sciences committee that reviewed the U.S. Inertial Confinement Fusion program.

He received an ASCIT teaching award in 1994-95 and was awarded the Northrop chair in February 1995. He has served associate editor for the Journal of Fluid Mechanics, and is presently a Fellow of the American Physical Society and an Associate Fellow of the American Institute of Aeronautics and Astronautics.

The colloquium will be broadcast on Labnet Channel 9 and can be accessed via the Internet using Real Media Player and IPTV technology.

For information about the Director's Colloquium program, go to http://stb.lanl.gov:8080/wosaserver/web?pg=/program/colloquium/upcoming.xml online.

-- Todd Hanson

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