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Dr. Paul E. Dimotakis John K. Northrop Professor of Aeronautics and Professor of Applied Physics; Chief Technologist at JPL 105
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| Expertise Turbulence, turbulent mixing, chemically-reacting flows, combustion, laser diagnostics, digital imaging, numerical simulations of turbulence & gas dynamics, aerooptics. Field of Study Our group's research effort focuses on several areas in fluid physics and the dynamics of turbulence. Flow regimes of interest range from incompressible, low Mach number flow to compressible, supersonic flow and the study of turbulence under such flow conditions. A large part of this effort involves the investigation of turbulent mixing, chemical reactions, and combustion, in flows ranging from low speed liquid flows, to high speed supersonic flows with highly exothermic reactants. The chemical reactions can be operated in the slow to moderate chemical kinetic rate regime, to study the interplay of chemical reaction rate and turbulent mixing rate in the rate of chemical product formation and heat release, to the fast chemical kinetic regime. The latter permits the quantitative determination of the fraction of the turbulent fluid that is mixed on a molecular scale, under flow conditions that preclude a direct measurement of this important quantity. The experiments are conducted in both liquids and gases in an effort to extend our understanding of the role of the molecular species diffusivity in high Reynolds number turbulent flows. In another part of this effort, we are attempting to characterize and understand the stochastic geometric properties of turbulent interfaces in high Reynolds number flows to investigate whether ideas from fractal analysis can be extended to describe the behavior of these random surfaces. In addition to the fundamental significance of this relatively new aspect of turbulent fluid dynamics, the results of this work are applicable to many technologies, ranging from hypersonic flight propulsion to reduction in pollutant formation in stationary combustors. A second part of this effort attempts to investigate the feasibility of using active control techniques for the purpose of altering the behavior of fully developed turbulent flow. Recent advances in this area, such as rotary oscillations, have permitted us to lower cylinder drag and associated wake mixing, and to control shear layer growth using actively controlled airfoils in the sheared turbulent region. The experimental work relies on a variety of technologies, including laser diagnostics, digital image acquisition and processing, high speed data acquisition, and high signal-to-noise data acquisition and processing. The effort extends to the development of new diagnostics, if experimental requirements cannot be met through the use of presently available methods. By way of example, a new effort attempts to develop a new family of high resolution image sensors that will permit the recording of multiple images in quick succession. This will be augmented by research in digital image processing techniques that aim to extract not only scalar field image data but also velocity field measurements in the field of view. While this research is primarily experimental, it extends to analytical as well as computational fluid dynamics, often in collaboration with other faculty in Aeronautics and Applied Mathematics at Caltech, the Jet Propulsion Laboratory, and investigators at other universities. Selected Publications P. L. Miller and P. E. Dimotakis, "Stochastic Geometric Properties of Scalar Interfaces in Turbulent Jets," Phys. Fluids A3, 168 (1991) P. T. Tokumaru and P. E. Dimotakis, "Rotary Oscillation Control of a Cylindrical Wake," J. Fluid Mech., 224, 77 (1991) P. E. Dimotakis and P. L. Miller, "Some Consequences of the Boundedness of Scalar Fluctuations," Phys. Fluids A2, 1919 (1990) D. R. Dowling and P. E. Dimotakis, "Similarity of the Concentration Field of Gas-Phase Turbulent Jets," J. Fluid Mech., 218, 109 (1990) M. Zhuang, P. E. Dimotakis, and T. Kubota, "The Effects of Walls on a Spatially Growing Supersonic Shear Layer," Phys. Fluids A2, 599 (1990) |
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© 2007 California Institute of Technology. All Rights Reserved. last
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9 March, 2007
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