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SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Monday, December 23, 2019 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Fast and Highly Compressible
Single- and Multi-Phase Reacting Flows

Dr. Yoram Kozak
Department of Aerospace Engineering
Texas A&M University, College Station, TX, USA

High flow speeds and significant compressibility levels can be found in a wide range of single- and multi-phase reacting flows. These include various propulsion and energy conversion systems, such as scramjet and detonation engines, industrial explosions, and different military applications. Better understanding of these extreme flow regimes is possible either by experimentation or numerical modeling. The latter requires the development of novel modeling approaches capable of providing high accuracy in these extreme regimes characterized by large spatial and temporal variability. In this talk, several unique numerical and experimental difficulties, each associated with a different flow configuration of interest, will be discussed. First, the limitations of the classical Eulerian-Lagrangian formulation for multi-phase flow modeling under highly compressible conditions will be presented. It is demonstrated that for highly compressible flows, typical interpolation methods fail and a Weighted-Essentially-Non-Oscillatory (WENO) interpolation can provide a superior alternative. This new formulation is then utilized to critically assess the accuracy of the classical Particle Image Velocimetry (PIV) technique for flow characterization in gas-phase detonations and high-speed turbulence. Also, newly developed numerical techniques and models for liquid spray and solid particle combustion will be discussed. Then, the dynamics of highly compressible, fast, turbulent flames capable of undergoing a transition to a detonation wave are studied using Direct Numerical Simulations (DNS) based on realistic experimental conditions. The results raise questions regarding the ability of the classical RANS and LES techniques to model properly the complex physics associated with these inherently unstable fast turbulent reacting flows. Finally, future research directions in the context of the problems discussed above will be presented.   

Bio: Dr. Yoram Kozak is a Postdoctoral Research Associate at the Department of Aerospace Engineering of Texas A&M University since 2017. He earned his BSc (2010), MSc (2012) and PhD (2016) degrees from the Department of Mechanical Engineering at Ben-Gurion University of the Negev in Beer-Sheva. His research interests include: Modeling of single- and multi-phase combustion processes; high-performance parallel computing including Direct Numerical Simulations (DNS); development of new numerical methods and Computational Fluid Dynamics (CFD) algorithms.

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New Opportunities with “Old” Material
By:
Boris Desiatov
Harvard University
Abstract

Lithium niobate (LN) is an "old" material with many applications in optical and microwave technologies. Conventional LN components, including modulators and periodically polled frequency converters, have been the workhorse of the optoelectronic industry. While its high χ2 nonlinearity, wide transparency window and low optical loss offer unique advantages, conventional LN devices are bulky and discrete due to the low index-contrast in ion-exchanged waveguides. In my talk, I will discuss our efforts aimed at the development of integrated LN platform, featuring sub-wavelength scale light confinement and dense integration of optical and electrical components, that has the potential to revolutionize optical communication networks and microwave photonic systems, as well as enable realization of integrated quantum photonic circuits.

On Thursday, December 19, 2019, 15:00
Room 011, EE-Class Building

Biomedical Spectroscopic Imaging with Scattered Light

Abstract

Optical spectroscopy emerged as a valuable tool to study live biological tissue at various scales and detect early disease in the human body. While fluorescence and Raman spectra are sensitive to molecular properties of tissue, light scattering spectra, originating from the extracellular matrix, subcellular structures, and other tissue inhomogeneities, carry information about tissue microscopic and macroscopic organization. In this talk we will discuss how scattered light can be used for noninvasive detection of invisible pre-cancer in such diverse organs as the esophagus or pancreas that seem to have little in common. We will show, however, that since pre-cancer in many organs is characterized by certain microscopic changes in epithelial cells, such as increase in nuclear size and nuclear density, light scattering signatures of those precancers are quite similar, allowing early cancer imaging and detection without the need for external markers.

                Light scattering signatures could also be used for sensing subnuclear and subcelluar structure of live cells, e.g. chromatin packing, organelle organization, and characterization of cell-derived exosomes. Nanoscale changes in the nuclear structure have been shown to play a critical role in genetic and transcriptional alterations and are a hallmark of neoplasia. However, due to the lack of technologies for label-free nanoscale-sensitive measurements in live cells, many aspects of these phenomena have remained an open problem. We will discuss how the approach based on the combination of confocal microscopy and spectroscopy of scattered light could help to solve this problem, providing several critical advantages over the existing methods.

Biography

Lev T. Perelman is Professor of Medicine at Harvard University and Director of the BIDMC Center for Advanced Biomedical Imaging and Photonics. His research interests are primarily focused on application of optics to medicine and biology. Perelman’s group pioneered biomedical light scattering spectroscopy for noninvasive detection of early precancerous changes in epithelial tissues and tissue characterization on a subcellular scale, and developed confocal light absorption and scattering spectroscopic (CLASS) microscopy for label-free functional imaging of live cells, recently employed, in collaboration with R. Kalluri, to demonstrate that subcellular exosomes perform cell-independent microRNA biogenesis and promote tumorigenesis. Working with K. Kneipp at MIT he demonstrated single molecule detection with surface-enhanced Raman scattering (SERS), and explained the role of stress confinement in short pulse laser ablation, a basic mechanism of laser surgery widely used now in neurosurgery and ophthalmology. He also developed, with J. Marshall, the first nonhydrostatic model of the ocean, the MIT General Circulation Model. Perelman has mentored 30+ graduate students and postdoctoral fellows, and 9 are now tenured professors at Princeton, Northwestern, and other universities.

ביום שני 9.12.19, בין 12:00-16:00 בלובי בניין וולפסון להנדסה מכנית צוות הגיוס של חברת Western Digital ספקית פתרונות האחסון הגדולה בעולם, מגיעים אלינו לפקולטה להנדסה אוניברסיטת תל אביב ומחפשים את הסטודנטיות והסטודנטים של הנדסת חשמל ומדעים להייטק