Conferences, Lectures, & Seminars
Events for October
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Aerospace and Mechanical Engineering Seminar Series
Wed, Oct 01, 2014 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Lin Ma, Associate Professor in Department of Aerospace and Ocean Engineering at Virginia Tech, Blacksburg, VA
Talk Title: High Speed and Multidimensional Combustion Diagnostics
Series: Aerospace and Mechanical Engineering Seminar Series
Abstract: This talk describes our efforts to enable high speed and multidimensional measurements in turbulent combustion systems, which have been long desired for resolving the inherent three-dimensional spatial features and temporal dynamics of turbulent flames. This talk uses several examples to introduce our recent work on multidimensional diagnostics using tomography, and to discuss the unique opportunities that they can enable. Examples include the multidimensional measurements of mixture fraction, temperature fields, chemical species distribution, and instantaneous 3D flame topography. Combined with ruggedized hardware and robust data analyzing algorithms, such measurements have been successfully demonstrated in both laboratory flames and also practical combustion systems including a model scramjet combustor.
Biography: Lin Ma worked as a graduate research assistant from 2000-2006 in the High Temperature Gasdynamics Laboratory (HTGL) at Stanford University. He started his faculty career in 2006 after completing his PhD work, focusing on multidimensional laser diagnostics. His work on 2D mixture fraction measurement was recognized by the National Science Foundation with a CAREER award. He is also active in teaching and professional services. His teaching and research efforts were recognized by a Board of Trustee Award, and he is an active member of several professional organizations and technical committees.
Host: Professor Paul Ronney
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Valerie Childress
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
Aerospace and Mechanical Engineering Seminar Series
Wed, Oct 08, 2014 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Anirban Guha, Postdoctoral Fellow in Atmospheric and Oceanic Sciences at the University of California at Los Angeles, Los Angeles, CA
Talk Title: On the Connection between Wave Resonance, Shear Instability and Oscillator Synchronization
Abstract: Homlboe (Geophys. Publ., vol. 24, 1962, pp. 7-112) postulated that interaction between two or more progressive, linear interfacial waves produces exponentially growing instabilities in idealized (broke-line profiles), homogeneous or density-stratified, inviscid shear layers. We have generalized Holmboe's mechanistic picture of linear shear instabilities by (i) not initially specifying the wave type, and (ii) providing the option for non-normal growth. We have demonstrated the mechanism behind linear shear instabilities by proposing a purely kinematic model consisting of two linear, Doppler-shifted, progressive interfacial waves moving in opposite directions. Moreover, we have found a necessary and sufficient condition for the existence of exponentially growing instabilities in idealized shear forms. The two interfacial waves, starting from arbitrary initial conditions, eventually phase-lock and resonate (grow exponentially), provided the necessary and sufficient condition in satisfied. The theoretical underpinning of our wave interaction model is analogous to that of synchronization between two coupled harmonic oscillators. We have re-framed our model into a nonlinear autonomous dynamical system, the steady-state configuration of which corresponds to the resonant configuration of the wave interaction model. When interpreted in terms of the canonical normal-mode theory, the steady-state/resonant configuration corresponds to the growing normal mode of the discrete spectrum. The instability mechanism occurring prior to reaching steady state is non-modal, favoring rapid transient growth. Depending on the wavenumber and initial phase-shift, non-modal gain can exceed the corresponding modal gain by many orders of magnitude. Instability is also observed in the parameter space, which is deemed stable by the normal-mode theory. Using our model we have derived the discrete spectrum non-modal stability equations for three classical examples of shear instabilities: Rayleigh/Kelvin-Helmholtz, Holmboe and Taylor-Caulfield. We have shown that the necessary and sufficient condition provides a range of unstable wave numbers for each instability type, and this range matched the predictions of normal-mode theory.
Biography: Anirban Guha is currently a Postdoctoral fellow in the Atmospheric and Oceanic Sciences at UCLA. He is particularly interested in stratified shear instabilities, Rossby and gravity waves, vortices, and flow over topography. Dr. Guha obtained an Undergraduate Degree in Mechanical Engineering from Jadavpur University, India, and Ph.D. in Civil Engineering from The University of British Columbia, Canada. He received various awards during his Ph.D. studies at UBC - the Four year fellowship, the Earl R. Peterson memorial scholarship, and the Faculty of applied science graduate award. Dr. Guha was also the 2013 recipient of the prestigious David Crighton Fellowship from DAMTP, University of Cambridge.
Host: Professor Paul Ronney
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Valerie Childress
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
Aerospace and Mechanical Engineering Seminar Series
Wed, Oct 15, 2014 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Paul Newton, Professor of Applied Mathematics in Department of Aerospace & Mechanical Engineering at University of Southern California, Los Angeles, CA
Talk Title: Random Walks, Markov Chains, and Cancer Progression Models from Longitudinal and Autopsy Data
Series: Aerospace and Mechanical Engineering Seminar Series
Abstract: We will describe models of metastatic cancer progression using Markov chain modeling on a directed graph of nodes that are the various anatomical sites where metastatic tumors can form for a given type of primary cancer. We use metastatic tumor distributions gathered from historical autopsy data, as well as current longitudinal data sets to estimate the transition probabilities (stochastic parameters) from site to site. This creates a systemic network diagram from which we can calculate reduced two-step diagrams using the fact that the systems converge to their steady-state distribution after roughly two steps. The diagrams are used to categorize metastatic sites as `sponges' or `spreaders', as well as to run hypothetical therapeutic scenarios based on Monte Carlo simulations of progression with mean first-passage times as a surrogate timescale measure. A useful metric which we describe is the notion of metastatic entropy and how is correlates with graph conductance dictating Markov convergence rates, mixing times, and complexity. If time permits, we will describe a more fine-scale cell based model which is driven by a stochastic Moran process acting on a heterogeneous population of cells trafficking across the directed graph to various sites, governed by a fitness landscape, with simple point-mutations, interacting via the prisoner’s dilemma paradigm in which the cancer cells are the `defectors’ and the healthy cells are the `cooperators'.
Biography: Paul Newton received his B.S. in Applied Math/Physics at Harvard University and his Ph.D. in Applied Mathematics from Brown University. After a post-doctoral fellowship at Stanford University, he was Assistant and Associate Professor of Mathematics and The Center for Complex Systems Research at the University of Illinois, Champaign-Urbana. He has held visiting appointments at Caltech, Brown, Hokkaido University, The Kavli Institute for Theoretical Physics at U.C. Santa Barbara, and The Scripps Research Institute. He is currently Professor of Applied Math, Engineering, and Medicine in the Viterbi School of Engineering and the Norris Comprehensive Cancer Center at the University of Southern California. He serves as Managing Editor of The Journal of Nonlinear Science, Advisor on Texts in Applied Mathematics Series, Springer-Verlag, New York, and is on The Center Advisory Committee for The Physical Sciences Oncology Center at The Scripps Research Institute in La Jolla, CA where he serves as Project Leader, Mathematical Modeling: Physics and Mathematics of Cancer Metastasis.
Host: Professor Paul Ronney
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Valerie Childress
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
Aerospace and Mechanical Engineering Seminar Series
Wed, Oct 22, 2014 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Kevin Chen, Viterbi Fellow in Department of Aerospace & Mechanical Engineering at the University of Southern California, Los Angeles, CA
Talk Title: Vortex Breakdown, Instability, and Sensitivity of a T-Junction Flow
Series: Aerospace and Mechanical Engineering Seminar Series
Abstract: The fluid flow through a T-shaped pipe bifurcation (with the inlet at the bottom of the "T") is a very familiar occurrence in both natural and man-made systems. Everyday examples include industrial pipe networks, microfluidic channels, and blood flows near the heart and brain. Yet, many questions about the flow physics remain, and prior analyses have been rudimentary. This seminar addresses three important questions: 1) How does the flow evolve with Reynolds number? 2) What are the important flow structures? 3) Lastly, where in the flow do the stability eigenvalues exhibit high sensitivity to dynamical perturbations? Much of this research focuses on the relation between vortex breakdown in the outlet pipes and the regions of stability, receptivity, and sensitivity as defined by linear global stability theory. The vortex breakdown, which occurs above a Reynolds number of 320, gives rise to recirculation regions near the junction; a supercritical Hopf bifurcation first occurs at a Reynolds number of 556. Regions of growth are concentrated in the outlet pipes, but regions of receptivity to initial conditions and external disturbances are confined to small regions near the walls of the inlet and junction. Finally, the flow is most sensitive to localized feedback and to base flow modifications in the recirculation regions, which we explain using an inviscid Lagrangian short-wavelength theory. To the best of our knowledge, this is the most complicated flow for which anyone has observed the relation between sensitivity and recirculation.
Biography: Kevin Chen is presently a Viterbi Postdoctoral Fellow at the University of Southern California, in the Aerospace and Mechanical Engineering department. He attended Caltech as an Axline Scholar, where he received a B.S. with Honor in Engineering and Applied Science, with a focus in Aeronautics, in 2009. At Caltech, he conducted research in experimental and computational fluid dynamics with Mory Gharib, Beverley McKeon, and Tim Colonius. He attended Princeton University as a Gordon Y. S. Wu fellow, where he received an M.A. and a Ph.D. in Mechanical and Aerospace Engineering in 2011 and 2014, respectively, under the advising of Clancy Rowley and Howard Stone. He has received support from the Barry M. Goldwater Scholarship, the DOD NDSEG and NSF GRFP fellowships, and awards from Caltech and Princeton University. Kevin's primary research interest is the development of feedback flow control, where fluid mechanics intersect with modern control theory, stability theory, dynamical systems, and computational methods.
Host: Professor Paul Ronney
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Valerie Childress
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor. -
Aerospace and Mechanical Engineering Seminar Series
Wed, Oct 29, 2014 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Joe Klewicki, Professor in Department of Mechanical Engineering University of New Hampshire, Durham, NH & University of Melbourne, Parkville, VIC, Australia
Talk Title: Self-Similarity in the Inertial Region of Wall Turbulence
Series: Aerospace and Mechanical Engineering Seminar Series
Abstract: The inverse of the von Karman constant, K, is the leading coefficient in the equation describing the logarithmic mean velocity profile in wall bounded turbulent flows. Previous research demonstrates that the asymptomatic value of K derives from an emerging condition of dynamic self-similar hierarchy of scaling layers. First-principles based analyses are used to reveal a number of properties associated with the asymptomatic value of K. The development leads toward, but terminates short of, analytically determining a value for K. Consistent with the differential transformations underlying the invariant form admitted by the governing mean equation, it is further demonstrated that the value of K arises from two geometric features associated with the inertial turbulent motions responsible for momentum transport. One nominally pertains to the shape of the relevant motions as quantified by their area coverage in any given wall-parallel plane, and the other pertains to the changing size of these motions in the wall-nominal direction. Data from direct numerical simulations and higher Reynolds number experiments convincingly support the self-similar geometric structure indicated by the analysis.
Biography: Joseph Klewicki holds joint appointments in the Departments of Mechanical Engineering at the University of Melbourne, Australia and the University of New Hampshire. He is a Fellow of the American Society of Mechanical Engineers (ASME) and a Distinguished Alumnus of the Michigan State University (MSU) Department of Mechanical Engineering. He received his BS (1983), MS (1985) and PhD (1989) degrees from MSU, Georgia Tech and MSU respectively. His areas of specialization include experimental methods in fluid mechanics, turbulent and unsteady flows, vorticity dynamics, boundary layers, atmosphere surface layer phenomena.
Host: Professor Paul Ronney
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Valerie Childress
This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor.
