Seminars

Seminars are held Wednesdays, at 3:30 pm, in Seaver Science Library, Room 150 (SSL 150), unless otherwise noted. Refreshments are served at 3:00 pm. Call (213) 740-8762 for further information.

Archive of Past Seminars:

2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004

Keynote Lecture Series Archive

Spring, 2017

Aircraft Propulsor Modeling and Design for Boundary Layer Ingestion

David K. Hall

Postdoctoral Fellow
MIT Gas Turbine Laboratory
Massachusetts Institute of Technology
Cambridge, MA

Propulsion with Boundary Layer Ingestion (BLI), where a craft’s boundary layer or wake fluid is ingested and re-accelerated by the propulsor, has long been recognized to provide a theoretical propulsive efficiency benefit. A major challenge associated with aircraft BLI is non-uniform flow at the engine inlet, which can lead to decreased engine efficiency, decreased engine stall margin, and increased unsteady force on rotating turbomachinery. This presentation describes a new conceptual framework for three-dimensional turbomachinery flow analysis and its use to assess fan stage attributes for mitigating the adverse effects of BLI. The turbomachinery is modeled in CFD calculations using momentum and energy source distributions that are determined as a function of local flow conditions and an approximate blade geometry. Comparison with higher-fidelity computational and experimental results shows the analysis captures the principal flow redistribution and distortion transfer effects associated with BLI fans, which differ from established models for compressor distortion response. The distortion response is assessed for a range of fan stage design parameters, and the results indicate that circumferential variations in the design of the downstream fan exit guide vanes yield the greatest reductions in flow non-uniformities in the rotor, and may offer the most potential for improved performance with BLI inlet distortion.

David K. Hall received his Bachelor of Science in Engineering from Duke University, where he majored in Mechanical Engineering and Mathematics, and his SM and PhD in Aeronautics and Astronautics from MIT, where his thesis work was associated with development and assessment of the D8 advanced aircraft concept under the NASA N+3 program. His research interests include aircraft propulsion, gas turbines, engine-aircraft integration, aerodynamics, aeromechanics, and design of turbomachinery, and computational modeling for fluid dynamics. In 2015, he taught at the Singapore University of Technology and Design as a postdoctoral fellow, and he is now continuing his fellowship at the MIT Gas Turbine Laboratory, with research on advanced propulsion concepts for efficient air transportation.

Wednesday, January 11, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Cross-Shore Thermally Driven Exchange Flows: Dynamic Regimes and Variability

Geno Pawlak

Professor
Mechanical & Aerospace Engineering Department
University of California at San Diego
La Jolla, CA

Observations of the velocity structure at the Kilo Nalu Observatory on the south shore of Oahu, Hawaii show that thermally driven baroclinic exchange is a dominant mechanism for cross-shore transport for this tropical forereef environment. Although cross-shore wind stress influences the diurnal cross-shore exchange, surface heat flux is identified as the primary forcing mechanism from the phase relationships and from analysis of momentum and buoyancy balances for the record-averaged diurnal structure. Dynamic flow regimes are characterized based on a two-dimensional theoretical framework and the observations of the thermal structure at Kilo Nalu are shown to be in the unsteady temperature regime. Diurnal phasing and the cross-shore momentum balance suggest that turbulent stress divergence is dominant. While the thermally driven exchange has a robust diurnal profile in the long term, there is high temporal variability on shorter time scales. Some of this variability can be accounted for by influence of strong along-shore flow that is forced at semidiurnal frequencies. The along-shore flow affects the cross-shore exchange through its influence on turbulent diffusivity and via Coriolis driven cross-shore accelerations. A theoretical model is developed to examine the role of multi-frequency forcing. The solution uses a linear perturbation to the baseline pressure-stress divergence balance introducing a time-dependent eddy viscosity and Coriolis accelerations associated with a semidiurnal along-shore flow.

Wednesday, January 18, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Dynamics and Control of Wall-Bounded Shear Flows

Mihailo Jovanovic

Professor
Ming Hsieh Department of Electrical Engineering
USC
Los Angeles, CA

Understanding and controlling transition to turbulence is one of the most important problems in fluid mechanics. In the first part of the talk, techniques from control theory are used to examine the early stages of transition in wall-bounded shear flows. We demonstrate high sensitivity of the flow equations to modeling imperfections and show that control theory can be used not only to design flow control algorithms but also to provide valuable insights into the transition mechanisms.

In the second part of the talk, we examine the efficacy of streamwise traveling waves generated by surface blowing and suction for controlling the onset of turbulence in a channel flow. For small amplitude actuation, we utilize weakly-nonlinear analysis to determine base flow modifications and to assess the resulting net power balance. Sensitivity analysis of the velocity fluctuations around this base flow is then employed to design the traveling waves. Our simulation-free approach reveals that, relative to the flow with no control, the downstream traveling waves with properly designed speed and frequency can significantly reduce sensitivity which makes them well-suited for controlling the onset of turbulence. In contrast, the velocity fluctuations around the upstream traveling waves exhibit larger sensitivity to disturbances. Our theoretical predictions, obtained by perturbation analysis (in the wave amplitude) of the linearized Navier-Stokes equations, are verified using simulations of the nonlinear flow dynamics. These show that a positive net efficiency as large as 25% relative to the uncontrolled turbulent flow can be achieved with downstream waves. We conclude that the theory developed for the linearized flow equations with uncertainty has considerable ability to predict full-scale phenomena.

Mihailo Jovanovic is a professor of Electrical Engineering and the founding director of the Center for Systems and Control at the University of Southern California. He was a faculty in the Department of Electrical and Computer Engineering at the University of Minnesota, Minneapolis, from December 2004 until January 2017, and has held visiting positions with Stanford University and the Institute for Mathematics and its Applications. His current research focuses on design of controller architectures, dynamics and control of fluid flows, and fundamental limitations in the control of large networks of dynamical systems. He serves as an Associate Editor of the SIAM Journal on Control and Optimization, Vice Chair of the APS External Affairs Committee, and had served as an Associate Editor of the IEEE Control Systems Society Conference Editorial Board from July 2006 until December 2010. Prof. Jovanovic received a CAREER Award from the National Science Foundation in 2007, the George S. Axelby Outstanding Paper Award from the IEEE Control Systems Society in 2013, and the Distinguished Alumni Award from UC Santa Barbara in 2014.

Wednesday, January 25, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Hyperloop One: Be Anywhere, Move Anything, Connect Everyone

George O’Neal

Director of Controls

Shibing Liu

Controls and Dynamics Engineer

Hyperloop One
Los Angeles, CA

As the next mode of transport, Hyperloop is a new way to move people and cargo quickly, safely, efficiently, on-demand and with minimal impact to the environment. Hyperloop One is the Los Angeles company that aims to build the first deployable Hyperloop system by 2020. The Propulsion Open Air Test (POAT), which was successfully demonstrated in 2016, showed that we are more than just theories and artist renditions. We make real and functional hardware. Our “Kitty Hawk” moment, full size and full speed test track, will start in the first quarter of 2017. After which, years of testing will be continued to deliver a safe and efficient Hyperloop system to move cargo by 2020 and passengers by 2021. Hyperloop will fundamentally change the barriers of distance and time. In this talk, we will introduce the cutting-edge technologies under development of Hyperloop One, including electromagnetic propulsion systems, structural tubes, pods, electromagnetic levitation system, and system modeling and analysis.

George O’Neal was the founding member of Hyperloop One’s propulsion and electronics division and its current Director of Controls. He spearheaded the effort to design and test Hyperloop One’s state-of-the-art propulsion system at its Nevada test site. He is focused now on building the embedded electronics and controls that will enable the autonomous operation of the Hyperloop One transportation system. This includes autonomous vehicle protection and operation, vehicle-to-vehicle and vehicle-to-ground communication, model based preventive maintenance as well as the integration of these core systems to the supervisory services.

For nearly 20 years Dr. O’Neal has developed complex electromechanical control systems across a variety of high-tech industries, obtaining extensive experience in embedded controls, vehicle dynamics, modeling, simulation, spacecraft guidance & navigation, and robotics. Dr. O’Neal holds several patents and has co-authored multiple award-winning journal publications. He holds a Ph.D. from the University of Michigan in Mechanical Engineering: Systems and Control and received the prestigious William Mirsky Memorial Award for Outstanding Research as well as a NSF graduate research fellowship.

Shibing Liu is a Controls and Dynamics Engineer at the Hyperloop One. He received his Bachelor of Science in Mechanical Engineering Technology from the Southern Polytechnic State University and Mechanical Engineering from the North China University of Technology, and his MS and PhD is Mechanical Engineering from the University of Southern California (USC), where his thesis work was associated with modeling, analysis and experimental validation of flexible rotor systems with water-lubricated rubber bearings. His research interests are dynamics and control, vibrations, rotordynamics, structural health monitoring, and optimization of mechanical systems. His current duties at the Hyperloop One include development of route analysis tools, system optimization, and system dynamics.

Wednesday, February 1, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Advanced Manufacturing of Prepreg Composites Structures

Timotei Centea

Research Assistant Professor
Department of Aerospace & Mechanical Engineering
University of Southern California
Los Angeles, CA

Fiber-reinforced composites enable the production of lightweight, high-performance structures in aerospace, marine, automotive, and clean energy sectors. As composites use grows and diversifies, traditional manufacturing methods increasingly restrict structural designs, limit production rates, inhibit applications in new sectors, and conflict with economic and environmental concerns. These challenges motivate research into advanced manufacturing methods for composites. This seminar will focus on the major topic of prepreg processing, describing fundamental and applied research that connects material, structural, and manufacturing scales in order to advance technical, cost and environmental efficiency.

Prepregs, or carbon fiber reinforcement sheets pre-impregnated with an uncured polymer matrix, deposed on a metal tool and cured to produce high-performance structures for aircraft and spacecraft. Most prepreg parts are cured in autoclaves, or pressurized ovens. However, recently, a new generation of vacuum bag-only (VBO) prepregs have enabled out-of-autoclave (OOA) cure in a variety of simpler, lower-cost manufacturing environments. VBO prepreg processing was studied at fundamental and applied levels. First, key relationships between material characteristics, part design, physical phenomena occurring during cure, manufacturing conditions, and structural quality were investigated using advanced imaging methods, in-situ process analysis, and modeling. Then, resulting insights were used to develop science-based defect reduction strategies.

Prepregs can also be used to fabricate high-stiffness, low-density honeycomb core sandwich structures used applications such as aircraft control surfaces, rocket fairings, and marine vessel hulls. The co-cure of honeycomb core structures using autoclave and VBO methods was studied in order to develop an accurate, reliable physics-based process model. The major physical phenomena governing co-cure were clarified and analyzed using a custom-designed lab-scale manufacturing cell capable of accurate control and in-situ diagnostics. Now, these phenomena are being modeled, and integrated into a simulation that will enable structural and manufacturing optimization.

Finally, manufacturing efficiency was advanced by developing science-based technical methods for reducing resource consumption. The use of efficient cure environments based on in-situ diagnostics and multi-zone thermal management was shown to improve control over material state and reduce energy use. Moreover, the reuse of in-process waste for structural applications was studied and validated.

Overall, the seminar will highlight multi-scale, interdisciplinary research that combines fundamental scientific analysis with the development of applied engineering solutions to some of the major challenges facing composites, advanced manufacturing, aerospace, and related fields.

Timotei Centea is a Research Assistant Professor in the Department of Aerospace and Mechanical Engineering at the University of Southern California, and is affiliated with the M.C. Gill Composites Center. He studied mechanical engineering at McGill University in Montreal, Canada, earning Bachelor’s and Ph.D. degrees in 2008 and 2013, respectively. His research interests and expertise center on the fundamental science and applied engineering of the manufacturing of high-performance composites, and aim to advance technical quality and performance, cost-competitiveness and environmental sustainability. Dr. Centea’s work has been supported by personal fellowships as well as research funding from government, institutional and industry sources. His activities have resulted in several awards, including the Best Paper of the 26th Annual Conference of the American Society for Composites (2011).

Wednesday, February 8, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Advancement of Non-Intrusive Optical Diagnostics for the Study of Supersonic Aerothermodynamics

Christopher S. Combs

Research Assistant Professor
The University of Tennessee Space Institute
Tullahoma, TN

The continued development of non-intrusive diagnostics will be critical to the advancement of the state-of-the-art in high-speed aerodynamics research. Realizing the high-speed capabilities that have become an elevated national priority such as sustained hypersonic flight, atmospheric reentry, commercial supersonic flight, and air-breathing propulsion will require measurements at high-speed and high-enthalpy conditions that are currently difficult or impossible to make. Moreover, measurements in high-enthalpy and reacting flows are in increasing demand given the DoD’s push for research in hypersonics. Recent advances in imaging and laser technology—such as cheaper high-speed cameras, development of plenoptic cameras, and advances with pulse-burst lasers—have increased the potential capabilities for non-intrusive diagnostics. Considering the recent strides made in the development of non-intrusive diagnostics and the current measurement challenges faced by the experimental community, there is a need for researchers to leverage the recent advances in imaging and laser technology to develop the next generation of game changing non-intrusive diagnostics that will drive the next fifty years of high-speed aerothermodynamics research. Here, a review of recent diagnostics developments at The University of Texas and The University of Tennessee Space Institute will be presented, including an overview of the naphthalene planar laser-induced fluorescence technique—a diagnostic used to explore ablation physics by investigating scalar transport due to sublimation in supersonic flows. Results from an investigation of the Orion Multi-Purpose Crew Vehicle reaction control system jets using NO planar laserinduced fluorescence will be shared, as well. Lastly, data will be presented from research on the dynamics of transitional shock-wave/boundary layer interactions collected using a variety of measurement techniques.

Christopher Combs received his B.S. in Mechanical Engineering from the University of Evansville in Evansville, IN in 2010 and completed his Ph.D. in Aerospace Engineering at The University of Texas at Austin in 2015. His primary area of research interest is laser diagnostics applied to supersonic flows and his research in the application of PLIF to characterize low-temperature ablation was supported through NASA’s Space Technology Research Fellowship program. Dr. Combs joined the faculty at UTSI for the Fall Semester of 2015 and has been leading the development of diagnostic capabilities within the UTSI High-Speed/Hypersonics initiative, HORIZON (High-speed Original Research and Innovation ZONe). Dr. Combs’ research has been funded by multiple government agencies including NASA, AFOSR, ONR, AEDC, TRMC/HSST, and DARPA and he is a current member of the AIAA Aerodynamic Measurement Technology Technical Committee.

Wednesday, February 15, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Transport of Particles, Drops, and Small Organisms in Density Stratified Fluids

Arezoo Ardekani

Assistant Professor
School of Mechanical Engineering
Purdue University
West Lafayette, IN

Many aquatic environments are characterized by regions where water density varies over depth, often due to temperature or salinity gradients. These ‘pycnoclines’ are associated with intense biological activity and can affect carbon fluxes by slowing the descent of particles. Despite this, the fundamental fluid dynamics of settling and swimming in a stratified fluid have remained largely unexplored. I take first strides into this area by rationalizing the effects of stratification by conducting a broad, in-depth investigation on the fundamental hydrodynamics of small organisms, settling particles, and rising drops. These results demonstrate an unexpected effect of buoyancy, potentially affecting a broad range of abundant processes at pycnoclines in oceans and lakes.

Arezoo Ardekani is currently an assistant professor at the Purdue University. Prior to joining Purdue, she was an O’Hara Assistant Professor at the University of Notre Dame and a Shapiro Postdoctoral Fellow at the Massachusetts Institute of Technology. In summer 2015, she was a visiting professor at the Institut de Mécanique des Fluides de Toulouse. She graduated from University of California Irvine with her Ph.D. in 2009. She received the Society of Women Engineers and Amelia Earhart awards in 2007, Schlumberger Foundation faculty for the future grant in 2009, and NSF CAREER award in 2012.

Prof. Ardekani was awarded the Presidential Early Career Award for Scientists and Engineers (PECASE) in 2016. She has presented 50 invited lectures in conferences, universities, and industries worldwide. She is a member of the board of editors of the European Journal of Computational Mechanics and Scientific Reports. Her expertise is in fluid mechanics, biological and environmental flows.

Wednesday, February 22, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

A Route Towards Next-Generation Soft Robotics, Wearable and Implantable Electronics

Kitty Kumar

Postdoctoral Associate
Department of Mechanical Engineering
Carnegie Mellon University
Pittsburgh, PA

For most of the past century, strength and rigidity have been the engineering focus, but in the past decade we have come to value soft matter and flexibility, and have directed engineering efforts in which we could, indeed, turn a dime. Many forms of soft flexible technologies such as wearable health monitors, soft exosuits for rehabilitation and implants for localized drug delivery continue to develop and have the potential to revolutionize healthcare in various ways. In this talk, I will discuss the current challenges for the advancement of soft technologies and show how the research in materials, smart architectures, and manufacturing methods is contributing towards the development of the next generation of soft technologies such as wearables, implants, and robotics.

Kitty Kumar is a postdoctoral associate at Carnegie Mellon University. Her interests broadly encompass smart materials and structures for soft devices and fabrication methods to manufacture such devices at a large scale. She is interested in developing next-generation soft devices and systems by seamlessly fusing biological principles, chemistry and engineering. Kitty received her Ph.D. from the University of Toronto, where she focused on the fabrication of flexible solar cells and developed a novel laser processing technique to structure dielectric thin films for flexible electronics. During the postdoctoral position at the Wyss Institute for Biologically Inspired Technologies, Harvard University, she concentrated on the design and fabrication of bio-inspired advanced soft robotic systems for biomedical applications.

Wednesday, March 1, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Bioelectronic Devices for Personalized and Precision Medicine: From Wearable Biosensors to Medical Nanorobots

Wei Gao

Postdoctoral Fellow
Department of Electrical Engineering and Computer Sciences
University of California at Berkeley
Berkeley, CA

The rising clinical and basic research interest in personalized and precision medicine promises to revolutionize traditional medical practices. This presents a tremendous opportunity for developing bio-electronic devices toward predictive analytics and treatment. An ecosystem consisting of emerging wearable biosensors and medical nanorobots can combine health monitoring with delivery of therapy and offer distinct advantages in realizing personalized and precision medicine. In this talk, I will firstly introduce fully-integrated biosensors for multiplexed in-situ perspiration analysis, which can selectively measure a wide spectrum of sweat analytes (e.g. metabolites, electrolytes and heavy metals) and provide insightful information about our health state. Then I will discuss the propulsion and applications of the synthetic nanorobots which have the potential to navigate through the human body for precision therapy internally, without the need for invasive surgical incisions. The ecosystem opens the door to a wide range of personalized diagnostic and therapeutic applications.

Wei Gao is a postdoctoral fellow in the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley. He received his PhD in Chemical Engineering at University of California, San Diego in 2014 as a Jacobs Fellow and HHMI International Student Research Fellow. He is a recipient of 2016 MIT Technology Review 35 Innovators Under 35 (TR35) and 2015 ACS Young Investigator Award (Division of Inorganic Chemistry). His research interests include wearable and flexible electronics, biosensors, internet of things, nanorobotics and nanomedicine.

Thursday, March 2, 2017
2:30 PM
Tutor Hall, Room 324 (RTH 324)

Reliable CFD and Simple Computational Grids

Alexandre Marques

Postdoctoral Associate
Aerospace Computational Design Laboratory
Massachusetts Institute of Technology
Cambridge, MA

Computational Fluid Dynamics (CFD) is a technology that supports innovation in a number of industries. Aerospace, automotive, energy, construction, and biomedical are just some of the industries that benefit from detailed simulations of complex flows. However, despite its widespread use, CFD is still restricted to a relatively small number of engineers. In this presentation I will talk about two fronts of research in which I am engaged to make CFD more accessible: (i) data-driven models, and (ii) embedded grid methods.

Data-driven models can improve the predictive capability of CFD, and also quantify uncertainties due to model inadequacy. Physical formulations used in CFD are often based on reduced versions of the flow dynamics. In my research I use recent advances in computer and information science and machine learning to create data-driven models that complement these reduced physical formulations. The combination of predictive models and quantification of model inadequacy leads to CFD results that are reliable, and that can be interpreted with confidence by users that are not CFD experts. I will discuss examples of a data-driven model for the boundary layer in the laminar and incompressible regime, and a data-driven wall model for large-eddy simulation.

Embedded grid methods simplify the tasks of grid generation and simulation of moving boundaries. Most CFD tools are based on body-fitted grids, i.e., grids that conform to the geometry of the boundaries. Generating body-fitted grids around complex geometries is a labor-intensive and difficult task. In contrast, in embedded grid methods the boundaries are embedded in a relatively simple computational grid and the boundary conditions are enforced through modifications to the discrete equations. As a consequence, embedded grid methods are also robust to simulate problems with moving boundaries, as is the case in flapping wings, multi-phase flows, and flows around flexible membranes. In particular, I will present the Correction Function Method (CFM), which is an embedded grid method capable of producing accurate solutions up to the boundaries.

Alexandre Marques is a Postdoctoral Associate at the Aerospace Computational Design Laboratory at MIT. He obtained a Ph.D. in Aerospace Computational Engineering at MIT, a M.Sc. in Aeronautical and Mechanical Engineering at ITA (Brazil), and B.S. in Aeronautical Engineering at ITA (Brazil). He works with Computational Fluid Dynamics (CFD), with focus on data-driven models for numerical simulation, and accurate embedded grid methods. Prior to his postdoc position at MIT, he worked at the R&D division of Embraer (Brazil) in industry applications of CFD and Computational Aeroelasticity.

Monday, March 6, 2017
11:00 AM
Hughes Aircraft Electrical Engineering Center, Rm 132 (EEB 132)

Soft Robots for Delicate and Effective Interactions with Humans: Multi-Scale Soft Biomedical Robots

Tomasso Ranzani

Postdoctoral Fellow
Harvard Microrobotics Laboratory
and
Harvard Biodesign Laboratory
Harvard University
Cambridge, MA

Soft robots are constructed from compliant materials, resulting in machines that can safely interact with the natural environments. Given their inherent compliance, they are particularly suitable for exploring and interacting with unstructured environments, and manipulating soft, delicate, and irregular objects. These properties make soft robots particularly promising for biomedical applications, such as wearable and medical devices, given the highly compliant and delicate structures of the body. On the other hand, the compliance of soft robots limits their ability to effectively apply forces on objects whose stiffness is comparable to the one of the robot itself, leading to the challenge of matching the compliance of soft devices with the environment or objects they will encounter. During this talk, I will describe progress in soft robotics and its potential for revolutionizing biomedical devices. I will introduce a soft manipulator inspired by the structure and the manipulation capabilities of the octopus tentacle, which is able to selectively tune its stiffness to address the challenge of impedance matching. I will also introduce the potential of soft robotics at the millimeter and micrometer scales, addressing the challenge of manufacturing complex meso-scale three-dimensional soft structures using two-dimensional processes involving laser machining, lamination, and soft lithography. These manufacturing processes could pave the way for soft microrobots as well as a new class of deployable, small, and safe medical devices.

Tommaso Ranzani received the Master’s degree in biomedical engineering from the University of Pisa, Pisa, Italy, in 2010 and the Ph.D. degree in BioRobotics in 2014 at the BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Italy. During his Ph.D., he explored soft robotic technologies to develop a bioinspired manipulator, which integrates design principles from biological systems for performing advanced procedures in minimally invasive surgery. He is currently a postdoctoral fellow at the Harvard Microrobotics Laboratory and at the Harvard Biodesign Laboratory working on different manufacturing paradigms, materials, and actuation technologies to develop novel mm-scale robotic tools and structures able to overcome current challenges in medicine and surgery. His research interests include soft and bioinspired robotics, medical robotics and advanced manufacturing.

Wednesday, March 22, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Fluid Dynamics of Phonation

Michael W. Plesniak

Professor
Department of Mechanical & Aerospace Engineering
The George Washington University
Washington, DC

Speech production involves unsteady pulsatile flow and turbulent structures that affect the aeroacoustics and fluid-tissue interaction. The goal of our human phonation research program is to investigate the dynamics of flow past the vocal folds (VF) and the aerodynamic interaction with the VF. Over the course of the program we have studied static, driven and self-oscillating models of the VF system. Silicone-based, self-oscillating synthetic vocal fold (VF) models are fabricated with material properties representative of the different layers of human VFs and then evaluated experimentally in a life-size vocal tract simulator to replicate physiological conditions. Our experimental investigations utilize high-speed imaging, particle image velocimetry (PIV), pressure transducers and microphones, and the clinical Rothenberg mask. Studies are performed under both normal and pathological conditions of speech. In particular, recent attention has been focused on understanding the role of polyps (growths on the VF) in altering voice quality. This has led to very fundamental studies of 3D flow separation in pulsatile flows. We have also collaborated with colleagues in the Department of Speech and Hearing Sciences to better understand the effects of ageing on voice. Our overarching motivation for studying flow associated with phonation is to facilitate evaluation and design of treatment interventions and for surgical planning, i.e. to enable physicians to assess the outcomes of surgical procedures by using faithful computer simulations. Such simulations are on the horizon with the advent of increasingly more powerful high performance computing and cyberinfrastructure, but they still lack many of the necessary physical models. We also seek to inform non-surgical clinical treatment strategies of voice disorders.

Michael W. Plesniak is Professor and Chair of the Department of Mechanical & Aerospace Engineering at The George Washington University, with a secondary appointment in the Department of Biomedical Engineering. He was formerly Professor of Mechanical Engineering at Purdue University and Eugene Kleiner Professor for Innovation in Mechanical Engineering at Polytechnic University in Brooklyn, NY. He served as the Director of the Fluid Dynamics & Hydraulics program at the National Science Foundation from 2002-2006. Prof. Plesniak earned his Ph.D. degree from Stanford University, and his M.S. and B.S degrees from the Illinois Institute of Technology; all in Mechanical Engineering. Dr. Plesniak is a Fellow of AIAA, ASME, the American Physical Society (APS), the American Institute for Medical and Biological Engineering (AIMBE) and the Association for the Advancement of Science (AAAS). He has authored over two hundred fifty refereed archival publications, conference papers and presentations. He has presented numerous invited seminars and keynote addresses. His research group is currently studying the physics of phonation and cardiovascular flows. Dr. Plesniak is the Director of GW’s Center for Biomimetics and Bioinspired Engineering. Prof. Plesniak was a recipient of the 2017 ASME Fluids Engineering Award, the 2011 NASA DC Space Grant Consortium’s Outstanding STEM Faculty Award, awarded to faculty that make an outstanding contribution to STEM that goes above and beyond the classroom. Dr. Plesniak was also named the American Institute for Aeronautics and Astronautics, National Capital Section Engineer of the Year 2010-2011.

Wednesday, April 5, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Low-Order Modeling of Agile Flight

Jeff Eldredge

Professor
Mechanical & Aerospace Engineering Department
University of California at Los Angeles
Los Angeles, CA

The highly agile flight exhibited by many flying creatures has, for many years, been the promise for the next generation of flight vehicles. However, the reality still falls short, in part because such agility requires flight control strategies that work robustly in the regime of separated flows. This regime, generally avoided by human-engineered vehicles, is often exploited by airborne creatures in order to make rapid maneuvers or maintain tolerance to gusts. Recent control strategies based on flapping wings or managed separation over fixed wings have shown promise, but are limited to slow maneuvers because they rely on linearized and/or quasi-steady models of the aerodynamics, only effective at low frequencies or averaged over many flapping cycles. In this presentation, I will report on our recent progress in developing unsteady non-linear (vortex-based) models of separated flows. The premise is to construct a low-degree-of-freedom template model, with the simplest description of the flow that still contains the non-linear vortex-vortex and vortex-wing interactions. The model is then closed with empirical data from sensors. I will demonstrate progress on several canonical problems in two dimensions, and discuss our extensions to fully three-dimensional flows. I will also highlight some future directions of the work.

Jeff Eldredge is a Professor in the Mechanical & Aerospace Engineering Department at UCLA. His research interests are in computational and theoretical studies of problems in fluid dynamics, including those in unsteady aerodynamics, bio-inspired locomotion, micro-particle manipulation, and biomedical and physiological flows. He has received the NSF CAREER Award and is an Associate Fellow of AIAA. Prior to starting at UCLA, Prof. Eldredge was a research associate at the University of Cambridge. He received his M.S and Ph.D. at Caltech and his B.S. at Cornell, all in mechanical engineering.

Wednesday, April 12, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Transport Phenomena over Patterned Surfaces

Ilenia Battiato

Assistant Professor
Energy Resources Engineering
Stanford University
Stanford, CA

Coupled flows over patterned surfaces occur in a variety of natural phenomena, biological systems and industrial processes. Some example includes bioreactors, micro- and nano-patterned water filtration membranes, superhydrophobic ridges surfaces, and submerged vegetation, just to mention a few. Designing and optimizing the topology of the structure to achieve target performance at the system-scale (or macroscale) is still an open question since fully resolved numerical simulations are too prohibitive when a great disparity of scales between the pattern and the device exists. By treating the patterned surface as a permeable layer, we formulate a system of coupled Navier-Stokes/Brinkman equations, which is amenable of analytical solution for the mean filtration velocity inside the pattern, and allows one to uncover and quantify the relationship between microstructure and macroscopic response. We employ this effective-medium framework to model a number of physical systems including channel turbulent flows over arrays of carbon nanotubes, superhydrophobic ridged surfaces, and submerged vegetation. We finally investigate the appropriateness of treating the pattern as a porous medium by conducting experiments in microfluidic channels with controlled microtexture.

Dr. Battiato received her MSc. In Engineering Physics in 2008 and a Ph.D. in Engineering Science with a specialization in Computational Sciences from the Mechanical and Aerospace Engineering department at the University of California San Diego in 2010. She did her postdoctoral training in Theoretical Physics at the Max Planck Institute for Dynamics and Self-Organization in Goettingen, Germany. In 2012 she joined the Mechanical Engineering Department at Clemson University as assistant professor and then in 2014 the Mechanical Engineering Department at SDSU. In 2016, she moved to the department of Energy Resources Engineering at Stanford University. Her research interests lie in theoretical/computational fluid mechanics and transport processes in porous media, multiscale and hybrid computational methods, effective medium theories, and multiphase flows. In 2015 she was awarded of the Department of Energy Young Investigator award in Basic Energy Sciences for her work on multiscale models of reactive transport in the subsurface.

Wednesday, April 19, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

—John Laufer Lecture—

Structure, Stability, and Simplicity in Complex Fluid Flows

Clarence W. Rowley

Professor
Department of Mechanical and Aerospace Engineering
Princeton University
Princeton, New Jersey

Fluid flows can be extraordinarily complex, and even turbulent, yet often there is structure lying within the apparent complexity. Understanding this structure can help explain observed physical phenomena, and can help with the design of control strategies in situations where one would like to change the natural state of a flow. This talk addresses techniques for obtaining simple, approximate models for fluid flows, using data from simulations or experiments. We discuss a number of methods, including balanced truncation, linear stability theory, and dynamic mode decomposition, and apply them to several flows with complex behavior, including a transitional channel flow, a jet in crossflow, and a T-junction in a pipe.

Clancy Rowley is a Professor in the Mechanical and Aerospace Engineering department at Princeton University. He received his undergraduate degree from Princeton in 1995, and his doctoral degree from Caltech in 2001, both in Mechanical Engineering. He returned to Princeton in 2001 as an Assistant Professor and was appointed Associate Professor in 2007, and Full Professor in 2012. He has received several awards, including an NSF CAREER Award and an AFOSR Young Investigator Award. His research interests lie at the intersection of dynamical systems, control theory, and fluid mechanics, and focus on reduced-order models suitable for analysis and control design.

Wednesday, April 26, 2017
1:00 PM
Ronald Tutor Campus Center, Trojan Ballroom A

Refreshments will be served at 12:00 NOON in Trojan Ballroom B.