2017 Seminar Archive

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.

Human Health in Long Duration Spaceflight

Allison Anderson

Assistant Professor
Ann and H.J. Smead Aerospace Engineering Sciences
University of Colorado at Boulder
Boulder, CO

Human spaceflight has led to some of the most inspirational achievements of the space program, such as walking on the surface of the Moon or repair of the Hubble space telescope, but not without cost to the astronauts performing these feats. The human body is well adapted to its 1G environment on Earth, but experiences physiologic adaptation when living and working in micro- and hypo-gravity. My research develops technologies to measure and improve human health in space. I will discuss ocular changes astronauts experience in long-duration spaceflight, the cause of which is currently unknown. We are developing non-invasive measures of intracranial pressure and exploring the use of artificial gravity to mitigate these changes. I will also discuss mental health in isolated, confined environments. We have used computer-based training and treatment, including virtual reality, to improve behavioral health outcomes in the Arctic and HI-SEAS Mars simulations. Finally, I will discuss injuries that occur while working and training inside the spacesuit and in-suit sensing systems we built to measure and mitigate performance decrement during extravehicular activity. This research is used not only to improve the health of astronauts, but also to improve health for patients on Earth, soldiers, athletes, and people living and working in extreme environments.

Allison Anderson graduated with a B.S. in Astronautics Engineering from USC in 2007 with a minor in Astronomy. She was involved in the AeroDesign team, the LeapFrog team, the Viterbi Student Ambassadors, and Spirits in Action while at USC. She received an M.S. in Aerospace Engineering and an M.S. in Technology Policy in 2011 from MIT, and a Ph.D. in Aerospace Biomedical Engineering in 2014 from MIT. She received a postdoctoral fellowship from the National Space Biomedical Research Institute to work at Dartmouth Hitchcock Medical Center studying human space physiology. She is currently an Assistant Professor at the University of Colorado – Boulder Smead Department of Aerospace Engineering Sciences.

Wednesday, August 23, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Wall Turbulence Structure in the Atmospheric Surface Layer. Scaling and Implications on Wind Turbine Siting

Michele Guala

Associate Professor
St. Anthony Falls Laboratory
Dept. of Civil, Environmental and Geo Engineering
University of Minnesota
Minneapolis, MN

The atmospheric surface layer, under special geophysical conditions, has been used as a canonical representation of wall turbulence flows at high Reynolds numbers. In this presentation I will describe how hotwire field measurements in the SLTEST (Utah) and Super-large-scale particle image velocimetry (SPIV, Hong et al., 2014, Toloui et al. 2014) during natural snowfalls in Minnesota, gave us the opportunity to explore atmospheric flows with unprecedentedly high spatio-temporal resolution. Results from SPIV measurements in the thermally neutral atmospheric surface layer, collected at the EOLOS field station over relatively flat, snow-covered farmland, will be introduced as a fully rough wall boundary layer with a Reynolds number Re _τ ~ 10⁶. The data include three time-resolved 15-minute acquisition periods with a field of view extending from 3 m to 19 m above the ground and up to 14 m wide. The flow statistics are validated and supplemented by sonic anemometers from a meteorological tower immediately downstream of the SPIV field of view. The time-resolved planar measurements provide temporal and spatial characterization of key wall turbulence features at high Reynolds number, including ramp-like structures, spanwise vortices, and uniform momentum zones. In comparing the findings to laboratory studies, Reynolds number similarity and the scaling behavior of characteristic properties will be discussed. The limitations of SPIV measurements will be presented using concepts of particle-turbulence interaction and further observations of snow flake dynamics. The impact of large scale flow measurements and turbulent motions will be discussed in the context of wind energy.

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

Refreshments will be served at 3:15 pm.

Coupled Flow and Geomechanics of Petroleum Reservoirs, Aquifers, and Faults

Birendra Jha

Assistant Professor of Petroleum Engineering
Mork Family Department of Chemical Engineering and Materials Science
USC
Los Angeles, CA

Can we inject and produce fluids out of subsurface reservoirs without causing damaging earthquakes? Can we design and control hydraulic fracturing or "fracking" of rocks to maximize productivity but minimize risks? Will underground sequestration of CO₂ lead to induced seismicity and eventually CO₂ leakage along faults? Did Indian monsoon rainfall have something to do with the Nepal earthquake? These are some of the questions facing the petroleum industry, geothermal industry, environmental scientists, and the geoscience community-at-large. One way to approach these questions, and the approach that we follow, is physics-based modeling of the underlying processes of fluid flow, rock deformation, and faulting or fracturing. We specialize in computational modeling and simulation of continuum scale coupled flow, transport and geomechanical processes. We develop mathematically rigorous and computationally efficient numerical frameworks and conduct lab experiments to understand, forecast and eventually control these processes in nature. I will present some of the salient features of our computational framework that includes a finite element--finite volume method to solve the flow and deformation problems sequentially. Then I will show results from a few studies that attempt to answer the questions posed in the beginning.

Birendra Jha is an Assistant Professor of Petroleum Engineering in the Mork Family Department of Chemical Engineering and Materials Science at USC. He received his masters in Petroleum Engineering from Stanford University and PhD in Civil and Environmental Engineering from MIT. He has several years of experience in the petroleum industry in India and US. In the Geosystems Engineering and Multiphysics Lab (gemlab.usc.edu) at USC, Birendra's group conducts research in computational and experimental geomechanics funded by the Department of Energy and the Rose Hills Foundation.

Wednesday, September 13, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Design of Linkage Systems to Draw Specified Curves

J. Michael McCarthy

Professor
Mechanical & Aerospace Engineering
University of California at Irvine
Irvine, CA

Kinematic synthesis is a set of mathematical techniques to calculate the dimensions of a mechanism or robot to achieve a desired task. Since the time of James Watt, whose "parallel motion generator" made the double-acting steam engine practical, engineers and mathematicians have studied curve-drawing linkages for practical as well as theoretical purposes. Recent mathematical results prove that such linkages exist for every algebraic curve, and this talk presents an overview of a variety of techniques to design these linkages. One interesting result is that the equations for kinematic synthesis rapidly expand beyond the ability of current computers to solve completely. On the other hand, because Bezier curves can be written as parameterized trigonometric curves, there is a way to design relatively simple linkage systems that draw Bezier approximations to arbitrary curves.

Michael McCarthy is the Director of UCI’s Performance Engineering Program, having completed a eight year term as the Henry Samueli Professor and Director of the Center for Engineering Science in Design at the University of California, Irvine, which supports the design and execution of team engineering projects across the School of Engineering. He received his Ph.D. at Stanford University, and has taught at Loyola Marymount University and the University of Pennsylvania before joining UCI in 1986.
He has over 200 publications and five books including The Geometric Design of Linkages (Springer 2000, 2nd Ed. 2010). He has served as the Editor-in-Chief of the ASME Journal of Mechanical Design (2002-2007) and is the founding Editor-in-Chief of the ASME Journal of Mechanisms and Robotics (2007-2014). His research team is responsible for the Sphinx, Synthetica and MecGen software packages, which extend computer-aided design to spherical and spatial linkage systems and integrate this process with geometric modeling. He has organized and presented tutorials on the design of linkages and robotic systems at ASME and IEEE conferences, including the NSF sponsored 2012 Workshop on 21st Century Kinematics.
He is a Fellow of the American Society of Mechanical Engineers (ASME), and has received the 2009 ASME Machine Design Award, the 2011 ASME Mechanisms and Robotics Award, and the 2013 Robert E. Abbott Lifetime Service Award from the Design Engineering Division of ASME International. At the 2015 Mechanisms and Robotics Conference, he and his co-author received the A.T. Yang Memorial Award in Theoretical Kinematics for their paper on the design of a linkage system that reproduces the flapping motion of a bird in flight.

Wednesday, September 20, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Acoustic Nanofluidics

James Friend

Professor
Medically Advanced Devices Lab
University of California, San Diego
Center for Medical Devices and Instrumentation
Department of Mechanical and Aerospace Engineering
University of California, San Diego
La Jolla, CA

Acoustic waves have found new utility in microfluidics, providing an enormously powerful ability to manipulate fluids and suspended particles in open and closed fluid systems. In this talk, we cover some fundamental and powerful concepts of acoustic wave generation and propagation often overlooked in the literature, and follow it with exploration of new phenomena observed at the nanoscale. In fact, the usefulness of acoustic waves at the micro-scale is even more compelling at the nano-scale, in ways not predicted by classical theory. Particle deagglomeration, fluid pumping, pattern formation, and other curious physical phenomena will be shown in the context of potentially useful applications. Along the way, the fascinating underlying physics tying together the acoustics, fluid dynamics, and free fluid interface in these systems will be described.

James Friend James Friend is a Professor in the Center for Medical Devices and Instrumentation, Department of Mechanical and Aerospace Engineering, at the University of California, San Diego, having received his PhD in mechanical engineering from the University of Missouri-Rolla in 1998. His research interests are diverse, but principally lie in exploring and exploiting acoustic and vibration phenomena at small scales. He has over 260 peer-reviewed research publications, including 138 journal papers and eight book chapters, and 27 patents in process or granted, completed 33 postgraduate students and supervised 18 postdoctoral staff, and been awarded over $25 million in competitive grant-based research funding over his career. He has been fortunate to receive an AIAA Jefferson Goblet Student Paper Award and an ASME Best Paper of Conference Award for a single talk at the AIAA/ASME/AHS/ASC/ASCE Structural Dynamics & Mechanics Conference in 1996; excellence in teaching, early career research, and research awards from the Monash Faculty of Engineering in 2006, 2008, and 2011, respectively; a Future Leader award from the Davos Future Summit in 2008; a Top 10 emerging scientific leader of Australia by Microsoft and The Australian newspaper award in 2009; an award as the corresponding author of one of the top 50 papers of the past 50 years of Applied Physics Letters in 2012; and the IEEE Carl Hellmuth Hertz Ultrasonics Award from the IEEE in 2015.

Wednesday, September 27, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Predator Sensing and Evasion in Fish

Matthew McHenry

Professor
Ecology & Evolutionary Biology
University of California at Irvine
Irvine, CA

The ability to survive encounters with predators is fundamental to the biology of a broad diversity of species. However, it is largely unclear how prey animals sense and evade predators. We study how the sensory and motor systems of fishes facilitate predator evasion with a focus on zebrafish (Danio rerio), where the adults prey on larvae of the same species. We have learned that the flow-sensitive lateral line system is necessary for survival by rapidly triggering a ‘fast start’ escape response. By replicating these conditions with a predator robot and modeling the flow stimulus with computational fluid dynamics, we were able to examine the cues that prey fish use to sense a predator. We similarly modeled the visual stimuli presented by a predator’s approach. For both stimuli, we found that larvae direct their escape rapidly with coarse directionality. By examining these interactions with pursuit-evasion game modeling, we found that these directional responses are effective due to the high speed of the escape relative to the slow approach of the predator. Therefore, zebrafish survive encounters with a predator using either visual or flow cues that trigger a poorly-directed, but fast, escape response.

Matt McHenry is a Professor of Ecology and Evolutionary Biology at UC Irvine. Since his freshman year at Vassar College, Matt has studied biomechanics and sensing in aquatic animals. He earned a doctorate with Mimi Koehl at UC Berkeley and completed postdoctoral studies with George Lauder at Harvard. His lab’s research is supported by the National Science Foundation and the Office of Naval Research.

Wednesday, October 4, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Engineering Reverse Innovations: Using Emerging Markets’ Constraints to Drive the Creation of High-Performance, Low-Cost, Global Technologies

Amos Winter

Ratan N. Tata Career Development Associate Professor
and
Director, Global Engineering and Research (GEAR) Laboratory
 
Department of Mechanical Engineering
Massachusetts Institute of Technology
http://gear.mit.edu/

This presentation will demonstrate how the Global Engineering and Research (GEAR) Lab at MIT characterizes the unique technical and socioeconomic constraints of emerging markets, then uses these insights with engineering science and product design to create high-performance, low-cost, globally-relevant technologies. The talk will focus on three areas of GEAR Lab’s research: high-performance, low-cost prosthetic feet; low-pressure, low-power drip irrigation, and solar-powered desalination. We have created a novel method of connecting the mechanical design of a foot to its biomechanical performance, which allows the stiffness and geometry to be optimized to induce able-bodied walking kinematics and kinetics. This theory has resulted in a single-part foot architecture which can be made of nylon to hit a $10 price point for developing countries, and which will be ruggedized and customizable for the US military/veteran population. By characterizing the coupled fluid/solid mechanics within drip irrigation emitters, we have designed new drippers that operate at 1/7th the pressure of existing products. This technology can cut the overall pressure, pumping power, and energy usage of drip irrigation systems by approximately 50%, and lower the capital cost of off-grid systems by up to 40%. GEAR Lab elucidated a disruptive market opportunity in arid countries for photovoltaic-powered electrodialysis (PV-ED) desalination, which requires half the energy and reduces water wastage from 60% to <10% compared to reverse osmosis. These market insights have led to new spiral-wound and voltage-controlled architectures which substantially reduce capital cost, as well as co-optimized PV and ED systems that are 40% less expensive than current technology. These projects demonstrate how rigorous engineering theory combined with insights on emerging market constraints can yield high-value solutions relevant to poor and rich countries alike.

Amos Winter is the Ratan N. Tata Career Development Associate Professor of Mechanical Engineering at MIT. His research focuses on machine and product design for developing and emerging markets. Prof. Winter earned a BS from Tufts University (2003) and an MS (2005) and PhD (2011) from MIT, all in mechanical engineering. He received the 2010 Tufts University Young Alumni Distinguished Achievement Award, the 2012 ASME/Pi Tau Sigma Gold Medal, was named one of the MIT Technology Review’s 35 Innovators Under 35 (TR35) for 2013, and received the MIT Edgerton Faculty Achievement Award and an NSF CAREER award in 2017. Prof. Winter is also the principal inventor of the Leveraged Freedom Chair (LFC) developing world wheelchair, which was a winner of a 2010 R&D 100 award, was named one of the Wall Street Journal’s top innovations in 2011, received a Patents for Humanity award from the U.S. Patent and Trademark Office in 2015, and was the subject of “Engineering Reverse Innovations”, winner of the 2015 McKinsey Award for the best article of the year in Harvard Business Review.

Tuesday, October 10, 2017
11:00 AM
Ronald Tutor Hall, Room 211 (RTH 211)

Bioinspired Robots: Embracing the Environment

Mark R. Cutkosky

Fletcher Jones Professor
Dept. of Mechanical Engineering
Stanford University
Stanford, CA

As we bring robots out of the laboratory and into the world, one of the most important lessons we can learn from nature is how to exploit interactions with materials and surfaces in the environment. Examples of robots that need to take advantage of surface interactions include multimodal flying/climbing robots, microtugs, and free-flying robots that grasp objects using gecko-inspired adhesives. These robots use specialized materials and mechanisms to manage interactions with the surfaces they contact. In each case dynamic models and tests lead to computed “envelopes” of conditions for which the robot is expected to perform reliably – for example, to latch onto a surface without slipping or bouncing off. As contact takes place the dynamics are typically fast, so passive properties of mechanisms are more effective than closed-loop control to dissipate energy, distribute forces and stabilize the robot. Nature offers many examples of structures and functional materials that help to manage these interactions. Investigations of surface interactions also allow us to discover new opportunities for synergy when combining multiple locomotion modes (e.g., flying and climbing). Here again, we find parallels in nature.

Mark R. Cutkosky Mark R. Cutkosky is the Fletcher Jones Professor in the Dept. of Mechanical Engineering at Stanford University. He joined Stanford in 1985, after working in the Robotics Institute at Carnegie Mellon University and as a design engineer at ALCOA, in Pittsburgh, PA. He received his Ph.D. in Mechanical Engineering from Carnegie Mellon University in 1985.
Cutkosky's research activities include robotic manipulation and tactile sensing and the design and fabrication of biologically inspired robots. He has graduated over 47 Ph.D. students and published extensively in these areas. He consults with companies on robotics and human/computer interaction devices and holds several patents on related technologies. His work has been featured in Discover magazine, The New York Times, National Geographic, Time magazine and other publications and has appeared on PBS NOVA, CBS Evening News, and other popular media.
Cutkosky’s awards include a Fulbright Faculty Chair (Italy 2002), Fletcher Jones and Charles M. Pigott Chairs at Stanford University, an NSF Presidential Young Investigator award and Times Magazine Best Innovations (2006) for the Stickybot gecko-inspired robot. He is a fellow of ASME and IEEE and a member of Sigma Xi.
Cutkosky’s laboratory and research can be found at http://bdml.stanford.edu.

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

Refreshments will be served at 3:15 pm.

Field Cancerization in Head and Neck Squamous Cell Carcinoma

Jasmine Foo

Associate Professor
School of Mathematics
University of Minnesota, Twin Cities
Minneapolis, MN

High rates of local recurrence in tobacco-related head and neck squamous cell carcinoma (HNSCC) are commonly attributed to unresected fields of precancerous tissue. Because they are not easily detectable at the time of surgery without additional biopsies, there is a need for noninvasive methods to predict the extent and dynamics of these fields. Here, we developed a spatial stochastic evolutionary model of tobacco-related HNSCC at the tissue level and calibrated the model using a Bayesian framework and population-level incidence data from the Surveillance, Epidemiology, and End Results (SEER) registry. Our model predicted a strong dependence of the local field size on age at diagnosis. Similarly, the probability of harboring multiple, clonally unrelated fields at the time of diagnosis was found to increase substantially with patient age. This work highlights the importance of spatial structure in models of epithelial carcinogenesis and suggests that patient age at diagnosis may be a critical predictor of the size and multiplicity of precancerous lesions.

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

Refreshments will be served at 3:15 pm.

Thermoacoustic Dynamics in Aeronautical Gas Turbine Combustors

Adam Steinberg

Associate Professor
University of Toronto Institute for Aerospace Studies (UTIAS)
University of Toronto
Toronto, Ontario
Canada

Thermoacoustic instability in combustion systems refers to the tendency for small perturbations to grow into sustained high-amplitude oscillations, driven by feedback between heat release and pressure dynamics. This seminar will explore various aspects of thermoacoustic instabilities that were studied experimentally in a practical aeronautical gas turbine combustor using optical measurement techniques. Specific challenges arising in the application of optical diagnostics to high-pressure, liquid-fueled combustors will be addressed. We then will discuss two types of thermoacoustic behavior. The first involves apparently spontaneous increases and decreases in oscillation amplitude that occurred at particular operating points. The second pertains to conditions exhibiting steady and intense oscillations, but with extreme sensitivity between the operating point and oscillation amplitude. Both of these behaviors can be explained using the experimental data. Such insights help guide engine designers to more robust systems, and provide important information regarding the application of computational fluid dynamics simulations to thermoacoustically oscillating combustion systems.

Adam Steinberg is an Associate Professor at the University of Toronto Institute for Aerospace Studies, where he holds a Canada Research Chair (Tier II) in Turbulent Reactive Flows. His research focuses on the application of laser-based measurement techniques to solve problems in fundamental and applied thermo-fluids, with particular emphasis on aerospace and power generation systems. He obtained his PhD from the University of Michigan in 2009, and worked at the German Aerospace Center (DLR) before joining the University of Toronto in 2011. He is the recipient of the inaugural Hiroshi Tsuji Early Career Research Award from the Combustion Institute, as well as several other distinctions. He is a member of the Editorial Board of Combustion and Flame and the AIAA Propellants and Combustion Technical Committee, and is a Colloquium Co-Chair for the International Symposium on Combustion.

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

Refreshments will be served at 3:15 pm.

On the Physical Mechanisms of Droplet/Turbulence Interaction

Antonino Ferrante

Associate Professor
William E. Boeing Department of Aeronautics and Astronautics
University of Washington
Seattle, WA

The interactions of liquid droplets with turbulence are relevant to both environmental flows and engineering applications, e.g., rain formation and spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown. The main goal of this research is to investigate the physical mechanisms of droplet-turbulence interaction for both non-evaporating and evaporating droplets.

Droplets in turbulent flows behave differently from solid particles, e.g., droplets deform, break up, coalesce and have internal fluid circulation. We have developed a new pressure-correction method for simulating incompressible two-fluid flows with large density and viscosity ratios. The method’s main advantage is that, for example, on a 1024³ mesh, our new pressure-correction method using the FFT-based parallel Poisson solver is forty times faster than the standard method using multigrid. In general, the new pressure-correction method could be coupled with other interface advection methods such as level-set, phase-field, or front-tracking. We have coupled the pressure-correction method with a volume-of-fluid method for its properties of being mass conserving and sharp-capturing of the interface.

We performed direct numerical simulation (DNS) of finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale in decaying isotropic turbulence. We studied the effects of Weber number, viscosity ratio and density ratio. We derived the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. This allows us to explain the pathways for TKE exchange between the carrier turbulent flow and the flow inside the droplet. The role of the interfacial surface energy is explained through the power of surface tension term of the two-fluid TKE equation. Also, we derive the relationship between the power of surface tension and the rate of change of total droplet surface area. This allows us to explain how droplet deformation, breakup and coalescence plays a role on the temporal evolution of TKE. Our DNS results show that increasing Weber number, the droplet to fluid density or viscosity ratios increases the decay rate of the two-fluid TKE relative to that of single-phase flow. Via analysis of the DNS results, the revealed physical mechanisms will be presented.

Recently, we have also extended the volume-of-fluid method to simulate evaporating droplets. The verification and validation of the method and the DNS results will be presented in comparison to theory and experiments.

Antonino Ferrante is an Associate Professor of the William E. Boeing Department of Aeronautics & Astronautics at the University of Washington (UW). In 2004, he received the Ph.D. in Mechanical and Aerospace Engineering from the University of California, Irvine, where he continued his research as Postdoctoral Scholar until 2007. From 2007 to 2009, he was Postdoctoral Scholar in Aeronautics at the California Institute of Technology at GALCIT. In 2009, he joined the UW as Assistant Professor where was tenured in 2015. Ferrante is recipient of the NSF CAREER Award (2011). His research is focused to the understanding of the physical mechanisms of complex flows, e.g. multiphase and wall-bounded turbulent flows, and enable that through the development of parallel computational methodologies for simulating such flows on supercomputers.

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

Refreshments will be served at 3:15 pm.

The Effects of Stable Density Stratification Initially Homogeneous, Isotropic Turbulence

James J. Riley

PACCAR Professor of Engineering
Department of Mechanical Engineering
University of Washington
Seattle, WA

Stable density stratification occurs in various situations in the atmosphere and in the oceans. For example, in the atmosphere stable density stratification is found near the tropopause and above, and often in nocturnal boundary layers, while in the oceans it usually is observed below the mixed layer. And, through its effects on turbulent mixing, stable stratification has relevance to a number of important issues such as the overall ocean thermal energy balance and the transfer rates of heat and chemicals to/from the atmosphere.

In this seminar the results are presented of a study of the effects of stable density stratification on the simplest of turbulent flows, initially homogeneous, isotropic turbulence, using direct numerical simulations. Simulations were carried out at an initially moderate Froude number, but for a range of initial Reynolds numbers such that, for the high Reynolds number cases, the flows had buoyancy Reynolds numbers in the hundreds, similar to typical oceanic values. A number of aspects of the flows have been addressed, including their energetics, the behavior of various velocity and length scales describing the flows, their mixing characteristics, and their spectral behavior. In particular, how the behavior of the flows depend on the local Froude and buoyancy Reynolds numbers is emphasized. It is found, for example, that as the flows decay, stratification modifies them such that, compared to non-stratified cases, the energy decay rates decreased, the growth rate of the horizontal scales increased, while the growth rates of the vertical scales became negative. These results are consistent with the analysis of Davidson (J. Fluid Mech., 2010), based upon the behavior of the effects of density stratification on the large-scale motions. On the other hand if the buoyancy Reynolds number becomes too low, then the flows, especially the vertical velocity, begin to decay much more rapidly. It is also found, for example, that the behavior of the spectra of the velocity gradient tensor is consistent with the heuristic arguments of Lilly (J. Atmos. Sci., 1983) and the scaling arguments of Billant & Chomaz (Phys. Fluids, 2001). Finally, previous results of the USC group (e.g., Spedding J. Fluid Mech., 1997) are interpreted in terms of the Froude and buoyancy Reynolds numbers.

James J. Riley is the PACCAR Professor of Engineering at the University of Washington. He received his PhD from the Johns Hopkins University in 1972, having worked under the guidance of Stanley Corrsin. After a year as a post-doctoral fellow at the National Center for Atmospheric Research, he spent ten years in industry at Flow Research Company in Kent, Washington, ultimately as the Director of the Fluid Mechanics Division. He joined the University of Washington in 1983, where he is now a Professor in the Department of Mechanical Engineering, and an Adjunct Professor in both the Departments of Applied Mathematics and of Aeronautics and Astronautics. While on sabbatical at the Joseph Fourier University in Grenoble, France, Riley occupied the Visiting Chair in Industrial Mathematics. More recently he was a Senior Fellow at the Isaac Newton Institute for the Mathematical Sciences at Cambridge University. Riley's research interests have included particle dispersion in turbulent flows, waves and turbulence in stably-stratified and in rotating fluids, boundary layer and shear layer transition and turbulence, fluid/compliant surface interactions, and chemically reacting turbulent flows. He is an associate editor of the Journal of Fluid Mechanics and of the Journal of Turbulence, and until recently was a member of the editorial boards of the Annual Review of Fluid Mechanics and of the Applied Mechanics Reviews. Riley is a member of the National Academy of Engineering, and of the Washington State Academy of Sciences.

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

Refreshments will be served at 3:15 pm.

Unsteady Combustion Problems in Modern Energy and Propulsion Systems

Tim Lieuwen

Professor
Daniel Guggenheim School of Aerospace Engineering
Georgia Institute of Technology
North Avenue, Atlanta, GA

The operational limits of modern power generation and propulsion devices are strongly influenced by the combustor. For example, combustion instabilities have emerged as one of the leading challenges associated with low emissions combustion technologies. More fundamentally, the combustion instability problem involves the nonlinear interactions of harmonic flow disturbances with flames in a highly turbulent flow. This talk will describe the key processes controlling the flame response - flame anchoring, excitation of wrinkles by flow oscillations, tangential convection of wrinkles upon the flame, and kinematic restoration.

Tim Lieuwen is a professor and the David S. Lewis, Jr. Chair at Georgia Institute of Technology, and the Executive Director of the Strategic Energy Institute. He has a Ph.D. in mechanical engineering and is a licensed professional engineer in the state of Georgia. He leads a diverse research group investigating a range of problems associated with clean power, energy, and combustion, including such issues as emissions, efficiency, and alternative fuels. Prof. Lieuwen has edited/written four books, written 7 book chapters and over 300 papers, and received 5 patents.

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

Refreshments will be served at 3:15 pm.

Learning from Fish: The Mechanics of Aquatic Propulsion

Iman Borazjani

Associate Professor
Department of Mechanical and Aerospace Engineering
SUNY Buffalo
Buffalo, NY

The grand challenges facing society today, let it be environment, energy, or health, typically involve fluids whose flow physics are not well-understood. To investigate the flow physics and even discover new ones, computational tools can play a major role. Nevertheless, simulating flows with complex shapes and moving boundaries, fluid-structure interactions, pulsatile flows, and at a resolution to resolve are relevant scales is quite challenging. We have overcome many of these challenges using our computational framework, parallelized to efficiently utilize high-performance computing clusters, which handles moving bodies using a sharp-interface immersed boundary method, and solves the flow equations and the immersed bodies in a fully implicit manner using a Newton-Krylov method with an analytical Jacobian. The method has been validated against experimental and benchmark data, and applied to several application from cardiovascular flows, aquatic swimming, wind turbines, and suspension of complex-shaped particles to drive discovery and provide insights into the flow physics. In this talk, we will show how numerical simulations provide us the capability to test hypothetical cases, which are quite difficult to test experimentally with live fish, e.g., we cannot ask a fish to swim with a desired kinematics. We will discuss the main mechanisms of propulsion for fish based on our simulations and show that our results agree with the reactive force theory. In addition, we discuss how the discovery of the leading edge vortex in simulations of aquatic swimming has resulted in new ideas for flow control in engineering applications. At the end, future challenges and research directions are discussed.

Iman Borazjani is an associate professor at the department of mechanical and aerospace engineering SUNY Buffalo and will move to Texas A&M in January 2018. He got his PhD, MSc, and BSc degrees in mechanical engineering from University of Minnesota, Georgia Tech, and Sharif University in 2008, 2005, and 2002, respectively, and was a post-doctoral researcher at the St Anthony Falls Laboratory, University of Minnesota. He is the recipient of the 2013 Scientific Development award from American Heart Association, the 2013 Doctoral New Investigator from American Chemical Society, 2015 NSF CAREER, and 2017-18 Fulbright award.

Wednesday, November 29, 2017
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

To Be (High-Order), Or Not To Be: A Perspective on Next-Generation Computational Tools for Engineering Applications

Gianmarco Mengaldo

Senior Postdoctoral Scholar
Division of Engineering and Applied Science
California Institute of Technology
Pasadena, CA

Advanced computational tools in applied science are becoming increasingly crucial for the analysis, design and decision-making processes commonly required to drive technological and societal innovation. In engineering, high-fidelity simulations constitute an essential mean to provide otherwise unreachable insights that can significantly improve the understanding of complex systems. An area of particular interest is computational fluid dynamics (CFD), where the adoption of high-fidelity simulation technologies, namely large-eddy simulation (LES) is considered of paramount importance to advance the fields where a detailed understanding of flow physics is critical (CFD Vision 2030 Study, Slotnick et al. 2014). LES can provide substantial advantages over more commonly used steady-state tailored techniques. In fact, LES can significantly extend the simulation predictive skills to off-design conditions that include unsteady separated flows, thus providing high-resolution data that can be used in the analysis and design processes as well as to devise reduced-order models.

The key enabler to develop such high-fidelity CFD tools is the underlying numerical discretization, as it drives the accuracy, robustness and time-to-solution of the simulations. In this talk, I will provide an overview of the challenges that CFD is facing in the near future focusing on key aspects that the community needs to consider to push the current boundaries, namely (i) the development of numerical discretizations that can accurately handle complex geometries and that are competitive in terms of time-to-solution and robustness, (ii) the better understanding of numerical vs. physical dissipation to improve LES models and (iii) the co-design of software and hardware to achieve extreme computational performance on heterogeneous computing architectures. The discussion will primarily debate whether high-order finite element methods (also referred to as spectral element methods (SEM)), are a valid choice to build high-fidelity tools for next generation CFD or low-order alternatives are also an adequate option. From this perspective, I will show how SEMs are extremely competitive to describe unsteady separated flows over complex geometries for applications where accuracy is of paramount importance. On the other hand, I will emphasize the role of low order methods – e.g. mimetic finite-volume immersed boundary formulations – in effectively tackling problems with moving surfaces, where body-fitted discretizations may struggle, and for applications where resolution and accuracy are weaker constraints. The talk will also include some ideas from the weather community, where similar issues are being discussed. While the initial question might not have a definitive answer, I hope to provide a clearer view on its implications and on how “to be high-order” can be extremely competitive for certain applications and less for others.

Gianmarco Mengaldo is a senior postdoctoral scholar at the California Institute of Technology and he actively collaborates with Imperial College London, the Massachusetts Institute of Technology, University of Cologne and the European Centre for Medium-Range Weather Forecast (ECMWF), the world leader in numerical weather prediction. Gianmarco graduated among the top of his class from Politecnico di Milano, one of the most prestigious Italian universities, with a master of science in aerospace engineering. He went on to obtain a PhD from Imperial College London in aeronautical engineering, where he worked on novel approximation strategies for partial differential equations, including discontinuous Galerkin and flux reconstruction approaches, using the spectral element library Nektar++. During the PhD, he joined McLaren Racing for an internship in the Formula 1 R&D department where he worked on the aerodynamic design of the competing car. After the PhD, Gianmarco worked for one year at ECMWF leading the technical side of a project, ESCAPE, devoted to test several numerical algorithms for weather and climate simulations on emerging computing technologies and he contributed building the new data-structure for handling different numerical discretization for massively parallel weather applications. Currently, he is working at the California Institute of Technology, where he is developing next generation numerical algorithms for multi-scale and multi-physics problems, with applications that include energy harvesting, bio-inspired micro aerial vehicles and drones, among others. He is also an active senior developer of Nektar++, where he leads the development of discontinuous spectral element discretizations for compressible flow problems and continues his collaboration with ECMWF on a range of topics, including the evaluation of different numerical discretization strategies for weather and climate applications on next generation hardware.

Monday, December 4, 2017
11:00 AM
Laufer Library (RRB 208)