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. Note—several seminars this semester are not at the regularly scheduled day, time, and place.

Archive of Seminar Announcements:

2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004

Keynote Lecture Series Archive

Spring, 2018

Entrapment, Escape, and Diffusion of Active Particles in Complex Environments

Saverio Spagnolie

Assistant Professor
Department of Mathematics
University of Wisconsin at Madison
Madison, WI

The swimming kinematics and trajectories of microorganisms and active synthetic particles are altered by the presence of nearby boundaries, be they solid or deformable, and often in perplexing fashion. When an organism’s swimming dynamics vary near a boundary, a natural question arises: is the change in behavior fluid mechanical, biological, or perhaps mediated by other physical laws? We will explore the hydrodynamic interactions between active particles and nearby surfaces, which can result in entrapment or escape depending on the propulsive mechanism used by the swimming body and its size (through the strength of Brownian fluctuations). If the confining geometry is regular, the swimming dynamics can settle towards a stable periodic orbit or can be chaotic depending on the nature of the scattering dynamics. Yet more stunning effects are achieved by large suspensions of active particles swimming en masse when bounded by freely moving interfaces. Applications are envisioned in bioremediation and sorting of active particles or microorganisms, and the work may speak to the behavior of biofilms and motile suspensions in heterogeneous or porous environments.

Saverio Spagnolie is an assistant professor in mathematics at the University of Wisconsin-Madison with a courtesy appointment in chemical and biological engineering. His research interests include fluid dynamics, soft matter, biolocomotion and numerical analysis. He is the founder of the Madison Applied Mathematics Laboratory, an interdisciplinary research lab with a focus on fluid-structure interactions. Before arriving in Madison, Saverio received a Ph.D. in mathematics at the Courant Institute of Mathematical Sciences, then held postdoctoral positions in the Mechanical/Aerospace Engineering department at UC San Diego and in the School of Engineering at Brown University.

Wednesday, January 10, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Using Coupled Fire/Atmosphere Modeling to Advance Wildland Fire Science and Assist Decision Makers

Rod Linn

Senior Scientist
Los Alamos National Laboratory (LANL)

Advancements in computing and numerical modeling have generated new opportunities for the use of coupled fire/atmosphere models in wildfire research. Models such as FIRETEC attempt to represent the interaction between dominant processes that determine wildfire behavior, including: convective and radiative heat transfer, aerodynamic drag and buoyant response of the atmosphere to heat released by the fire. Such models are not practical for operational faster-than-real-time fire prediction due to their computational and data requirements. However, their process-based model-development approach creates an opportunity to provide additional perspectives concerning aspects of fire behavior that have been observed in the field and in the laboratory; allow for sensitivity analysis that is impractical through observations and pose new hypothesis that can be tested experimentally. Specific examples of the use of FIRETEC in this fashion include: 1) investigation of the 3D fire/atmosphere interaction that dictates multi-scale fireline dynamics; 2) the influence of vegetation heterogeneity and variability in wind fields on predictability of fire spread; 3) the interaction between ecosystem disturbances such as insect attacks and potential fire behavior. Additionally, couple wildfire/atmosphere modeling opens new possibilities for understanding the sometime counterintuitive impacts of fuel management and exploring the implications of various prescribed fire tactics. Results from these studies highlight critical roles coupled fire/atmosphere interaction, which is directly affected by the structure of the vegetation in the vicinity of the fire. Vegetation structure not only impact the amount and distribution of combustible material, but it also influences the winds and turbulence that control the convective heating and cooling of unburned fuels Certainly there need to be continued efforts to validate the results from these numerical investigations, but, even so, they suggest relationships, interactions and phenomenology that should be considered in the context of the interpretation of observations, design of fire behavior experiments, development of new operational models and even risk management.

Rod Linn is a senior scientist in the Computational Earth Science group at Los Alamos National Laboratory (LANL), where he studies and models a wide range of atmospheric phenomenon using computational physics. Linn has led much of the development and application of the FIRETEC computer program for predicting wildfire behavior. Dr. Linn received his doctorate from New Mexico State University.

Wednesday, January 17, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Thermal Ignition of Gaseous Mixtures: Experiments and Simplified Modeling

Stephanie A. Coronel

Postdoctoral Scholar
California Institute of Technology
Pasadena, CA

In recent decades, there have been significant advances in flow visualization techniques, including the development of sophisticated optical diagnostics that yield quantitative information. In spite of the existence of newer diagnostics, older and less expensive techniques can still be used today to quantitatively measure parameters of interest in flows. This talk focuses on interferometry, an imaging technique that dates back more than a century but which has only recently been applied to visualization and measurement of ignition of gaseous reactive flows. In addition to interferometry, I discuss the image processing algorithms required to extract temperature from images of optical phase difference (directly measured through interferometry). The technique and algorithms are applied to ignition of reactive mixtures by moving hot particles, an explosion hazard that is present in the nuclear, aircraft, and industrial sectors. Spatio-temporal temperature measurements of the flow (Re < 200) indicate that ignition preferentially occurs in the region of flow separation of the particle. Furthermore, a simplified model of reactive flow adjacent to a hot surface indicates that ignition occurs some distance away from the surface. At this location, heat release in the gas from the chemical reactions exceeds heat losses back to the surface.

Wednesday, January 24, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: J.A. Domaradzki

Intracardiac Blood Flow Quantification in the Clinical Setting. Ready for Prime Time?

Juan Carlos del Alamo

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

Recent advances in imaging technology and computational fluid dynamics now allow physicians to obtain non-invasive robust measurements of intracardiac blood flow in the clinical setting. These advances have revealed that blood flow inside the heart chambers is characterized by the formation of unsteady vortex structures, generated during filling, that eventually last until the chambers are emptied.

This talk will summarize our recent efforts toward understanding how these flow patterns contribute to the function of the left ventricle (the main pumping chamber of the heart). We will show that the normal ventricular flow patterns: 1) Contribute to efficient filling of the ventricle. 2) Efficiently redirect the transit of blood towards the ventricle’s outflow tract. 3) Minimize the number of cardiac cycles that blood stays in ventricular transit, thereby reducing the risk of intraventricular blood clotting.

We will also illustrate how intraventricular flow quantification can be translated to the clinical setting in order to characterize and optimize the impact of clinical interventions and cardiac device implantation (e.g. bi-ventricular pacemakers and ventricular assist devices). In addition, we will provide examples of clinical studies in which we use intraventricular flow analysis to predict the risk of intracardiac blood clot formation and stroke, both in patients with regularly beating hearts and in patients with atrial fibrillation.

Juan Carlos del Alamo received a B.S., M.S. and Ph. D. in Aerospace Engineering at the Polytechnic University in Madrid. He was a Fulbright postdoctoral fellow at Harvard University and UC San Diego, where he received training in experimental cell mechanics and cardiovascular flows. Prof. del Alamo’s lab at UCSD focuses on biological fluid mechanics and cardiovascular physiology, with particular emphasis on cellular biomechanics and non-invasive characterization of intracardiac flows. This research has been recognized with a US Geological Survey Director’s Award (2010), the NSF CAREER Award (2011), the Hellman Family Fellowship (2012), and the William Parmley Award from American College of Cardiology (2015).

Monday, January 29, 2018
11:00 am
Hughes Aircraft Electrical Engineering Center, Room 132 (EEB 132)

Refreshments will be served at 10:45.

host: J.A. Domaradzki

—REMARKABLE TRAJECTORY LECTURE SERIES—

Catching The Wave

Larry Redekopp

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

In this lecture we will engage in a “jet-ski ride” over and through a variety of wave phenomena explored during the span of my research career. Various hydrodynamic and gas dynamic wave types will be considered encompassing a range of scales extending from 10+7m to 10-4m, and several requisite mathematical contributions will be noted. Particular wave contexts and attendant applications vary from aerodynamics to planetary atmospheres to ocean physics to lake hydrodynamics to ink-jet printers, and involve both stable and unstable dynamics. This excursive “wave rider” tour will conclude with brief comments relating to career perspectives on educator experience, administrative involvements, professional contributions, and personal philosophy.

Wednesday, January 31, 2018
Reception 12 NOON – 12:45 PM
Lecture 12:45 PM – 2:00 PM
The Vineyard Room, International Academy Building/Davidson Conference Center

Experimental Mechanics Across Multiple Time and Spatial Scales

Kara Peters

Professor
Department of Mechanical and Aerospace Engineering
North Carolina State University
Raleigh, NC

This presentation will provide an overview of research programs at NCSU, focused on the development of new experimental mechanics techniques to collect information simultaneously across multiple time and spatial scales. This information can then reveal how failure and energy dissipation phenomena are coupled between these scales. Many of these techniques have been specifically created for extreme environments, e.g. high temperature or high-energy dynamic events. I will first discuss current research at NCSU towards integrating sensor networks into aircraft structures for monitoring of the airframe during fabrication, service and repair. Embedding sensors into the airframe structures can provide information not obtainable from surface mounted sensor systems, however also presents issues of interpretation of sensor signals and potential changes to the airframe durability. Example projects to be discussed include high-speed, full spectral interrogation of fiber Bragg grating sensors for damage assessment; optimization of sensor networks embedded in the airframe structure; and remote bonding of fiber Bragg grating sensors for Lamb wave detection in structures. The unique direction of these research activities is that they bridge the gap between the material and structural mechanics and optics/photonics communities to enable these new measurement techniques. Afterwards, I will present a general overview of other research areas in my group, for example high-speed polarization imaging for the measurement of collagen fiber realignment in the tendon-to-bone insertion region during dynamic impact events.

Kara Peters is a Professor in the Department of Mechanical and Aerospace Engineering at North Carolina State University. She received her PhD in Aerospace Engineering from the University of Michigan in 1996. For her dissertation work, she received the Ivor K. McIvor Award for Applied Mechanics at the University of Michigan. Following her PhD, Dr. Peters worked as Post-Doctoral Researcher in the Laboratory of Applied Mechanics at the Ecole Polytechnique Fédérale de Lausanne (Swiss Institute of Technology at Lausanne). Dr. Peters is a member of the ASME Adaptive Structures and Material Systems Technical Committee and was the chair of the SPIE Smart Structures and Materials Symposium in 2010 and 2011. She is an Associate Editor of the journal Smart Materials and Structures and on the editorial board of Measurement Science and Technology. Currently, Dr. Peters is serving as a rotator as the Program Manager of the Mechanics of Materials and Structures Program at the National Science Foundation.

Wednesday, February 7, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: J.A. Domaradzki

Flame Hole Dynamics Applied to the Modeling of Turbulent Nonpremixed Combustion

Carlos Pantano

Professor
Department of Mechanical Science and Engineering
University of Illinois at Urbana-Champaign
Urbana, Il

Turbulent diffusion flames can be quenched in regions of high strain owing to increased heat loss away from the reaction zone. These chemically inert regions are sometimes called flame holes (Dold et al. 1991). Turbulent flames with extinction are relevant in modern combustors where the flame temperature is kept low to reduce pollutant formation or in lifted jet flames used for thermal protection of the burner liner. Modeling the dynamical behavior of flame holes, without incorporating a detailed chemical-transport description, requires new numerical methods that describe the evolution in time of the flame boundary (or rim) on the moving stoichiometric surface. The kinematics of the flame rim is normally approximated as that of a two-dimensional edge flame whose speed of propagation is controlled by the local strain conditions. The computational challenge is the efficient numerical evolution of the flame rim using a state field defined on a two-manifold (of varying shape, and possibly multiply connected). In this talk, I will describe recent progress on the numerical and physical modeling of flame holes as it applies to turbulent nonpremixed flames with extinction. Special emphasis is made to achieve high-order of accuracy, flexibility, and robustness, while maintaining relatively low computational cost.

Carlos Pantano received his Bachelor degree in Industrial Engineering with specialization in Electrical Engineering from the University of Sevilla in Spain. He received a Masters in Applied Mathematics from Ecole Centrale Paris in France, and a Masters and PhD in Mechanical Engineering from the University of California San Diego. He held a Senior Postdoctoral position in Engineering from 2000 to 2001 at the Office National d’Etudes et de Recherches Aerospatiales in France and then moved to the California Institute of Technology as a senior post-doctoral associate and later as a senior research scientist until 2006. Currently, he holds the rank of Professor in Mechanical Engineering at Illinois. Professor Pantano received the Presidential Early Career Awards for Scientists and Engineering (PECASE) in 2006. He is currently an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA) and member of American Physical Society (APS), Society for Industrial and Applied Mathematics (SIAM), and the Combustion Institute.

Thursday, February 15, 2018
11:00 AM
Location TBD

Refreshments will be served at 10:45 am.

host: J.A. Domaradzki

Tutorial on Machine Learning and Neural Networks, Part I

Kevin Chen

Center for Communications Research
La Jolla, CA

Tuesday, February 20, 2018
1:00 PM
Laufer Library (RRB 208)

host: Eva Kanso

Data Driven Computing

Trenton Kirchdoerfer

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

Data Driven Computing is a new field of computational analysis which uses constitutive data sets to directly produce predictive outcomes without the need to formulate constitutive models. These methods directly associate data inputs and simulation outputs to provide insights into the causality of specific simulation outcomes. This presentation will give an overview of what makes a solver Data-Driven, how to test such solvers for convergence, and then explore developed methods. The demonstrations of efficacy focus on problems in mechanics, including both static and dynamic truss problems. Though this class of solvers is newly developed, it offers a data-based solution strategy that is uniquely suited for multi-scale simulations in many fields. A brief description of the presenter’s other research interests is also included.

Trenton Kirchdoerfer is a postdoctoral researcher at the California Institute of Technology where he earned his PhD in 2017. Prior to attending Caltech, he worked at the Southwest Research Institute where his projects included the simulation and testing of blasts, detonations and ballistic impacts. The focus of his graduate work was the developement of Data Driven Computing, with additional work in simulated lightning attachment to aircraft components. He is presently making use of topology optimization methods to suggest improvements for solid rocket propellants.

Wednesday, February 21, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: G. Spedding

Tutorial on Machine Learning and Neural Networks, Part II

Kevin Chen

Center for Communications Research
La Jolla, CA

Thursday, February 22, 2018
1:00 PM
Laufer Library (RRB 208)

host: Eva Kanso

Diving Wedges and Tumbling Wings

Lionel Vincent

Postdoctoral Scholar
Aerospace and Mechanical Engineering
University of Southern California
Los Angeles, CA

In the animal and vegetal world, shape and flexibility are two crucial parameters, ultimately impacting fitness and reproduction chances. In this talk, I will cover two fundamental projects aiming to investigate the role of these two parameters on water entry dynamics and aerodynamic performance of flying wings.

Diving induces large pressures during water entry, accompanied by the creation of cavity and water splash. We investigate the impact forces and splash evolution of diving wedges as a function of the wedge opening angle. We observe a gradual transition from smooth to impactful, injury-prone entry entry as the wedge angle decreases. We characterize the shapes of the cavity and splash created by the wedge and find that they are independent of the entry velocity at short times, but that the splash exhibits distinct variations in shape at later times. Combining experimental approach and a discrete fluid particles model, we show that the splash shape results from the interplay between a destabilizing aerodynamic suction force. These findings may have implications in a wide range of water entry problems, with application in naval engineering, disease spreading or platform diving.

Auto-rotating wings are well-accepted experimental surrogate to flying seedpods, which come with a wide variety of shapes and degrees of flexibility. Using a combination of experiments and theoretical approach, we first investigate how span-wise flexibility affects the flying performance. We find that while whole-wing flexibility is unconditionally detrimental to flight, tuned flexibility of the wingtip area can be beneficial. Using wind tunnel experiments, we shed some light on the mechanism behind this unexpected behavior. In a second part, we turn our focus to the effect of planform geometry with the same question: are some shapes intrinsically better than other? Our findings have implication on the design of micro-air vehicles and the prediction of the dispersion of objects of arbitrary shapes.

Tuesday, February 27, 2018
Noon
Laufer Library (RRB 208)

host: Eva Kanso

The Reference Map Technique for Simulating Complex Materials and Multi-Body Interactions

Chris Rycroft

Associate Professor
Harvard John A. Paulson School of Engineering and Applied Sciences
Harvard University
Cambridge, MA

Conventional computational methods often create a dilemma for fluid-structure interaction problems. Typically, solids are simulated using a Lagrangian approach with grid that moves with the material, whereas fluids are simulated using an Eulerian approach with a fixed spatial grid, requiring some type of interfacial coupling between the two different perspectives. Here, a fully Eulerian method for simulating structures immersed in a fluid will be presented. By introducing a reference map variable to model finite-deformation constitutive relations in the structures on the same grid as the fluid, the interfacial coupling problem is highly simplified. The method is particularly well suited for simulating soft, highly-deformable materials and many-body contact problems, and several examples will be presented. This is joint work with Ken Kamrin (MIT).

Chris Rycroft is an associate professor of applied mathematics in the Harvard John A. Paulson School of Engineering and Applied Sciences. He is interested in mathematical modeling and scientific computation for interdisciplinary applications in science and engineering. Prior to his appointment at Harvard, Rycroft was a Morrey Assistant Professor in the Department of Mathematics at the University of California, Berkeley. While in Berkeley, he was part of the Bay Area Physical Sciences-Oncology Center, where he investigated how cancer cells mechanically interact with each other and their environment. Rycroft is a visiting faculty scientist at the Lawrence Berkeley Laboratory, where he has worked on several projects relating to energy production and efficiency. He obtained his Ph.D. in Mathematics in 2007 from the Massachusetts Institute of Technology.

Wednesday, February 27, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Eva Kanso

Smart Additive Manufacturing: Bioinspired Algorithmic Driven Design of Composites

Grace X. Gu

Doctoral candidate and National Defense Science and Engineering Graduate (NDSEG) Fellow
Department of Mechanical Engineering
MIT
Cambridge, MA

After billions of years of evolution, it is no surprise that biological materials are treated as an invaluable source of inspiration in the search for new materials. Bone, teeth, and spider silk are high-performing biological composites that possess impressive mechanical properties unmatched by their engineering counterparts. Many desired mechanical properties of engineering materials are inherently conflicting. In contrast, natural materials can often avoid these fundamental compromises through their sophisticated hierarchical structures. Additive manufacturing, with its layer-by-layer fabrication capabilities, facilitates leveraging natural material design to create complex bioinspired architectures. Our research focuses on emulating the simple, yet elusive, design paradigms of nature – simple in their constituent building blocks and elusive in their underlying complexity. These concepts lay the foundation for our approach to design rationally toughened composites to be used in protective gear, energy applications, industrial components, and beyond. In this talk, I will discuss ways we have mimicked nature’s designs using simulation, additive manufacturing, and testing to learn how to create synthetic materials with superior mechanical properties (e.g. toughness, strength, impact resistance). Additionally, I will discuss how to further improve and adapt biological designs for engineering requirements through machine learning. In the future, this bioinspired machine learning approach will enable materials-by-design of complex architectures to tackle demanding engineering challenges.

Grace X. Gu is a doctoral candidate and National Defense Science and Engineering Graduate (NDSEG) fellow in the Department of Mechanical Engineering at MIT working in Prof. Markus J. Buehler’s lab. Her current research combines numerical methods with additive manufacturing to produce and study bioinspired optimized multi-phase composites with enhanced impact resistant microstructures. She received her MS from MIT and BS from the University of Michigan, Ann Arbor. During her undergraduate and graduate studies, Grace had the opportunity to intern at Procter & Gamble, Boeing, and ExxonMobil. Grace is the recipient of several awards, including the Materials Research Society Graduate Student Medal and the Materials Science and Technology Graduate Excellence in Materials Science award. Her research is featured in many media outlets such as MIT news, Smithsonian magazine, Popular Science, among others.

Thursday, March 1, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM

host: J.A. Domardzki

Nanoscale Thermal Transport and Energy Conversion

Zhiting Tian

Assistant Professor
Department of Mechanical Engineering
Virginia Tech
Blacksburg, VA

Understanding and manipulating thermal transport in various materials are essential to intentionally design energy-efficient devices and systems while limiting deleterious effects of adverse temperatures on system performance. Nanoengineering offers unique opportunities to achieve unprecedented material properties. It also poses challenges on the scientific understanding because of the intrinsic differences between energy transport processes at the nanoscale and macroscale due to quantum and classical size effects. The overarching goal of my research is to fundamentally understand nanoscale thermal transport and energy conversion processes to enable the design and discovery of materials with desired thermal transport properties for thermal management and energy conversion. My research group leverages a rich set of cutting-edge modeling and experimental techniques including density functional theory, molecular dynamics, Green’s function, time-domain thermoreflectance, transient thermal grating, and inelastic x-ray scattering. In this talk, I will present my research group’s efforts to improve the energy conversion efficiency of inorganic, organic, and hybrid thermoelectric materials as well as thermoelectric devices. I will also illustrate two novel phenomena we recently discovered in polymers – thermal rectification and thermal switching, which lays the groundwork for organic thermal diodes and switches.

Zhiting Tian joined Virginia Tech as an Assistant Professor of Mechanical Engineering in 2014. She is also an affiliated faculty member of Macromolecules Innovation Institute at Virginia Tech. She obtained her Ph.D. in Mechanical Engineering at MIT in 2014, where she received Graduate Women of Excellence Award and Wunsch Foundation Silent Hoist and Crane Award for Academic Excellence. Zhiting’s most recent awards include Office of Naval Research (ONR) Young Investigator Award, NSF CAREER Award, ACS Petroleum Research Fund Doctoral New Investigator Award, 3M Non-Tenured Faculty Award, and Virginia Tech College of Engineering Outstanding New Assistant Professor Award.

Monday, March 5, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM

host: Paul Ronney

Energy Conversion and Storage Explored with Synchrotron X-ray Tomography and Modeling

I.V. Zenyuk

Assistant Professor
Department of Mechanical Engineering
and
Department of Chemical and Biological Engineering
Tufts University
Medford, MA

Understanding transport processes in electrochemical devices (fuel cells, electrolyzers and batteries) is critical for effective energy conversion and storage. Interfacial phenomena of charge and mass transfer depends on local species distribution and probing these interfaces remains a challenge. Tools that are designed for characterization of porous media on a larger scale are not always applicable for thin (< 10 µm) electrodes. Furthermore, nano- and micro-scale transport processes need to be bridged, as these electrodes are hierarchically structured. Fine nano-structures of carbon and other materials are desirable for high surface area and the features of a larger size are needed for higher mass and ion transport. Synchrotron X-ray techniques, such as transmission X-ray microscopy (TXM) and a three-dimensional version of it — X-ray computed tomography (CT) are well-fit to characterize transport in porous electrodes due to the fast, non-intrusive measurements and relatively high resolution 1-2. Spatial resolution is inversionally proportional to the field of view, the higher the resolution the smaller area of observations, therefore imaging at multiple scales is needed to map out processes at micro and nano-scales.

For polymer-electrolyte fuel cells (PEFCs) and anion exchange membrane fuel cells (AEMFCs) effective water management is critical. By introducing the capabilities for operando synchrotron X-ray CT mapping water distribution under various operating condition became possible. Micro X-ray CT is specifically useful tool for probing water distribution in platinum group metal-free (PGM-free) electrodes, as they are order or two order of magnitude thicker (~200 µm) compared to conventional Pt/C electrodes. At 40 mA/cm2 we observed water saturation of 0.4-0.5 at locations near the membrane for both 30oC and 60oC operating temperatures. These large saturation values are due to water pooling in the large voids (mean radius of 25 µm) near the membrane due to fabrication method of depositing ink onto the gas diffuion layer (GDL), forming gas diffusion electrode (GDE)3. With nano X-ray CT swelling of ionomer in nano-pores was observed when comparing the data at 50 % and 100 % RH, where mean radius increased from 273 to 325 nm.

Gas removal in PEM electrolyzers on the anode side is accomplished via bubbles nucleation, growth and removal into the channel. This process is a function of materials selection and operating conditions. The subsecond nature of bubble growth dynamics requires imaging at higher scan-rates that are difficult to achive with X-ray CT. We use X-ray radiography to capture subsecond dynamics, copled to X-ray CT to get three-dimensional layers microstructure for constant current densities (50, 100 and 200 mA/cm2) operating conditions. Bubble detachment frequency was a strong function of current density.

For Li-ion batteries evaluating morphological changes as a function of cycles number can help assessing degradation phenomena. Using X-ray CT and macro, micro and nano-scales we compared morhpology of pristine to cycled commercial battery. Micro-scale allowed observation of current collector pitting, whereas nano-CT allowed observation of tortuosity and porosity changes at the electrode-scale level.

[1] Zenyuk, I. V.; Lamibrac, A.; Eller, J. J.; Parkinson, D. Y.; Marone, F.; Büchi, F. N.; Weber, A. Z., Investigating Evaporation in Gas Diffusion Layers for Fuel Cells with X-Ray Computed Tomography. The Journal of Physical Chemistry C 2016.
[2] Zenyuk, I. V.; Parkinson, D. Y.; Connolly, L. G.; Weber, A. Z., Gas-Diffusion-Layer Structural Properties under Compression Via X-Ray Tomography. Journal of Power Sources 2016, 328, 364-376.
[3] Serov, A.; Shum, A. D.; Xiao, X.; De Andrade, V.; Artyushkova, K.; Zenyuk, I. V.; Atanassov, P., Nano-Structured Platinum Group Metal-Free Catalysts and Their Integration in Fuel Cell Electrode Architectures. Applied Catalysis B: Environmental

Iryna Zenyuk holds a B.S. (2008) in mechanical engineering from the New York University Tandon School of Engineering. She continued her studies at Carnegie Mellon University, where she earned M.S. (2011) and Ph.D. (2013). Her graduate work focused on fundamental understanding of meso-scale interfacial transport phenomena and electric double layers in electrochemical energy-conversion systems. After a postdoctoral fellowship at Lawrence Berkeley National Laboratory in Electrochemical Technologies Group with Dr. Adam Z. Weber Prof. Zenyuk joined the faculty of the Mechanical Engineering Department at Tufts University in 2015.

With the recent technological advances in the transportation sector, robotics and implantable electronics, there is a growing need for reliable, lightweight and durable energy sources to power these technologies. At Tufts, Prof. Zenyuk’s group works on enabling energy solutions by researching high power-density low-temperature hydrogen fuel-cells, Li-metal batteries and electrolyzers. Currently fuel cells durability, low-temperature operation, cost and water flooding are still issues that need to be solved. Prof. Zenyuk works on addressing the problems of the existing state-of-the-art fuel cells through a design strategy encompassing novel materials, chemistries, diagnostic tools and device-level testing. She is a recipient of NSF CAREER award (2017), Interpore society Fraunhofer Award for Young Researchers (2017) and Research Corporation for Science Advancement, Scialog Fellow in Advanced Energy Storage (2017).

Wednesday, March 7, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: J.A. Domaradzki

Energy Conversion and Storage Explored with Synchrotron X-ray Tomography and Modeling

José A. Camberos

Aerospace Engineer, Lead for High Speed Systems Analysis & Design
Air Force Research Laboratory’s Multidisciplinary Science and Technology Center

The world is experiencing an era of rapid change and globalization in which increased competition for resources, access to Information Technology, and changing demographics has the potential to shift the balance of power. In this era, the U. S. Air Force is facing conditions that diverge significantly from the strategic environment of the last two decades as potential adversaries use emergent globalized technology and manufacturing infrastructure to rapidly develop sophisticated military capabilities that create more contested operational environments. The challenge is to ensure our Defense forces obtain the best technology, at the right time, while affordably meeting mission needs. Specifically, future Air Force missions will require all the modern systems performance characteristics: supersonic dash speed, efficient super-cruise, stealth, flexible weapon payloads, maneuverability, active and passive defensive systems and countermeasures, small logistical footprint, and extended standoff ranges beyond that of current systems. To meet the challenge, the Air Force Research Laboratory’s Multidisciplinary Science and Technology Center is developing (conceptual) design capabilities that integrate multiple technical disciplines, effectively, efficiently, and affordably. The payoff envisioned will mitigate the adverse performance impact that comes with unwanted or unanticipated systems interactions and will proactively enable the discovery and exploitation of new phenomena for the development of revolutionary aerospace systems.

Wednesday, March 14, 2018
10:15-11:15 AM
EEB 132

Refreshments will be served at 10:00 am.

host: A. Oberai

New Results on Self-Excitation in Circulatory and Parametrically Excited Systems

Peter Hagedorn

Professor
Mechanical Engineering
Technische Universität Darmstadt
Darmstadt, Germany

In mechanical engineering systems, self-excited vibrations are in general unwanted and sometimes dangerous. There are many systems exhibiting self-excited vibrations which up to this day cannot be completely avoided, such as brake squeal, the galloping vibrations of overhead transmission lines, the ground resonance in helicopters and others. Most of these systems have in common that in the linearized equations of motion the self-excitation terms are given by non-conservative, circulatory forces and/or parametric excitation. The presentation will discuss some recent results in linear and nonlinear systems of this type.

Self-excited vibrations have of course been mathematically modelled and studied at least since the times of van der Pol. The van der Pol oscillator is a one degree of freedom system; its linearized equations of motion correspond to an oscillator with negative damping. Sometimes also other self-excited systems present negative damping, which can be made responsible for self-excited vibrations. In all the engineering systems mentioned above however, the self-excitation mechanism is mainly related to the interaction between different degrees of freedom (modes), and the linearized equations of motions contain circulatory terms. This together with parametric resonance is the main excitation mechanism discussed in this paper. Destabilization by ‘negative damping’ will not be considered. Also stick-slip phenomena are not in the focus of this presentation; they also do not seem to play an important role in all the examples given above.

The systems analyzed in this presentation therefore are characterized by the M, D, G, K, N matrices (mass, damping, gyroscopic, stiffness and circulatory matrices, respectively) which may all be time-dependent. In the unstable case, additional nonlinear terms do of course limit the vibration amplitudes. Different types of bifurcations relevant for these systems have recently been studied in the literature.

In the first part, MDGKN-systems with constant coefficients will be discussed. For a long time it has been well known, that the stability of such systems can be very sensitive to damping, and also to the symmetry properties of the mechanical structure. Recently, several new theorems were proved concerning the effect of damping on the stability and on the self-excited vibrations of the linearized systems. The importance of these results for practical mechanical engineering systems will be discussed. It turns out that the structure of the damping matrix is of utmost importance, and the common assumption, namely representing the damping matrix as a linear combination of the mass and the damping matrices, may give completely misleading results for the problem of instability and the onset of self-excited vibrations.

The second case considered deals with MDGKN-systems with time-periodic coefficients. The stability of these systems can be studied via Floquet theory. A typical property of parametric instability behavior is the existence of combination resonances. However, if parametric excitation in the system is simultaneously present in the K and the N matrices and/or there are excitation terms which are not all in phase, an atypical behavior may occur: The linear system may then for example be unstable for all frequencies of the parametric excitation, and not only in the neighborhood of certain discrete frequencies. Such atypical parametric instability happens even for M, D, G constant and zero mean values for the matrices K(t) and N(t). This was recently observed at the linearized equations of motion for a minimal model of a squealing disk brake. It turns out, that an even much simpler example of such a situation was given about 70 years ago by Lamberto Cesari, but seems to have fallen into oblivion. Until recently it was thought that such out of phase terms in the parametric excitation would not occur in engineering systems. In the presentation it is shown that they may indeed occur for example in the model of a squealing brake and probably in many other mechanical engineering systems, as long as there is slip with friction between solid bodies.

In the unstable case, additional nonlinear terms do of course limit the vibration amplitudes. Different types of bifurcations relevant for these systems are studied using normal form theory, in particular for the ‘Cesari equations’ with additional nonlinearities.

Wednesday, March 21, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Firdaus Udwadia

Manufacturing and Energy Conversion/Storage with Nanostructured Graphitic Carbon

Choongho Yu

Associate Professor
Department of Mechanical Engineering
Texas A&M University
College station, Texas

This seminar presents exciting opportunities with nanostructured graphitic carbon in manufacturing and energy conversion/storage. They have extraordinary electrical/thermal properties and large surface areas, and their properties can be tailored by substituting other elements for carbon. Exemplary research activities with graphitic nanostructures in Dr. Yu’s research group will be introduced.

First, three-dimensional (3D) porous bulk structures manufactured by an in-situ self-assembly process will be presented. The free-standing sponge-like structures are made of covalently-bonded carbon nanotubes (CNTs) using a scalable facile chemical vapor deposition (CVD) method. The covalently-bonded CNTs can provide exceptional mechanical properties and electrical charge transport characteristics. The large surface areas and porous structures offer reaction sites and mass transport channels, which are ideal in electrochemical cells such as rechargeable batteries and fuel cells.

As an example, super-resilient porous structures have been fabricated by strengthening the junctions between CNTs with an elastomer. The key enabling technology is selective and local heating of CNTs by microwave, which cures only near the surface of CNTs. The microwave manufacturing method is being studied for the development of multi-functional composite structures, and a novel roll-to-roll manufacturing process is currently under development.

The porous structures have been utilized for electrochemical cells including rechargeable Li batteries and fuel cells. The covalently-bonded sponge-like CNTs unlike conventional powdery CNTs embedded in a matrix also allow for eliminating inactive/insulating binders. High loadings of active materials have resulted in the next generation Li-S batteries whose energy density can be five times higher than that of conventional Li-ion batteries. Furthermore, the carbon structures were modified/coordinated with nitrogen and a transition metal for substituting prohibitive Pt electrocatalysts, and tested in microbial fuel cells for prolonged time periods over 3 months, demonstrating stable power outputs comparable to those from conventional cells with Pt catalysts.

Lastly, thermal-to-electrical energy conversion using graphitic carbon and polymers will be presented. A novel “thermally chargeable” supercapacitors made of graphitic carbon and/or polymers have been developed by utilizing the Soret effect to simultaneously harvest and store energy. In addition, flexible thermoelectric energy conversion using organic composites and their applications will be introduced.

Choongho Yu is a Gulf/Oil Thomas A. Dietz Career Development Professor in the department of mechanical engineering at Texas A&M University. He received his Ph.D. degree in mechanical engineering from the University of Texas at Austin. His research is closely related to nanomanufacturing and energy conversion/storage. Specific topics include manufacturing methods with nanostructured carbon structures, thermal and electrical transport behaviors in nanostructured materials, organic and inorganic thermoelectric materials, Li-S and Li-air batteries, supercapacitors, electrode/catalysts design for fuel cells, and water desalination.

Thursday, March 22, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM.

Light- and Heat-Managing Nanomaterials for Personal Health and Energy Efficiency

Po-Chun Hsu

Postdoctoral Researcher
Department of Mechanical Engineering
Stanford University
Stanford, CA

Ever since fire was discovered, energy and health have become two vital and interconnected necessities for humans. While energy is an indispensable factor for our prosperity, the huge consumption of energy also produces excessive greenhouse gas emission, causing global warming and extreme climate change. In the US, 12% of total energy is used for maintaining comfortable indoor temperatures, which is the very fundamental needs for human health. Without air conditioning and heating, our productivity and longevity would be greatly limited. Therefore, how to develop new science and technology to reduce the building energy consumption while maintaining thermal comfort and personal health has become a crucial topic in the 21st century.

In this talk, I will present several nanomaterials that can manage photons and heat transfer to enhance building energy efficiency and personal health in an unconventionally effective way. The first part introduces the concept of personal thermal management. Personal thermal management focuses on controlling the temperature around the human body rather than the whole space, so it can provide the same thermal comfort with lower energy demand and shorter turnaround time. For passive personal thermal management, i.e., no additional energy input, the key parameter is the heat transfer coefficient of the clothing. Thermal radiation, as the dominant heat transfer pathways for the indoor scenario, is an extremely effective yet less explored tuning knob. I will demonstrate infrared-reflective metallic nanowires textile for heating and infrared-transparent nanoporous polyethylene (nanoPE) for cooling, both of which achieve superior heating/cooling properties than traditional textiles. The nanoPE textile is further used to fabricate the dual-mode textile that can switch between heating and cooling modes by reversing the textile. This interesting dual-modality can expand the wearers’ adaptability to ambient temperature fluctuation to maintain thermal comfort and potentially prevent cardiovascular and respiratory diseases. The second part introduces transparent electrodes and electrochromic windows. The transparent electrode is the key component for many optoelectronic devices, including photovoltaic cells, touchscreen displays, and smart windows. Transparent electrodes with both high optical transparency and low electrical resistance will greatly benefit the device performances. For building energy efficiency, smart windows are capable of changing its color to control solar heat gain by applying only a few volts of electricity, and the energy demand for indoor temperature control can be reduced. I will introduce metal nanofiber transparent electrodes with the superior electrical and optical properties and durability which can achieve electrochromic windows with high switching speed, mechanical bendability, and long cycle life. Fabricated by electrospinning and various metallization techniques, the metal nanofibers are infinitely long and well-connected and have minimal wire-to-wire junction resistance.

Po-Chun Hsu is a postdoctoral researcher in Department of Mechanical Engineering at Stanford University. He received his PhD in Materials Science and Engineering also at Stanford in 2016. His research interests focus on rational design and synthesis of nanomaterials for photonic and thermal management, which are transformative for sustainable energy and health. He has published 45 papers with multidisciplinary subjects involving radiative heating/cooling textiles, transparent electrodes, lithium-ion batteries, electrocatalysis, and aerosol filters.

Monday, March 26, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM.

Avian Inspired Design

David Lentink

Assistant Professor
Department of Mechanical Engineering
Stanford University
Stanford, CA

Many organisms fly in order to survive and reproduce. My lab focusses on understanding bird flight to improve flying robots—because birds fly further, longer, and more reliable in complex visual and wind environments. I use this multidisciplinary lens that integrates biomechanics, aerodynamics, and robotics to advance our understanding of the evolution of flight more generally across birds, bats, insects, and autorotating seeds. The development of flying organisms as an individual and their evolution as a species are shaped by the physical interaction between organism and surrounding air. The organism’s architecture is tuned for propelling itself and controlling its motion. Flying animals and plants maximize performance by generating and manipulating vortices. These vortices are created close to the body as it is driven by the action of muscles or gravity, then are ‘shed’ to form a wake (a trackway left behind in the fluid). I study how the organism’s architecture is tuned to utilize these and other aeromechanical principles to compare the function of bird wings to that of bat, insect, and maple seed wings. The experimental approaches range from making robotic models to training birds to fly in a custom-designed wind tunnel as well as in visual flight arenas—and inventing methods to 3D scan birds and measure the aerodynamic force they generate—nonintrusively—with a novel aerodynamic force platform. The studies reveal that animals and plants have converged upon the same solution for generating high lift: A strong vortex that runs parallel to the leading edge of the wing, which it sucks upward. Why this vortex remains stably attached to flapping animal and spinning plant wings is elucidated and linked to kinematics and wing morphology. While wing morphology is quite rigid in insects and maple seeds, it is extremely fluid in birds. I will show how such ‘wing morphing’ significantly expands the performance envelope of birds during flight, and will dissect the mechanisms that enable birds to morph better than any aircraft can. Finally, I will show how these findings have inspired my students to design new flapping and morphing aerial robots.

Professor Lentink’s multidisciplinary lab studies biological flight, in particular bird flight, as an inspiration for engineering design. http://lentinklab.stanford.edu He has a BS and MS in Aerospace Engineering (Aerodynamics, Delft University of Technology) and a PhD in Experimental Zoology cum laude (Wageningen University). During his PhD he visited the California institute of Technology for 9 months to study insect flight. His postdoctoral training at Harvard was focused on studying birds. Publications range from technical journals to cover publications in Nature and Science. He is an alumnus of the Young Academy of the Royal Netherlands Academy of Arts and Sciences, recipient of the Dutch Academic Year Prize, the NSF CAREER award and he has been recognized in 2013 as one of 40 scientists under 40 by the World Economic Forum.

Wednesday, March 28, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Geoff Spedding

Process Modeling and System Design for Scalable and Affordable Nanomanufacturing

Sourabh Saha

R&D Engineer
Lawrence Livermore National Laboratory
Livermore, CA

There is a demonstrated need for scalable and affordable manufacturing of complex micro and nano-scale structures for applications such as photonics-based sensing, mechanical metamaterials, electrochemical energy storage, and fluidics-based medical diagnostics. Although high-rate patterning of such structures is feasible via replication of templates/stamps, overall scalability is limited by expensive and slow template generation processes. Here, I will present case studies for three different pattern generation techniques to demonstrate how I utilize process modeling and system design to quantify and overcome scalability versus performance tradeoffs. First, I will present process modeling of dip pen nanolithography which is a tip-based nanofabrication technique capable of writing <50 nm features. I will demonstrate how simplified yet physically accurate models can generate valuable process knowledge that cannot be obtained through experimentation alone. Next, I will present my work on predictive design and fabrication of multi-period hierarchical structures via wrinkling/buckling of thin films – an inherently scalable mechanical self-organization technique. I will demonstrate how I have utilized custom-made experimental and computational tools to systematically study and increase the complexity of patterns generated via wrinkling. Finally, I will present my recent work on two-photon lithography (TPL). TPL is a point-scanning additive manufacturing technique capable of generating 3D structures with <150 nm features. Past attempts to parallelize TPL have failed to preserve the ability to fabricate arbitrarily complex 3D structures. At LLNL, we have successfully overcome this tradeoff by harnessing the temporal properties of ultrafast lasers to achieve at least two orders of magnitude increase in the curing rate without sacrificing the submicron feature resolution.

Sourabh Saha is an R&D Engineer at Lawrence Livermore National Laboratory. He previously held a postdoctoral position at LLNL from 2015 to 2017. He received his PhD in Mechanical Engineering from MIT in 2014 and his Bachelors and Masters in Mechanical Engineering from IIT Kanpur, India in 2008. His research is in the area of scalable and affordable nanomanufacturing with the goal of breaking traditional engineering tradeoffs through process and system innovations. His wrinkling research was recognized at ASME IMECE 2013 conference with a best poster award and at MIT he was a recipient of the Pappalardo graduate fellowship and the Martin family fellowship for sustainability. At LLNL, he is leading a Laboratory Directed Research & Development (LDRD) project to scale up two-photon lithography. He holds 4 issued/allowed patents on wrinkling and is licensed in California as a Professional Engineer.

Monday, March 29, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM.

Manipulating Matter Down to the Single-Cell Level with Acoustic Tweezers

David Collins

Postdoctoral Research Fellow
Massachusetts Institute of Technology
and
Singapore University of Technology and Design

How can we move something too small to touch? Very high frequency sound fields (>100 MHz) provide a promising avenue for microscale manipulation, yielding acoustic wavelengths on the order of individual cells. Using surface acoustic waves (SAW), a dynamic actuation method uniquely suited to generating microscale forces, I’ve performed deterministic sorting, nanoparticle concentration, droplet generation and the first acoustic 2D patterning of individual cells. In recent work, I’m creating microscale acoustic waveguides for even more refined activities. Combined with other approaches, acoustic forces show substantial promise for structuring materials and human tissues at the microscale and as a probe for studies in mechanobiology.

David Collins is a joint Postdoctoral Research Fellow at the Massachusetts Institute of Technology (MIT) and the Singapore University of Technology and Design (SUTD). He has 24 publications on novel acoustic actuation methods and the physics of advanced microscale manipulation, including work appearing in Physical Review Letters, Nature Communications and Science Advances. Interests include acoustofluidic waveguides and arbitrary acoustic field generation for nonuniform micropatterning. David completed his degrees in Melbourne (Australia) and was awarded the Bill Melbourne Medal for best engineering PhD thesis.

Monday, April 2, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM.

Building a Better Nonuniform Fast Fourier Transform

Alex H. Barnett

Group Leader, Numerical Algorithms
Center for Computational Biology
Flatiron Institute (Simons Foundation)New York, NY
New York, NY

The NUFFT allows Fourier analysis of data on non-uniform points at close-to-FFT speeds. It has many applications in science and engineering. I will explain what happens “under the hood” in our new implementation (FINUFFT). This includes 1) a simpler spreading kernel that accelerates run-times for the same accuracy, while preserving a rigorous error analysis, and 2) smart multi-threading. Along the way we will discover how the nationally known bluegrass fiddler Tex Logan fits into the story. Joint work with Jeremy Magland.

Alex Barnett is an applied mathematician and numerical analyst. He was a faculty member in the mathematics department at Darmouth College for 12 years, becoming a full professor in 2017. He obtained his Ph.D. in physics at Harvard University, followed by a postdoctoral fellowship in radiology at Massachusetts General Hospital and a Courant Instructorship at New York University. His research interests include scientific computing, partial differential equations, integral equations, biomedical imaging, neuroscience, inverse problems and quantum chaos. Barnett is well known for numerical work in wave scattering, high-frequency eigenvalues, potential theory, periodic geometries and fast algorithms. He has received several grants from the National Science Foundation, and Dartmouth’s Karen E. Wetterhahn Memorial Award for Distinguished Creative or Scholarly Achievement.

Wednesday, April 4, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Eva Kanso

Solid Stress and Elastic Energy as New measures of Tumor Mechanopathology

Hadi T. Nia

NIH Postdoctoral Fellow
Massachusetts General Hospital
and
Harvard Medical School

Solid stress and tissue stiffness affect tumor progression, metastasis and treatment. Unlike stiffness, which can be precisely mapped in tumors, the measurement of solid stresses is challenging. In this seminar, I will present three distinct and quantitative techniques to obtain two-dimensional spatial mappings of solid stress and the resulting elastic energy in excised or in situ tumors with arbitrary shapes and wide size ranges. I will present major findings from the application of these methods in mouse models of primary tumors and metastasis including: (i) solid stress generation depends on both cancer cells and their microenvironment; (ii) solid stress increases with tumor size; and (iii) mechanical confinement by the surrounding tissue significantly contributes to intratumoral solid stress. Finally, I will discuss my more recent work on neurological and vascular impairments induced by solid stress from primary and metastatic brain tumors, and potential pharmacological remedies to counter these effects.

Hadi T. Nia is an NIH postdoctoral fellow at Massachusetts General Hospital and Harvard Medical School, supervised by Dr. Rakesh Jain. His research interests include multiscale cancer mechanobiology, and the development of innovative tools and model systems to investigate the physical microenvironment of tumors. He received his Ph.D. under Profs. Alan Grodzinsky and Christine Ortiz at MIT, investigating the molecular origin of solid-fluid interactions in cartilage and its association with osteoarthritis. Hadi has been awarded fellowships from the National Cancer Institute (F32), Fund for Medical Discovery, and Whitaker Health Sciences Fund.

Thursday, April 5, 2018
11:00 AM
Laufer Library (RRB 208)

Refreshments will be served at 10:45 AM.

John Laufer Lecture

New Analytical Models for Turbulence Spectra and Turbine Wakes in Wind Farms

Charles Meneveau

Louis M. Sardella Professor of Mechanical Engineering
Department Of Mechanical Engineering
Johns Hopkins University
Baltimore, MD

Reduced order, analytically tractable models remain an important tool in the wind energy area, both for design and control purposes. In this presentation we focus on two fluid mechanical themes relevant to wind farm design and control. The first topic deals with spectral characteristics of the fluctuations in power generated by an array of wind turbines in a wind farm. We show that modeling of the spatio-temporal structure of canonical turbulent boundary layers coupled with variants of the Kraichnan’s random sweeping hypothesis can be used to develop analytical predictions of the frequency spectrum of power fluctuations of wind farms. In the second part we describe a simple (deterministic) dynamic wake model, its use for wind farm control, and its extension to the case of yawed wind turbines. The work to be presented arose from collaborations with Juliaan Bossuyt, Johan Meyers, Richard Stevens, Michael Wilczek, Laura Lukasen, Michael Howland, Carl Shapiro and Dennice Gayme. We are grateful for National Science Foundation support.

Charles Meneveau is the Louis M. Sardella Professor in the Department of Mechanical Engineering at Johns Hopkins University and is Associate Director of the Institute for Data Intensive Engineering and Science (IDIES) at Hopkins. He received his B.S. degree in Mechanical Engineering from the Universidad Técnica Federico Santa María in Valparaíso, Chile, in 1985 and M.S, M.Phil. and Ph.D. degrees from Yale University in 1987, 1988 and 1989, respectively. During 1989/90 he was a postdoctoral fellow at the Center for Turbulence Research at Stanford. He has been on the Johns Hopkins faculty since 1990. His area of research is focused on understanding and modeling hydrodynamic turbulence, and complexity in fluid mechanics in general. The insights that have emerged from Professor Meneveau’s work have led to new numerical models for Large Eddy Simulations (LES) and applications in engineering and environmental flows, including wind farms. He also focuses on developing methods to share the very large data sets that arise in computational fluid dynamics. He is Deputy Editor of the Journal of Fluid Mechanics and served (until 2015) for 13 years as the Editor-in-Chief of the Journal of Turbulence. Professor Meneveau is a member of the US National Academy of Engineering (2018), a foreign corresponding member of the Chilean Academy of Sciences (2005), and a Fellow of the American Academy of Mechanics, the U.S. American Physical Society and the American Society of Mechanical Engineers. He received an honorary doctorate from the Danish Technical University (in 2016), the inaugural Stanley Corrsin Award from the American Physical Society (2011), the Johns Hopkins University Alumni Association’s Excellence in Teaching Award (2003), and the APS François N. Frenkiel Award for Fluid Mechanics (2001).

Wednesday, April 11, 2018
3:00 PM
Michelson Hall, Room 101 (MCB 101)

Reception following

host: Mitul Luhar

High-Throughput Microfluidics for Affinity-Based Isolation of Rare Cells in Blood

Cagri Savran

Professor
School of Mechanical Engineering
Purdue University
West Lafayette, IN

The Savran Laboratory at Purdue University performs research at the intersection of engineering and
healthcare, with an emphasis on development of novel microtechnologies and Lab-On-a-Chip systems for
non-invasive diagnostics and single cell analysis. In this talk, Dr. Savran will present recent developments
in capturing and analyzing rare tumor cells in blood samples.

Circulating tumor cells (CTCs) detach from solid tumors and enter blood circulation. They can therefore
be captured by a blood test and provide a glimpse into the tumor without having to perform invasive
procedures like biopsies. Their sheer count provides information about the overall tumor burden; they
provide access to an intact genome; they allow RNA sequencing; and they can be cultured in vitro as well
as in vivo to form mouse surrogates for personalized therapy. However, their isolation is utterly
challenging. They are very scarce (~1 in a billion) and cannot be found by analyzing finger-pricks
(~microliter) of blood. Analyzing larger (~10 milliliters) volumes quickly requires new engineering
approaches and high-throughput designs that are different from conventional microfluidics. Dr. Savran
will describe new affinity-based microfluidic detection modalities that can process blood samples at
unprecedented volumetric throughputs to find and compartmentalize rare single cells. He will also
present the underlying engineering design challenges, as well as the application of the platforms to
analyze blood samples of cancer patients. Dr. Savran will present future opportunities both from an
engineering perspective as well as the potential impact in fields that range from oncology to prenatal
medicine.

Cagri Savran received his B.S. from Purdue University in 1998 and his S.M. and Ph.D. from MIT in 2000
and 2004, all in mechanical engineering. His undergraduate and masters studies were focused on
vibrations, noise control, smart structures and feedback systems. During his Ph.D. he made a transition
into MEMS, nanotechnology and their application to biology and medicine, which has been his general
field of research since. He is currently a professor in the School of Mechanical Engineering at Purdue
University.

Dr. Savran developed the first mechanical biosensor with an inherent disturbance rejection modality, allowing detection of extremely small, nanometer level motions that result from biomolecular adsorption.
He also demonstrated the first use of aptamers in MEMS-based biosensing. The numerous patented
platforms Dr. Savran developed include novel mechanical biosensors and manipulators for single cell
studies, diffraction-based biomolecular detectors as well as microfluidics for Next Generation Sequencing
applications. Dr. Savran is particularly interested in development of novel engineering platforms for noninvasive
diagnostics that save patients from repeated invasive procedures such as biopsies and
amniocentesis. Microfluidic blood tests developed in the Savran Lab have the fastest volumetric
throughput in their class and are currently being used in clinical studies to monitor progression and
recurrence of cancer.

Dr. Savran’s technologies are patented in 11 countries and are currently being commercialized in fields
that range from cancer diagnostics to prenatal medicine.

Wednesday, April 18, 2018
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Paul Newton