Hollow Vortices

Stefan Llewellyn Smith

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

Hollow vortices are vortices whose interior is at rest. They posses vortex sheets on their boundaries and can be viewed as a desingularization of point vortices. After giving a history of point vortices, we obtain exact solutions for hollow vortices in linear and nonlinear strain and examine the properties of streets of hollow vortices. The former can be viewed as a canonical example of a hollow vortex in an arbitrary flow, and its stability properties depend on a single non-dimensional parameter. In the latter case, we reexamine the hollow vortex street of Baker, Saffman and Sheffield and examine its stability to arbitrary disturbances, and then investigate the double hollow vortex street. Implications and extensions of this work are discussed.

Stefan G. Llewellyn Smith received his Ph.D. in applied mathematics from the University of Cambridge in 1996. He was a research fellow of Queens’ College, Cambridge, from 1996 to 1999, working in the Department of Applied Mathematics and Theoretical Physics. He spent a year from 1996 to 1997 on a Lindemann Trust Fellowship at the Scripps Institution of Oceanography in La Jolla. He joined the Department of Mechanical and Aerospace Engineering at UCSD in 1999 as Assistant Professor of Environmental Engineering. His research interests include fluid dynamics, especially its application to environmental and engineering problem, acoustics and asymptotic methods.

Wednesday, January 13, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Biomechanical Imaging: Shall We See How You Feel?

Assad A. Oberai

Mechanical Aerospace and Nuclear Engineering
Scientific Computation Research Center
Rensselaer Polytechnic Institute
Troy, NY

Certain types of diseases lead to changes in the microstructural organization of tissue. Altered microstructure in turn leads to altered macroscopic tissue properties, which are often easier to image than the microstructure itself. Thus the measurement of macroscopic properties offers a window into tissue microstructure and health. In Biomechanical Imaging (BMI) we aim to utilize this association between the macroscopic mechanical properties of tissue and its health by generating images of the mechanical properties and using these to infer tissue microstructure and health.

At the heart of BMI lies the solution of an inverse problem in continuum mechanics: given the deformation of the medium (tissue) and a constitutive model, determine the spatial distribution of the material properties. In this talk, I will discuss the well-posedness of this inverse problem and describe efficient and robust algorithms for solving it. I will also describe the development of new constitutive models that are motivated by tissue microstructure, and applications of BMI that include improved in‐vivo diagnosis of breast cancer, and imaging elastic properties of tissue at the cellular, and sub-cellular levels.

Assad Oberai is a Professor in the Department of Mechanical Aerospace and Nuclear Engineering at Rensselaer Polytechnic Institute (RPI). He is also the Associate Dean for Research and Graduate Studies in the School of Engineering, and the Associate Director of the Scientific Computation Research Center (SCOREC). Assad started his academic career at Boston University, where he was an Assistant Professor of Aerospace and Mechanical Engineering from 2001 to 2005. He joined the Rensselaer faculty in 2006 as an Assistant Professor, was promoted to Associate Professor in 2007, and to Professor in 2011. Assad received a PhD in Mechanical Engineering from Stanford University in 1998, an MS in Mechanical Engineering from the University of Colorado in 1994, and a Bachelors degree in Mechanical Engineering from Osmania University in 1992.

Assad is a recipient of the National Science Foundation Career award in 2005 and the Department of Energy Early Career award in 2004. He was awarded the Thomas J.R. Hughes Young Investigator Award by the American Society of Mechanical Engineers in 2007. He received the Humboldt Foundation Award for experienced researchers in 2009, and the Erasmus Mundus Master Course Lectureship at Universidad Politécnica de Cataluña, Barcelona in 2010. In 2015, he was awarded the Research Excellence Award by the School of Engineering at RPI, and was elected as a Fellow of the United States Association of Computational Mechanics (USACM). In 2016, he was elected as a Fellow of the American Institute of Medical and Biological Engineering (AIMBE). He is on the board of academic editors for the journal PlosOne.

Wednesday, January 20, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Boomerang Flight Dynamics

John Vassberg

Lead Engineer
Boeing Commercial Airplanes Design Center
Long Beach, CA

Aerodynamic characteristics and flight dynamics of boomerangs are investigated. A basic aerodynamic model, developed in the 1960’s, is expanded upon using Blade Element Theory. The new aerodynamic model is coupled with a gyroscope model for rudimentary analyses. Some significant findings are made regarding the radius of a boomerang’s circular flight path, the required inclination angle of its axis-of-rotation, its trim state, as well as its dynamic stability. These discoveries provide a basic understanding of how the interplay between aero-dynamic forces and moments, and gyroscopic precession combine to return the boomerang to its rightful owner by way of a circular flight path.

A traditional V-shaped boomerang design is developed as a case study for further detailed analyses. Unsteady Reynolds-averaged Navier-Stokes solutions provide accurate aerodynamic characteristics of the subject boomerang. The high-fidelity aerodynamic model is coupled with the equations of motion to provide accurate six-degree-of-freedom simulations of boomerang flight dynamics. Boomerang orientation during its flight trajectory is described by the classical Euler angles.

Wednesday, January 27, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Hosted jointly with the USC Biomedical Engineering Department

Rays vs. Shadows: Fighting Global Blindness through Ophthalmic Genetic & Bioengineering

Balamurali K. Ambati

Professor
and
Director of Corneal Research
Moran Eye Center
University of Utah
Salt Lake City, UT

Over 30 million people are blind in both eyes, with another 200 million patients with significant loss of vision in one or both eyes. This is an unnecessary tragedy—80% of this vision loss is preventable or treatable. Dr. Ambati shares his journey in vision research and global health by showing how ocular biology and drug delivery can be married and employed to combat the principal challenges of our time in the world of vision – cataract, corneal scarring, macular degeneration, and diabetic retinopathy. He will his discuss his laboratory’s innovations in drop-free cataract surgery, targeted intraceptor nanoparticles for macular degeneration and corneal transplant rejection, and neurovascular restoration in the diabetic retina. He will also lay out the landscape and opportunities in eye research and global blindness.

Bala Ambati, MD, PhD, MBA is a cornea specialist with a research focus in angiogenesis. Splitting his time equally between clinic and research, his most significant basic science research advances have been the identification of sFlt-1 as the prime mediator of corneal avascularity (published in Nature and recognized by Science as a Signaling Breakthrough of the Year) and the development of Flt-1 intraceptors as a novel intracellular anti-VEGF therapy, of significant impact as current anti-VEGF agents work only extracellularly. Dr. Ambati’s team is presently focused on the role of sFlt-1 in maintaining ocular vascular demarcations, work which was awarded the 2012 ARVO/Genentech Award for Research in Macular Degeneration, the 2013 Troutman-Veronneau Prize and the 2014 Ludwig von Sallmann Clinician-Scientist Award. In collaboration with Dr. Uday Kompella, targeted nanoparticles delivering Flt-1 intraceptor therapy have demonstrated significant anti-angiogenic activity in corneal, retinal, and cancer models in multiple species.

Clinically, Dr. Ambati was the first to describe use of bevacizumab (Avastin) to treat corneal transplant rejection. He has developed key surgical innovations and is developing transformational ocular drug delivery implants which will serve as a versatile platform for treating macular degeneration, glaucoma, and other diseases by sustained release of multiple drugs from within the lens capsule. This will mark a major advance over the use of intravitreal injections or complex regimens of topical polypharmacy. He was recently cited at the #1 eye surgeon in the Top 40 under 40 global competition by The Ophthalmologist magazine.

Dr. Ambati has been recognized for his teaching excellence by a University of Utah Resident Research Mentor Award, the Gold Humanism Award, and by serving as an Instructor at the Harvard Cataract Course for 2009 and 2010. His community and overseas service is consistent and giving: he has conducted free eye screenings in New York, Georgia, and Utah, and served as a volunteer eye surgeon with ORBIS, Sight for the Sightless, and Help Mercy International in Ghana, Zambia, India, the Philippines, and Malaysia.

Wednesday, February 3, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Plasma-Assisted Combustion: Fundamental Studies and Engine Applications

Joseph K. Lefkowitz

NRC Research Associate
Aerospace Propulsion Division
Aerospace Sciences Branch
Wright-Patterson AFB, OH

Plasma-assisted combustion is a growing area of research focusing on the use of plasma discharges to improve the efficiency and widen the limits of combustion devices. The governing processes linking electrical discharges and hydrocarbon ignition remains largely unexplored, especially considering the wide variety of temperatures and densities involved in different types of plasma discharges. This work focuses on linking the high energy electrons to fuel oxidation kinetics, using both experimental and numerical methods, in both diffuse and localized plasma discharges in order to explore the specific chemical and thermal effects involved. Implications of this work and further extensions are discussed, including current work in high speed propulsion devices.

Joseph K. Lefkowitz received his Ph.D. in Mechanical and Aerospace Engineering from Princeton University in 2016. He is currently a research associate in the Aerospace Systems Directorate of the Air Force Research Laboratory, working in the High Speed Systems Branch. In 2009 he received the Professor Martin Summerfield Memorial Graduate Fellowship from Princeton University, and in 2016 he received a Research Associate Program Fellowship from the National Research Council. His research interests are in plasma-assisted combustion, high-speed propulsion, optical diagnostics for combustion applications, low temperature and alternative fuel oxidation kinetics, and flame ignition and extinction phenomena.

Wednesday, February 17, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Mechanics of Thin Elastic Rods: Computer Graphics Meets Engineering

Khalid Jawed

Ph.D Candidate
Department of Mechanical Engineering
Massachusetts Institute of Technology
Cambridge, MA

Thin rods are ubiquitous in both nature (e.g. bacterial flagella, human hair) and engineering (ropes, cables), from the micron to the kilometer scale, and often undergo extreme deformation. The geometric nonlinearities that result from the deformation process pose enormous challenges to traditional analytical and numerical tools. Moreover, it is often unfeasible to perform experiments at the original length scale of these systems. We overcome these challenges by combining model experiments and cutting-edge computational tools ported from computer graphics. The prominence of geometry in this class of systems enables the scaling (up or down) of the problem to the desktop scale, which allows for systematic experimental exploration of parameter space. In parallel, we conduct numerical simulations using the Discrete Elastic Rods (DER) method, which was originally developed for the animation industry. For the first time, we port DER into engineering as a predictive computational tool and test ride it against model experiments by studying two a priori unrelated problems, at disparate length scales: (1) coiling of rods on rigid substrate motivated from laying of submarine cables on seabed (kilometer scale), and (2) propulsion and instability in bacterial flagella (micron scale). The excellent agreement found between experiments and simulations illustrates the predictive power of our approach. Scaling (up or down) to the original application then offers unprecedented tools for rationalization and engineering design.

Khalid Jawed is a PhD candidate in mechanics at the Department of Mechanical Engineering, Massachusetts Institute of Technology (expected graduation: May 2016). His research focuses on the mechanics of slender rods; e.g. fuel pipelines, knots in ropes, bacterial flagella. He attained his Master’s degree from the same institution in 2014. He received his undergraduate degrees in Aerospace Engineering and Engineering Physics from the University of Michigan in 2012. His career vision is centered around using computational, experimental, and modeling tools to characterize, enhance, control, and apply the material properties and mechanical instabilities to program the mechanical response of structures. His academic awards include GSNP best speaker award at American Physical Society March Meeting (2014) and outstanding teaching assistant award from MIT Mechanical Engineering (2015).

Monday, February 22, 2016
3:00 AM
Ronald Tutor Hall, Room 211 (RTH 211)

Refreshments will be served at 2:45 pm.

Constitutive Modeling of Soft Engineering and Biological Materials: The Role of Microstructure

Reza Avazmohammadi

Postdoctoral Fellow
Institute for Computational Engineering and Science
The University of Texas at Austin
Austin, TX

The need for a better understanding of structure-function relationships in soft materials is on the rise. This need lies beneath several disciplines including the engineering materials industry and biomechanics. The study of multiscale mechanics of soft engineering materials offers unique opportunities to design multifunctional materials with novel properties. Also, in the field of biomechanics, investigating the mechanistic interplay between the diseased tissue microstructure and the organ-level response helps to develop computational tools that allow clinicians to efficiently predict the progression of diseases.

In the first part of my talk, I will briefly present homogenization-based models for the constitutive behavior of soft engineering materials with particulate microstructure subjected to large deformations. In particular, I will discuss applications in characterization and design of elastomeric composites and microgel suspensions.

In the second part of my talk, I will present a combined theoretical, computational, and experimental approach to characterize and predict the biomechanical behavior of myocardium (the functional tissue of the heart wall) in the light of its fibrous structure. In particular, I will discuss the importance and application of this approach in the context of pulmonary hypertension and myocardial infarction during which the myocardium undergoes substantial mechanical and structural adaptations. Understanding and predicting such adaptations will enable us to develop patient-specific computational models that ultimately allow clinicians to craft therapies optimized for individual patients.

Reza Avazmohammadi is a postdoctoral fellow in the area of cardiovascular simulations at the Institute for Computational Engineering and Sciences at UT Austin. Reza received his B.Sc. in Mechanical Engineering from Iran University of Science and Technology (2005), and his M.Sc. in Applied Mechanics from Sharif University of Technology (2007). Reza continued to work as a researcher at Sharif University in the area of mechanics of composite materials (2007-09). Reza received his Ph.D. degree in Applied Mechanics from University of Pennsylvania (2014) in the area of constitutive modeling of soft composite materials. His research interests are in multiscale-multiphysics modeling of soft materials, with an emphasis on understanding and exploiting the mechanistic link between the microstructure of these materials and their overall response.

Wednesday, February 24, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Accelerating PDE-Constrained Optimization Problems using Adaptive Reduced-Order Models

Matthew Zahr

Ph.D. Candidate
Institute for Computational and Mathematical Engineering
Stanford University
Stanford, CA

Optimization problems constrained by partial differential equations are ubiquitous in modern science and engineering. They play a central role in optimal design and control of multiphysics systems, as well as nondestructive evaluation and detection, and inverse problems. Methods to solve these optimization problems rely on, potentially many, numerical solutions of the underlying equations. For complicated physical interactions taking place on complex domains, these solutions will be computationally-expensive – in terms of both time and resources – to obtain, rendering the optimization procedure difficult or intractable.

I will introduce a globally convergent, non-quadratic trust-region method to accelerate the solution of PDE-constrained optimization problems by adaptively reducing the dimensionality of the underlying computational physics discretization. In this approach, the method of snapshots and Proper Orthogonal Decomposition (POD) are used to build a reduced-order model whose fidelity is progressively enriched while converging to the optimal solution. This ensures the reduced-order model is trained exactly along the optimization trajectory and effort is not wasted by training in other regions of the parameter space. A novel minimum-residual framework for computing surrogate sensitivities of the reduced-order model is introduced that equips the trust-region method with desirable properties. The proposed method is shown to solve canonical aerodynamic shape optimization problems several times faster than accepted methods. This work has been extended to address the specific challenges posed by topology optimization, where high-dimensional parameter spaces are inevitable.

Matthew Zahr is a PhD candidate in Computational and Mathematical Engineering at Stanford University, with minors in Mechanical Engineering and Aeronautics/Astronautics, under the advisement of Prof Charbel Farhat. He received his BSc in Civil and Environmental Engineering, with a minor in Mathematics, from UC Berkeley in 2011.

Friday, February 26, 2016
10:00 AM
EEB 248

Experimental and Numerical Investigations of Flames with Gas Turbine Applications at the University of Cambridge

Jennifer Sidey

Research Assistant
Department of Engineering
University of Cambridge
Cambridge
UK

With growing concern over anthropogenic climate change and increasingly stringent emission standards, the development of low-emission combustion technologies is a necessity. This seminar is concerned with the motivation, development, and implementation challenges associated with gas turbine and reciprocating engine pollutant reduction and the tools the combustion community is using to meet them. Of particular interest is the investigation of processes in which hot combustion products are used as a diluent for fresh reactants. The underlying physics of these processes will be discussed with results from laminar flame calculations, droplet autoignition simulations, and fundamental turbulent flame investigations with high speed laser diagnostics, while their application potential will be assessed through the investigation of a novel gas turbine combustor concept.

Jenni Sidey is a research associate at the University of Cambridge. Her postdoctoral position, funded by the European Commission Joint Clean Sky Initiative, focuses on the investigation of non-premixed, premixed, and spray flame extinction and thermoacoustic oscillations in gas turbine combustors. She completed her PhD in the summer of 2015, investigating heavily preheated and diluted flames. While studying Mechanical Engineering at McGill University, she took part in alternative fuel production and microgravity flame propagation experiments.

Monday, February 29, 2016
10:00 AM
Ronald Tutor Hall, Rm. 211 (RTH 211)

From a Multiscale Computational Framework to Introducing a Novel Surgical Technique for Single Ventricles

Mahdi Esmaily-Moghadam

Postdoctoral Fellow
Center for Turbulence Research
Stanford University
Stanford, CA

Mortality rate among newborns diagnosed with single ventricle heart is as high as 50%. A high rate of morbidity is also observed among the remaining patients. Despite these poor outcomes, the current surgical procedures have remained unchanged in the last five decades. With the recent advancement in computational sciences, it is now possible to simulate novel surgical techniques before adopting them in clinic, allowing to test new ideas without posing any risk to patients.

In the first part of this talk, I will introduce a multiscale framework for accurate modeling of the circulatory system and describe a set of numerical techniques for improving the stability and efficiency of these computations. In the second part, I will present the results of a formal optimization of the conventional surgery. Then, I will introduce a novel surgical technique, which may revolutionize the single ventricle palliation pathway, as an alternative to the conventional surgery.

Mahdi Esmaily-Moghadam received his PhD in Mechanical Engineering from UCSD in 2014. Mahdi is currently a postdoctoral fellow at the Center for Turbulence Research (CTR) at Stanford University, studying particle-laden turbulent flows. He is the author and co-author of twenty peer-reviewed papers in leading journals, recipient of a Kaplan dissertation fellowship, a postdoctoral fellowship from the CTR, and Outstanding Graduate Student award from MAE department, among others. Mahdi’s research interests center around emerging applications in cardiovascular mechanics, computational science, multiscale modeling, and particle-laden flows.

Wednesday, March 2, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Multi-Scale Simulations to Uncover Flow and Transport Behavior in a Physiologically-Realistic Lung

Jessica M. Oakes

UC Presidential Postdoctoral Fellow
Mechanical Engineering
University of California at Berkeley
Berkeley, CA
and
INRIA Paris Rocquencourt

Pulmonary diseases cause a substantial medical and financial burden worldwide and are typically caused by inhalation of air pollution or cigarette smoke over a long period of time. The coupling of multi-physics simulations with animal or human experimental data is necessary to validate model predictions and to improve emerging medical technology. While recent advances in computational resources have enabled sophisticated simulations of airflow and particle transport in the pulmonary airways, it is not currently feasible to resolve the physics for all length and time scales of the lung. To address this challenge, the computational domain may be split into sections, where lower-dimensional models of the small airways may be connected to the three dimensional (3D) models of the large airways. In this seminar, experimentally parameterized 3D-0D and 3D-1D finite element simulations of airflow and particle transport in the lung will be introduced. Regional and local deposition differences between inspiration and expiration will be highlighted as well as the excellent agreement between model predictions and rat experimental data. This work highlights the role of simulations in healthcare and the necessity of coupling modeling with experiments. In addition to these findings, future directions in early diagnosis and optimization of therapeutic delivery in asthmatic and emphysematous patients and the potential health consequences to electronic cigarette aerosol exposure will be discussed.

Jessica Oakes is a UC Presidential Postdoctoral Scholar at UC Berkeley. Following her PhD completion in 2013, Jessica traveled to Paris, France for a one-year postdoctoral appointment at INRIA. The NSF, the Burroughs Wellcome Fund, a Whitaker Scholarship, and an INRIA Postdoctoral Grant have supported her work. Recently, Jessica was awarded an American Lung Association Grant to investigate the health effects of e-cigarettes. Jessica grew up in Western New York and enjoys hiking, reading, art, and traveling.

Monday, March 7, 2016
10:00 AM
Ronald Tutor Hall, Rm. 115 (RTH 115)

Multiscale Fluid Sensing and Transport in Biological and Engineered Systems

Janna C. Nawroth

Postdoctoral Technology Development Fellow
Wyss Institute for Biologically Inspired Engineering
Harvard University
Cambridge, MA

Deformable substrates mediate fluid transport and sensing in many biological systems (e.g., marine animals, inner organs), as well as in some engineered systems (soft microfluidics, soft robots). The latter, however, employ only a fraction of the multitude of mechanisms found in nature. Partly, this reflects the difficulty of isolating straightforward structure-function relationships in multiscale biological tissues that could be translated to engineered materials. The same difficulty has impeded the development of in vitro assays and diagnostics tools for (fluid-) mechanically mediated diseases, such as polycystic kidney syndrome, hearing loss, osteoporosis, and cardiomyopathy. I approach this challenge by studying native and engineered tissues specialized for a particular transport function, which enables me to isolate, quantify, and reverse-engineer selected structure-function relationships. For this, I combine the powers of flow visualization, microfluidic platforms, tissue engineering, and computational studies. Here, I will present major results and goals of my research including (1), quantifying the structure-function relationships of muscle and cilia in health and disease, with applications in biophysical studies, diagnostics, and drug discovery (“organs-on-chips”); (2), designing and building cell-based microfluidic analyzers and processors; and (3), developing biologically-inspired multiscale surfaces for controlling dynamic fluid-structure interactions, such as biofilm formation.

Janna C. Nawroth is a postdoctoral Technology Development Fellow at the Wyss Institute for Biologically Inspired Engineering at Harvard University. She attended Heidelberg University, Germany, where she received her B.S. (2004) and M.S. (2007) in Biotechnology. For her master thesis, Nawroth joined Yale University as a research associate in computational biology with Professor Gordon Shepherd. After Yale, Nawroth attended the California Institute of Technology as a Moore Fellow and obtained her Ph.D. (2012) in Biology. Nawroth’s Ph.D. research, with Professor John Dabiri, received Caltech’s award for the Best Thesis in Nanotechnology and involved the study and design of muscle-powered pumps to manage microfluidic propulsion and particle transport. After her Ph.D., Nawroth spent a year as a Caltech Postdoctoral Fellow in Aeronautics collaborating with Professors John Dabiri, Eva Kanso (USC), Scott Fraser (USC), and Margaret-McFall-Ngai (U Hawaii) to study transport phenomena in ciliated surfaces. At the Wyss, she develops microfluidic devices and signal processing algorithms for exploring the mechanics and flow physics of dynamic tissues for applications in biomedical engineering, disease modeling, and biophysical research.

Wednesday, March 9, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Intrinsic Frequency Method: From Fluid Mechanics to a Novel Point-of-Care Disease Diagnosis

Niema Pahlevan

Clinical Research Investigator
at
Huntington Medical Research Institute
Pasadena, CA
and
James Boswell Postdoctoral Scholar
at
California Institute of Technology
Pasadena, CA

Cardiovascular diseases (CVD) have reached epidemic proportions with serious consequences in terms of human suffering and economic impact. Therefore, there is increasing motivation to develop low-cost and non-invasive methods to monitor, diagnose, and treat CVD. Traditionally, the aorta has been viewed as a resistive conduit with a Windkessel effect or as a resistive wave conduit connected to an active pump, the left ventricle (LV) of the heart. However, these perceptions fail to explain many observed physiological results. Here, we introduce the heart-aorta as a system which accounts for a wave-pumping mechanism that exists inside the aorta. Based on this new look, we developed a novel method and index, the Intrinsic Frequency, for analyzing the dynamics of the cardiovascular system. This concept leads us to a deeper understanding of the physiology and can significantly impact the diagnosis of related clinical diseases. Following this approach, we are able to measure LV ejection fraction using a smartphone (iPhone). In addition, our systems approach has provided us a framework to derive a non-dimensional number (wave condition number) that predicts the optimum arterial wave reflection in mammals.

Niema Pahlevan is James Boswell postdoctoral scholar at California Institute of Technology (Caltech) and clinical research investigator at Huntington Medical Research Institutes (HMRI). Dr. Pahlevan received B.S. in Mechanical Engineering from University of Tehran, M.S. in Mechanical Engineering from California State University, Northridge, and PhD in Bioengineering from Caltech in 2013 under supervision of Professor Mory Gharib. Dr. Pahlevan joined HMRI in 2014 and established a clinical trial to develop a non-invasive and inexpensive method to measure heart’s performance under supervision of Dr. Marie Csete and Dr. Robert Kloner. His research is focused on establishing new techniques and devices of translational medicine, in which mathematical and engineering principles are used to develop novel diagnostic and therapeutic approaches for cardiovascular and cerebrovascular diseases.

Monday, March 21, 2016
10:00 AM
Ronald Tutor Hall, Rm. 115 (RTH 115)

—John Laufer Lecture—

On the Generation of Toroidal Micro-Plasmas in the Flow Field of Impinging Water-Jets

Morteza Gharib

Hans W. Liepmann Professor of Aeronautics
and
Professor of Bioinspired Engineering
Director of Graduate Aerospace Laboratories
Vice Provost
Division of Engineering and Applied Science
California Institute of Technology
Pasadena, CA

There is a renewed interest in atmospheric pressure plasma (APP), also known as atmospheric pressure corona, for its broad scientific and industrial applications. As a weakly ionized non-equilibrium plasma, APP has no defined shape or volume and, in general, is unstable and non-uniform. Therefore, it is desirable to have a source of stable and uniform APP with defined morphologies for scientific investigations that could take advantage of the highly collisional state of the plasma medium. Here, we report an approach to produce atmospheric pressure micro-plasmas in which the plasma cloud presents a stable, and topologically-connected and self-confined toroidal shape. We show that this unique toroidal APP morphology can be uniquely generated when a high-speed laminar micro-jet of de-ionized water impinges on a di-electric solid surface. This toroidal micro-plasma shows a unique and previously unreported plasma resonance mode characterized by a strong and discrete radio frequency emission.

Wednesday, March 23, 2016
1:00 PM
Ronald Tutor Campus Center, Trojan Ballroom A

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

Acoustic Levitation and Propulsion Based on Traveling Waves Control

Ran Gabai

Postdoctoral Researcher
Dynamics and Mechatronics Laboratory
Faculty of Mechanical Engineering, Technion IIT
Haifa, Israel

Acoustic levitation is generated by inducing ultrasonic vibrations to a surface above which a levitated object is held by elevated pressure. A thin film of gas separating the vibrating surface and the levitated body exhibits both rapid fluctuations and a rise in the average pressure. An application being researched currently involves the handling of silicon wafers in clean rooms with no mechanical contact thus eliminating a significant contamination source. The elevated pressure is capable of levitating objects weighting several kg by a vibrating surface 100mm in diameter. By creating a traveling pressure wave, it is possible to add a propelling forces to the levitating component thus creating a contactless transportation system. By sensing the position of the levitated object one can control, in a closed loop feedback scheme, the levitation height and the planar position and orientation.

The dynamics of the mechanical structure has to be carefully tailored to enhance the electromechanical efficiency leading to sufficient amplitudes of the ultrasonic vibrations to provide appropriate levels of acoustic levitation and traveling waves. Ultrasonic structural traveling waves are generated by exciting two modes of vibrations that are tuned, in real time, to generate the required traveling wave direction and amplitude. Small structural uncertainties spoil the symmetry of the structure and detune the conditions for traveling waves. Therefore, an optimization process is introduced to experimentally map the exact traveling wave excitation conditions.

This work presents the analytical background, numerical simulations and several experimental set-ups validating the applicability of acoustic levitation and propulsion.

Ran Gabai is a post-doctoral researcher at the Dynamics and Mechatronics laboratory at the Technion working with Prof. Izhak Bucher. He earned his PhD (2008) at the Faculty of Mechanical Engineering at the Technion as well as his M.Sc (2003) and B.Sc (2000). His research focuses on dynamic and vibrations, mechatronics, signal processing, control and embedding digital brains in dynamical systems. During 2009-2014 Dr. Gabai is the co-founder and CTO of a start-up company developing a Coriolis based mass flow meters.

Wednesday, March 30, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

High Rate Loading of Woven Composite Materials

Mark Pankow

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

Composite materials are rate sensitive materials, meaning that their properties and failure modes change as a function of the loading time. This talk will discuss the dynamic response of composites subjected in impact, blast and dynamic loading. The work will focus on experimental testing to understand the dynamic response and characterization of the failure modes at the elevated rates of loading. Uniaxial testing will be covered from the the stand point of the Hopkinson Bar, while biaxial testing will be carried out through the use of shock loading. The work will examine the difference in the uniaxial vs. bi-axial response of the material to examine the effect on failure. During deformation high speed in-situ measurements are made through the use of DIC, to monitor the local displacement and strain fields. Finally, architecture dependent mechanisms of the woven structure are linked to the failure mechanisms. These localizations are related to how the onset and propagation of failure.

Mark Pankow is currently an Assistant Professor of Mechanical and Aerospace Engineering at North Carolina State University where he runs the Ballistic Loading and Structural Testing Lab (BLAST). Dr. Pankow completed his B.S. in Mechanical Engineering at California Polytechnic State University (Cal Poly) in San Luis Obispo, his M.S. and his Ph.D. in Mechanical Engineering from University of Michigan in Ann Arbor working with Tony Waas. Prior to joining NC State, he worked as a post-doc at the ARMY Research Laboratory understanding composite materials in extreme environments. He is currently involved in many different projects related to understanding composite materials at high rates including, how kevlar vests dissipate the energy of projectiles and the deformation of composite panels subjected to lighting strike.

Wednesday, April 6, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Engineering Organs on Chips

Megan McCain

Gabilan Assistant Professor of Biomeical Engineering
Department of Biomedical Engineering
University of Southern California
Los Angeles, CA

Biomedical research has traditionally been limited to model systems that lack relevance to native human tissues, such as animal models or overly-simplified cell culture platforms. These model systems have hindered our ability to understand human diseases, identify therapeutic targets, and screen drugs for toxicity and efficacy at the pre-clinical stage. In this talk, I will describe our efforts in leveraging biomaterials, microfabrication techniques, and human stem cells to engineer micro-scale, functional models of human tissues, known as “Organs on Chips,” for cardiac and skeletal muscle.

Megan McCain completed her BS in Biomedical Engineering at Washington University in St. Louis. She earned her PhD in Engineering Sciences under Prof. Kit Parker at Harvard University, where she used tissue engineering to study the role of mechanotransduction in cardiac development and disease. Megan continued as a post-doctoral researcher at the Wyss Institute for Biologically Inspired Engineering at Harvard University, where she helped develop micro-scale mimics of human cardiac tissue, known as “Heart on a Chip.” In 2014, Megan joined the University of Southern California as the Gabilan Assistant Professor of Biomedical Engineering, where she also holds an appointment in the Department of Stem Cell Biology and Regenerative Medicine. Her research group, the Laboratory for Living Systems Engineering, is focused on developing and utilizing novel “Organ on Chip” platforms for human disease modeling.

Wednesday, April 13, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

A Few Fringe Topics in Combustion: Electric Actuation of Flames, Methane Hydrate Burning, and Miniature Liquid Fuel Combustors

Derek Dunn-Rankin

Professor
Department of Mechanical and Aerospace Engineering
University of California, Irvine
Irvine, CA

This presentation covers some unusual flame configurations and problems tangential to the general combustion objectives of maximizing efficiency and minimizing harmful emissions. For example, hydrocarbon flames have long been known to contain naturally a small quantity of charged species that allow them to act as weak plasmas. Electric fields can influence these flames, including changing their shape and direction, their sooting behavior, and their ignition limits. Methane hydrates are thermodynamically stable ice-like crystalline solids that encapsulate methane. As water evaporates during the hydrate burn, steady combustion of this methane as it is released from the clathrate cages naturally creates a watery-fuel diffusion flame. Compact combustion systems that utilize liquid hydrocarbon fuels are rare but miniature liquid film combustors evaporate fuel from the chamber walls and can burn stably even with dimensions below one centimeter. Each of these examples is explored experimentally, as they all demonstrate the rich multi-physics environment that arises when combustion is involved.

Derek Dunn-Rankin is Professor in the Department of Mechanical and Aerospace Engineering at the University of California, Irvine (UCI). He is co-Director for CAMP, the California Louis Stokes Alliance for Minority Participation, a program designed to increase minority representation in science and technology. Dr. Dunn-Rankin’s research is in combustion and energy, droplet and sprays, and applications of laser diagnostic techniques to practical engineering systems. He has been faculty advisor for 25 Ph.D. and 56 M.S. graduates at UCI. He received a Japan Society for the Promotion of Science Fellowship in 2008 and the Oppenheim Prize of the Institute for the Dynamics of Explosions and Reactive Systems in 2013.

Wednesday, April 20, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Singularity Approximations for Flow: Cooperative Feeding by Cells and Microfluidic Crystallization

Marcus Roper

Associate Professor
Department of Mathematics
University of California at Los Angeles
Los Angeles, CA

I will discuss two problems that seem, at first glance to be totally unrelated. 1. What evolutionary forces caused animals to first evolve from single cells to complex multicellular organisms? Choanoflagellates, a group of single-celled organisms that sprung off from the animals just before the evolutionary transition to multicellularity, allows the transition to be directly observed: One species of choanoflagellate, Salpingoeca rosetta, shifts reversibly from single celled to multicellular forms depending on food conditions. But in its multicellular form it swims very poorly. What advantage then, is there to being multicellular? We will show how cooperatively create feeding currents allow even poorly swimming cells to access more food than single celled counterparts. 2. Inertial microfluidic devices are highly minaturized labs on chips that take fluid flows at high speeds, creating fluid mechanical phenomena that don’t occur in conventional microfluidic devices. An outstanding mystery of these devices is that particles and droplets in an inertial microfluidic device spontaneously self-assemble into uniformly spaced chains; eliminating the problems of drop arrival timing that conventional microfluidic devices suffer from. We show that this chain formation is an example of a peculiar hydrodynamic form of crystallization. Weirdly, although inertial microfluidic crystals are evenly spaced, they have no preferred length scale for this spacing, creating incredible opportunities to design particle spacings according to applications.

Although these topics do not seem to be related, the key to successful modeling in both systems is to develop singularity methods for representing the flows. Although singularity methods are well established for modeling Stokes flow; our work shows that they can be used even to solve the fully nonlinear Navier-Stokes equations.

Marcus Roper uses math and experiments to study fluid flows in Nature, focusing in particular on how microorganisms overcome fluid dynamical challenges to grow, feed and evolve. He received his PhD in Applied Math from Harvard University in 2007. He then spent four years working in biology labs, first as a Farlow Fellow in fungal systematics at Harvard, and then as a Miller Fellow working in cell biology at UC Berkeley. He is now an Associate Professor of Mathematics at UCLA. His work is supported by an NSF Career award, and an Alfred P. Sloan foundation fellowship.

Wednesday, April 27, 2016
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.