2021 Seminar Archive

Additive Manufacturing of Bio-inspired Structures via Multi-scale, Multi-material, and Multi-functional 3D Printing

Yong Chen

Professor & Director of Epstein Institute

Epstein Department of Industrial and Systems Engineering
and
Department of Aerospace and Mechanical Engineering (courtesy)
USC
Los Angeles, CA

Many natural structures out-perform conventional synthetic counterparts due to the specially evolved multi-scale, multi-material, and multi-functional architectures. However, most current 3D printing systems are designed to fabricate parts using a single material on a single scale, mainly for structural purposes. Such complex yet beautiful designs existing in natural structures are far beyond the fabrication capability of current 3D printing systems. This talk will report some of our recent work on developing new multi-scale, multi-material, and multi-functional additive manufacturing processes to fabricate bio-inspired structures, including the lobster structure, the nacre shell structure, the Salvinia molesta leaf structure, the limpet tooth structure, etc. After a brief overview of current 3D printing technology, several additive manufacturing (AM) processes to fabricate complex reinforcement architectures and functional surfaces will be presented. Some novel designs and promising applications enabled by the 3D-printed structures will also be discussed. The talk will conclude with remarks and thoughts on future 3D printing developments and potential opportunities for mechanical engineers.

Yong Chen is a professor of Industrial and Systems Engineering and Aerospace and Mechanical Engineering and the Director of Daniel J. Epstein Institute at the University of Southern California (USC). His research focuses on additive manufacturing (3D printing) in micro- and meso-scales. He has published more than 150 publications in refereed journals and conferences and 12 issued and pending U.S. patents. He received fourteen Best/Outstanding Paper Awards in major design and manufacturing conferences. Other major awards he received include the NSF CAREER Award and USC’s Innovation Commercialization Awards. Dr. Chen is a Fellow of the American Society of Mechanical Engineers (ASME). He has served as conference/program chairs and keynote speakers in several international design and manufacturing conferences.

Wednesday, January 20, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

Let Droplets Drop the Temperature: Fluids-Based Thermal Management

Patricia Weisensee

Assistant Professor

Institute of Materials Science and Engineering
Department of Mechanical Engineering and Materials Science
Washington University in St. Louis
St. Louis, MO

The coupling of fluid dynamics and heat transfer dominates many environmental and industrial processes, including the natural water cycle (evaporation from lakes and oceans, condensation in clouds), electronics thermal management, power generation, and materials manufacturing and processing. In this talk I will highlight two such phenomena: Condensation and evaporation, and advanced thermal management solutions using room-temperature liquid metals. I will focus on droplets, which are omnipresent in our daily lives, and provide the ability to actively manipulate the flow of matter and heat.

The major focus of my lab lies on understanding phase change phenomena, with a special emphasis on vapor-liquid (condensation) and liquid-vapor (evaporation or boiling) heat transfer. In this talk, I will show that water condensation on so-called lubricant-infused surfaces (LIS) can have up to 10-fold increased water collection efficiency due to an extremely high droplet mobility compared to bare metal surfaces. Lubricant wetting ridges surrounding droplets introduce an attractive capillary force, leading to self-propelled and gravity-independent droplet motion, which efficiently clears the surface for frequent re-nucleation. On the other hand, wettability-patterning a surface and thus restricting the mobility of droplets can be advantageous during evaporation. I will show that the alteration of convection within the droplets and localized evaporation-enhancement at the contact lines can effectively increase the overall heat transfer rates. In the last part of this talk I will introduce an ongoing project in collaboration with NASA, where my research group is developing a passive and compact thermal heat switch. I will present some preliminary results and highlight the challenges associated with using gallium-based liquid metals.

Patricia Weisensee is an Assistant Professor of Mechanical Engineering and Materials Science at Washington University in St. Louis (WashU). She earned her PhD in Mechanical Engineering from University of Illinois at Urbana-Champaign in 2016. She received a Diplom-Ingenieur in Mechanical Engineering from TU Munich in 2013 and also holds a M.S. in Materials Sciences from University of Illinois at Urbana-Champaign (2011). For her Diplom thesis on condensing steam bubbles in sub-cooled flow, Dr. Weisensee received the Siemens Energy Award 2014. She is an alumna of the German National Academic Foundation (“Studienstiftung des deutschen Volkes”), Germany’s largest, oldest, and most prestigious scholarship foundation.

At WashU, Dr. Weisensee leads the Thermal Fluids Research Group, which focuses on understanding the interplay of fluid dynamics and heat transfer of droplets and other multi-phase systems. Practical applications of interest are phase change heat transfer for thermal management, thermal storage, and water harvesting, metallic additive manufacturing, and droplet interactions with natural systems. To fundamentally study these thermal-fluidic interactions, her group combines multiple experimental techniques, such as high-speed optical and infrared (IR) imaging, interferometry, confocal fluorescence microscopy, and conventional heat transfer measurements. Dr. Weisensee is a very recent recipient of the NSF CAREER award and currently also holds a 3-year NSF research award to study nucleation and condensation of water on lubricant-infused surfaces (LIS). She was awarded the ACS Petroleum Research Fund Doctoral New Investigator grant to study the pore-scale interactions between fluid flow and heat transfer for oil-water emulsion flow through porous media, and received the prestigious NASA Early Career Faculty Award to develop a passive and compact thermal heat switch to be used on satellites and robots during lunar missions. Recently, Dr. Weisensee also received the 2020 ASME ICNMM Outstanding Early Investigator Award and 2020 Emerson Excellence in Teaching award.

Wednesday, January 27, 2021
3:30 PM
This seminar was held as a webinar.

host: Sadhal

Saliva Particle Transport During Cough & Breathing: Insights on Effective Social Distancing & Face Mask Wearing Gained by LES

Ali Khosronejad

Assistant Professor of Civil Engineering
Civil Engineering Department
The State University of New York at Stony Brook
Stony Brook, NY

The Coronavirus disease outbreak of 2019 has been causing significant loss of life and unprecedented economical loss throughout the world. Social distancing and face masks are widely recommended around the globe in order to protect others and prevent the spread of the virus through breathing, coughing, and sneezing. To expand the scientific underpinnings of such recommendations, we carry out high-fidelity computational fluid dynamics simulations of unprecedented resolution and realism to elucidate the underlying physics of saliva particulate transport during human cough and normal breathing with and without facial masks. Our simulations: (a) are carried out under both a stagnant ambient flow (indoor) and a mild unidirectional breeze (outdoor); (b) incorporate the effect of human anatomy on the flow; (c) account for both medical and non-medical grade masks; and (d) consider a wide spectrum of particulate sizes, ranging from 0 µm (passive tracer) to 300 µm. We show that during indoor coughing some saliva particulates could travel up to 0.48 m, 0.73 m, and 2.62 m for the cases with medical-grade, non-medical grade, and without facial masks, respectively. Thus, in indoor environments either medical or non-medical grade facial masks can successfully limit the spreading of saliva particulates to others. Under outdoor conditions with a unidirectional mild breeze, however, leakage flow through the mask can cause saliva particulates to be entrained into the energetic shear layers around the body and transported very fast at large distances by the turbulent flow, thus, limiting the effectiveness of facial masks.

Ali Khosronejad earned his Ph.D. in Civil Engineering (Hydraulic Engineering) from Tarbiat Modarres University (Tehran) in 2006. He earned a BS in Water Resources Engineering from Tehran University and a MS in Civil Engineering (Hydraulic Engineering) from Sharif University of Technology (Tehran). During his Ph.D. work he was a Research Assistant at the University of Ottawa, Canada. After graduating he became an Assistant Professor at the University of Guilan (Rasht, Iran) before becoming a postdoc at the University of Minnesota's St. Anthony Falls Lab in Minneapolis. In 2016, he moved to Stony Brook as an Assistant Professor.

Ali's research interests center around high performance computing tools. He develops algorithms for fluid-structure interaction; immersed boundary methods; coupled sediment transport in turbulent flow; and large eddy simulations of turbulent atmospheric and aquatic flows, free-surface and bubbly flows, density current and stratified flows, turbulent flows over natural and engineered rough surfaces, and transport and mixing of particles and conservative/non-conservative contaminants in natural riverine and coastal areas.

Wednesday, February 3, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

Learning From the Past

Gen(ret) Ellen Pawlikowski

Judge Widney Professor of Systems Architecting and Systems Engineering

USC
Los Angeles, CA

Department of Defense acquisition programs are the means that new capabilities are developed, acquired and fielded to support military operations. These programs can span decades as they often include evolving complex systems of systems. New practitioners (program managers and engineers) tend to get overwhelmed and at the same time discover that the tools to apply such information to their current task are deficient or lacking. In today’s world of ever-growing complexity and increasingly compressed timelines, there is seldom enough time to gain the depth and breadth of experience needed. This recognition provides the impetus to leverage case studies as an “experience accelerator.” Case studies provide tools for acquisition practitioners to learn from the experience of those program managers and systems engineers that preceded them. This presentation provides a foundation for conducting and using case studies in systems engineering and management.

General (retired) Ellen M Pawlikowski is an independent consultant providing expertise on strategic planning, program management, logistics, and research and development. She is the Judge Widney Professor at the Viterbi School of Engineering at the University of Southern California. She serves on the Boards of Directors for the Raytheon Company, Intelsat SA, Applied Research Associates, and SRI International. Ellen Pawlikowski was the third woman to achieve the rank of General in the US Air Force. In her last assignment, she served as Commander, Air Force Materiel Command, Wright-Patterson Air Force Base, Ohio. The command employs some 80,000 people and manages $60 billion annually, providing the Air Force with research and development, life cycle systems management, test and evaluation, installation support, depot maintenance and supply chain management.

She entered the Air Force in 1978 as a distinguished graduate of the ROTC program at the New Jersey Institute of Technology, Newark, NJ. She then attended the University of California at Berkeley as a Fannie and John Hertz Foundation fellow and received a Doctorate in chemical engineering in December 1981.

General Pawlikowski's career has spanned a wide variety of technical management, leadership and staff positions. She commanded five times as a general officer, commanding the MILSATCOM Systems Wing, the AF element of the National Reconnaissance Office, AF Research Laboratory, the Space and Missile Systems Center, and Air force Materiel Command. She also served as the program director and program executive officer for several multibillion-dollar military-system acquisitions.

General Pawlikowski is nationally recognized for her leadership and technical management acumen. Among her recognitions are the Women In Aerospace Life Time Achievement Award, the NDIA’s Peter B Teets Award, and the Air Force Association Executive Management Award. She is a Honorary Fellow of the American Institute of Aeronautics and Astronautics, a Fellow of the Directed Energy Professional Society, and a member of the National Academy of Engineers.

Ellen Pawlikowski was born in Bloomfield, NJ and currently resides in Macon, GA.

Wednesday, February 10, 2021
3:30 PM
This seminar was held as a webinar.

host: Ronney

Simple Rules for the Wrinkle Patterns of Confined Elastic Shells

Ian Tobasco

Assistant Professor
Department of Mathematics, Statistics, and Computer Science
Univ. Illinois Chicago
Chicago, IL

Dried fruits wrinkle for the same reason that leaves and flowers do — mechanical instabilities arising from a mismatch in lengths. Can such geometric incompatibilities be used to design and control wrinkle patterns at will? This talk will discuss the possibility of designing wrinkle patterns "in the large" using a recently derived model for the wrinkles of confined elastic shells. After recalling the basic mechanics and introducing our model, we show how it can be solved by hand in many cases to predict the wrinkled topography. Solving this model produces a few geometric rules, which explain the layout of the wrinkle peaks and troughs across examples. These simple rules reproduce the patterns seen in numerous experiments and simulations, even ones that exhibit a surprising coexistence between orderly wrinkles and a more disordered response. Knowing such rules for wrinkles opens the way towards designer wrinkle patterns, with potential applications from flexible electronics to synthetic skins.

Ian Tobasco is an Assistant Professor at the University of Illinois at Chicago Department of Mathematics, Statistics, and Computer Science. He holds a Ph.D. in Mathematics from the Courant Institute of Mathematical Sciences at New York University, and a B.S.E. in Aerospace Engineering from the University of Michigan.

Ian’s research on the calculus of variations and partial differential equations concerns problems that sit at the interface of mathematics, physics, and engineering, where advances in pure mathematical analysis can lead to scientific breakthroughs in the lab and vice versa. Ian’s recent work involves the use of energy minimization to explain and classify the zoo of wrinkling, crumpling, and folding patterns exhibited by thin elastic sheets. Other interests include the design of optimal transport mechanisms in fluid dynamics and their comparison with naturally occurring turbulent transport, as well as the variational analysis of spin glasses.

Wednesday, February 17, 2021
3:30 PM
This seminar was held as a webinar.

host: Plucinsky

Mesoscale Modeling for Next Generation DNA Sequencing and Sustainable Energy

Giovanna Bucci

Senior Research Engineer
Energy Technologies Division
Bosch

There is great potential for genome sequencing to enhance patient care through improved diagnostic sensitivity and more precise therapeutic targeting. The opportunity to detect repetitive regions and structural variation in the genome has incentivized the development of long-read DNA sequencing. Nano-channel analysis is one of the emerging strategies for non-optical DNA sequencing. However, high cost, low throughput, and low accuracy have so far limited the adoption of long-read technologies. In this work, mesoscale modeling tools are employed to simulate the mechanics of DNA loading and reading, and predict the statistics of polymer-chain conformation under confinement. A workflow was developed to quantify competing requirements of efficiency and accuracy and extract metrics that guide design optimization. Several design variables (geometry, electric field, materials and interfaces, buffer solution, etc.) can be tuned to achieve high throughput base-pair detection. This multi-dimensional design space offers a great opportunity for modeling to provide understanding and accelerate innovation.

Finally, I will provide an overview of my recent work in energy storage/conversion technologies, with a brief discussion of a new theoretical and computational framework to study electrochemical instability and coarsening of catalyst nano-particles.

Giovanna Bucci is a Senior Research Engineer in the Energy Technologies Division at Bosch, where she has been responsible for the mesoscale modeling of aging in Li-ion batteries and in proton exchange membrane fuel cells. Currently, she leads a modeling effort to optimize the design of a DNA sequencing device based on nano-confinement.

Giovanna began her career in the field of computational solid mechanics, with an emphasis on fracture and large-scale simulation. She worked on next-generation energy storage devices, with postdocs at Brown University and in the Carter/Chiang research group at MIT DMSE. Her analyses have established design rules for silicon anodes, and identified failure-tolerant battery microstructures and operating conditions. In recognition of her cross-disciplinary accomplishments, she received the 2015 Rising Stars in Nuclear Science and Engineering award at MIT.

Giovanna took her Ph.D. in Structural Mechanics from the Politecnico di Milano and her M.S. and B.S. in Architecture from Università di Pavia.

Wednesday, February 24, 2021
3:30 PM
This seminar was held as a webinar.

host: Balakrishna

Machine Learning for High-Throughput Experiment and Analysis of Processing-Property Relationships

Samantha Daly

Professor
Department of Mechanical Engineering
University of California at Santa Barbara
Santa Barbara, CA

Materials have hierarchical and heterogeneous structures that drive their deformation and failure mechanisms. The relationship between structure and behavior -- such as the impact of the microstructure of a polycrystalline metal on twinning, dislocation slip, grain boundary sliding, and multi-crack systems -- includes complex stochastic and deterministic factors whose interactions are under active debate. In this talk, the application of data-driven approaches to microscale displacement data for the high-throughput segmentation, identification, and analysis of twinning in magnesium (a deformation mechanism that is critical to its ductility and forming) will be discussed. This will include an analysis of deformation twinning over thousands of grains per test, including an analysis of the impact of microstructure on the relative activity of specific twin variants (automatically identified from microscale strain fields) and their evolution under load. The newly developed experimental and analytical approaches are length scale independent and material agnostic, and can be modified to identify a range of deformation and failure mechanisms.

Samantha (Sam) Daly is a Professor in the Department of Mechanical Engineering at the University of California at Santa Barbara. She received her Ph.D. from Caltech in 2007 and subsequently joined the University of Michigan, where she was on the faculty until 2016 prior to her move to UCSB. The Daly group investigates the mechanics of materials, with a focus on fatigue, fracture, creep, composites, multi-functional materials, and new experimental and data-driven approaches for the characterization of processing – structure – property relationships. Her recognitions include the Experimental Mechanics Best Paper of the Year Award, IJSS Best Paper of the Year Award, DOE Early Career Award, NSF CAREER Award, AFOSR-YIP Award, ASME Eshelby Mechanics Award, Journal of Strain Analysis Young Investigator Award, ASME Orr Award, and Caddell Award. She currently serves on the Executive Board of the Society of Experimental Mechanics, and as an Associate Editor of the journals Applied Mechanics Reviews, Experimental Mechanics, and Strain.

Wednesday, March 3, 2021
3:30 PM
This seminar was held as a webinar.

host: Balakrishna

Toward Predictive Yet Affordable Computations of Practical Wall-Bounded Turbulent Flows

George Park

Assistant Professor
Department of Mechanical Engineering and Applied Mechanics
School of Engineering and Applied Sciences
University of Pennsylvania
Philadelphia, PA

Kinetic energy of turbulence is generated at large scales controlled by boundary conditions, but it is dissipated into heat at the smallest scales. The ratio of these two length scales increases rapidly with Reynolds number. Solid walls add another dimension in this scale landscape, where the scale separation gets progressively less pronounced toward the wall. This has significant ramifications on the cost of scale-resolving simulation of practical engineering flows, such as those found in aircraft, wind turbines, and ship hydrodynamics. Direct approaches with full resolution of length and times scales close to the wall are still infeasible with current computing power. The demand for superior designs at reduced cost has led researchers to explore alternative computational approaches that have potential to be predictive yet affordable. Large-eddy simulation (LES) is one such approach where only the energy-containing scales are resolved directly, and the effect of the unresolved motions are modeled. In practical LES calculations, subgrid-scale (SGS) models are used in conjunction with wall models to augment the turbulent shear stress, which otherwise is underpredicted on coarse grids and leads to inaccurate prediction of mean and turbulence quantities.

In this talk, I will discuss the research in my group on this wall-modeled LES approach. Widely used wall-modeling techniques will be discussed with their applications to canonical and complex wall-bounded flows. Challenges in robust and efficient implementation of the models in flow solvers for handling practical geometries will be discussed. I will also highlight recent work to predict flow over realistic aircraft geometries at flight conditions and a boundary layer with mean three dimensionality.

George Park is an Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. He received his Ph.D. and M.S. in Mechanical Engineering (ME) from Stanford University in 2014 and 2011, respectively, and his B.S. in ME from Seoul National University, South Korea in 2009. He worked as a postdoctoral fellow and an engineering research associate at the Center for Turbulence Research (Stanford) prior to joining UPenn as a faculty member in 2018. His research interests include high-fidelity numerical simulation of complex wall-bounded turbulent flows, computational methods with unstructured grids, non-equilibrium turbulent boundary layers, and fluid-structure interaction.

Wednesday, March 10, 2021
3:30 PM
This seminar was held as a webinar.

host: Bermejo-Moreno

Vortex in the Eye: Thermal Effects on Fluid Mixing in the Eye

Morteza Gharib

Hans W. LiepmannProfessor of Aeronautics and Bioinspired Engineering; Booth-Kresa Leadership Chair, Center for Autonomous Systems and Technologies; Director, Graduate Aerospace Laboratories; Director, Center for Autonomous Systems and Technologies

Graduate Aerospace Laboratory and Medical Engineering Department
California Institute of Technology
Pasadena, CA

Age-related macular degeneration (AMD) is the leading cause of central vision loss in the developed world. Wet AMD can be managed through serial intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents. However, sometimes the treatment is ineffective. Given that the half-life of the drug is limited, inefficient mixing of the injected drug in the vitreous chamber of the eye may contribute to the ineffectiveness. Here, we introduce thermal heating as a means of enhancing the mixing-process in the vitreous chamber and investigate parameters that potentially influence its effectiveness. Our in-vitro studies point to the importance of the location of the heating on the eye. A significant increase in the mixing and delivery of drugs to the targeted area (the macula) could be achieved by placing heating pads so that a current against gravity is induced in the vitreous. The presented results can potentially help in the development of a better strategy for intravitreal injection and improve the quality of patient care.

Mory Gharib is Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering; Chair of Graduate Aerospace Department (GALCIT); Director of Center for Autonomous Systems and Technologies. He received his B.S. degree in Mechanical Engineering from Tehran University (1975) and his M.S. 1978, in Aerospace and Mechanical Engineering from Syracuse University and his Ph.D.1983, in Aeronautics from Caltech. He joined Caltech as a professor of Aeronautics.

Professor Gharib's current research interests in conventional fluid dynamics and aeronautics include Vortex dynamics, active and passive flow control, autonomous flight, and underwater systems. His Biological flows research includes cardiovascular and ophthalmology, and medical devices.

Dr. Gharib's honors and affiliations include: Member, American Academy of Arts and Sciences; Member, National Academy of Engineering; Charter Fellow, National Academy of Inventors; Fellow, American Association for the Advancement of Science; Fellow, American Physical Society; Fellow, American Society of Mechanical EngineeringHe has received the G.I. Taylor Medal from the Society of Engineering Sciences, The Fluid Dynamics Prize from the American Physical Society and five new technology recognition awards from NASA in the fields of advanced laser imaging and nanotechnology. In 2008 he received R&D Magazine's "R&D 100 innovation award" for one of the year's best inventions for his 3-D imaging camera system. Additionally, Dr. Gharib has published more than 250 papers in refereed journals and has been issued 120 U.S. Patents.

Wednesday, March 17, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

The Fluid Mechanics of Hypersonic Fluid-Structure Interactions

Daniel Bodony

Blue Waters Professor
Department of Aerospace Engineering
Univ. Illinois Urbana-Champaign

The interaction of high-speed aerodynamics with thermo-mechanically compliant structures is a critical design consideration for single-use and reusable hypersonic vehicles. Historical techniques for predicting fluid-thermal-structure interaction (FTSI) are insufficient for envisioned hypersonic flight systems, leading to a resurgent effort towards understanding, modeling, and predicting FTSI-coupled systems. In this talk, we will present the impact of FTSI on two fundamental scenarios -- boundary layer transition and shock-boundary layer interaction -- informed using a combination of stability analyses and direct numerical simulation techniques. In each scenario, focus will be given to the fluid mechanics involved in the fluid-structure coupling. Supporting details on the relevant theoretical and numerical details required for accurate prediction will also be discussed.

Daniel J. Bodony is the Blue Waters Professor, Donald Biggar Willett Faculty Scholar and Associate Head for Graduate Programs in the Department of Aerospace Engineering at the University of Illinois. He received his Ph.D. in Aeronautics & Astronautics from Stanford University in 2005. After working at the NASA Ames/Stanford Center for Turbulence Research he joined the University of Illinois in late 2006 as an assistant professor. He received an NSF CAREER award in 2012 in Fluid Dynamics, is an Associate Fellow of the AIAA, and received the University of Illinois' Promotion with Distinction Award in 2020

Wednesday, March 24, 2021
3:30 PM
The Zoom webinar is at https://usc.zoom.us/j/91084441303.

host: Bermejo-Moreno

Hypervelocity Spherically-Blunted Cone Flows in Mars Entry Ground Testing

Joanna Austin

Professor of Aerospace
Graduate Aerospace Laboratories
Caltech
Pasadena, CA

The intent to launch larger vehicles in future Mars missions increases the requirements for ground testing in the high-stagnation enthalpy environment encountered by the vehicle during the hypersonic phase of entry, descent and landing. During atmospheric entry, strong shock compression and high post-shock temperatures lead to significant chemical dissociation and vibrational excitation in the shock layer in front of a sphere-cone capsule, particularly near the stagnation region. For Mars missions, accurate thermochemical modeling of carbon dioxide, a principal component of the atmosphere with complex vibrational energy exchange, is particularly important. We examine the shock layer over sphere and spherically-blunted cone geometries through reacting Navier-Stokes simulations and experiments in two facilities capable of high-stagnation enthalpy, hypersonic flows simulating Mars planetary entry conditions: the T5 Reflected Shock Tunnel and the Hypervelocity Expansion Tube. A recently-developed unified model for sphere and sphere-cone behavior is first verified for high-stagnation enthalpy CO2 flows through simulations with thermal and chemical nonequilibrium. Shock standoff distance measurements in both facilities are in good agreement with model predictions. The need to account for the divergence of the streamlines in conical nozzles is highlighted and an existing model is extended to account for changes in shock curvature between parallel and conical flow. The contributions of vibrational and chemical nonequilibrium to the stagnation line density profile are quantified using the simulation results comparing three chemical kinetic models. Experimental measurement of fore- and aftbody MWIR radiation will also be discussed.

Joanna Austin is Professor of Aerospace at the Graduate Aerospace Laboratories, California Institute of Technology. She received B.E. (Mechanical and Space Engineering) and B.Sc. (Mathematics) degrees from the University of Queensland, Australia, and M.S. followed by Ph.D. (2003) degrees in Aeronautics from the California Institute of Technology. Austin then joined the faculty in the Aerospace Engineering department at the University of Illinois, becoming Associate Professor and Willett Faculty Scholar, before moving back to Caltech in 2014, where she is a co-PI in the Caltech Hypersonics Group. Austin's research is focused on fundamental problems in reactive, compressible flows across a broad range of applications including hypervelocity flight, supersonic combustion and detonation, bubble dynamics, and explosive geological events.

Wednesday, March 31, 2021
3:30 PM
This seminar was held as a webinar.

host: Bermejo-Moreno

A Nanoscale View on Electromechanical Phenomena

Nina Balke

Member of the Technical Staff
Center for Nanophase Materials Sciences
Oak Ridge National Laboratory
Oak Ridge, TN

The ability to transform electrical energy into mechanical energy and vice versa is the foundation to many technologies in the area of information and energy, such as sensors, piezotronics, energy harvesting, piezoelectric, electrochemical, and polymer actuators, and artificial muscles. Despite the importance of electromechanical phenomena and numerous applications, fundamental interdisciplinary studies needed to understand, and control electromechanical phenomena on the nanoscale are lacking. Atomic force microscopy (AFM) is well suited to measure local volume changes in the picometer range and has a lateral resolution of 10’s of nanometer which makes this an ideal technique to address electromechanical phenomena on the nanoscale. Despite the technical advances and the development of new SPM-based characterization techniques, the quantification of functional material parameters based on electromechanical phenomena is still elusive. The lack of quantitative and accurate measurement can also lead to the misinterpretation of relevant material physics. Only if quantitative material parameters can be extracted, can a correlation of nanoscale structure-function relationships be derived, and AFM can be integrated with techniques probing smaller or larger length and time scales as well as theoretical efforts for a full information integration across different disciplines. I will give an overview over which electromechanical phenomena can be probed quantitatively including electro-chemo-mechanical coupling to understand local electrochemical reactions and processes in electrochemical capacitors. Then I will talk in depth about AFM and ferroelectric materials and how the quantitative measurement of piezoelectric material properties led to the discovery of layered 2D van der Waals ferroelectrics with highly unusual material properties and functionalities based on the presence of four polar phases and high ion conductivity. These materials demonstrate, for the first time, how physical order parameter can be controlled by ionic degrees of freedom which will open new concepts for functional heterostructures and electronic devices.

Nina Balke received her Ph.D in Materials Sciences from the Technical University of Darmstadt, Germany, in 2006. After being a Feodor-Lynen fellow of the Alexander von Humboldt foundation at the University of California in Berkeley she became a research staff at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory in 2010. She is specialized in nanoscale characterization of electromechanical effects and electro-chemo-mechanical coupling using atomic force microscopy in oxides and vdW layered materials. Her scientific focus includes ferroelectrics, dielectrics, and energy storage materials as well as in-situ characterization of solid-liquid interfaces.

Wednesday, April 14, 2021
3:30 PM
The Zoom webinar is at https://usc.zoom.us/j/92982374143.

host: Balakrishna

Probing Phase Transformations and Twinning Across Length Scales Using 3D X-Ray Microscopy

Ashley N. Bucsek

Assistant Professor
Mechanical Engineering
University of Michigan
Ann Arbor, MI

Advanced materials are broadly defined as innovative materials that have atypical sizes, microstructures, and responses. These atypical characteristics enable major, previously impossible technological breakthroughs, yet many advanced materials owe their desirable properties to complex underlying micromechanics including twinning, detwinning, and martensitic phase transformations. Establishing the relationships between these local micromechanics and macroscopic material behavior is critical to accelerating the implementation of advanced materials. Toward these goals, we utilize modern 3D X-ray diffraction techniques that offer the capability to measure the deformation and microstructure evolution inside bulk materials, in situ, and across nine orders of magnitude in length scales (nm to mm). Measured quantities include the 3D microstructure “map” and spatially-resolved crystallographic orientation, elastic strain tensor, and phase fraction. These techniques can be used to simultaneously measure local microstructure events and the consequent macroscopic response, resulting in a tool uniquely suited for linking local micromechanics to material behavior. These capabilities will be illustrated using a number of research examples involving twinning and phase-transforming materials, using nickel-titanium shape memory alloys as a model material system. Ongoing and future work will also be discussed, including the development of a first-of-its kind laboratory-scale instrument to conduct 3D X-ray diffraction experiments in-house.

Ashley Bucsek is an assistant professor in Mechanical Engineering at the University of Michigan. Previously, she was a President's Postdoctoral Fellow at the University of Minnesota and a visiting scientist on beamline ID06 at the ESRF. She holds an MS and PhD from Colorado School of Mines and a BSE from the University of Wyoming. Bucsek's research combines 3D X-ray diffraction microscopy with micromechanical theory to study deformation and microstructure evolution in structural and functional materials. She is a regular user at the APS, CHESS, and the ESRF and is currently developing a laboratory-scale high energy diffraction microscopy microscope. Bucsek is also a board member on ASM’s International Organization on Shape Memory and Superelastic Technologies, an editorial advisory board member of the Shape Memory and Superelasticity journal, an APS Imaging/Microbeam proposal review panel member, and a member of the DOE-funded PRISMS Center.

Wednesday, April 21, 2021
3:30 PM
This seminar was held as a webinar.

host: Plucinsky

Wearable Opto-mechanical System for Cardiovascular Monitoring: From Methodological Design to Device Development

Jing Liu

Postdoctoral Scholar
Department of Aerospace and Mechanical Engineering
USC
Los Angeles, CA

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. There are about 47% of sudden cardiac deaths occurring outside a hospital, which reveals the demand for wearable medical devices that can monitor the cardiovascular risk factors of individuals frequently, accurately, and unobtrusively in their daily life. At the same time, the use of wearable medical devices allows healthcare givers to assess patient’s health conditions and provide medical guidance in a timely and non-contact way.

The photoplethysmography (PPG) sensor composed of light-emitting diode and photodetector has been widely adopted by various wearable fitness trackers owing to its low cost, compact size and ease of use. However, so far, the applications of PPG are mainly limited to heart rate and blood oxygen saturation measurement. By utilizing the wavelength dependence of the light penetration depth into the skin, we have developed a multi-wavelength PPG (MWPPG) sensing approach which allows for probing blood pulsations in different types of skin blood vessels.

In this talk, two MWPPG applications for cardiovascular monitoring will be presented: 1) cuffless arterial blood pressure measurement with a single MWPPG sensor; and 2) an opto-mechanical device equipped with an MWPPG sensor to enable arterial and capillary blood pressure measurement.

Jing Liu is a postdoctoral scholar in the Department of Aerospace and Mechanical Engineering, University of Southern California. She received her Ph.D. in Electronic Engineering from the Chinese University of Hong Kong in 2018 and her B.S. degree in Computer Science from Wuhan University in 2014. Her main achievements include the inventions of multi-wavelength photoplethysmography for wearable blood pressure monitoring, which is under commercialization in the Hong Kong Technology Start-up Support Scheme for Universities Programme. Her current research interests are cardiac modeling, physiological signal processing, and machine learning for cardiovascular health informatics.

Wednesday, April 28, 2021
3:30 PM
This seminar was held as a webinar.

host: Pahlevan

Symmetry, Deformations and the Search for Unprecedented Materials from First Principles

Amartya Banerjee

Assistant Professor
Department of Materials Science and Engineering
University of California at Los Angeles
Los Angeles, CA

The mathematical framework of Objective Structures generalizes ideas associated with crystals to atomic/molecular configurations with non-periodic symmetries. Some of the most widely studied structures in materials science, biology and nano-technology can be described as objective structures. The list of objective structures includes nano-tubes, nano-ribbons, buckyballs, tail sheaths and capsids of viruses, many common proteins, graphene and phosphorene sheets as well as molecular bilayers. The presence of high degrees of symmetry in objective structures makes them likely to be associated with remarkable material properties (particularly, collective material properties such as ferromagnetism, ferroelectricity and superconductivity) and their departure from the bulk phase makes them likely to demonstrate such properties in manners that are otherwise unavailable in crystalline systems.

A systematic study of objective structures is likely to lead to the discovery of unprecedented materials. At the same time, formulation and implementation of theoretical and computational methods specifically designed for studying objective structures, is likely to lead to the development of new simulation methodologies in nano-mechanics and materials science.

Following these lines of thought, we have been developing Objective Density Functional Theory (Objective DFT) – a suite of rigorously formulated quantum mechanical theories and numerical algorithms for carrying out ab initio simulation studies of objective structures. Objective DFT is intended to be a natural extension of the traditional Periodic Density Functional Theory method for studying crystalline systems, just as objective structures are a natural generalization of periodic structures. In this talk, I will describe some of the principal mathematical ideas and algorithmic techniques behind Objective DFT, as well as some of the key features and capabilities of this novel computational tool. Additionally, I will highlight how Objective DFT allows the non-periodic symmetries associated with objective structures to be exploited, to investigate non-uniform deformation modes in various nano-materials, from first principles.

Finally, I will discuss some of the many applications that have sprouted from the development of Objective DFT. These include (but are not limited to) the use of the computational packages developed in this work to study the mechanical stability and optical properties of nano-clusters, nano-ribbons and nano-tubes (with potential applications to energy materials and nano-structured meta-materials), ab initio studies of the mechanical and electronic properties of nano-beams, nano-tubes and various 2D materials, as well as the investigation of functional nano-materials with strongly correlated electronic states (with potential applications to the development of novel sensors and quantum hardware materials).

Amartya Banerjee leads the Ab Initio Simulations Laboratory at UCLA, and is an Assistant Professor of Materials Science & Engineering. His research interests include first principles calculations, simulations of energy, quantum and biological materials, mechanics of materials and structures, applications of symmetry principles, multi-scale methods, numerical analysis and scientific computation. Dr. Banerjee obtained his Ph.D. in Aerospace Engineering & Mechanics from the University of Minnesota in 2013. He also holds M.S. degrees in Mathematics, and Aerospace Engineering & Mechanics from the University of Minnesota. He received his undergraduate degree in Aerospace Engineering from the Indian Institute of Technology, Kharagpur, India in 2007. Prior to joining UCLA in 2019, he held postdoctoral appointments at the Computational Research Division of the Lawrence Berkeley National Laboratory, and at the University of Minnesota.

Dr. Banerjee has held visitor positions at the Hausdorff Research Institute for Mathematics, University of Bonn, Germany and the Institute of Mathematics and its Applications, Minneapolis, USA. He has received several awards and travel grants (including the John A. & Jane Dunning Copper Fellowship from the University of Minnesota and the US Junior Oberwolfach Fellowship), and has delivered invited presentations at numerous prestigious research laboratories and universities.

Wednesday, August 25, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: Renuka Balakrishna

Wakes in the Natural Environment

Sutanu Sarkar

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

Environmental wakes are produced by flows past structures which are engineered (e.g., oceanic submersibles, aerial vehicles, wind turbines, urban structures) or in nature (hills, mountain ranges, islands, seamounts). These wakes impact drag on the incident flow as well as transport of material, pollutants and environmental constituents. We will illustrate wake flow physics with a few examples studied using high-resolution simulation. The wake of a blunt object such as a disk will be contrasted with a streamlined object such as a prolate spheroid with respect to mean velocity, turbulence levels, flow instabilities and coherent structures. We will discuss both a constant density fluid and a density-stratified fluid where buoyancy inevitably alters the wake of the body. We will also present an example from nature, an oceanic current past a submerged hill, where we find synchronization of wake vortices with subharmonics of the oscillating tide and also states of high drag.

Sutanu Sarkar received his B. Tech. from IIT Bombay, M. S. from Ohio State University and Ph. D. from Cornell University. After 4 years as a staff scientist at ICASE, NASA Langley Research Center, he joined UCSD where he currently holds the Blasker Chair of Environmental Engineering, is a Distinguished Professor in the department of Mechanical & Aerospace Engineering (MAE), and is an affiliate professor at the Scripps Institution of Oceanography. He was Chair of MAE from 2009-2014. He has broad interests in the simulation and modeling of turbulent flows. He has worked in problems concerning the environment, energy, aerospace and propulsion. His current research interests are turbulence and mixing in the ocean and atmosphere, wakes and boundary layers of engineered structures in the natural environment, and renewable energy. He has received a NASA group achievement award (1994), the Bessel Award from the Humboldt Foundation (2001), and was elected Fellow, American Physical Society (2006), Associate Fellow, AIAA (2009) and Fellow, ASME (2010). He is an associate editor of JFM.

Wednesday, September 1, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: AME Department

Turbulence in Vegetation Canopies – From Biometeorology to Wildfires

Tirtha Banerjee

Assistant Professor
Department of Civil and Environmental Engineering
University of California at Irvine
Irvine, CA

The traditional motivation behind studying the dynamics of turbulent wind flow in vegetation canopies has been to understand the nature of mass, momentum and energy exchange between the land surface and the atmosphere. The nature of this interaction determines the microclimate in a forest environment where plants exchange carbon and water and its understanding is relevant for a plethora of applications ranging from ecology, hydrology, agriculture and the modeling of weather and climate. However, the fundamental nature of turbulence in a vegetation canopy is significantly different from the atmospheric surface layer lying above, which means that scaling laws and exchange coefficients from traditional wall bounded flows are not applicable. In a forest canopy, momentum absorption happens not only at the ground surface but throughout the depth of the canopy, resulting in a unique ‘roughness sub layer’. Instead of a log-layer, the mean velocity profile is inflected, second order moments are variable with height and skewnesses are large. Large scale coherent structures impart significant impact on the turbulence dynamics. Sweeping motions arising out of downdraft motions of counter-rotating vortices dominate eddy fluxes. A mixing layer model is found to be a better model for describing canopy flows. High frequency measurements and computational fluid dynamics modeling, especially Large Eddy Simulations (LES) has been instrumental in revealing the nature of canopy turbulence in the last few decades. Now this knowledge is being used to push the frontiers of our limited understanding of how wildland fires behave. The main controls on wildland fire behavior – fuel (canopy and grasslands), weather and topography are strongly influenced by fine scale physics of canopy turbulence. We will demonstrate that further developments in the understanding of canopy turbulence can benefit wildfire modeling tools and developing actionable management strategies.

Tirtha Banerjee is an Assistant Professor at the Department of Civil and Environmental Engineering, University of California, Irvine. He received his Bachelor of Science degree in Civil Engineering from Jadavpur University, Calcutta, India in 2011. During his undergraduate studies, he conducted research in the areas of structural dynamics and Aerospace Engineering in India and Germany as a DAAD (German Academic Exchange Service) Fellow. Upon completion of his undergraduate studies in 2011, he moved to the U.S. and joined Duke University in Durham, NC, as a Ph.D. student and conducted theoretical, numerical and experimental studies involving environmental fluid dynamics and turbulent flows. He received his Ph.D. in 2015 and joined the Karlsruhe Institute of Technology (KIT) in Germany for postdoctoral research in atmospheric boundary layer dynamics. He relocated to the U.S. in early 2017 to join the Los Alamos National Laboratory (LANL) in New Mexico and started working on wildfires, ecosystem disturbance as well as wind energy resources. At LANL he received a Chick Keller Postdoctoral Fellowship in 2017 and a Director’s Fellowship in 2018. He joined UC Irvine in fall 2019. Research in the Boundary Layers and Turbulence Lab led by Banerjee studies mass, momentum and energy exchange between the land surface and the atmosphere using a range of theoretical, numerical and experimental techniques. He currently serves as an associate editor of the journal Earth Systems and Environment (Springer) and as an editorial board member of the journal Agricultural and Forest Meteorology (Elsevier).

Wednesday, September 8, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: Luhar

Simulation of Bubbly, Cavitating Flows with Application to Shock- and Ultrasound-Based Medical Therapies

Tim Colonius

Professor
Department of Mechanical and Civil Engineerng
California Institute of Technology
Pasadena, CA

Models and numerical methods for simulating bubbly, cavitating flows have benefitted from recent advances in sharp and diffuse interface-capturing schemes, but many challenges remain to be solved before they can be routinely used to predict the complex, multiscale flows associated with important applications in engineer ing and medicine. In particular, the complex phase boundary, small length scales, and fast time scales associated with the dynamics of bubbles and clouds of bubbles strain existing algorithms and computational resources. In this talk, I will review different formulations for multiphase/multicomponent flows that involve large changes in volume, including methods that explicitly resolve the material interface, and ones that model the mixture as either homogeneous, or as a dilute dispersion of spherical bubbles. These methods are demonstrated in applications involving the high-intensity ultrasound and shock waves used for medical imaging and intra- and extra-corporeal manipulation of cells, tissue, and urinary calculi. Such waves are currently used to treat kidney stone disease, plantar fasciitis, and bone nonunion, and they are being investigated as a technique to ablate cancer tumors and mediate drug delivery. In many applications, acoustic waves induce the expansion and collapse of preexisting or newly cavitating bubbles. The resulting bubble dynamics generate large, localized stresses and strains that can be beneficial or deleterious depending on how effectively they can be controlled. I will describe efforts aimed at simulating the collapse of bubbles, both individually and in clusters, in order to characterize these mechanical stresses and strains.

Tim Colonius is the Frank and Ora Lee Marble Professor of Mechanical Engineering at the California Institute of Technology. He received his B.S. from the University of Michigan in 1987 and M.S and Ph.D. in Mechanical Engineering from Stanford University in 1988 and 1994, respectively. He and his research team use numerical simulations to study a range of problems in fluid dynamics, including aeroacoustics, flow control, instabilities, shock waves, and bubble dynamics. Prof. Colonius also investigates medical applications of ultrasound, and is a member of the Medical Engineering faculty at Caltech. He is a Fellow of the American Physical Society and the Acoustical Society of America, and he is Editor-in-Chief of the journal Theoretical and Computational Fluid Dynamics. He was the recipient of the 2018 AIAA Aeroacoustics Award and the 2021 APS Stanley Corrsin Award.

Wednesday, September 15, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at
https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: AME Department

Dragonfly’s Titan Entry and Descent System and DrEAM Instrumentation Suite

Aaron Brandis

Senior Research Scientist
Aerothermodynamics Branch
NASA Ames Research Center
Moffett Field, CA

This presentation will discuss the entry and descent phase for the Dragonfly missions arrival at Titan, a moon of Saturn. Dragonfly is a rotorcraft lander mission designed to take advantage of Titan's environment to sample materials and determine surface composition in different geologic settings, and even to search for chemical signatures that could indicate water-based and/or hydrocarbon-based life. The DrEAM instrumentation suite will take measurements of pressure, temperature and heatflux around the aeroshell during the Dragonfly entry.

Dr Brandis is a senior research scientist employed by AMA Inc in the Aerothermodynamics branch at NASA Ames Research Center. He is the PI for NASA’s Entry Systems Modeling project, Dragonfly aerothermal lead and PI for Dragonfly’s Titan entry instrumentation, known as DrEAM. His research focuses on shock layer radiation with the NEQAIR code and EAST shock tube facility.

Wednesday, September 22, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: AME

Initiated Chemical Vapor Deposition of Polymer Coatings and Membranes

Malancha Gupta

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

Initiated chemical vapor deposition (iCVD) is a solventless process that can be used to synthesize polymer films and coatings with a range of functionalities including hydrophilicity, hydrophobicity, light-responsiveness, and thermo-responsiveness. This talk will present the mechanism, capabilities, and advantages of the iCVD process. We will demonstrate that the iCVD process can be used to modify the surface properties of fibers, membranes, and microfluidic channels for applications in textiles, separations, and diagnostics. We will also demonstrate that polymers can be deposited onto low vapor pressure liquids including ionic liquids and silicone oils to fabricate ultrathin freestanding polymer films, nanoparticles, core-shell particles, and gels. We will also show that lowering the temperature of the substrate below the freezing point of the monomer leads to the formation of polymer membranes. These membranes can be deposited onto porous substrates to create hierarchical porous-on-porous structures that can enable improved filtration for water purification and sensor applications.

Malancha Gupta is the Gabilan Distinguished Professor at the Mork Family Department of Chemical Engineering and Materials Science at the University of Southern California. She received her B.S. in chemical engineering from The Cooper Union in New York City in 2002. She received her Ph.D. in chemical engineering from Massachusetts Institute of Technology in 2007 under the guidance of Professor Karen Gleason. From 2007-2009, she was a postdoctoral fellow in the department of chemistry and chemical biology at Harvard University working under the guidance of Professor George Whitesides. Her current research interests include polymer coatings and thin films, chemical vapor deposition, ionic liquids, and microfluidics. She has mentored 16 doctoral students and published 68 peer-reviewed manuscripts. She received the Jack Munushian Early Career Chair in 2013, the National Science Foundation CAREER award in 2013, and the USC Viterbi School of Engineering Junior Faculty Award in 2014. She was director of the chemical engineering program from 2018-2020 and she has served as chair of the Women in Science and Engineering (WiSE) engineering committee at USC since 2015.

Wednesday, September 29, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: Luhar

Rethinking Compressible Turbulence: From New Regimes to Extreme Simulations

Diego A. Donzis

Associate Professor
Department of Aerospace Engineering
Texas A&M University
College Station, TX

Compressible turbulence is much more common than incompressible turbulence and plays a critical role in countless natural and engineering systems such as astrophysical flows, high-speed aerodynamics, turbulent combustion, among many others. However, much less is known about compressible turbulence due to its larger parameter space; the additional complexity associated with coupling between hydrodynamics and thermodynamics; and the greater challenges to develop theory, attain realistic conditions in simulations, and conduct carefully controlled experiments.

In the first part of this talk I will review recent work that highlights some qualitative differences observed in compressible turbulence using a massive database of very well-resolved direct numerical simulations. After some illustrations of specific compressibility effects on turbulent flows, I will show why current approaches as "corrections" to well-known laws in incompressible turbulence present fundamental problems and then `provide a new alternative interpretation of statistical equilibria in an expanded parameter space in which new compressible universal scaling laws can be found. In the second this part, I will present current computational challenges to achieve more realistic conditions and a novel numerical approach in which the main well-known obstacles towards simulations on exascale systems and beyond can be removed. We will present some examples for smooth flows as well as flows with shocks and reactions.

Diego A. Donzis is an associate professor and Director of Graduate Programs in the Department of Aerospace Engineering at Texas A&M University where he directs the Turbulence and Advanced Computations Lab (TACL). He received his PhD from the Georgia Institute of Technology and continued his research at the University of Maryland and the International Centre for Theoretical Physics, Italy. His main interests are in high-performance computing at extreme scales, and the physics of turbulence and turbulent mixing in incompressible and compressible flows. Among his major recognitions Dr. Donzis received an NSF CAREER award, the Francois Frenkiel Award from the American Physical Society, TAMU Dean of Engineering Excellence Award, three TEES Faculty Awards for research, the McElmurry Teaching Excellence Award, and is a best graduate from Argentina by the National Academy of Engineering. In 2018, he was named a Presidential Impact Fellow by Texas A&M University for his scholarly influence. He is an AIAA Associate Fellow.

Wednesday, October 6, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: AME

Dynamics of Acoustically Coupled Combustion Instabilities

Ann Karagozian

Distinguished Professor
Department of Mechanical and Aerospace Engineering
UCLA
Los Angeles, CA

Acoustically-coupled combustion instabilities can result in large scale, potentially catastrophic pressure oscillations in aerospace propulsion systems, including liquid rocket engines (LREs) and gas turbine engines. A fundamental understanding of the interactions among flow and flame hydrodynamics, acoustics, and reaction kinetics is essential to determining combustor stability and controlling combustion processes. Over the past several years our group at the UCLA Energy and Propulsion Research Laboratory has been pursuing fundamental experiments that can shed light on combustion instabilities and their control, including exploration of the effects of external acoustic perturbations on liquid nanofuel combustion as well as gas-phase fuel jet combustion for alternative geometrical configurations. The dynamics of phenomena such as periodic liftoff and reattachment, periodic partial extinction and reignition, and full extinction are explored and quantified via phase-locked OH* chemiluminescence and high speed visible imaging. Proper orthogonal decomposition (POD) modes and phase portraits extracted from time-resolved imaging enables characterization of characteristic signatures associated with different phenomena. Understanding such signatures enables development of reduced order models that can impact eventual combustion control strategies.

Ann Karagozian is a Distinguished Professor in the Department of Mechanical and Aerospace Engineering at UCLA and heads the UCLA Energy and Propulsion Research Laboratory and the UCLA-Air Force Research Laboratory Collaborative Center for Aerospace Sciences. Her research interests lie in fluid mechanics and combustion as applied to improved energy efficiency, reduced emissions, and advanced air breathing and rocket propulsion systems. Professor Karagozian was a member of the Air Force Scientific Advisory Board for over 15 years, serving as SAB Vice Chair from 2005-2009 and twice receiving the Air Force Decoration for Exceptional Civilian Service. She is a Member of the National Academy of Engineering and is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA), the American Physical Society (APS), and the American Society of Mechanical Engineers (ASME). She received her B.S. in Engineering from UCLA and her M.S. and Ph.D. in Mechanical Engineering from the California Institute of Technology. She is a member of the Board of Trustees of the Institute for Defense Analyses (IDA) and is an alumna of and mentor for the IDA Defense Science Study Group. Prof. Karagozian also recently became the Inaugural Director of The Promise Armenian Institute, an endowed scholarly and cross-disciplinary outreach entity at UCLA.

Wednesday, October 13, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: Bermejo-Moreno

Capillary Flows of Suspensions

Alban Sauret

Assistant Professor
Department of Mechanical Engineering
University of California at Santa Barbara
Santa Barbara, CA

Interfacial flows of multiphase systems containing a dispersed solid or liquid phase occur in a broad range of manufacturing, environmental, and bioengineering processes. However, the classical capillary dynamics is strongly modified when the length scale of the liquid becomes comparable to the particle size. This configuration may lead to a failure of classical models based on a rheological approach. For instance, particles can destabilize thin-films, lead to defects in additive manufacturing, reduce transport efficiency, and result in the contamination of substrates.

In this talk, I will present some of our recent studies that characterize the role of interfaces in suspension dynamics. I will first describe the formation of a thin-film of suspension on a substrate to illustrate how the particles are entrained and deposited depending on the flow configuration and suspension properties. I will discuss how these results can be used to develop passive capillary filtering and sorting mechanisms. The second part of the talk will characterize how particles can modify the formation of droplets and the atomization of suspension sheets and ligaments. Our approach, bridging different length and time scales, describes how the bulk behavior and local heterogeneities contribute to the dynamics of multiphase capillary objects.

Alban Sauret is an Assistant Professor in the Department of Mechanical Engineering at UC Santa Barbara. He graduated with a BS and an MS in Physics from ENS Lyon (France) and earned a Ph.D. in Mechanical Engineering from the University of Aix-Marseille (France) in 2013. During his graduate studies, he was awarded a Geophysical Fluid Dynamics Fellowship from the Woods Hole Oceanographic Institution. He then worked as a Postdoctoral Fellow at Princeton University from 2013 to 2014 and then spent four years as a tenured CNRS Research Scientist in a joint academic and industrial laboratory, while also being a visiting research scholar at NYU Tandon School of Engineering. He joined UC Santa Barbara in 2018. His research aims at understanding the dynamics of multiphase systems. He is particularly interested in the couplings between the fluid dynamics, interfacial effects, and particle transport mechanisms involved in environmental and industrial processes. Alban Sauret was named a Soft Matter Emerging Investigators in 2017, was elected a UC Regents Junior Faculty Fellow in 2019, and received the NSF CAREER Award in 2020. His past results were highlighted in various media, including the Los Angeles Times, The Wall Street Journal, and Science Friday.

Wednesday, October 20, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: AME

Releasing Insights from Data: Quarrying vs. Sculpting

Paul D. Ronney

Professor and Chairman
Department of Aerospace & Mechanical Engineering
USC
Los Angeles, CA

When Michelangelo surveyed a block of marble he saw a figure trapped inside; his goal was to release the figure that in his mind was already there. Research involves not only “quarrying” (obtaining) blocks of experimental, computational or theoretical data but more importantly releasing the insights trapped within. For example, every student of physics learns about the H atom spectrum - but why this block of data? Because, trapped within the spectrum is a critical, unequivocal insight - that energy levels of matter are quantized.

In that famous example the insight and its significance are “obvious” given the benefit of years of hindsight - but what important insights are trapped inside freshly-quarried data? The focus of this presentation is on examples of and methods for sculpting data into works of insight. Starting with the aforementioned case studiy and others the audience’s sculpting skill will be challenged with case studies from both the presenter’s own work (some not yet published) and elsewhere, with an emphasis on examples where the insights were both difficult to sculpt and led to counterintuitive insights.

Paul Ronney is a Professor in the Department of Aerospace and Mechanical Engineering at the University of Southern California in Los Angeles, CA. Prof. Ronney received a Bachelor of Science degree in Mechanical Engineering from the University of California, Berkeley, a Master of Science degree in Aeronautics from the California Institute of Technology, and a Doctor of Science degree in Aeronautics and Astronautics from the Massachusetts Institute of Technology. He held postdoctoral appointments at the NASA Lewis (now Glenn) Research Center and the Laboratory for Computational Physics at the U. S. Naval Research Laboratory and a position as Assistant Professor in the Department of Mechanical and Aerospace Engineering at Princeton University before assuming his current position at USC. Prof. Ronney was the Payload Specialist Astronaut (Alternate) for Space Shuttle mission MSL-1 (STS-83, April 4 - 8, 1997) and the reflight of this mission (STS-94, July 1 - 16, 1997).

Professor Ronney has extensive research experience in small-scale combustion and power generation, turbulent combustion, flame ignition by transient plasma discharges, micro-scale combustion, bioengineering (robotic insect propulsion), edge flames, flame propagation in confined geometries (Hele-Shaw cells), internal combustion engines, premixed-gas combustion at microgravity and flame spread over solid fuel beds. One of his experiments, a study of premixed-gas flames at low gravity, flew on three Space Shuttle missions.

Prof. Ronney has published over 80 technical papers in peer-reviewed journals, made over 250 technical presentations (including over 35 invited presentations at international conferences), holds 7 U.S. patents, and has received over $12 million in funding for his research projects. In recognition of his achievements, he is a Fellow of the American Society of Mechanical Engineers and the Combustion Institute, an Associate Fellow of the American Institute of Aeronautics and Astronautics, and is a recipient of the National Science Foundation Presidential Young Investigator Award. He has received the Distinguished Paper Award from the Combustion Institute (for a work published in the Proceedings of the Combustion Institute, Vol. 37) and the Starley Premium Award of the Institution of Mechanical Engineers (for the best paper of the year published in the Journal of Automobile Engineering.)

Wednesday, October 27, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: Plucinsky

Development of a Linear Surface-Based Model for the Jet Noise Source

Dimitri Papamoschou

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

The seminar will discuss an effort to formulate an elementary physical model for the jet noise source that can be used for practical prediction of aircraft noise. Although the present analysis is confined to a round single-stream jet, the basic principles can be extended to more complex configurations. The model is defined on a “radiator” surface at the rotational/irrotational boundary of the jet on which the footprint of the vortical eddies, including their convective speed, is captured. The model’s building block at a given frequency is a linear pressure event with random origin and random helical mode. The probability density function for the event's axial origin is derived from the statistics of coherent structures in shear layers. The distribution for the helical mode is currently empirical and driven by the need to match the polar directivity of sound emission in the far field. The generic form of the event is a self-similar wavepacket with convective speed based on the mean centerline velocity and shape parameters determined by least-squares matching of the far-field sound pressure level at a wide range of frequencies and polar angles. Initial results indicate that the model reproduces, in a qualitative sense, key statistics of the jet acoustic field, including the near-field space-time correlation, the broadening of the far-field spectral density with increasing polar angle from the jet axis, and the coherence between the near and far fields. For the latter, the analysis indicates that the rapid decline in the coherence with increasing polar angle is primarily due to the randomness of the event's axial origin.

Dimitri Papamoschou is a professor of mechanical and aerospace engineering at University of California, Irvine (UCI). He received his PhD in Aeronautics at Caltech. His research interests include compressible turbulence, jet and fan aeroacoustics, and advanced noise source imaging methods. In jet aeroacoustics, he has shown the potential for noise reduction by asymmetric distortion of the jet velocity field, a concept that has led to several patents. He has also developed low-cost predictive methods for this type of noise reduction based on a special formulation of the acoustic analogy. At UCI he has served in various administrative roles, including department chair, associate dean, and interim dean. He is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA) and recipient of the 2017 AIAA Aeroacoustics Award. He serves as an associate editor of the AIAA Journal.

Wednesday, November 10, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

—Seminar will be held in the Laufer Conference Room, OHE 406—

Fish and Fish-Like Swimming Interactions

Ramiro Godoy-Diana and Benjamin Thiria

Physique et Mécanique des Milieux Hétérogènes laboratory (PMMH)
École Supérieure De Physique et De Chimie Industrielles De La Ville De Paris (ESPCI)
Paris, France

The interaction between two neighboring swimmers forms the basis of the collective dynamics observed in a school of fish in nature. We will discuss different aspects of our recent work on swimmer-to-swimmer interactions, in which we have designed experiments with real fish or with simple robotic models, as well as numerical simulations, to examine the issues of swimmer synchronization, pattern formation, and energy expenditure, examining the most basic interactions between a pair of neighboring swimmers.

Tuesday, November 16, 2021

3:30 PM

Laufer Conference Room, (OHE 406)

The Zoom webinar is at https://usc.zoom.us/j/92868857794.

host: Kanso

Additives in Extrusion-Based Additive Manufacturing

Paul Krueger

Professor and Chair
Department of Mechanical Engineering
Southern Methodist University
Dallas, TX

Material additives in additive manufacturing (AM) can serve a variety of functions from improving the manufacturing process to adjusting material properties in the final build. This talk will discuss several uses of additives in extrusion-based additive manufacturing. The first focuses on using carbon-black-based additives in AM for silicones. Silicones have a range of desirable properties (durability, large elongation, bio-compatibility, etc.) that make them appealing for AM, but because they are thermosets, additional complexity is required to use them in AM, including in-situ curing of the material. In this work, carbon-black additives are shown to improve the print quality of silicone parts with UV-curing due to reducing disturbance of material deposition from electro-static forces, even though the concentration is too low to promote material conductivity. Carbon black is also shown to be an effective radiation absorbing agent, allowing for material heating via an infrared laser in printing of thermally-cured silicones.

The second considers metallic micro-spheres as additives to promote electrical conductivity at sufficient concentrations to create printable electrically conductive polymer composites (ECPCs). ECPCs are useful for providing electrical connections, resistors, or other electrical functionality in printed parts. But for high conductivity, high concentrations of particles are required, making extrusion of the composite material difficult. Investigation of the rheology of these materials will be presented, using non-Newtonian silicones as a surrogate for the molten polymers during printing. The results show that the composite materials behave like power-law materials with a strong dependence on the particle concentration and the ratio of the diameter of the extrusion tube/nozzle to the mean particle diameter (𝜔). For 𝜔 decreasing toward 1, the flow consistency index (effective viscosity) decreases and then sharply increases as particles begin to jam within the tube. A semi-empirical model reproducing these effects will be presented.

Stay after the seminar for a brief overview of graduate programs in Mechanical Engineering at SMU. Learn about research opportunities and unique degree programs including MS in Manufacturing Management and the direct admission PhD program.

Paul Krueger received his B.S. in Mechanical Engineering in 1997 from the University of California at Berkeley. He received his M.S. in Aeronautics in 1998 and his Ph.D. in Aeronautics in 2001, both from the California Institute of Technology (Caltech). In 2002 he joined the Mechanical Engineering Department at Southern Methodist University (Dallas, TX) where he is currently a Professor and department chair. He is a recipient of the Rolf D. Buhler Memorial Award in Aeronautics, the Richard Bruce Chapman Memorial Award for distinguished research in Hydrodynamics, the Faculty Early Career Development (CAREER) Award from the National Science Foundation (2004), and the Ford Senior Research Fellowship from SMU (2012). His research interests include unsteady hydrodynamics and aerodynamics, vortex dynamics, bio-fluid mechanics, bio-morphic propulsion, fluid-boundary and fluid-particle interactions, and fluid processes in additive manufacturing.

Wednesday, November 17, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202)

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.

host: Ronney

Pushing Boundaries: Flow in Low Permeability Media

Emilie Dressaire

Assistant Professor
Department of Mechanical Engineering
University of California at Santa Barbara
Santa Barbara, CA

Generating and controlling fluid flow in low permeability environments is a challenge in natural and engineered systems. In this talk, I will discuss two studies involving the opening of fractures in a soft substrate and the clogging of microchannels. The injection of fluid in brittle elastic materials drive the formation of cracks. Besides, when the pressure is released, the fluid flows out of the crack, in a process called backflow. Using a model experiment, we characterize the growth of a disk-like crack that propagates upon injection of the fluid, and its collapse as the injection pressure is released. The viscous dissipation, elastic deformation, and toughness of the matrix are important physical parameters that control the fluid flow in the crack or blister. This strategy is commonly used in rocks of low permeability and could find applications in bioengineering. Yet the increase in permeability is only transient. A solution to avoid the closing of the crack formed by injection is to use suspensions of particles. However, the behavior of particles in confined systems remains mainly qualitative. I will discuss recent results obtained on the clogging of microchannels. When a suspension of particles flows in a microchannel, deposition and assembly can lead to the formation of a clog, followed by a stable aggregate of fixed porosity. I will present a model for the growth of the aggregate at the pore scale, which allows us to rationalize the evolution of the flow rate in networks of microchannels. Bridging the injection of fluid in elastic media with suspension dynamics is a promising route to advance printing in soft materials.

Emilie Dressaire received a B.S. in Engineering from ESPCI, France, in 2005, and a Ph.D. in Mechanical Engineering from Harvard University in 2009. She joined the Mechanical and Aerospace Engineering Department at NYU Tandon School of Engineering in 2014 and CNRS in 2017. She is now a faculty member in the Department of Mechanical Engineering at UCSB. She currently serves as a Member-at-Large on the Executive Committee of APS Division of Fluid Dynamics. Her research interests are centered around the areas of small scale fluid mechanics and soft matter physics, specifically focusing on interdisciplinary projects to develop bio-inspired methods to control and monitor fluid flows.

Wednesday, December 1, 2021

3:30 PM

Seaver Science Library, Room 202 (SSL 202) via Zoom

The Zoom webinar is at https://usc.zoom.us/j/97427241653?pwd=UGd2aXY2b3dsQkxMdzdvcnNBMjRJZz09.