Seminars

Linda Shi, Assistant Professor, Architecture Art Planning, Cornell University and Hanne van den Berg, Urban Adaptation Expert, European Environment Agency

Abstract: These are exciting times for civil and environmental engineers, who have an immense role to play in societal transformation under climate change. Cities, funders, public agencies, and policymakers are increasingly advocating infrastructure projects that mitigate flood risks, especially in the aftermath of disasters. Whether projects are green or grey, we are seeing a resurgence of infrastructure proposals that are large in scale and ambition after decades of more decentralized stormwater management. These projects, nevertheless, respond only to the physical vulnerabilities of place by shifting water from one site to another. Decades of social science research demonstrate that vulnerability to environmental hazards are socially constructed by laws, policies, and politics that together shape a household or communities’ ability to overcome the impacts of a disaster event. From this perspective, major infrastructure works are not only a technical, apolitical, value-neutral proposition, but a physical intervention that reflects and entrenches politics of inequality. In the United States, many have disproportionately benefitted wealthier, whiter, and otherwise more privileged groups, while socially vulnerable groups whose communities were disinvested and neglected for decades have had to relocate to make way for infrastructure - often leaving for other environmentally precarious sites. 

This double-header talk presents concepts of social and spatial justice, and how water management projects have contributed to inequitable social vulnerability to hydrological risks. We then share a case study of how flood management in Houston reflects the tensions in how traditional engineering practices have contributed to inequitable local flood risks, and how engineers there have grappled with questions of equity, justice, and fairness. We argue that engineers have an opportunity and a need to reflect on the epistemological roots of the profession, mainstream modes of analysis, and cultural attitudes towards change and more diverse ways of knowing. 

Becca Neumann, Associate Professor, Civil & Environmental Engineering, University of Washington

Abstract: Northern high latitudes are expected to get warmer and wetter. There is consensus that warming will intensify permafrost thaw and increase wetland methane emissions, facilitating a positive climate feedback. However, the effects of increased precipitation are uncertain. At two different thawing wetland complexes in Alaska, we found that rain rapidly altered soil temperature, both within the permafrost plateau and within the thaw wetland. To a first approximation, rain has the same temperature as air, and when air and soil temperatures are mismatched, rainwater inputs can rapidly change subsurface soil temperatures through thermal conduction. At one site, we found that when wetland soils were warmed by spring rainfall, methane emissions increased by ~30%. The warm, deep soils early in the growing season likely enhanced both microbial and plant processes that increased emissions. At the other site, data showed rapid thaw of frozen soil within the permafrost plateau during a large rain event. This result indicates, but does not prove, that thermal transport by rain could be an important mechanism for thawing permafrost. The collective datasets clearly demonstrate the ability of rain to advect thermal energy into soils, and indicate that through this mechanism, rain notably affects the radiative forcing of thawing permafrost landscapes.

About the Speaker: Becca joined the Civil and Environmental Engineering Department at University of Washington in 2011 and is currently an associate professor. She leads the hydro-biogeochemistry research group, which investigates how hydrologic, chemical and biological processes interact in soils, aquifers and surface waters to control the movement and concentration of chemicals in air, water, plants and animals. The group harnesses knowledge and techniques from multiple disciplines to tackle societally relevant topics, such as food and water quality and global climate change. Prior to UW, Becca was a NOAA Climate and Global Change postdoctoral fellow at Harvard University and a Ph.D. student at the Massachusetts Institute of Technology. She worked as an environmental engineering consultant for EG&G Technical Services before graduate school, and received her B.S. in Civil and Environmental Engineering and B.A. in Art and Art History from Rice University. Outside of work, Becca enjoys hiking, skiing and rock climbing with her husband and two kids.

Devaraj van der Meer, Professor, University of Twente

Abstract: The impact of liquid masses onto solid substrates constitutes a research field of paramount importance for many applications. These range from the microscopic scale of, e.g., inkjet printing, to large-scale oceanic wave impacts onto maritime structures, and many of them have been active, but largely disconnected research topics for many decades. In this work, we investigate to what extent the many phenomena observed within this vast range of impact parameters can be captured and connected using simple scaling laws. With focus on determining the pressures occurring during impact, we formulate a framework that aims to incorporate the influence of gas compressibility, air cushioning, liquid compressibility, and surface instabilities. This approach leads to remarkable conclusions, e.g., why for droplets impacting at low and moderate speeds liquid compressibility is expected to play no significant role.

About the Speaker: Devaraj van der Meer studied theoretical high-energy physics in Leiden in the Netherlands and, after spending several beautiful years as a high-school and college physics teacher, obtained his PhD in 2004 in experimental granular physics, after a radical switch of topics. He is currently professor in the Physics of Fluid group at the University of Twente, also in the Netherlands, where he is working on a broad range of topics ranging from granular physics, via liquid impact problems, to mass and heat transfer. He is Applied Physics Chair, member of the Dutch Physics Council and is a Vidi and a Vici laureate within the Dutch Talent programme.      

Julie Lundquist, Associate Professor, Department of of Atmospheric and Oceanic Sciences, University of Colorado Boulder; Courtesy Appointment, Dept. of Applied Mathematics; Fellow, Renewable and Sustainable Energy Institute, University of Colorado Boulder; Joint Appointee Scientist, National Renewable Energy Laboratory

Abstract: As the world moves away from fossil fuels and towards more renewably-generated electricity, interdisciplinary challenges become more prominent. In the wind energy arena, the nexus of atmospheric science and engineering offers several interesting areas of research. In this talk, I will survey some of the “Grand Challenges” of wind energy and delve into details of specific areas of my research.

At the most fundamental scale, the representations of atmospheric turbulence in numerical weather prediction models require revision, especially given that our simulation capabilities have outstripped some of the theoretical underpinnings. New observational approaches have let us measure the dissipation rate of turbulence kinetic energy in a broad range of circumstances so that we can document the inadequacies of current model parameterizations.  I will present our observational methods and the variability of dissipation rate, and suggested machine-learning-based approaches for improving representation of dissipation rate in numerical weather prediction models.

At a larger spatial scale, an individual wind turbine will create a wake downwind. This wake region of slower wind will undermine power production of neighbouring turbines. The wake itself will vary with atmospheric conditions, and so predicting wake variability becomes critical for integrating large amounts of renewably-generated electricity into power grids.  I will survey approaches for representing approaches for representing wakes in numerical weather prediction models and share some recent results regarding both onshore and offshore wind deployments.

About the Speaker: Prof. Lundquist leads an interdisciplinary research group in the Dept. of Atmospheric and Oceanic Sciences, University of Colorado, with a joint appointment at the National Renewable Energy Laboratory. Her research group uses observational and computational approaches to understand the atmospheric boundary layer, with emphasis on atmospheric influences on turbine productivity, turbine wake dynamics, and downwind impacts of wind energy.  Before joining CU-Boulder, Dr. Lundquist designed and led wind energy projects at Lawrence Livermore National Laboratory. Her Ph.D. is in Astrophysical, Planetary, and Atmospheric Science from CU-Boulder, as is her M.S. degree. She studied English and Physics as an undergraduate at Trinity University, San Antonio, Texas. She has authored or co-authored over 100 refereed publications and over 200 conference presentations. Beyond wind energy, her current research projects include assessment of dissipation rate in the atmospheric boundary layer (NSF-CAREER), flow in complex terrain (NSF: Perdigão), and improving simulation capabilities for wildfire (DOI) and urban fires (OPP).

Claire Masteller, Assistant Professor of Earth and Planetary Sciences, Washington University in St. Louis

Abstract: Rivers transmit environmental signals across landscapes.  In the wake of a changing climate, predicting river channel response to variations in flow magnitude and flood frequency is of significant importance for floodplain communities and ecosystems. As these environmental perturbations propagate across a drainage basin, it’s important to consider the role of prior flow history in a channel when predicting its future evolution. However, widely used models for fluvial sediment transport currently do not integrate these history effects. This omission represents a fundamental, outstanding knowledge gap in earth surface processes. 

In this talk I will focus on the process of bedload sediment transport in gravel-bed rivers, where memory effects are observed over a variety of time-scales.  I will first discuss the origins of memory in gravel bed rivers, using results from a series of laboratory flume experiments.  I will then apply these new insights to a unique, continuous record of coarse sediment transport to quantify the thresholds for memory formation and destruction in a steep mountain stream. I will discuss the development and implementation of a history-dependent function to better describe sediment mobility by accounting for these memory effects. 

About the Speaker: Claire Masteller started as an Assistant Professor of Earth and Planetary Sciences at Washington University in St. Louis just this last year. She received her PhD in Earth and Planetary Sciences at the University of California in Santa Cruz in 2017 and her BA in Earth Science at the University of Pennsylvania in 2012. She spent time as a post-doctoral researcher at GFZ - German Research Center for Geosciences in Potsdam Germany from 2017-2019. Masteller is broadly interested in sediment transport and erosion mechanics and their role in driving landscape evolution. She uses interdisciplinary methods to address research questions across a wide range of spatial and temporal scales.

Craig Hill, Assistant Professor, Swenson College of Science and Engineering, University of Minnesota Duluth

Abstract: Lake Superior is known for its Gales of November, when The Lake shows its strength and unpredictability during large storms with intense winds and awe-inspiring waves that resemble the oceans. Unfortunately by this point, most real-time surface observation systems have been recovered for the winter, so we lack detailed over-water surface observations during late fall, winter, and early spring seasons. Engineering observation systems and deployment logistics under these conditions is certainly no easy task. Relying on numerical modeling and satellite observations become increasingly important during these periods, yet further insight is needed to validate these resources that are heavily relied on by mariners, coastal warning systems, and Great Lakes municipalities. This talk will look at ongoing development of a low-cost, open-source platform for Lagrangian measurements across the Great Lakes, providing potential for new insight into large freshwater system air-sea interactions, contaminant transport, extreme waves, ice tracking, and other mobile observations. Discussion will focus around the development process, applications for a growing Smart Great Lakes Initiative, and in the context of exploring marine energy technologies for Blue Economic opportunities.

About the Speaker: Craig Hill is a new assistant professor in the Mechanical & Industrial Engineering Department at the University of Minnesota Duluth. He spent nearly 10 years at SAFL, from working on the Technical and Engineering Staff, to completing his PhD investigating the interactions between marine hydrokinetic energy technology performance and hydro-morphodynamics. Since then, Craig spent time as a Postdoc in the University of Washington’s Department of Mechanical Engineering continuing R&D in marine energy technologies, leading R&D and new composite material product design for Werner Paddles, and as an observation system marine engineer for the UMD Large Lakes Observatory.  In his faculty role, he is working to develop low-cost sensing platforms for marine and atmospheric engineering applications, with specific focus on Great Lakes environments during seasons when many observation systems are no longer deployed.

Presentation of the 2020 Edward Silberman Fellowship
Award Recipient: Aliza Abraham, Department of Mechanical Engineering, UMN for her research "The effect of dynamic operation and incoming flow on the wake of a utility-scale wind turbine."

Distinguished Lecture: Employing environmental turbulence data for renewable energy prediction and environmental sustainability
Distinguished Speaker: Corey Markfort, Assistant Professor, Department of Civil and Environmental Engineering, University of Iowa

With increasing demand for renewable energy and development of wind farms over large areas of land and coastal seas, accurate prediction of atmospheric boundary layer flow and interactions with wind turbines is needed for optimizing design and improving efficiency of individual turbines and wind power plants. Once developed, wind plant operators must ensure energy generation meets regulations to minimize environmental impacts. This requires quantification of impacts to wildlife and surface ecosystems. As wind plants are built in more diverse locations, non-ideal flows with greater shear and turbulence necessitate new models for accurate flow field and power prediction. Interactions between arrays of wind turbines and underlying ecosystems, water waves, and even effects on blowing and drifting snow present new challenges. Advanced models supported by high-fidelity environmental data provides new opportunities for optimizing wind plants to both maximize power production and minimize negative environmental impacts.

This presentation will focus on efforts by our team to integrate environmental turbulence measurements to improve wind energy models and guide efforts to quantify environmental impacts for use in next generation wind plant design and control algorithms. Using turbulence measurements from tall towers and nacelle-mounted Doppler wind LiDAR, we have developed advanced power prediction and wake models to improve wind turbine and wind plant power forecasts. We also investigate use of mobile Doppler radar and infrared cameras to monitor bat activity around individual wind turbines and wind farms. Finally, new efforts to quantify the effects of offshore wind energy development on wind-wave processes will be shown, using highly resolved measurements of coupled wind-wave dynamics in a new atmospheric boundary layer wind-wave tunnel.

Judy Yang, Assistant Professor, Department of Civil, Environmental, and Geo- Engineering, University of Minnesota

Abstract: The transport of carbon and bacteria regulates the biogeochemical cycle of soil carbon and controls the spread of microbial pathogens in soil. The fate of soil carbon is particularly becoming an emergent concern because recent studies observed a burst release of carbon from soil in controlled environments with increasing temperature and/or atmospheric CO2, suggesting that soil may become a carbon source and accelerate climate change. However, these transport processes in soil have remained mysterious, and one major reason is that direct observation of opaque soil is difficult.

In the first part of the talk, I will discuss the new 4D imaging technology we developed that traces the transport of carbon in a microfluidic soil in real time. Using this new technology, we identified the secret interactions among carbon, clay, and bacteria, which control the fate of soil carbon. We proposed a new soil-carbon-bacteria interaction model that can potentially be used to improve our predictions of global carbon cycle. In the second half of the talk, I will discuss a new mechanism for bacteria to spread in soil. Specifically, I discovered that bacteria can self-generate flows in unsaturated porous materials by producing biosurfactants that change the wettability of typical soil surfaces. This new bacterial transport mechanism can potentially be used to improve predictions of soil biogeochemical cycles and the spread of microbial contamination in soil and other similar unsaturated porous materials such as granular materials and tissues. At the end of the talk, I would like to introduce the Environmental Transport (ET) - Lab at SAFL and share my visions about the lab.

About the Speaker: Judy Yang is a new assistant professor in the Department of Civil, Environmental, and Geo-Engineering. She got her master and PhD from the Department of Civil and Environmental Engineering at MIT in 2015 and 2018, respectively. Afterwards, she was a postdoc in the Department of Mechanical Engineering at Princeton University. Judy is interested in problems related to coastal and riverine erosion, the sequestration and release of carbon from soil, and the spread of bacteria in nature. Her lab will focus on developing interdisciplinary approaches to mimic and understand our complex natural environment in the lab. She has been a MIT presidential fellow, MIT Martin Fellow for Sustainability, the founder of a science communication club at MIT (http://trees.mit.edu/ ), and 2018 Caltech young investigator lecturer.

Talk Title: Pattern formation in suspension flows
Sungyon Lee, Benjamin Mayhugh Assistant Professor, Mechanical Engineering

Abstract: 
In this talk, we focus on two complementary flow configurations in which the presence of suspended particles drastically alters the dynamics of the fluid-fluid interface and leads to pattern formation. First, we discuss the result of injecting air into a packing of soft hydrogel beads that are saturated in water. We find that this new combination of buoyancy, capillarity, and elasticity under confinement leads to complex morphologies of air migration, as well as nontrivial dynamics in the amount of trapped air in the system. In the second part of the talk, we report a particle-induced fingering instability when a mixture of particles and viscous oil is injected radially into an air-filled Hele-Shaw cell. Our experimental results show that the characteristics of fingering depend on the particle volume fraction and on the ratio of the particle diameter to gap size. A reduced model is also presented to rationalize the fingering behavior. 

About the Speaker: Sungyon Lee is a Benjamin Mayhugh Assistant Professor in Mechanical Engineering at the University of Minnesota. She completed her Ph.D. and M.S. in Mechanical Engineering at Massachusetts Institute of Technology, and B.S. in Mechanical Engineering at University of California, Berkeley. Following a post-doc at Ecole Polytechnique and adjunct faculty position in Applied Math at University of California, Los Angeles, she was an assistant professor in the Mechanical Engineering at Texas A&M University from 2013-2017. Dr. Lee's fluid mechanics research group specializes in reducing complex physical phenomena into tractable problems that can be visualized with table-top experiments and solved with mathematical modeling. The physical systems of interest range from drops and bubbles, particle-laden flows and interfaces, to two-phase flows through porous media. 

Presentation of the 2017 Lorenz G. Straub award
Award Recipient: Allison Goodwell, University of Colorado Denver

Distinguished Lecture: Identification of physically-interpretable dynamical modes from big data: from turbulence to climate
Distinguished Speaker: Efi Foufoula-Georgiou, Distinguished Professor, Henry Samueli Endowed Chair in Engineering, Departments of Civil and Environmental Engineering
 and Earth System Science, University of California Irvine

Coherent spatio-temporal patterns (modes) in complex systems are regular features whose evolution is expected to be more predictable than the general background variability, whose impact on other parts of the system is often significant, and which reveal physical aspects of the system and its response to change. Two specific systems of interest exhibiting multi-scale variability and coherent spatio-temporal patterns are turbulence and climate. Here we will present a new methodology recently developed in our group, called rotated spectral Principle Component Analysis (rsPCA), and demonstrate its ability to robustly identify physically interpretable propagating modes even in the presence of noise. The innovation of rsPCA lies on (1) a wavelet-based implementation of sPCA using the continuous Morlet wavelet as a robust estimator of the cross-spectral matrices with good frequency resolution, and (2) a rotation of the complex-valued eigenvectors to optimize their spatial regularity (smoothness) using a regularization of their spatial Laplacian.  The combination of these two innovations improves interpretability and reduces the sensitivity of the extracted modes to noise and sampling variability as well as unmixes competing modes with similar amplitude within the same frequency band.  In this talk, the theory and application of rsPCA to a wave propagating example and to extracting dynamical modes from climate observations will be discussed.