Every two weeks during the academic year, SAFL hosts prominent figures in environmental science and fluid mechanics. They come from all over the US and the world to share their insight and inspire us to tackle important questions in the field. These seminars are free and open to the public. Join us to learn about the latest research advancements and network with contacts in the field.

SAFL seminars are be held on Tuesdays, from 3:00 to 4:15 p.m. in the SAFL Auditorium. 

We will record seminars and post them here when given permission by the speaker. To see if a recording is available, scroll down this page to "Past Seminars."

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Upcoming Seminars

SAFL Seminar: Developing low-cost, open-source observation systems for the Great Lakes - Craig Hill - UMD

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.

Past Seminars

Edward Silberman Award Ceremony and Distinguished Lecture

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 SpeakerCorey 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.


The Mysterious Transport of Carbon and Bacteria in Soil

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 ( ), and 2018 Caltech young investigator lecturer.

Pattern formation in suspension flows - Sungyon Lee - UMN Mechanical Engineering

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

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. 

Straub Award Ceremony and Distinguished Lecture

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 SpeakerEfi 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.

Multi-source analysis of river networks and connectivity across scales

Paola Passalacqua, Associate Professor, Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin

Abstract: In the analysis of Earth-surface processes and response to changes in forcings and anthropogenic modifications, we are often challenged by the wide range of spatial and temporal scales that are involved and need to be accounted for. This is a challenge for numerical modeling as well and for collecting field observations representative of the system of interest across scales. The integration of remotely sensed data can help in this regard, as these data offer information at global scales and their spatial and temporal resolutions keep increasing. In this talk, I will focus on river systems and cover examples in which remotely sensed observations, numerical modeling, and field observations are integrated to gain a deeper understanding of system functioning and response to future changes. I will also discuss challenges we still face either due to missing information or lack of tools for data analysis and opportunities for future research.

About the SpeakerPaola Passalacqua is an Associate Professor of Environmental and Water Resources Engineering, in the Department of Civil, Architectural and Environmental Engineering at the University of Texas at Austin. She graduated from the University of Genoa, Italy, with a BS (2002) in Environmental Engineering, and received a MS (2005) and a PhD (2009) in Civil Engineering from the University of Minnesota. Her research interests include network analysis and dynamics of hydrologic and environmental transport on river networks and deltaic systems, lidar and satellite imagery analysis, multi-scale analysis of hydrological processes, and quantitative analysis and modeling of landscape forming processes. 

Mesoscale to microscale simulations for wind energy applications

Tina Chow, Professor, Department of Civil and Environmental Engineering, University of California Berkeley

Abstract: Wind turbines sit at the very bottom of the atmospheric boundary layer, where winds are highly turbulent and land-surface interactions may be strong. Variations in surface topography, from shallow depressions to steep mountains, also greatly affect flow development. High-resolution simulations of atmospheric flow are currently being developed to provide predictions for wind turbine micrositing and operational wind power forecasting. Here we present an overview of mesoscale to microscale simulations at real wind farms with complex terrain, including implementation of detailed models for turbine wake effects. The Weather and Research Forecasting (WRF) model is used here in grid nested configurations starting from the mesoscale (~ 10 km resolution) and ending with fine scale resolutions (~10 m) suitable for large-eddy simulation (LES) and comparison to field observations.

About the Speaker: Tina’s current research focuses on the atmospheric boundary layer, the lowest region of the Earth’s atmosphere, which is where we live and where weather events take place. Her research group aims to improve the numerical models used for weather prediction and air quality forecasts. She and her students have worked on predicting how winds are affected by complex mountainous terrain, how plumes spread in an urban environment, and how wind turbines respond in turbulent flow, among other applications. Tina received a B.S. in Engineering Sciences from Harvard University and M.S. and Ph.D. degrees in Civil and Environmental Engineering from Stanford University. She spent one year in the Atmospheric Sciences Division at Lawrence Livermore National Laboratory as a post-doctoral researcher. Tina joined the UC Berkeley Department of Civil and Environmental Engineering in 2005. At Cal, Tina teaches fluid mechanics, computer programming, and numerical methods to both undergraduate and graduate students.

Deforming bubbles in strong turbulence

Rui Ni, Assistant Professor, Department of Mechanical Engineering, Johns Hopkins University

Abstract: A persistent theme throughout the study of multiphase flows is the need to model and predict the detailed behaviors of all involved phases and the phenomena that they manifest at multiple length and time scales. When combined with background turbulent flows with similar multiscale nature, they pose a formidable challenge, even in the dilute dispersed regime. For many applications, from nuclear thermal hydraulics to bubble-mediated air-sea gas exchange, the dispersed phase often consists of many bubbles, bounded by surface tension and separated from the surrounding fluid by a deformable interface. Although many analytic and empirical models of multiphase flows have been formulated strictly for spherical or spheroidal particles with fixed shapes, in turbulent flows, finite-sized bubbles are constantly deforming with altogether different dynamics and momentum couplings over a wide range of scales. In this talk, I will share some ongoing efforts on developing new experimental facilities and techniques to simultaneously measure both the bubble deformation and surrounding turbulent flows in a Lagrangian framework. These preliminary results unveil different mechanisms of bubble deformation and breakup and will help to validate future closure models for Eulerian-Eulerian and Eulerian-Lagrangian two-fluids simulations in a turbulent environment.

About the Speaker: Dr. Ni recently joined the Johns Hopkins University as Assistant Professor of Mechanical Engineering in 2018. Before this position, he was the endowed Kenneth K. Kuo Early Career Professor at Penn State since 2015. He received his Ph.D. in Physics Department in 2011 from the Chinese University of Hong Kong and worked as a postdoctoral scholar at Yale and Wesleyan University. He won the NSF CAREER award in fluid dynamics and ACS-PRF New Investigator Award in 2017. His primary research focus is the development of advanced experimental methods for understanding gas-liquid and gas-solid multiphase flow as well as two-phase heat transfer problem. His other research interests include collective animal behaviors and physiological flows.

Simplified Stochastic Event Flood Modeling (SSEFM) for the Alcona Dam Hydroelectric Project

2018-2019 Nels Nelson Memorial Fellowship Ceremony:

Award recipient: Rochelle Widmer, MS student in the Department of Civil, Environmental, and Geo- Engineering

Keynote speaker: Cory Anderson, Water Resources Engineer, Barr Engineering

Abstract: One of the objectives and supporting strategies in FERC’s Strategic Plan for fiscal years 2014-2018 is to minimize risk to the public by using Risk-Informed Decision-Making (RIDM) for evaluating dam safety in parallel to traditional dam safety methods. Resulting risk estimates can be used, along with standards-based analyses, to decide if dam safety investments are justified. Consumers Energy Company (CEC) identified a concern at their Alcona Dam in Michigan regarding potential erosion of the unlined, earthen auxiliary spillway, and the potential subsequent failure of the dam during flood events more frequent than the inflow design flood (the PMF). However, given the possible consequences downstream, the estimated dam fragility, and the proposed and completed risk reduction measures, the risk may be low enough such that modifications to the auxiliary spillway are not warranted. Therefore, in 2017 CEC began a RIDM study of the Alcona Dam auxiliary spillway for submission to FERC.

RIDM requires a set of hydrologic hazard curves (HHCs) to estimate the overall risk. A Simplified Stochastic Event Flood Modeling (SSEFM) approach was used to develop the HHCs for Alcona Dam. The SSEFM method is a compromise between a purely deterministic approach which tends to be conservative and a fully stochastic, Monte-Carlo approach. The resulting HHCs are estimates of peak inflow rates for a range of annual exceedance probabilities (AEPs) from 0.01 to less than 1x10-7 for both cool-season (rain on snow) and warm-season (rain only) events. The SSEFM approach is the cornerstone of this RIDM study, allowing all other aspects of the study to relate important loading characteristics (peak water level, hydrostatic pressure, auxiliary spillway flow duration, etc.) to AEPs and therefore, a proper estimate of the risk.

About the speaker: Cory Anderson has about 10 years of experience in water resources engineering, working at Barr Engineering Co after graduating from UW in Madison in 2009. He specializes in hydrologic modeling, one- and to-dimensional hydraulic modeling, risk and uncertainty analysis, and probabilistic environmental modeling.

It rained two feet, now what?

William Hunt, William Neal Reynolds Distinguished University Professor & Extension Specialist, Department of Biological Agricultural Engineering, North Carolina State University

Abstract: Hurricane Florence dumped as much as 3 feet of water on parts of Southeastern North Carolina. This occurred only 1 year after massive flooding in Houston, Texas. Epic rainfall events, while still 'epic,' may no longer be considered infrequent. What does this mean for engineering design standards? What storms should we consider? Where is it OK to develop? What guidance does the engineering code of conduct provide? Insights to these questions and more are the focus of "It just rained 2 feet, now what?"

Regional Interdependence in Climate Change Adaptation: Sea Level Rise in the San Francisco Bay Area

2018-2019 Heinz G. Stefan Fellowship award ceremony
Award Recipient:
 Jackie Taylor, PhD Student in Civil, Environmental, and Geo- Engineering; advisors Miki Hondzo and Vaughan Voller

Keynote Speaker: Mark Stacey, Department Chair, Henry and Joyce Miedema Professor of Environmental Engineering, University of California- Berkeley

Abstract: Coastal communities around the world are facing a growing threat from sea level rise, which manifests itself as coastal flooding events of increasing frequency, magnitude and duration. Adapting to these changing conditions requires reconsideration of shorelines and other infrastructure systems, but  decisions by communities to take action in anticipation of future conditions both influence and are influenced by regional conditions and decisions. These interdependencies are a result of geographic interactions that emerge from either environmental processes or the function of infrastructure systems, and may be compounded by interactions between infrastructure systems, or through feedback with the environmental system.

In this talk, I will present a series of studies of how sea level rise will transform the San Francisco Bay Area, and the implications for regional adaptation planning. The interdependencies will be established through detailed analysis of tidal dynamics in combination with simulations of other infrastructure systems and the disruption of their function by coastal inundation events. Through these analyses, three distinct types of interdependence emerge, which will provide a foundation for consideration of the opportunities for and barriers to regional adaptation planning.

About the Speaker: Dr. Mark Stacey is the Henry & Joyce Miedema Professor and Chair in Civil & Environmental Engineering at the University of Califonia, Berkeley. He received his B.A.S. in Physics and Political Science and his M.S. and Ph.D. in Civil and Environmental Engineering from Stanford University. Throughout his career, his research and teaching have emphasized environmental physics, particularly the fluid mechanics of coastal environments. In the last decade, through the lens of sea level rise, he has focused on the interaction of environmental processes and infrastructure systems, including consideration of adaptation and resilience.