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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Past Seminars

SAFL Spring Awards Ceremony

SAFL is excited to host a virtual special awards ceremony on May 4th, 2021 that will celebrate students in the St. Anthony Falls Laboratory (SAFL) community. We are tremendously grateful to have such talented, dedicated students at SAFL, and it is a privilege to celebrate them with awards that honor not only them and their accomplishments, but the legacies of the people who have helped SAFL become what it is today.

We will be presenting the 2020 - 2021 Alvin G. Andersen Award, the Heinz G. Stefan Fellowship, and the Nels Nelson Memorial Fellowship. Family members will be present to speak about the award namesakes, the recipients will be introduced by their respective advisors, and the recipients will give remarks on their research.  We expect the event to last approximately an hour. 

2020 - 2021 Award Recipients:

Alvin G. Anderson Award - Kerry Callaghan, former PhD student from the Department of Earth and Environmental Sciences (advisor Andrew Wickert)
Heinz G. Stefan Fellowship - Lun Gao, PhD student from the Department of Civil, Environmental, and Geo- Engineering (advisor Ardeshir Ebtehaj)
Nels Nelson Memorial Fellowship - Yuanqing Liu, PhD student from the Department of Mechanical Engineering (advisor Lian Shen)

You can learn more about this year’s recipients in this linked program

Simulation and modeling of non-canonical turbulent flows - Junlin Yuan, Michigan State University

Junlin Yuan, Assistant Professor, Department of Mechanical Engineering, Michigan State University

Abstract: The bulk of wall turbulence research has focused, perhaps disproportionately, on canonical flows along smooth flat plates with uniform freestream conditions. However, in engineering and environmental applications, such as flow around hydraulic turbine blades, navy platforms and in rivers, we see a wide range of dynamically complicated flow fields, affected by surface roughness, curvature, freestream pressure gradients, and unsteadiness. The consequence is that existing descriptions and models of turbulence have limited utility to design practice. My long term goal is to build essential physics into models, to enable a consistent description for turbulence across a wide range of flow complexities. The first part of the talk will be focused on understanding and modeling for rough-walled, equilibrium turbulence or non-equilibrium ones subjected to longitudinal pressure gradients. Using data from direct and large-eddy simulations (DNS and LES), I will show that roughness significantly modifies turbulence under strong spatial or temporal accelerations. I will also show an example of machine-learned modeling of hydrodynamic drag from roughness with arbitrary topography.

The second part of the talk is on using DNS to better understand river hyporheic exchange, a phenomenon of turbulent flow bounded by rough, permeable walls. In our understanding of riverine systems, a gap of knowledge exists in how pore-scale heterogeneities affect multiscale hydrologic and biogeochemical processes. I will show that dynamics at the scale of sediment grains and small roughness formed by uppermost-layer grains—typically ignored in existing predictive approaches—can be important for exchanges across a flat bed. Specifically, pore-resolved DNS of flows bounded by beds modeled as closely packed spheres were carried out. Results showed that bed roughness induces deep, multiscale subsurface flow paths that yield residence time distribution with a power-law tail. The main driver appears to be the interfacial pressure variation generated by roughness, a mechanism fundamentally similar to the effect of bedforms. Future work will investigate (i) pore-scale dynamics in transient or spatially varying river flows, (ii) reactive solute transport affected by pore-scale dynamics, and (iii) potential link with reduced-order transport models used for water management practice.

About the Speaker: Dr. Junlin Yuan is an assistant professor in Department of Mechanical Engineering at Michigan State University. She obtained both MS and PhD degrees (2015) from Queen's University, Canada. Her PhD research focused on simulation (DNS and LES) and modeling of turbulent flows in the context of rough hydraulic turbine blades. At MSU, she continued to use large-scale simulations to identify the dynamics of wall-bounded turbulence with various complexities, and to develop physics-based, data-driven models. Topics include turbulence responses to acceleration/deceleration, wall roughness, wall permeability, curvature, and rotation. Applications cover engineering, environmental and bio-locomotive topics. Her research group is currently funded by ONR, NSF and the industry.

Straub Award Ceremony and Distinguished Lecture, featuring Dr. Tracy Mandel and Dr. Veronica Morales

Prior to our keynote presentation, we are excited to welcome and celebrate the most recent winner of the Lorenz G. Straub Award. Dr. Tracy Mandel completed her 2018 dissertation under Jeffrey Koseff at Stanford University. She will provide a brief remarks about her graduate thesis, titled Free-surface Dynamics in the Presence of Submerged Canopies. Dr. Mandel currently serves at University of New Hampshire as an Assistant Professor in Ocean Engineering and Mechanical Engineering. Her research group uses experimental and field approaches to study turbulent environmental flows, with a focus on coastal hydrodynamics. 

Keynote Presentation: Transport Phenomena Under Spatial Heterogeneity: Bridging the Pore and Darcy Scales

Veronica Morales, Assistant Professor Civil & Environmental Engineering, University of California Davis

Abstract: Solving the flow and mass transport through environmental porous media is central to many technological applications spanning groundwater remediation, oil recovery, and geotechnical engineering. Under spatial heterogeneity, the phenomena of flow and transport significantly differ from those in uniform media. The variability of natural pore-spaces gives rise to complex flow patterns and non-Gaussian velocity fluctuations that complicate predictions. Classic models for the field-scale omit this variability and use average system parameters to solve governing equations for flow and transport. Such types of models might acceptably capture the average time of arrival of a substance (e.g., a groundwater contaminant), but consistently fail to predict the often-observed early arrival and prolonged tailing in concentration signals. Capturing the variance and skewness of such concentration signals requires more information than is contained in average system descriptors. To this end, this talk will discuss work carried out to represent large-scale transport processes as the collective phenomena resulting from interactions between the pore-scale heterogeneity and the local-scale flow. The first part of the talk will discuss the rules of particle motion ascertained at the pore-scale that are efficiently upscaled with stochastic models to describe large-scale transport problems. We demonstrate how our model accurately captures the changeover from intense to weak spreading, which is poorly understood but crucial for problems in groundwater contamination. The second part of the talk focuses on flow distribution and recasts flow path resistance into a graph-theory problem. Through this work we learn where and why preferential pathways form and offer a simple metric to estimate the time of first arrival based on structural information of the porous medium alone.

About the Speaker: As a hydrogeologist, Veronica Morales’s research focuses on the physics of flow and reactive transport in porous media with a keen interest in understanding how particles move and interact in confined spaces. In 2017, Morales joined the faculty at the University of California, Davis where she was awarded the NSF-CAREER and the AGU Early Career Award. Previously, she was a postdoctoral associate at the Environmental Fluid Mechanics lab at ETH Zürich and the Soil Physics group at the SIMBIOS Centre. She holds a PhD in Biological & Environmental Engineering from Cornell University (2011), and dual Bachelor degrees in Environmental Science and Spanish Literature from the University of California, Santa Barbara (2004).

Transform Engineering for a Climate Changed Future – What Role for Reflexive Practice? Linda Shi, Cornell University

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. 

Transport of thermal energy by rain in thawing permafrost landscapes - Becca Neumann, University of Washington

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.

A scaling-law approach to liquid impact - Devaraj van der Meer, University of Twente

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.      

Turbulence to turbine wakes: challenges in the atmospheric science of wind energy - Julie Lundquist, University of Colorado Boulder

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).

How rivers remember: the effects of flow history on sediment mobility in gravel-bed rivers - Claire Masteller, Washington University in St. Louis

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.



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.

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.