Seminars

seminar room safl

Every other week 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 held on Tuesdays from 3:00 to 4:15 p.m. unless otherwise noted. Join us in the SAFL Auditorium or via Zoom.

 
Spring 2024 Seminar Series
Tuesday, Jan 23-Katey Anthony
Tuesday, Feb 6th-No Seminar 
Tuesday, Feb 20th-Neal Iverson
Tuesday, March 12- Jennifer Stucker 
 
Tuesday, March 26th-Mike Shelley
Tuesday, April 9th-Sergio Fagherazzi
Tuesday, April 23rd-Ruben Juanes
Tuesday, May 7th-Walter Musial

Recordings
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."

Seminar Notifications
To sign-up for our SAFL Seminar email list, click here.


Upcoming Seminars

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Past Seminars

Use of Hollow Glass Spheres in Lightweight Cements

Clara Mata, Senior Product Development Specialist, 3M

Cementing across highly depleted zones and weaker formations requires low density cement systems capable of reducing the hydrostatic pressure of the fluid column during cement placement. If wellbores encounter weak or depleted zones, standard cement cannot be used because the bottom-hole pressure will exceed the pressure gradient and cement will get lost to the formation. Service companies offer cement solutions made light enough to circulate in such situations while retaining the ability to withstand down-hole conditions and maintaining adequate compressive strength to meet regulatory guidelines. Lightweight cements can be achieved using water extension, foamed cement or lightweight microspheres. The seminar focuses on the use of lightweight microspheres as density reducing agent. Selected experimental data comparing different types of hollow microspheres and guidelines on the selection of the appropriate microsphere grade will be discussed.

Buoyancy modulation and scalar transport in turbulent flows over smooth and rough walls

Edward Silberman Award Ceremony and Seminar

Silberman Award Recipient: Michael Heisel, PhD Candidate in Civil, Environmental, and Geo- Engineering

 

Keynote Speaker: Elie Bou-Zeid, Associate Professor of Civil and Environmental Engineering; Director, Program in Environmental Engineering and Water Resources, Civil and Environmental Engineering, Princeton University

The workings of how buoyancy modifies the statistics and structure of turbulence in wall-bounded flows, such as the atmospheric boundary layer (ABL), continues to be a topic with various open fundamental questions and multiple pressing applied needs. In the first part of this talk, a model that connects the budgets of the three velocity variance components and captures how the energy redistribution terms vary with the flux Richardson number is proposed. The results of this model are first tested against large eddy and direct numerical simulations. The model is then used to inquire about how the turbulence transitions between different regimes as the Richardson number varies. It is shown that the asymptotic limits of this transition are reasonably reproduced and are consistent with a large corpus of experiments under both unstable and stable conditions.

The complexity added to the problem by wall roughness is then considered. Since heat (or buoyancy) is advected with the flow, broad similarity is expected between the widely-studied momentum transfer problem and its scalar counterpart. However, unlike momentum that is dominated by form drag over very rough walls, scalar transport must occur through the viscous exchanges at the solid-fluid interface, which might result in transport dissimilarity. To examine underlying physics of the problem, a suite of large-eddy simulations (LES) is conducted over large three-dimensional roughness elements. The results point to (i) the importance of matching the Reynolds number of the simulations to real-world values, and (ii) the significance and dissimilarity (momentum versus scalars) of the dispersive fluxes inside and right above near the canopy. Implications for parameterizations in urban canopy models are then discussed.

Mixing and Atomization in Multiphase Flows with Insights from Linear Stability

Vinod Srinivasan, Assistant Professor, Mechanical Engineering, University of Minnesota

The control of mixing processes in shear flows is of interest in a variety of industrial applications, such as thermal plasma torches, infra-red signatures of aircraft, combustion and environmental remediation. IN the case of mutlphase flows, these processes require intensive simulation. However, many shear flows have been shown to be controllable using aspects of linear stability theory, by relying on the idea that the nonlinear breakdown of the flow can be traced back to the linear origins of specific instabilities. Suppression or enhancement of these instabilities in the linear regime may offer significant performance benefits. This talk presents a few instances where experimental studies have been combined with insights from linear stability theory to suppress or produce high rates of mixing/atomization. The cases considered are the low-density jet issuing into a high-density ambient, simulating a DC plasma arc, and the atomization of high viscosity fluids representative of biomass-derived fuels.  

Bio-economic Modeling in Water Resources

Lucia Levers, Research Associate, Water Resources Center at the University of Minnesota

Bio-economics, the combination of natural science and socio-economic data and methods, can be used to address a number of issues in the water resources field.  Two applications will be discussed.  The first is identifying potential water transfers from agricultural to environmental uses in the Salton Sea Region of California, in order to increase environmental quality and reduce costs.  The second is more local--determining economic triggers to induce land use change from traditional row crops to more environmentally friendly species in Minnesota with the goal of reducing nitrogen and sediment flows into the Mississippi.  

The Role of Salt in the Subaqueous Construction of Continental Margins

Lorenz G. Straub Award Ceremony

2015 Award Recipient: Filip Schuurman, dissertation completed at the Universiteit Utrecht, The Netherlands

Keynote speaker: Gary Parker, Professor, Department of Civil and Environmental Engineering, University of Illinois Urbana-Champaign 

 

Every continent is surrounded by a bench-like feature known as the continental margin. It consists of three parts: the near-shore continental shelf, the continental slope which dips toward deep water, and the continental rise which connects the margin to the abyss. The continental shelf has been traditionally interpreted to be drowned coastal plain associated with sea level rise. We show, however, that continental shelves are also presently being actively constructed subaqueously by the action of hypopycnal flows, i.e. sediment-laden rivers flows that are too light to overcome the barrier of dissolved salt and sink to deep water. Our model results show that the combination of hypopycnal flows and wave action gives rise to the seaward-migrating clinoform characteristic of active continental margins. We compare our results with the freshwater Lake Baikal, which is old, deep and has no continuous shelves.

From hillslopes to floodplains: controls on fluvial networks in mountainous landscapes

Fiona Clubb, Postdoctoral Researcher, University of Edinburgh

Link to Video

https://umn.webex.com/umn/ldr.php?RCID=b280be4cf29933efd19d0d66258da9bf

Mountainous regions are ubiquitously dissected by river networks.  These networks are the main drivers by which climate and tectonic signals are transmitted to the rest of the landscape, and control the response timescale of the landscape to these external forcings.  Furthermore, river systems set the downslope boundary conditions for hillslope sediment transport, which controls landscape denudation.  Therefore, understanding the controls on the organisation and structure of river networks in upland landscapes is an important goal in Earth surface processes research.  

The recent introduction of high-resolution topographic data, such as airborne lidar data, has revolutionised our ability to extract information from the topography, providing new opportunities for linking geomorphic process with landscape form.  In this talk, I will present novel methods of identifying and quantifying fluvial networks from high-resolution topographic data. I then use these methods to explore links between channel network density and erosion rate, which I use to explore different models of long-term landscape evolution.

Minnesota Narratives of Extreme Weather, Urban Runoff, and Climate Adaptation

Mae Davenport, Professor, Department of Forest Resources, University of Minnesota

Across Minnesota’s urban, rural and agricultural landscapes, exposure and sensitivity to climate change impacts and extreme weather vary. Scientists, natural resource managers, engineers and local officials have begun to assess community and ecosystem vulnerability and to develop targeted plans for emergency preparedness, infrastructure improvements, and ecological adaptation. However, much less work has been done to build community and social capacity to anticipate and respond to climate impacts. Empowering community members in high-risk regions has multiple, long-term benefits including increased individual motivation to act; strengthened social networks, social norm and identity development around sustainability; leadership and organizational development in climate readiness; and cross-sector programmatic coordination and resource sharing.

In this talk, I will explore multiple narratives of extreme weather, urban runoff, and climate adaptation emerging from social data gathered in Minnesota over the past 5 years. Analysis of these data suggests some significant opportunities as well as constraints for building community capacity to adapt to climate change in Minnesota. I will share key lessons from listening to multiple community voices and lead a discussion on potential strategies and tactics for place-based community adaptation. 

From Flocking Birds to Swarming Bacteria: A Study of the Dynamics of Active Fluids

Xiang Cheng, Assistant Professor, Chemical Engineering and Materials Science, University of Minnesota

Link to Video

https://umn.webex.com/umn/ldr.php?RCID=2b94b5fda91f2dde19db0b6d126600ec

Active fluids are a novel class of non-equilibrium complex fluids with examples across a wide range of
biological and physical systems such as flocking animals, swarming microorganisms, vibrated granular
rods, and suspensions of synthetic colloidal swimmers. Different from familiar non-equilibrium systems
where free energy is injected from boundaries, an active fluid is a dispersion of large numbers of self-
propelled units, which convert the ambient/internal free energy and maintain non-equilibrium steady
states at microscopic scales. Due to this distinct feature, active fluids exhibit fascinating and unusual
behaviors unseen in conventional complex fluids. Here, by combining high-speed confocal microscopy,
holographic imaging, rheological measurements and biochemical engineering, we experimentally
investigate the dynamics of active fluids. In particular, we use E. coli suspensions as our model system
and illustrate three unique properties of active fluids, i.e., (i) abnormal rheology, (ii) enhanced diffusion
of passive tracers and (iii) emergence of collective swarming. Based on theoretical tools of fluid
mechanics and statistical mechanics, we develop a quantitative understanding of these interesting
behaviors. Our study illustrates the general organizing principles of active fluids that can be exploited for
designing “smart” fluids with controllable fluid properties. Our results also shed new light on
fundamental transport processes in microbiological systems.

Influence of Fluid Motion on Blue Green Algae: Microcystis aeruginosa

Shahram Missaghi, associate extension professor, UMN extension, University of Minnesota

Algae blooms can turn the water green and smelly, contribute to fish kills, and may produce toxins that pose a health risk to people and animals. These types of algae blooms are referred to as Harmful Algal Blooms or HABs.   Microcystis aeruginosa (Microcystis) under suitable conditions may rapidly grow and reach extremely high cell concentrations (bloom) in just a few days. Microcystis HABs are on the rise globally, and there is an urgent need to understand and identify the forcing factors that influence Microcystis growth and bloom.  

We hypothesized that fluid motion has an influence on the growth and the vertical variability of Microcystis, and its influence can be quantified by measuring the corresponding rate of energy dissipation levels of fluid motion.  In this presentation, I will share how we conducted laboratory experiment measuring the population growth and vertical distribution of Microcystis in a bioreactor.  We also measure fluid velocities using a two-dimensional particle image velocimetry.  Our results showed that Microcystis growth rate and vertical heterogeneity were coupled.  The results will be instrumental in developing mechanistic models of the spatial and temporal distribution of Microcystis that can improve management of aquatic ecosystems. 

Microwave Land Atmosphere Remote Sensing over Radiometrically Complex Terrains

Ardeshir Ebtehaj, Assistant Professor, St. Anthony Falls Laboratory and Department of Civil, Environmental, and Geo-Engineering

 

This presentation discusses complexities in land-atmosphere microwave signals and explore modern data science methodologies that can be used to improve land-atmosphere remote sensing . In particular, snow-cover and precipitation microwave signals are difficult to discern from space, as both scatter the upwelling land surface radiation in a similar way over high-frequency bands >80 GHz.  We present the results using multi-satellite data from visible-to-microwave bands that enable better understanding of the distinct microwave signatures of precipitation at liquid and solid phases, especially over snow-covered surfaces. Using the data by the recently launched NASA’s Global Precipitation Measurement (GPM) satellite, we demonstrate that our new passive microwave retrieval algorithm--called shrunken locally linear embedding algorithm for retrieval of precipitation (ShARP)--promises improved snowfall detection skills without relying on any ancillary data.  The results of the algorithm are compared with the standard NASA precipitation products.