AEM Seminar: TODAY, March 7th - Prof. Laura Villafañe, Department of Aerospace Engineering, University of Illinois at Urbana-Champaign

[Molly Schmitz]

University of Minnesota

Aerospace Engineering and Mechanics
Spring 2025 Seminar Series

Friday, March 7, 2025

209 Akerman Hall

2:30pm-4:30pm

AEM Seminar:  

Ejecta clouds by plume impingement on granular surfaces, a challenge to planetary landings

Abstract:

As a manned heavy lander descends onto the natural surface of a planetary body or the Moon, the plumes of the thrusters required for deceleration impinge on the regolith eroding craters underneath the vehicle and lifting dense clouds of ejecta. Surface distance sensing and visibility, lander stability, and ejecta impacts in nearby infrastructure and vehicle sensors, are some of the risks caused by plume-surface interactions (PSI) whose assessment is critical for mission design. However, no empirical or engineering models are available that can reliably relate plume and soil properties to surface erosion or ejecta, numerical simulations of PSI are challenged by the extreme range of particle loadings and flow regimes that need modeling, and flight or ground test data from experiments reproducing the relevant physics have been impeded by the opacity of the dense particle cloud.
We present ongoing work on sub-scale PSI experiments using a Mach 5 jet impinging on a bed of 103 μm mean diameter glass microspheres under vacuum conditions. A novel mm-wave interferometric technique has been developed that circumvents the problem of optical opacity to enable high temporal resolution spatial ejecta concentration measurements when used in a tomographic setup. It leverages commercially available automotive frequency modulated
continuous-wave (FMCW) radars and passive reflectors, providing a cost effective and portable diagnostic to measure volume fraction in optically opaque dispersed multiphase flows. We combine distinct flow and particle diagnostics, including mm-wave techniques, NO Planar Laser Induced Fluorescence, high-speed pressure measurements and lateral cloud imaging, planar particle tracking velocimetry and post-test three-dimensional crater reconstruction, to interpret erosion phenomenology and the role of varying parameters such as jet expansion ratio, mass flow, and nozzle to surface distance. We will also discuss ongoing efforts to merge simplified particle trajectory models and sparse experimental data to reconstruct the 4D ejecta cloud evolution and estimate erosion rates as well as far field effects.

 

Bio:

Laura Villafañe is an Assistant Professor in the Department of Aerospace Engineering at the University of Illinois at Urbana-Champaign. Her research explores a wide range of fluid dynamic problems, with particular interest on turbulent and particle-laden flows, and on the development of data analysis tools and non-intrusive diagnostics, including non-conventional flow diagnostics such as Magnetic Resonance Imaging. She graduated on Aerospace Engineering at the
Polytechnic University of Madrid, completed her Ph.D at the von Karman Institute for Fluid Dynamics, Belgium, and was a Postdoctoral Fellow and Research Engineer at the Center for Turbulence Research at Stanford University prior to joining the faculty at UIUC in 2019. She is the recipient of three NASA Early-Stage-Innovation Awards for plume-surface interactions and parachute fluid and structural mechanics. Laura was elected Young Observer to the US National Committee for Theoretical and Applied Mechanics in 2024, and AIAA Associate Fellow Class of 2025.

*Refreshments to follow 

Molly Schmitz (She/Her/Hers)

Graduate Program Coordinator & Executive Accounts Specialist

Department of Aerospace Engineering & Mechanics

University of Minnesota - Twin Cities

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[Molly Schmitz]

University of Minnesota

Aerospace Engineering and Mechanics
Spring 2025 Seminar Series

Friday, March 28, 2025

209 Akerman Hall

2:30pm-4:30pm

AEM Midwest Mechanics Seminar:

Meshless Continuum Modeling of Dry and Wet Granular Media

Abstract:

Granular media are common in industry, the natural world, and our day-to-day lives, but have been historically resistant to modeling.  While grain-by-grain discrete element methods (DEM) exist, these are often far too costly at the length-scales of full-size industrial problems. This talk progressively develops continuum-based tools with the aim of realistic but computationally tractable full-scale flow simulation.  We begin with a discussion of dry granular rheology and its essential ingredients.  We provide a brief discussion of what sorts of problems can be solved accurately with a basic granular flow model, and discuss a meshless numerical method, the Material Point Method (MPM), which can be used to simulate these models up to huge deformations.  Second, we do a deeper dive on how the MPM-based approach can be extended to model submerged granular flow problems using two-phase mixture theory, where the fluid and granular phases are modeled as two separate but coupled continua. This methodology is shown able to replicate experimental results for saturated granular flows over a range of conditions and packing fractions, and can be extended to account for more obscure effects, such as those giving rise to shear-thickening suspensions.

Bio:
Ken Kamrin received a BS in Engineering Physics with a minor in Mathematics at UC Berkeley in 2003, and a PhD in Applied Mathematics at MIT in 2008.  Kamrin was an NSF Postdoctoral Research Fellow at Harvard University in the School of Engineering and Applied Sciences before joining the Mechanical Engineering faculty at MIT in 2011, where he was appointed the Class of 1956 Career Development Chair and later received a second faculty appointment in Applied Mathematics.  After 13 years as a professor at MIT, Ken joined the UC Berkeley Mechanical Engineering faculty in 2024.  Kamrin’s research focuses on constitutive modeling and computational mechanics for large deformation processes, with interests spanning elastic and plastic solid modeling, granular mechanics, amorphous solid mechanics, and fluid-structure interaction.  Kamrin’s honors include the 2010 Nicholas Metropolis Award from APS, the NSF CAREER Award in 2013, the 2015 Eshelby Mechanics Award for Young Faculty, the 2016 ASME Journal of Applied Mechanics Award, and the 2022 MacVicar Faculty Fellowship from MIT.  He sat for three years on the Board of Directors of the Society of Engineering Science and serves as an associate editor for the International Journal of Solids and Structures, Granular Matter, and Computational Particle Mechanics. He is co-author of the recent undergraduate textbook Introduction to Mechanics of Solid Materials (Oxford).

*Refreshments to follow 

Molly Schmitz (She/Her/Hers)