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The Department of Mechanical, Materials, and Aerospace Engineering presents its spring 2025 seminar series featuring Laura Villafañe, assistant professor in the Department of Aerospace Engineering at the University of Illinois at Urbana-Champaign, who will present “Ejecta Clouds by Plume Impingement on Granular Surfaces, a Challenge to Planetary Landings.” This seminar is open to the public and will take place on Wednesday, April 16, from 12:45–1:45 p.m. in room 104 of the Rettaliata Engineering Center.

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.

Biography

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 in 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 U.S. National Committee for Theoretical and Applied Mechanics in 2024, and AIAA Associate Fellow Class of 2025.