SUNMONTUEWEDTHUFRISAT
Events for the 2nd week of March
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AME Seminar
Wed, Mar 10, 2021 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: George Park, University of Pennsylvania
Talk Title: Toward Predictive Yet Affordable Computations of Practical Wall-Bounded Turbulent Flows
Abstract: Kinetic energy of turbulence is generated at large scales controlled by boundary conditions, but it is dissipated into heat at the smallest scales. The ratio of these two length scales increases rapidly with Reynolds number. Solid walls add another dimension in this scale landscape, where the scale separation gets progressively less pronounced toward the wall. This has significant ramifications on the cost of scale-resolving simulation of practical engineering flows, such as those found in aircraft, wind turbines, and ship hydrodynamics. Direct approaches with full resolution of length and times scales close to the wall are still infeasible with current computing power. The demand for superior designs at reduced cost has led researchers to explore alternative computational approaches that have potential to be predictive yet affordable. Large-eddy simulation (LES) is one such approach where only the energy-containing scales are resolved directly, and the effect of the unresolved motions are modeled. In practical LES calculations, subgrid-scale (SGS) models are used in conjunction with wall models to augment the turbulent shear stress, which otherwise is underpredicted on coarse grids and leads to inaccurate prediction of mean and turbulence quantities.
In this talk, I will discuss the research in my group on this wall-modeled LES approach. Widely used wall-modeling techniques will be discussed with their applications to canonical and complex wall-bounded flows. Challenges in robust and efficient implementation of the models in flow solvers for handling practical geometries will be discussed. I will also highlight recent work to predict flow over realistic aircraft geometries at flight conditions and a boundary layer with mean three dimensionality.
Biography: George Park is an Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. He received his Ph.D. and M.S. in Mechanical Engineering (ME) from Stanford University in 2014 and 2011, respectively, and his B.S. in ME from Seoul National University, South Korea in 2009. He worked as a postdoctoral fellow and an engineering research associate at the Center for Turbulence Research (Stanford) prior to joining UPenn as a faculty member in 2018. His research interests include high-fidelity numerical simulation of complex wall-bounded turbulent flows, computational methods with unstructured grids, non-equilibrium turbulent boundary layers, and fluid-structure interaction.
Host: AME Department
More Info: https://usc.zoom.us/j/97491401429
Webcast: https://usc.zoom.us/j/97491401429Location: Online event
WebCast Link: https://usc.zoom.us/j/97491401429
Audiences: Everyone Is Invited
Contact: Tessa Yao
Event Link: https://usc.zoom.us/j/97491401429
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AME PhD Student Seminar
Fri, Mar 12, 2021 @ 03:00 PM - 04:00 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Samuel Goldman, USC AME PhD Student
Talk Title: A Case Study of the Failure of a Compression Spring in a Lunar Percussion Mechanism
Abstract: The Regolith and Ice Drill for the Exploration of New Terrains (TRIDENT) is a rotary-percussive drill being used on several upcoming Lunar exploration programs. Life testing of this drill resulted in the unexpected early failure of a critical compression spring, which cannot be explained by quasi-static analysis. The purpose of this work is to determine if transient dynamic behavior resulting from percussion can explain this failure. An experiment is conducted comparing the effect of various types of spacers, and it is found that a neoprene spacer allows the spring to survive more than twice as many cycles compared to metallic spacers. Additionally, the dynamic response of this system to impact is modeled using the Distributed Transfer Function Method (DTFM), and is compared to FEA and discrete element techniques. It is found that DTFM is capable of bounding the response as computed by FEA, while the discrete element model underestimates peak shear stress by more than 25% in boundary coils. FEA and DTFM both show that wave propagation within the spring could result in peak shear stresses in boundary coils that are over 20% higher than middle coils. These results suggest that percussive wave propagation can explain the early failure of this spring.
Biography: Sam Goldman is a Ph.D. student under Dr. Flashner. His research focus is primarily in modeling and experimentation of percussion mechanisms used in extraterrestrial geotechnical tools. Sam has a B.S. in Biomedical Engineering from The Ohio State University, and an M.S. in Aerospace & Mechanical Engineering from USC.
Host: AME Department
More Info: https://usc.zoom.us/s/96549200347
Audiences: Everyone Is Invited
Contact: Christine Franks
Event Link: https://usc.zoom.us/s/96549200347