• November 12, 2018
  • 4:00 p.m.
  • 320 New Classroom Building
  • Dr. Eric Johnsen, University of Michigan
  • Faculty Host: Dr. Kevin G. Wang
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  • Abstract: Given the ubiquity of cavitation in naval hydrodynamics, considerable research has been dedicated to understanding cavitation dynamics in water and the impact on neighboring hard objects, e.g., vibrations, structural damage, etc. However, this knowledge does not immediately translate to bubble dynamics in or near soft materials, a phenomenon central to a variety of medical (therapeutic ultrasound, traumatic brain injury) and naval (elastomeric coatings) applications. The complex rheology of soft matter and the coupling between the bubble and its surroundings pose challenges for predicting soft matter response to cavitation, including potential damage, at such high rates. This presentation summarizes our efforts toward developing numerical models and methods for predicting bubble dynamics in soft materials and applying these techniques to understand the underlying mechanics. Our investigations of canonical, single-bubble problems have shed light on the role of viscoelasticity on the bubble dynamics characteristics, e.g., oscillation damping/frequency and bubble morphology, as well as quantified stresses and temperatures experienced in the surrounding medium. Our findings further indicate that, besides shock waves and liquid jet impacts known to erode hard materials, additional mechanisms such as viscous and elastic stresses, as well as local heating, are likely to contribute to damaging soft matter. Whether cavitation-induced damage is intended or not, this knowledge is essential to planning safe and efficient ultrasound procedures, as well as improving the design of cavitation-resistant materials.
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  • Bio: Eric Johnsen is an Associate Professor of Mechanical Engineering at the University of Michigan. He received his BS from UCSB in 2001, and MS and PhD from Caltech in 2002 and 2008, respectively; he then spent two years as a post-doctoral fellow at the Center for Turbulence Research at Stanford before moving to Michigan in 2010. His research interests lie broadly in scientific computing and fluid mechanics, including multiphase flows, turbulence, shock waves, high-energy-density physics, and high-order numerical methods. His group’s work finds applications in biomedical engineering, energy sciences, and transportation engineering. He is a recipient of the NSF CAREER and ONR Young Investigator awards.