Converging-diverging shock-driven instabilities along soft hydrogel surfaces
Daniel Pickard (Massachusetts Institute of Technology)
Dmitro Martynowych (Massachusetts Institute of Technology)
Jet Lem (Massachusetts Institute of Technology)
Anwar Koshakji (Massachusetts Institute of Technology)
Shaoting Lin (Massachusetts Institute of Technology)
Xuanhe Zhao (Massachusetts Institute of Technology)
Keith Nelson (Massachusetts Institute of Technology)
Bianca Giovanardi (Massachusetts Institute of Technology, TU Delft - Aerospace Structures & Computational Mechanics)
Raul Radovitzky (Massachusetts Institute of Technology)
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Abstract
Intense surface eruptions are observed along the curved surface of a confined cylindrical film of hydrogel subject to laser-induced converging-diverging shock loading. Detailed numerical simulations are used to identify the dominant mechanisms causing mechanical instability. The mechanisms that produce surface instability are found to be fundamentally different from both acoustic parametric instability and shock-driven Richtmyer-Meshkov instability. The time scale of observed and simulated eruption formation is much larger than that of a single shock reflection, in stark contrast to previously studied shock-driven instabilities. Moreover, surface undulations are only found along external, as opposed to internal, soft solid boundaries. Specifically, classic bubble surface instability mechanisms do not occur in our experiments and here we comment only on the new surface undulations found along the outer boundary of solid hydrogel cylinders. Our findings indicate a new class of impulsively excited surface instability that is driven by cycles of internal shock reflections.
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