Thermal effects mediating the flow induced by laser-induced optical breakdown

Jonathan M. Wang, Marco Panesi, and Jonathan B. Freund
Phys. Rev. Fluids 6, 063403 – Published 30 June 2021

Abstract

A short focused laser pulse can generate a hot plasma, which expands then contracts and can eject a hot jet, the speed and direction of which is sensitive to the details of the plasma kernel. The coupling of thermal and chemical nonequilibrium plasma mechanisms with this hydrodynamic development is assessed with detailed simulations of a two-temperature, three-species plasma model. Time scales for electron recombination, thermal relaxation, and diffusion are compared to that of the plasma expansion to anticipate conditions in which these mechanisms might affect the vorticity generation that leads to the ultimate flow pattern. The effect of these mechanisms are analyzed through comparison with corresponding inert-gas and equilibrium models. Thermal-nonequilibrium effects are found to be weak due to rapid relaxation of the heavy-particle and electronic temperatures. In contrast, chemical equilibration occurs at a rate comparable to the expansion and thereby enhance both it and subsequent hydrodynamic mechanisms as the energy stored in ion formation during the preceding breakdown is released by electron recombination. Thermal conduction, enhanced by high-temperature free electrons, weakens the ejection.

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  • Received 3 January 2021
  • Accepted 8 June 2021

DOI:https://doi.org/10.1103/PhysRevFluids.6.063403

©2021 American Physical Society

Physics Subject Headings (PhySH)

Fluid DynamicsPlasma Physics

Authors & Affiliations

Jonathan M. Wang1,*, Marco Panesi2,†, and Jonathan B. Freund2,‡

  • 1Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
  • 2Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

  • *Corresponding author: jmwang14@stanford.edu
  • mpanesi@illinois.edu
  • jbfreund@illinois.edu

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Vol. 6, Iss. 6 — June 2021

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