Third M.I.T. Conference on Computational Fluid and Solid Mechanics June 14–17, 2005  

Inviscid and viscous CFD modeling of plume dynamics in laser ablation

Kedar A. Pathak, Alex Povitsky*
Department of Mechanical Engineering, University of Akron, Akron, OH 44325, USA

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We model the dynamics of a laser ablated plume in production of carbon nanotubes using computational fluid dynamics techniques. A higher-order ENO scheme is used for modeling the plume. The exact physical phenomenon of laser ablation plume dynamics is comparatively complex. For simplicity we model the plume and surrounding laser furnace gas as a single-species ideal gas. We are aiming at capturing the basic features of a laser ablated plume that will help in future to control the plume's evolution using simplified models. We solve Euler equations, Navier-Stokes equations, and Navier-Stokes equations with an appropriate model of the turbulent flow field. A Euler equations-based model appears to be adequate for first dozens of microseconds. For modeling of several hundreds of microseconds after the ablation, the viscous terms are needed to model the plume's diffusion. For millisecond-range modeling, the influence of unsteady turbulent flow in the laser furnace may become significant. The baroclinic and viscous deposition of vorticity on the plume is obtained numerically and the interaction of the plume with reflected shock waves appears to be the major source of the deposited vorticity. In this paper, a relatively simple analytical model of dynamics of plume will be discussed. This model will be based on evaluation of vorticity on the plume and formation of the vortex couple.

Keywords:  Laser ablation; Plume gas dynamics; Vorticity deposition; ENO schemes

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