Vortex Identification and Tracking in Highly Turbulent Flows

Open Access
Author:
Linarez De La Cruz, Eros Darnel
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Jacqueline Antonia O'connor, Thesis Supervisor
  • Zoubeida Ounaies, Honors Advisor
Keywords:
  • Vortex cores
  • Hydrodynamic Instability
  • vortices
  • flame interaction
  • reacting and non-reacting flames
Abstract:
Hydrodynamic instability exists in turbulent shear flows. The presence of large-scale vortices (coherent structures) in these shear flows is due to the hydrodynamic instability that persists in these flows. It is considerably important to understand the development of these coherent structures in these flows and the effect that flames have on them because vortices can lead to flame wrinkling. For low vortex strengths, the flame wrinkles decrease the amplitude of the vortices through the flame due to expansion of the gases through the flame. For high vortex strengths, the amplitude of the vortices increase causing the flame to wrinkle and distort highly to the point where the flame itself can create/destroy coherent structures [1]. Interaction of flames with vortices also causes the heat release rate from the flame to fluctuate. This has implications on engine emissions based on the completeness of combustion in, for example, an internal combustion engine, and the heat loading to the structural components of the combustor. Consequently, the goal of this research is to identify and track vortices in flows with hydrodynamic instability, and understand the impact of flames on vortex generation, development, and dissipation downstream. To achieve a better understanding of this, a suite of analysis tools that use formulations depicting an accurate definition of a vortex core, or the negative λ2 eigenvalue requirement of the velocity gradient tensor, was created. These codes were then tested for accuracy using shear flows with known existence or absence of vortices. This suite of tools was used on velocity vector data gathered from a simple bluff-body flow field at conditions with and without a flame. The implications of these results are discussed and future work proposed.