Ph.D. Thesis Proposal by

Dan Fries

(Advisor: Dr. Suresh Menon)

“Experimental Multi-Scale Analysis of Supersonic Jets in Crossflow: Mixing and Combustion”

Friday, November 10, 2017 @ 2 p.m.
Montgomery Knight, Room 317

Abstract:
To achieve novel insights into passive and chemically active turbulent mixing under conditions relevant to the development of hypersonic propulsion systems, a multi-scale (nested) diagnostic setup is proposed. A jet in supersonic crossflow is selected as the experimental setup due to it providing a complex flowfield with phenomena of current fundamental research interest. Its near field is identified as the most interesting region to characterize the interaction between small and large scales. The momentum flux ratio and molecular weight are initially varied in a single jet configuration to understand the influence of gases heavier than air/nitrogen. Subsequently, spanwise distributed jet arrays reveal the influence of jet-jet interaction on turbulent mixing in a compressible flowfield. A laser ignition system provides highly localized regions of hot plasma to initiate chemical reactions at selected locations.

Multi-scale diagnostics reveal the effects of differential filtering on mixing, the identification of characteristic scales, coherent structures, dissipation and turbulent viscosity. Turbulent kinetic energy transport from the small to the large scales against the classical view of the Kolmogorov cascade is investigated experimentally. The effect of heat release on turbulent mixing processes and the interaction between chemical reactions and compressibility features (shock and expansion waves) is assessed. Additionally, the ignition and flameholding characteristics are analyzed. In the non-reacting cases, primarily PIV and a diagnostic suitable to asses qualitative mixing (acetone PLIF or nano-particle based planar laser scattering) are used, while in the reacting cases OH-PLIF and PIV are used. Schlieren imaging is used in initial assessments and to reveal density variations and heat release in the flowfield.

Committee:
Dr. Suresh Menon (advisor)
Dr. Devesh Ranjan
Dr. Jerry M. Seitzman