Doctoral Dissertations

Date of Award

8-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Aerospace Engineering

Major Professor

John D. Schmisseur

Committee Members

Phillip A. Kreth, James Coder, Kivanc Ekici, Ryan Glasby, Christopher Combs

Abstract

The objectives of this study were to provide time-resolved (1) characterizations of shock wave/transitional boundary layer interactions using schlieren flow visualization, and (2) correlations of unsteady shock motion to boundary layer features. The characteristics of cylinder-induced shock wave/transitional boundary layer interactions in a Mach 2 freestream flowfield were studied experimentally. The Reynolds number in the Mach 2 facility was 30,000,000 m-1. Incoming boundary layers were in transitional and fully turbulent states. Characterizing the shock wave motion was based on tracking the position of the shock wave on the model surface in schlieren images. The motion of the shock waves revealed an high-intensity resonance. When analysis of high-speed schlieren images were combined with unsteady pressure-sensitive paint studies, it was concluded that upstream scaling exhibited characteristics of laminar flow interactions, whereas the downstream separation mirrored turbulent interactions. This high-intensity resonance was duplicated using a blunt fin shock generator and an axisymmetric model. Furthermore, the unsteady dynamics of a boundary layer separation precursor upstream of the separation shock was highly correlated to the motion of the upstream influence (UI) shock and separation shock. The motion of the UI shock, separation shock and boundary layer separation precursor suggest that the unsteadiness in transitional interactions was driven by instabilities in the boundary layer. An initial characterization with changing Reynolds number and edge Mach number was made in the appendix.

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