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Type of Document Dissertation Author Matlis, Eric Hill Author's Email Address ematlis@nd.edu URN etd-12042003-181941 Title Controlled Experiments on Instabilities and Transition to Turbulence on a Sharp Cone at Mach 3.5 Degree Doctor of Philosophy Department Aerospace and Mechanical Engineering Advisory Committee
Advisor Name Title Thomas Corke Committee Member Keywords
- 3-D instabilities in compressible boundary layers
Date of Defense 2003-11-20 Availability unrestricted Abstract An experiment was conducted which was aimed at documenting the linear andnonlinear development of pairs of oblique waves over a 7-degree half-angle
cone in the Mach 3.5 "quiet" tunnel at NASA Langley Research Center. The
first element of this work was the calibration of a constant-current hot-wire
anemometer to obtain quantitative mean and time-resolved measurements in the
supersonic boundary layer at frequencies up to 100 kHz. Secondly an actuator
hub was designed to introduce controlled disturbances into the flow at up to
70 kHz. An azimuthal array of glow discharge actuators was positioned near
branch I of the TS instability and excited the oblique waves with a prescribed
initial amplitude, frequency and azimuthal wave number. Spectra of the
hot-wire voltage fluctuations without excitation, revealed an amplified band offrequencies which were consistent with the most amplified based on linear
theory. With excitation, we observed discrete modes at the excitation
frequency at the upstream locations. As this developed downstream, a
subharmonic was also found to emerge. Azimuthal measurements showed these two
modes to have azimuthal amplitude variations which were consistent with helicalmode pairs. The amplitude of the subharmonic was also found to vary
exponentially with the initial amplitude of the fundamental mode. Measurementsat angle-of-attack were also considered to investigate the development of a
cross-flow instability.
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