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Title page for ETD etd-12042003-181941

Type of Document Dissertation
Author Matlis, Eric Hill
Author's Email Address
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
  • 3-D instabilities in compressible boundary layers
Date of Defense 2003-11-20
Availability unrestricted
An experiment was conducted which was aimed at documenting the linear and

nonlinear 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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