An experiment was conducted which was aimed at documenting the linear andnonlinear development of pairs of oblique waves over a 7-degree half-anglecone in the Mach 3.5 “quiet” tunnel at NASA Langley Research Center. Thefirst element of this work was the calibration of a constant-current hot-wireanemometer to obtain quantitative mean and time-resolved measurements in thesupersonic boundary layer at frequencies up to 100 kHz. Secondly an actuatorhub was designed to introduce controlled disturbances into the flow at up to70 kHz. An azimuthal array of glow discharge actuators was positioned nearbranch I of the TS instability and excited the oblique waves with a prescribedinitial amplitude, frequency and azimuthal wave number. Spectra of thehot-wire voltage fluctuations without excitation, revealed an amplified band offrequencies which were consistent with the most amplified based on lineartheory. With excitation, we observed discrete modes at the excitationfrequency at the upstream locations. As this developed downstream, asubharmonic was also found to emerge. Azimuthal measurements showed these twomodes to have azimuthal amplitude variations which were consistent with helicalmode pairs. The amplitude of the subharmonic was also found to varyexponentially with the initial amplitude of the fundamental mode. Measurementsat angle-of-attack were also considered to investigate the development of across-flow instability.
Controlled Experiments on Instabilities and Transition to Turbulence on a Sharp Cone at Mach 3.5ETD
|Author||Eric Hill Matlis|
|Contributor||Thomas Corke, Committee Member|
|Degree Discipline||Aerospace and Mechanical Engineering|
|Degree Name||Doctor of Philosophy|
|Access Rights||Open Access|