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Characterization of the Quiet Flow Freestream and a Flat Plate Model in the Boeing/AFOSR Mach 6 Quiet Tunnel

thesis
posted on 22.11.2021, 13:51 by Derek V MamrolDerek V Mamrol
The ambient pressure fluctuations within a wind tunnel test environment can severely affect the boundary layer transition witnessed on test articles The Boeing/AFOSR Mach 6 Quiet Tunnel was designed to minimize these fluctuations, also referred to as noise, and is the world's premier facility for studying hypersonic boundary layer transition in a quiet flow environment. All experiments performed for this work were conducted at this facility.

The freestream flow field of this tunnel has been characterized multiple times since its creation, however an extensive three-dimensional spatial sweep has never been conducted. A pitot rake model was designed to allow for an extensive spatial survey of tunnel noise. This model created measurement capabilities that were previously unknown to the BAM6QT facility, including the ability to take concurrent freestream pitot probe measurements. The performance of this new measurement method was evaluated, and suggestions for future verification tests are made. The pitot rake appears to suffer from probe-probe interactions in certain configurations, and has demonstrated variation in measurements that depends on the individual sensor used.

This new measurement apparatus was used to investigate the effect that cavities in the tunnel wall created by the installation of new optical windows had on the freestream noise level. A control dataset corresponding to a perfectly conformal tunnel wall was not collected during this work. The experiments conducted provide evidence that the tunnel wall cavities do increase the noise downstream of their location by approximately 100%, however a control dataset is needed to verify this finding.

In addition to tunnel characterization, a novel flat plate model was evaluated for use in the BAM6QT. This model was intended for use as a platform for observing second mode instability growth. These experiments show that the initial flat plate geometry proved incompatible with the BAM6QT as the tunnel could not achieve nominal flow conditions with the model installed. The flat plate model was streamlined to rectify the startup issue, but no evidence of the second mode instability was found. A 2.5° half angle cone is being designed to replace the flat plate model as a platform for the continuation of this project.

Funding

National Defense Science and Engineering Graduate Fellowship Program

History

Degree Type

Master of Science

Department

Aeronautics and Astronautics

Campus location

West Lafayette

Advisor/Supervisor/Committee Chair

Joseph S. Jewell

Additional Committee Member 2

Steven P. Schneider

Additional Committee Member 3

Carlo Scalo

Additional Committee Member 4

Matthew P. Borg