Development of a Nanoscale Hot-Wire Probe for Supersonic Flow Applications

Abstract

Due to their three-dimensionality, chaotic nature and wide range of length and time scales, turbulent flows remain challenging to study. In order to better characterize their flow dynamics, highly resolved instrumentation is needed. The nanoscale thermal anemometry probe, also known as the NSTAP, was designed in response to this need. Advancements in semiconductor manufacturing enabled this miniature silicon-based device to be manufactured with reduced critical dimensions compared to conventional sensors. The NSTAP has been shown to exhibit reduced spatial and temporal filtering, demonstrating great potential for its use in supersonic flows.

However, due to the increased structural loading, presence of shock waves and added mathematical complexities associated with supersonic flows, the current design of the NSTAP required alterations in order to enable its use in supersonic flows. The manufacturing process was modified to produce a new NSTAP which addressed the shortcomings of the previous variant. Once fabrication was complete, characterization of this state-of-the-art sensor was initiated, starting with its calibration in compressible subsonic flows. A calibration was subsequently performed in a supersonic freestream in order to understand the sensor's behavior in high-speed flows. A combined experimental/numerical investigation was undertaken with the objective of quantifying the temporal response of the modified sensor; a lumped-capacitance model was tailored to investigate the heat transfer characteristics of the modified sensor and results were compared to data obtained with a shock tube.

After performing a thorough characterization of the newly designed NSTAP, boundary layer data were obtained and analyzed. It was shown that the sensor performs admirably well and has an unparalleled frequency response compared to other experimental techniques. The boundary layer data were also compared to a numerical simulation, where physical differences were found in the measured turbulence quantities.