Hot-Wire Anemometer for the Boundary Layer Data System

• Main Author: Neumeister, William D
• Format: Others
• Published: DigitalCommons@CalPoly 2012
• Subjects: Hot-wire; CVA; BLDS; boundary layer; flow transition; frequency response; Aerodynamics and Fluid Mechanics
• Online Access: https://digitalcommons.calpoly.edu/theses/830; https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1876&context=theses

Hot-wire anemometry has been routinely employed for laboratory measurements of turbulence for decades. This thesis presents a hot-wire anemometer suitable for use with the Boundary Layer Data System (BLDS). BLDS provides a unique platform for in- flight measurements because of its small, self-contained, robust design and flexible architecture. Addition of a hot-wire anemometer would provide BLDS with a sensor that could directly measure flow velocity fluctuations caused by turbulence. Hot-wires are commonly operated in constant-temperature mode for high frequency response, but require a carefully tuned bridge. The constant-voltage anemometer (CVA) uses a simple op-amp circuit to improve frequency response over constant-current operation. Due to its balance between ease of operation and performance, a CVA system built for this project was tested with a 3.8 micron diameter, platinum-coated tungsten probe. The CVA was calibrated in a steady jet and a power-law curve fit accurately represented the calibration data. The CVA successfully measured velocity fluctuations in a turbulent jet, as well as in laminar and tripped turbulent boundary layers over a flat plate in a 110 MPH wind tunnel. CVA frequency response was investigated using a thermal/electrical model, controlled oscillation in a steady flow, and with a square wave test; these three methods showed agreement. The CVA is selected for integration with BLDS.