Project Title:
Array Design for Wind Tunnel Acoustic Measurements
Planning Systems, Inc.
7923 Jones Branch Drive
McLean, VA 22102
93-1 02.07 3400
Array Design for Wind Tunnel Acoustic Measurements
Abstract:
We propose to determine the feasibility and the benefits of
making acoustic measurements in wind tunnels - such as the Ames
40-by-80 Foot Wind Tunnel using acoustic arrays. To prevent
acoustic path distortion due to the in-flow/ out-of-flow shear
layer, arrays must be placed in-flow. A major difficulty with
placement of sensors in-flow is self-noise. We propose as an
innovative solution to this problem the use of acoustic arrays
which reduce both ambient noise and self-noise. In particular,
we propose the use of Mills Cross arrays, which in addition
integrate out uncorrelated self-noise. Specifically, we propose
to determine the applicability of arrays by 1) analyzing
conventional and Mills Cross arrays of sensors, and 2) measuring
sensor self-noise characteristics, using innovative inexpensive
piezo-electric sensors developed by PSI for this purpose. Issues
such as potential array configuration, near-field vs. far-field
measurements, rejection of reflections, frequency coverage, and
robustness will be addressed. In the Phase I effort
computational, mechanical, and electrical specifications for the
proposed array and its signal processing will be produced. This
provides for a rapid implementation of improvements to the
measurement capabilities at Ames and other existing facilities.
Improved measurement capabilities for acoustic research in wind
tunnels is important to both the government and private sectors,
and both stand to gain from marketable advancements. This
project is a step toward providing a means by which existing
measurement facilities can achieve tangible improvement in
acoustic measurement capabilities, for a nominal cost. The
ensuing marketable products consist of specialized acoustic wind
tunnel arrays and processing systems.
Mills Cross, Arrays, Acoustic, Wind Tunnel, Piezo-electric Sensor