Design, Fabrication, and Characterization of an Anechoic Wind Tunnel Facility

The design, fabrication, and preliminary characterization of an anechoic wind tunnel facility at the University of Florida are presented. A previously existing and ISO 3745 validated 100 Hz anechoic chamber is upgraded to incorporate an open-jet anechoic wind tunnel facility suitable for airframe noise studies. The wind tunnel is driven by a 224 kW (300 HP), 69 m^3/s (147,000 cfm) centrifugal fan controlled by a variable frequency drive. Airflow enters the wind tunnel through a settling duct with a honeycomb section and a set of four screens for the purposes of flow straightening and turbulence reduction, respectively. An optimized, minimum length, 3-D contraction designed using various computational methods accelerates the flow into a rectangular test section that measures 0.74 m (29\") by 1.12 m (44\") by 1.83 m (6 ft). The contraction shape consists of matched polynomials and is constructed using 19 mm (0.75\") thick reinforced fiberglass. Static pressure measurements along the contraction length validate the design procedure. The estimated maximum velocity attainable in the test section is   76 m/s (250 ft/s); thus the maximum Reynolds number based on chord (=2/3 span) is Re = 3.4*10^6. Preliminary facility characterization experiments at a test section velocity of 17 m/s indicate the rms flow non-uniformity and the turbulence intensity level at the nozzle exit are < 0.7% and < 0.11%, respectively. The flow leaving the test section enters a 2-D diffuser, turns a 90