Calibration and Demonstration of the New Virginia Tech Anechoic Wind Tunnel

Abstract

A unique new removable anechoic system and new acoustic treatment for the Virginia Tech Stability Wind Tunnel is described. The new system consists of a Kevlar-walled acoustic test section flanked by two anechoic chambers. In its new configuration the facility is closed aerodynamically and open acoustically, allowing far-field acoustic measurements with a flow quality comparable to that of a hardwalled wind tunnel. An extensive program of experiments has been conducted to examine the performance of this new hardware under a range of conditions, both to examine the effects of acoustic treatment on overall test-section noise levels and to ascertain the aerodynamic characteristics of the new test section. Noise levels in the test section of the anechoic facility are down by as much as 25 dB compared to the original hard-walled configuration. Lift interference corrections (for a baseline NACA 0012 airfoil) are less than half those expected in an open-jet wind tunnel. Acoustic measurements of airfoil trailing edge noise using a microphone phased array are compared to past experiments conducted on similar airfoils in an open-jet facility.

Acoustic and aerodynamic design and characterization of a small-scale aeroacoustic wind tunnel

“…Some of the tunnels are of closed-circuit design [1][2][3][4][5] with a closed or semi-closed test section, where the air flow from the nozzle enters a collector. The others are open circuit tunnels [6][7][8][9][10] where the open jet from the nozzle is not collected, but expands freely into a larger room.…”

Design of a low-noise aeroacoustic wind tunnel facility at Brunel University

“…A very well known aeroacoustic wind tunnels is in the Virginia Tech of the United States 1 . The 1.83 m x 1.83 m test section can achieve maximum speed of about 75 ms -1 without blockage.…”

The Wall Pressure Spectrum of High Reynolds Number Rough-Wall Turbulent Boundary Layers

“…This subsonic wind tunnel utilizes a continuous, single return design and is capable of achieving speeds in excess of 80-m/s in the test section. Upgrades to the test section and wind tunnel circuit (Smith, et al 2005, Crede 2008, Remillieux, et al 2008) allow this facility to run in an anechoic configuration that has been shown to be acoustically quiet while still maintaining favorable aerodynamics (Remillieux, et al 2008, Devenport, et al 2010. The flow entering the test section has been found to have turbulence levels of 0.021% at 21-m/s and 0.031% at 57m/s.…”

“…The fan consists of 8 Clark-Y airfoil section blades and can be driven at over 600-RPM. A foam fan liner has been applied to reduce the tip gap and tip noise by almost 6-dB across the entire frequency range (Remillieux, et al 2008). Downstream of the fan, the flow enters an air exchange tower which is partially open to the atmosphere.…”