Abstract
On the purpose of accurate data acquisition for the aeroacoustic testing mostly in open jet test section of aeroacoustic wind tunnel, the large scale anechoic chamber is specifically designed to build the low background noise environment. A newly acoustic test section is presented in this paper, of which the contour is similar as the closed test section, and the wall is fabricated by the fiber fabric, both the characteristics of closed and open jet test section of conventional wind tunnel are combined in it. By thoroughly researching on the acoustics and aerodynamics of this acoustically transparent test section, significant progress in reducing the background noises in test section and improving the ratio of energy of the wind tunnel and some other aspects have been achieved. Acoustically transparent test section behaves better in acoustics and aerodynamics than conventional acoustic test section because of their high definition in detecting the sound sources and great performance in transmitting sounds.
Highlights
A newly acoustic test section is presented in this paper, of which the contour is similar as the closed test section, and the wall is fabricated by the fiber fabric, both the characteristics of closed and open jet test section of conventional wind tunnel are combined in it
Aeroacoustic experiments are mostly conducted in aeroacoustic wind tunnel with open jet test section for a long period, and the large-scale anechoic chamber must be used around the test section to reduce the background noises to simulate far-field environments as truly as possible [1]
Researchers in China Aerodynamic Research and Development Center (CARDC) have carried out a series of experiments to eliminate the noises caused by the open jet in the aeroacoustic wind tunnel
Summary
Aeroacoustic experiments are mostly conducted in aeroacoustic wind tunnel with open jet test section for a long period, and the large-scale anechoic chamber must be used around the test section to reduce the background noises to simulate far-field environments as truly as possible [1]. The acoustic attenuation and reflection on solid walls are too high and the noise interferences in boundary layers become obvious These drawbacks limit the application of closed test section in aeroacoustic experiments. Lowsonalgorithm [4], the boundary layer noise level in closed test section could reach to 103 dB at the flow speed of 30 m/s This kind of noise caused by the walls of test section influences the aeroacoustic experiments directly. The noise attenuation of aramid fiber is low when the noise frequency level is below 25 kHz. The experiment results of NACA0012 giraffe shows that the aerodynamic performances of this test section are nearly the same as the conventional hard-wall test section and the lift interference corrections are less than half those expected in an open-jet wind tunnel. The study on acoustic characteristics of acoustically transparent test section and exploration on acoustic and aerodynamic performances could greatly help to promote the experimental ability of relevant wind tunnels, broaden the range of experimental wind speed, and reduce the energy consumption as well as the background noises
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