Microphone-Array Measurements in cryogenic/pressurized Wind tunnels

Kurzfassung

In the development process of aircraft and rail vehicles, measurement techniques based on microphone-arrays are well-known and common practice on small-scaled models in wind tunnels with closed test section. Since conventional wind tunnels cannot generally achieve full-scale Reynolds numbers, measurements are often performed in cryogenic and/or pressurized wind tunnels which are capable of higher Reynolds number flows, thus adapting to the smaller scale of the model. The DLR Institute of Aerodynamics and Flow Technology has further developed the microphone array measurement technique for the use in cryogenic (down to 100 K) and pressurized (up to 450 kPa) wind tunnels. For the application in cryogenic wind tunnels a microphone array consisting of 144 microphones was designed and constructed. Measurements have been conducted in the cryogenic wind tunnel DNW-KKK. An overview of the results is given using a single-rod configuration and an airplane half model as aeroacoustic noise sources. The results show a significant Reynolds number dependency of the measured sound power.