AERODYNAMICALLY GENERATED SOUND.
Final scientific rept.,
TORONTO UNIV (ONTARIO) INST FOR AEROSPACE STUDIES
Pagination or Media Count:
The research accomplishments of the project are summarized. A study of surface motion in turbulence-induced panel vibration demonstrated that panel motion consists of running waves forced by the convected pressure field superposed on a more irregular pattern. Turbulent structure in the transition region, 4.5 to 8 diams downstream of the nozzle of a 4-in. low-speed jet was investigated with the aim of relating the turbulence to the noise generating features of such a jet. Progress has been made in improving the accuracy of the hot-wire and time-delay correlator instrumentation, and timing, gate, and relay circuits were developed to semi-automate data processing. Constanttemperature hot-wires were found to obey a sine law quite accurately over a wide range when inclined to the stream. An aerofoil probe for measuring the transverse component of turbulence was also developed. Lastly, an anomaly in the directivity pattern of jet noise was resolved. Measurements in an anechoic room with a harmonic point sound source placed in an air jet indicated that the sound appears to be refracted away from the jet axis. This gives a marked dimple in the sound directivity pattern very similar to the dimple found with random jet noise. Author