流カ騒音研究用の無音気流風洞の開発

抄録

For decreasing the noise of turbo-machineries, making clear the generation mechanism of fluid-dynamic noise is important and an air flow having quiet noise is very useful for the study of aerodynamic noise. A "Quiet Flow Wind Tunnel", whose measuring section is in the annechoic chamber, has been developed and established. The maximum velocity of air flow from the nozzle with a section size of 400 mm×400 mm is 42 m/s and its turbulence is less than 0.5 %. The noise levels around the measuring section are less than 48 dB(A) at a velocity of 35 m/s. By using this facility, further studies have been made, "vortex sound from crossing two cylinders", "flow-noise from finned-tube bank", "noise from ventilating-gallery", "noise of inner flow in straight ducts" etc.. It has been recognised, through these experiments, that this facility can measure both phenomena of fluid-dynamics and acoustics at the same time although these are still impossible by usual wind tunnels.