Abstract
Clarifying the generation mechanism of aerodynamic noise is essential in attempting to reduce noise deriving from turbomachinery and high velocity vehicles. For studying aerodynamic noise, an air flow with quiet noise is very useful. Under these bases, a “Quiet Flow Wind Tunnel”, with the measuring section eauipped in an anechoic chamber, was developed and installed in 1982. The maximum velocity of air flow from the nozzle, with a section of 400mm × 400mm, is 50m/s and the turbulent level is below 0.5%. The noise levels around the measuring section are below 48dB (A) at a velocity of 35m/s. Studyies utilizing this facility include among others : vortex sound from crossing two cylinders, flow-noise from finned-tube bank, noise from vanes for a flow leaning. These studies concluded that simultaneous measurment on both the fluid-dynamic and acoustic phenomena is enabled by this facility. Conventional type wind tunnels are incapable for such measurment. The Quiet Flow Wind Tunnel is proven capable of making quantitative estimations on the generation of flow-sounds. The results of studies obtained through it are being effectively used in developing low-noise machines and systems.
