INTERACTION BETWEEN AIR FLOW AND AIR -BORNE SOUND IN A DUCT.
Annual summary rept. no. 3, 1 Dec 61-30 Nov 62,
GOETTINGEN UNIV (WEST GERMANY) PHYSIKALISCHES INSTITUT
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The development of the flow boundary layer of a flat plate is influenced by different sound fields. In one series of measurements the sound field affects the flow at the stagnation point of the plate, in another series the boundary layer itself is affected. Depending on the frequency of the sound signal and on the flow velocity boundary layer distortions are either increased or suppressed. The cross distribution of the sound pressure in an absorbing duct with air flow is determined by the shape of the flow velocity profile. For a downstream -propagating sound signal the sound pressure is increased at the absorbing wall even for sound wavelengths greater than the flow boundary layer thickness. The acoustic radiation impedance of a tube orifice with an air outflow depends on the flow velocity and the turbulence level. With increased flow velocity the radiation resistance is decreased. Author
- Fluid Mechanics