INTERACTION BETWEEN AIR FLOW AND AIR -BORNE SOUND IN A DUCT.
Final technical rept. 1 Dec 62-31 Jan 63,
GOETTINGEN UNIV (WEST GERMANY) PHYSIKALISCHES INSTITUT
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The interaction of a surface bending wave with the flow boundary layer is of practical interest. Several types of surfaces conducting bending waves suitable for boundary layer interaction are tested. For the investigation of the influence of the flow velocity profile in a ducton the sound attenuation the sound pressure profiles in a wide duct with flow were measured. The acoustic impedance of an absorber with flow along its surface was measured. The sound radiation from an orifice with flow discharge depends on the flow velocity. The reflection coefficient of the orifice increases with flow velocity. It depends strongly on the turbulence level of the jet behind the orifice. Author
- Fluid Mechanics