Abstract
** An assessment of component installation effects on flow generated, far-field sound for a tandem cylinder configuration tested in the NASA Langley Research Center (LaRC) Quiet Flow Facility (QFF) is presented in this paper. The Fast Scattering Code (FSC) was used to simulate the insertion losses resulting from the interaction of incident sound generated by flow over the cylinders with the QFF apparatus. Two sources of sound were used to model the flow generated noise: 1) a line of point dipoles placed at the axis of the rear cylinder, and 2) CFD/CAA generated unsteady pressures on the cylinder surfaces in free flow. As observed at the microphone locations used in the test, the effects of the QFF components on the acoustic field were small, being on the order of 2 dB for all frequencies considered, when the dipole line source was employed. Installation effects were higher when the time dependent surface pressures were used as noise generators, being approximately 6 to 9 dB for the primary shedding frequency and 3 to 5 dB for the second harmonic. This difference is most likely due to the absence of near field flow non-uniformities in the FSC calculations. Inclusion of these effects through the use of penetrable data surfaces located in the linear flow region should yield better estimates of the incident sound field.
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