Abstract
Existing solutions to the problem of sound production by an axial-flow fan interacting with inlet turbulence and inflow distortion (Marvin E. Goldstein et al., NASA TN D-7676, May 1974 and NASA TN D-7667, June 1974) were evaluated over a range of inflow parameters. Sound power in the fan fundamental and second harmonic tones was computed and the modal power distributions contributing to the total tone power were identified. Comparisons and contrasts between the relations of input parameters to sound power produced were made for the two forms of inflow disturbance. It was found that the bulk of the modal power was carried by modes near cutoff for both forms of inflow disturbance when described by parameter values typical of those expected in practical fan test situations. The implications of the numerical results for the design of passive inlet flow control devices proposed to simulate flight conditions during static fan tests are discussed.
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