The Journal of the Acoustical Society of America · 1974 · 291 citations · 0 references
EngineeringAerospace EngineeringPhysicsAcousticsAerodynamicsVibrationAeroacousticsAirfoil TheoryExperimental AerodynamicsUnsteady AerodynamicsVortex DynamicsAcoustic WavesAerodynamic StabilityExperimental AeroacousticsSelf-excited OscillationsVortex SheddingWake DynamicsWake FlowWake Flow Analysis
Recent experimental measurements reveal that discrete tones are emitted by isolated airfoils under certain operating conditions. The authors propose that these tones arise from a self‑excited aerodynamic feedback loop. This loop involves large‑scale unstable disturbances in the boundary layer and wake flow coupled with feedback acoustic waves. The analysis demonstrates that the tones are unrelated to vortex shedding, that the feedback‑loop model quantitatively matches experimental data, and that it reproduces the characteristic features of the discrete tone phenomenon.
Recent experimental measurements reveal that discrete tones are emitted by isolated airfoils under certain operating conditions. Arguments are presented that these tones are unrelated to vortex shedding processes as has been suggested. It is proposed that the tones are generated by a self-excited feedback loop of aerodynamic origin. The loop consists of large-scale unstable disturbances in the boundary layer and wake flow and the feedback acoustic waves. Quantitative deductions based on the feedback loop model compare favorably with experimental measurements. It is also found that the proposed model is consistent with the observed characteristic features associated with the discrete tone phenomenon.