BROADBAND NOISE GENERATED BY TURBULENT INFLOW ROTOR OR STATOR BLADES IN AN ANNULAR DUCT

摘要

The Green's-function relating the radiated pressure field to the fluctuating forces on rotor or stator blades is developed in the presence of dissipation due to turbulent velocity fluctuations and sound speed fluctuations. The resonances in the output power spectrum which would occur at the cut-off frequencies in the absence of dissipation should be removed and smeared out by the incorporation of dissipation. Wave number dependence is developed for an effective eddy viscosity due to the aforementioned fluctuations in the background medium.nThe space-time correlation function RII for blade-normal velocity fluctuations on a single or on two different blades is developed in terms of the velocity correlation tensor for the inflow under the assumptions of isotropy and (Taylor) frozen behavior. The correlation function RII is then simplified under certain approximations and the behavior of the blade-force correlation function is inferred from that of RII.