Combined Quadrupole-dipole Model for Inlet Flow Distortion Noise from a Subsonic Fan |
Common terms and phrases
2π δ 51-centimeter acoustic power analysis Annular duct Axial Mach axial velocity blade force blade passing frequency BPF tone cascade combined quadrupole-dipole model complex conjugate coordinate system coth defined by eq denotes dimensionless dipole contribution dipole source distortion profile eigenfunctions entering the fan flow distortion noise fluctuation force per unit Fourier coefficient full-scale fan stages fundamental tone Gaussian profile Green's function harmonic Hence inlet flow distortion inlet turbulence integration with respect interblade spacing Lewis Research Center lift force Mach number measured NASA number of blades PD(w potential-flow field pressure field quadrupole contribution quadrupole source quiet fans tested radiated sound power ratio relative velocity Reynolds stress rotor velocity field shown in figure shown in reference sound field sound power level source term square wave subsonic fan tion V₁ various quiet fans w₁ width X₁ y₁ Σ Σ