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Abstract The coupling between the acoustic reflections of the intake and the fan vibration characterizes the fan flutter of aero-engines. Close to the intake cut-on/cut-off condition, the reflection of the intake is most significant and key to the appearance of the so-called flutter bite. Rienstra’s model has been thoroughly used in this work to compute the amplitude and phase of the reflected acoustic wave in a zero-thickness intake. The methodology is based on the Wiener-Hopf technique, whereby close expressions involving the complex integration of several kernels are given. Because of its complexity, its usage has been hindered since Rienstra provided just a few results as examples. Moreover, the existing results in the literature are intended for noise analyses, and the phase information of the reflected waves, which is critical for aeroelastic applications but irrelevant for most acoustic analyses, needs to be included. This work presents a thorough data set of the modulus and phase of reflection coefficients for a zero-thickness intake, including variations of the inlet Mach number, inner-to-outer radius ratio, and circumferential wavenumber as a function of the dimensionless frequency. In addition, a simple-to-compute model is presented to help the characterization of the modulus and phase of the dominant waves scattered in the intake of aero-engines, easing the assessment of the flutter-bite occurrence.
Perez et al. (Mon,) studied this question.