Abstract
This paper describes the application of the finite-element method in combination with Galerkin's method in the determination of the acoustic properties of turbofan inlets containing high subsonic Mach number steady flows. An approximate solution for the steady inviscid f Ion field is obtained using an integral method for calculating the potential flowfield in the inlet with a correction to account for compressibility effects. The accuracy of the finite element technique in predicting the acoustic properties of annular ducts has been checked by comparison with available analytical solutions for the problems of plane and spinning wave propagation through a hard-walled annular duct with a constant mean flow. Results are presented comparing low-frequency plane wave propagation through a hard-walled turbofan inlet containing a one-dimensional steady flow with the same inlet containing a fully two-dimensional axisymmetric steady flow. It is shown that when one-dimensional steady flow is assumed to exist in the duct, the plane wave propagates with relatively little distortion. However, propagation of a plane wave through the fully two-dimensional flowfield in the inlet produces severe distortion due to the excitation of higher order modes.
Published Version
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