A High Frequency Model of Cascade Noise

Envia, Edmane

Closed form asymptotic expressions for computing high frequency noise generated by an annular cascade in an infinite duct containing a uniform flow are presented. There are two new elements in this work. First, the annular duct mode representation does not rely on the often-used Bessel function expansion resulting in simpler expressions for both the radial eigenvalues and eigenfunctions of the duct. In particular, the new representation provides an explicit approximate formula for the radial eigenvalues obviating the need for solutions of the transcendental annular duct eigenvalue equation. Also, the radial eigenfunctions are represented in terms of exponentials eliminating the numerical problems associated with generating the Bessel functions on a computer. The second new element is the construction of an unsteady response model for an annular cascade. The new construction satisfies the boundary conditions on both the cascade and duct walls simultaneously adding a new level of realism to the noise calculations. Preliminary results which demonstrate the effectiveness of the new elements are presented. A discussion of the utility of the asymptotic formulas for calculating cascade discrete tone as well as broadband noise is also included.

Document ID

19980236870

Acquisition Source

Legacy CDMS

Document Type

Reprint (Version printed in journal)

Authors

Date Acquired

September 6, 2013

Publication Date

October 1, 1998

Subject Category

Report/Patent Number

Meeting Information

Meeting: Aeroacoustics Conference

Location: Toulouse

Country: France

Start Date: June 2, 1998

End Date: June 4, 1998

Sponsors: American Inst. of Aeronautics and Astronautics, Confederation of European Aerospace Societies

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Public

Work of the US Gov. Public Use Permitted.

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