RETRACTED: A component-based model for aircraft landing gear noise prediction

Abstract

This paper follows the general formulation of aircraft landing gear noise prediction to develop a component-based model, incorporating scaling laws of the theory of aerodynamic noise generation and correlations of these scaling laws with currently available test data. The method decomposes the landing gear noise into three spectral components, respectively, for the low, the mid and the high frequencies, which corresponds to cataloging the parts in the landing gear assembly into three groups, namely, the wheels, the main struts, and the small details. For all three spectral components, models are presented for their spectra, far-field directivities and amplitudes. The spectral characteristics of the three components are defined by normalized spectra, as functions of the Strouhal numbers based on the respective length scales of the three groups of parts in the landing gear assembly. Individual directivity factors are also presented for the three spectral components, with the low-frequency component having the smallest variations with emission angle and the high-frequency component having the largest variations. The amplitudes of the three spectral components are correlated to parameters unique to each group of landing gear parts, with the low- and mid-frequency noise essentially characterized by the physical dimensions of the wheels and the main struts, respectively, and the high-frequency noise, whose generation is associated with a large number of small details in practical landing gears, defined by a complexity factor. Quantities that affect this complexity factor are discussed and an empirical model is proposed for practical applications. The prediction model is validated by wing tunnel test data for an isolated Boeing 737 landing gear. In this case, the predictions agree well with data, both in parametric trends and in absolute noise levels.