Asymptotic Theory of Broadband Rotor Thrust, Part II: Analysis of the Right Frequency Shift of the Maximum Response

Abstract

One of the more intriguing features observed in rigorously computed frequency spectra of the random thrust on a turbulence-ingesting rotor is a shift of the broad peaks, or “haystacks,” to frequencies slightly higher than blade passage and harmonics. This paper applies the final results of an earlier Part I article to uncover the rotor and flow parameters responsible for that shift. The new work is analytical and asymptotic rather than numerical. It relies on the sole requirement that the rotor have a reasonably high number of blades. The theory shows that the statistical mechanism that causes the shift is fundamentally antitonal, and that it therefore has no corresponding counterpart in deterministic systems of blade/flow interaction.