Rotor Noise Due to Blade-Turbulence Interaction.
Abstract
The time-averaged intensity density function of the acoustic radiation from rotating blades is derived by replacing blades with rotating dipoles. This derivation is done under the following turbulent inflow conditions: turbulent ingestion with no inlet strut wakes, inflow turbulence elongation and contraction with no inlet strut wakes, and inlet strut wakes. Dimensional analysis reveals two non-dimensional parameters which play important roles in generating the blade-passing frequency tone and its multiples. The elongation and contraction of inflow turbulence has a strong effect on the generation of the blade-passing frequency tone and its multiples. Increasing the number of rotor blades widens the peak at the blade-passing frequency and its multiples. Increasing the rotational speed widens the peak under the condition that the non-dimensional parameter involving the rotational speed is fixed. The number of struts and blades should be chosen so that (the least common multiple of them)-(rotational speed) is in the cutoff range of Sears' function, in order to minimize the effect of the mean flow deficit on the time averaged intensity density function.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 25, 1983
- Accession Number
- ADA129757
Entities
People
- Kiyoto Ishimaru
Organizations
- Pennsylvania State University