Noise Sources and Spectral Characteristics of the Tip-Jet Driven Rotor


The noise sources of the tip-jet driven rotor are mainly classified as rotor blade noise and jet noise. The rotor blade noise includes thickness noise, loading noise, and nonlinear quadrupole noise, while the jet noise includes nozzle momentum noise and jet radiation noise. Each noise component has different noise source mechanisms related to flow characteristics and the rotating motion. Especially, the nozzle momentum noise has two noise source mechanisms based on the rotating steady aerodynamic load and the nozzle mass flow rate. The details of the time signal and spectrum are discussed to study the unique spectral characteristics. The tip-jet driven rotor noise has both tonal and broadband spectral characteristics. The periodicity of each instance of jet radiation noise is discussed, while the total jet radiation noise also has a tonal noise component. The noise source mechanisms and spectral characteristics are important considerations for an acoustically efficient tip-jet driven rotor.

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M :

Mach number vector with components Mi

\(\hat{n}\) :

Unit outward normal vector to source surface with components \(\hat{n}_{i}\)

\(\hat{r}\) :

Unit vector in the radiation direction

u i :

Components of local velocity of the fluid

v i :

Components of local velocity of the source surface

P ij :

Compressive stress tensor with constant p0δij subtracted

L :

Loading noise component

M :

Inner product by Mach number vector M

n :

Inner product by a unit normal vector \(\hat{n}\)

r :

Inner product by a unit vector \(\hat{r}\)


Term evaluated at the retarded time

T :

Thickness noise component

\(\cdot\) :

Derivative with respect to time


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This work was conducted at High-Speed Compound Unmanned Rotorcraft (HCUR) research laboratory with the support of Agency for Defense Development (ADD). Also, this work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry and Energy (MOTIE) of the Republic of Korea (No. 20194030202300).

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Correspondence to Soogab Lee.

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Ko, J., Kim, J., Saravanan, V. et al. Noise Sources and Spectral Characteristics of the Tip-Jet Driven Rotor. Int. J. Aeronaut. Space Sci. (2020).

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  • Tip-jet driven rotor
  • Noise sources
  • Spectral characteristics
  • Tonal noise
  • Acoustic analogy