Results 241 to 250 of about 94,319 (292)
Some of the next articles are maybe not open access.
High-Frequency Broadband Rotor Noise
AIAA Journal, 1976A method has been developed to find the absolute spectral level of high frequency far field sound of a rotor in terms of random load fluctuations on the rotor blades. The analysis deals with frequencies where the radiated sound spectrum is smooth, i.e., above 300 to 400 Hz for a typical helicopter.
George, A. R., Kim, Y. N.
openaire +1 more source
An investigation of impulsive rotor noise of a model rotor
Journal of Sound and Vibration, 1973The investigation of gust induced impulsive rotor noise was made by using a three bladed, 9 ft diameter, model rotor. The gust was produced by a series of air-jets placed under the rotor disc and the noise characteristics were determined for a range of gust lengths and amplitudes.
J.W. Leverton, C.B. Amor
openaire +1 more source
A theoretical study of helicopter rotor noise
Journal of Sound and Vibration, 1969Abstract A comprehensive theoretical study of the problem of helicopter rotor noise radiation is presented. The theory includes blade slap, rotation noise and vortex noise effects. Peak spectral levels over the “vortex noise” region are shown to be due to the higher harmonics of the rotational noise.
M. V. Lowson, J. B. Ollerhead
openaire +1 more source
Thermal Noise in Precision Rotors
Metrologia, 1985A first, simple theory of thermal fluctuations of ideal rigid rotors is presented, along with some representative measurements and analysis of a real rotor. The ideal rotor has a power spectrum of fractional frequency fluctuations with two regions. At low frequency it is flat, and at high frequency it varies as ω-2.
B E Bernard, L I Winkler, R C Ritter
openaire +1 more source
The Journal of the Acoustical Society of America, 1990
An improved centrifuge. The centrifuge may be a conventional centrifuge having a rotor and a plurality of tube receiving adaptors inserted into the rotor in a circular configuration. The improvement comprises a flexible flap having a fixed end mounted on the rotor at an adaptor and having an opposing free end.
openaire +1 more source
An improved centrifuge. The centrifuge may be a conventional centrifuge having a rotor and a plurality of tube receiving adaptors inserted into the rotor in a circular configuration. The improvement comprises a flexible flap having a fixed end mounted on the rotor at an adaptor and having an opposing free end.
openaire +1 more source
10th Aeroacoustics Conference, 1986
A study was made of helicopter tail rotor noise, particularly that due to interactions with the main rotor tip vortices, and with the fuselage separation mean wake. The tail rotor blade-main rotor tip vortex interaction is modelled as an airfoil of infinite span cutting through a moving vortex.
S.-T. CHOU, A. GEORGE
openaire +1 more source
A study was made of helicopter tail rotor noise, particularly that due to interactions with the main rotor tip vortices, and with the fuselage separation mean wake. The tail rotor blade-main rotor tip vortex interaction is modelled as an airfoil of infinite span cutting through a moving vortex.
S.-T. CHOU, A. GEORGE
openaire +1 more source
Journal of Fluid Mechanics
This study investigates noise generation from co-rotating rotors arranged in a side-by-side configuration. The analysis examines the effects of different phase delays and separation distances. A simple mathematical model is developed to provide insight into constructive and destructive noise interference.
Tiziano Pagliaroli +4 more
openaire +1 more source
This study investigates noise generation from co-rotating rotors arranged in a side-by-side configuration. The analysis examines the effects of different phase delays and separation distances. A simple mathematical model is developed to provide insight into constructive and destructive noise interference.
Tiziano Pagliaroli +4 more
openaire +1 more source
Open Rotor Broadband Interaction Noise
18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference), 2012A theoretical model is presented for calculating the broadband noise produced by the interaction of an open rotor with the wake from either an upstream contra-rotating rotor or a stationary pylon. The model is used to investigate the dependence of the radiated noise on parameters such as pylon–rotor gap and the polar and azimuthal directivity of the ...
openaire +2 more sources
Rotational Noise of Helicopter Rotors
The Journal of the Acoustical Society of America, 1965An analysis procedure has been developed to predict propeller rotational noise during nonuniform, as well as uniform, inflow conditions. Although many studies have been conducted since the development of Gutin's equations (NACA TM I195), none have been developed that adequately describe the near and far rotational-noise fields of a helicopter rotor ...
Robert King, Ronald G. Schlegel
openaire +1 more source
The Journal of the Acoustical Society of America, 1974
The present contribution is concerned with aerodynamic noise from isolated, subsonic tip rotors. With large axial spacing between blade rows and elimination of inlet guide vanes, at least the forward radiated noise from modern single-stage acre-engine fans is dominated by isolated rotor noise.
openaire +1 more source
The present contribution is concerned with aerodynamic noise from isolated, subsonic tip rotors. With large axial spacing between blade rows and elimination of inlet guide vanes, at least the forward radiated noise from modern single-stage acre-engine fans is dominated by isolated rotor noise.
openaire +1 more source