Prediction of propfan noise by a frequency-domain scheme

Gounet, H.; Léwy, S.

doi:10.2514/3.45599

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…3) were built according to a SNECMA design (static pressure holes, waveguide, remote microphone, and long tube avoiding standing waves); SNECMA used this device in turbojet exhaust ducts and its nose shape had to be modified for adaptation to transonic flows. Five probes (1,2,4,5,6) were fitted in streamlined masts (Fig. 4).…”

Section: Methodsmentioning

confidence: 99%

Noise Measurement of a Model Propfan in a High Speed Wind Tunnel

Gounet¹,

Léwy²

1990

Noise Control Eng. J.

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Tests were performed on a French design single-rotating 12-bladed model propfan (1 meter in diameter) in the S1-MA transonic wind tunnel. Acoustic measurements benefited from the very large diameter of the closed test section (8 meters), because free field conditions were approximately simulated around the propeller, even without anechoic lining on the walls. Results show that radiated tones are well above broadband noise. Parametric studies as a function of the helical tip Mach number and shaft power are presented. The measurements appear to be more valid in the propeller plane, around which noise directivity is a maximum. Comparisons are made with a far field prediction, based on the Ffowcs-Williams and Hawkings' wave equation, and with a near field computation, based on an Euler three-dimensional code. The main conclusion is that inplane measurements 1.15 m from the hub are not disturbed by reflections on the walls and may, be extrapolated to both longer and shorter distances.

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Section: Methodsmentioning

confidence: 99%

Noise Measurement of a Model Propfan in a High Speed Wind Tunnel

Gounet¹,

Léwy²

1990

Noise Control Eng. J.

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“…of (22) would change + n i to −n i in the last term on the r.h.s. of (22). For a uniform mean flow (23a) the last term on the r.h.s.…”

Section: §1 Introductionmentioning

confidence: 99%

On Sound Generation by Moving Surfaces and Convected Sources in a Flow

Campos¹,

Lau²

2012

International Journal of Aeroacoustics

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The theory of sound generation by surfaces in arbitrary motion is presented, with two generalizations relative to the Ffowcs-William Hawkins (FWH) equation: (i) it allows for the presence of a steady, non-uniform potential flow of low Mach number; (ii) it includes the effects on the radiation field of reflections from solid surfaces, e.g. these which cause non-uniformity of the flow. The final result is a generalization of the Kirchhoff integral with: (i) a retarded time modified by sound convection by the mean flow; (ii) position coordinates of observer and source modified to account for the presence of the obstacles which reflect sound waves and cause the mean flow to be non-uniform. An alternative generalization of the Kirchhoff integral is presented for sources in arbitrary motion in an uniform mean flow with unrestricted Mach number. The two generalized forms of the Kirchhoff integral also apply to convected sources of sound, such as the turbulence noise associated with vorticity and the entropy noise due to convected fluid inhomegeneities. The two noise sources are shown to be dominant at low Mach number, relative to other noise sources present in an inhomogeneous potential flow with unrestricted Mach number. In the latter case applies the (i) inhomogeneous high-speed wave equation, that includes as particular cases the (ii) convected and (iii) classical wave equations. The latter two (ii-iii) are obtained from (α) the Laplace equation using the retarded time. All three (i-iii) are obtained by two more distinct methods: (β) elimination among the equations of fluid mechanics for the stagnation enthalpy as acoustic variable; (γ) an acoustic variational principle for the acoustic potential in a steady homentropic nonhomogeneous potential mean flow with unrestricted Mach number. §1. INTRODUCTION In most of the aeroacoustics literature [1], the modeling of sound generation by surfaces in arbitrary motion is based on the FWH-equation [2], which has effectively superseded an earlier attempt at the same result [3]. Two of the most important applications of the FWH equation are propeller and rotor noise. A variety of methods have been used in connection with the noise aircraft propellers and the noise of helicopter rotors *luis.campos@ist.utl.pt

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“…The early pioneering work on propeller [3] noise [4], has led to more recent research [5,6,1,7,8], including prop-fans and supersonic propellers [9,10,11,12,13,14] and counter-rotating propellers [15,16,17]. The noise of a propeller is calculated more readily in the axisymmetric situation where the mean flow velocity is aligned with the propeller axis.…”

Section: Introductionmentioning

confidence: 99%

On a Generalized Multipole Expansion with Application to Propeller Design Synthesis

Campos

Lau

2014

International Journal of Aeroacoustics

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The radiation of sound by surfaces in motion in a non-uniform flow, including the effects of reflections from obstacles on noise, is specified by an extension of the Kirchhoff integral that leads to a generalized multipole expansion that extends the classical series of spherical harmonics to account for the effects of (i) the moving medium and (ii) the rotating sound sources. The corresponding radiation integrals are evaluated analytically for an arbitrary source distribution along the blades of a propeller at an angular inflow. The effects of the incident flow and propeller rotation on the amplitude and phase of sound, e.g. through the retarded time, lead to an extension of the generating function for Legendre polynomials; this provides the representation of the acoustic field as the generalized multipolar series. Each generalized multipole sound field is shown to consist of a fundamental blade passng frequency (BPF) plus all harmonics, with directivities specified by integrals of Bessel functions, that are evaluated analytically. The theory is validated by comparison with noise measurements using two different model propellers in two distinct aeroacoustic wind tunnels. The experimental results are used to illustrate the principle of propeller noise synthesis, relating the radiated sound field to the sound source distribution.

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Prediction of propfan noise by a frequency-domain scheme

Cited by 9 publications

References 14 publications

Noise Measurement of a Model Propfan in a High Speed Wind Tunnel

Noise Measurement of a Model Propfan in a High Speed Wind Tunnel

On Sound Generation by Moving Surfaces and Convected Sources in a Flow

On a Generalized Multipole Expansion with Application to Propeller Design Synthesis

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