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Succi, G. P.

Publications and source records attributed to Succi, G. P..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Propeller tone bursts

Intense high frequency (25-38 kHz) tone bursts have been observed in acoustic tests of a scale model of a general aviation propeller. The amplitude of the tone burst is approximately equal to the amplitude of the propeller noise signature. The conditions necessary for the production of these tone bursts are described. The experiments indicate that the origin of these bursts is a periodic flow oscillation on the suction surface of the propeller blade tips which may be due to the interaction between an oscillating shock wave and a laminar boundary layer.

Succi, G. P.↗
NASA NTRS1983

Limits on the prediction of helicopter rotor noise using thickness and loading sources: Validation of helicopter noise prediction techniques

The techniques of helicopter rotor noise prediction attempt to describe precisely the details of the noise field and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The Farassat noise prediction techniques was studied, and high speed helicopter noise prediction using more detailed representations of the thickness and loading noise sources was investigated. These predictions were based on the measured blade surface pressures on an AH-1G rotor and compared to the measured sound field. Although refinements in the representation of the thickness and loading noise sources improve the calculation, there are still discrepancies between the measured and predicted sound field. Analysis of the blade surface pressure data indicates shocks on the blades, which are probably responsible for these discrepancies.

Succi, G. P.↗
NASA NTRS1982

The prediction of helicopter rotor discrete frequency noise

An accurate prediction of the noise produced by helicopters requires a good understanding of the noise generating mechanisms involved. Such an understanding can lead to controlling the noise of existing helicopters by avoiding noisy regimes of flight or by redesigning the main and tail rotors. The present investigation is concerned with approaches which are suitable for the calculation of discrete frequency noise of helicopter rotors. The governing differential equation of acoustics used in a consideration of acoustic formulations is the Ffowcs Williams-Hawkings (FW-H) equation. Attention is given to a method reported by Farassat (1981), a method developed by Succi (1979), and a procedure discussed by Woan and Gregorek (1978).

Farassat, F.↗
NASA NTRS1981

On the design and test of a low noise propeller

An extensive review of noise and performance of general aviation propellers was performed. Research was done in three areas: The acoustic and aerodynamic theory of general aviation propellers, wind tunnel tests of three one-quarter scale models of general aviation propellers, and flight test of two low noise propellers. The design and testing of the second propeller is reviewed. The general aerodynamic considerations needed to design a new propeller are described. The design point analysis of low noise propellers is reviewed. The predicted and measured noise levels are compared.

Succi, G. P.↗
NASA NTRS1981

Validation of helicopter noise prediction techniques

The current techniques of helicopter rotor noise prediction attempt to describe the details of the noise field precisely and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The purpose of this paper is to review those techniques in general and the Farassat/Nystrom analysis in particular. The predictions of the Farassat/Nystrom noise computer program, using both measured and calculated blade surface pressure data, are compared to measured noise level data. This study is based on a contract from NASA to Bolt Beranek and Newman Inc. with measured data from the AH-1G Helicopter Operational Loads Survey flight test program supplied by Bell Helicopter Textron.

Succi, G. P.↗
NASA NTRS1981

Noise and performance of general aviation aircraft - A review of the MIT study

The primary objective of the study was to explore the possibility of reducing noise from a general-aviation-type propeller without altering significantly its aerodynamic performance or the engine characteristics. Our study of this possibility involved aerodynamic and acoustic theory, design, construction, and wind tunnel testing of model propellers, design and manufacture of full-scale propellers, and, finally, flight tests. One propeller exhibited an overall measured reduction of 4.8 dBA during a flight test. This reduction was achieved with minimal changes in performance.

Succi, G. P.↗
NASA NTRS1980

A review of propeller discrete frequency noise prediction technology with emphasis on two current methods for time domain calculations

A review of propeller noise prediction technology is presented which highlights the developments in the field from the successful attempt of Gutin to the current sophisticated techniques. Two methods for the predictions of the discrete frequency noise from conventional and advanced propellers in forward flight are described. These methods developed at MIT and NASA Langley Research Center are based on different time domain formulations. Brief description of the computer algorithms based on these formulations are given. The output of these two programs, which is the acoustic pressure signature, is Fourier analyzed to get the acoustic pressure spectrum. The main difference between the programs as they are coded now is that the Langley program can handle propellers with supersonic tip speed while the MIT program is for subsonic tip speed propellers. Comparisons of the calculated and measured acoustic data for a conventional and an advanced propeller show good agreement in general.

Farassat, F.↗
NASA NTRS1980

Experimental verification of propeller noise prediction

Results of experimental measurements of the sound fields of 1/4-scale general aviation propellers are presented and experimental wake surveys and pressure signatures obtained are compared with theoretical predictions. Experiments were performed primarily on a 1C160 propeller model mounted in front of a symmetric body in an anechoic wind tunnel, and measured the thrust and torque produced by propeller at different rotation speeds and tunnel velocities, wakes at three axial distances, and sound pressure at various azimuths and tip speeds with advance ratio or tunnel velocity constant. Aerodynamic calculations of blade loading were performed using airfoil section characteristics and a modified strip analysis procedure. The propeller was then modeled as an array of point sound sources with each point characterized by the force and volume of the corresponding propeller section in order to obtain the acoustic characteristics. Measurements are found to agree with predictions over a wide range of operating conditions, tip speeds and propeller nacelle combinations, without the use of adjustable constants.

Succi, G. P.↗
NASA NTRS1979

Design of quiet efficient propellers

A numerical computation scheme has been developed to determine the sound generated by propellers. A comparison of these calculations to the noise data taken in the flight test of a propeller driven aircraft shows good agreement. The method is then applied in a parametric study of fixed pitch propellers designed to reduce noise. All these techniques reduce noise while maintaining shaft speed so that the method presented here may be used in a retrofit option for the general aviation fleet.

Succi, G. P.↗
NASA NTRS1979

Acoustic analysis of the propfan

A review of propeller noise prediction technology is presented. Two methods for the prediction of the noise from conventional and advanced propellers in forward flight are described. These methods are based on different time domain formulations. Brief descriptions of the computer algorithms based on these formulations are given. The output of the programs (the acoustic pressure signature) was Fourier analyzed to get the acoustic pressure spectrum. The main difference between the two programs is that one can handle propellers with supersonic tip speed while the other is for subsonic tip speed propellers. Comparisons of the calculated and measured acoustic data for a conventional and an advanced propeller show good agreement in general.

Farassat, F.↗
NASA NTRS1978

Interaction of a turbulent-jet noise source with transverse modes in a rectangular duct

A turbulent jet was used to excite transverse acoustic modes in a rectangular duct. The pressure spectrum showed asymmetric singularities (pressure spikes) at the resonant frequencies of the duct modes. This validates previously published theoretical results. These pressure spikes occurred over a range of jet velocities, orientations, and inlet turbulence levels. At the frequency of the spike, the measured transverse pressure shape matched the resonant mode shape.

Succi, G. P.↗
NASA NTRS1977

Flow-generated noise in ducts

A turbulent jet was used to excite high order acoustic modes in a rectangular duct. The measured pressure spectra exhibited asymmetric singularities (pressure spikes) at the cutoff frequencies of the first few transverse modes. In the high frequency limit, where the number of propagating modes is large, the spectra resembles free space jet spectra. The spectra in these limits are determined by the acoustic response of the duct. A linear theoretical analysis, based on an isotropic model of the turbulent fluctuations, is developed to predict this spectra.

Succi, G. P.↗
NASA NTRS1975

Acoustic eigenmodes of corrugated ducts

Acoustic propagation in two-dimensional corrugated ducts is analyzed. A transform is made to a coordinate system that matches the duct walls. The resulting wave equation separates in space and time. The spatial differential equation is then solved by expanding in the eigenfunctions of a flat-walled duct. The prescription for this expansion is given by the appropriate application of time-independent perturbation theory. Calculations of first-order corrections for a periodic duct of both finite and infinite length are presented.

Succi, G. P.↗