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Preisser, J. S.

Publications and source records attributed to Preisser, J. S..

35 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Fluctuating surface pressure and acoustic radiation for subsonic normal jet impingement

Results are presented from an experimental study of fluctuating surface pressures and far-field noise produced by a subsonic circular jet impinging normally to a large, rigid, flat surface. The tests were performed in an anechoic room for jet Mach numbers from 0.54 to 0.85 and for jet-to-surface heights from 5 to 10 jet diameters. Space and time correlations of surface pressure indicated a radially spreading, decaying pressure field having correlation lengths on the order of one-half the jet diameter with convection speeds between 0.5 and 0.6 of the peak wall-jet velocity. Overall sound pressure level varied as the eighth power of the jet velocity. Large-scale orderly structures in the flow were suggested by the noise spectra which peaked at a Strouhal number of about 0.3. In addition, an analytical formulation was given to approximate the apparent noise-producing regions of the flow in terms of cross-correlations and cross-spectra between the surface and far-field measurements. Results pointed to the impingement region of the flow field as the major contribution to the far-field impingement noise.

Preisser, J. S.↗
NASA NTRS1979

Airframe noise measurements on a small-scale model of a supersonic transport concept in an anechoic flow facility

Airframe noise has been measured on a .015 scale model of an advanced supersonic transport concept (AST-100) in an anechoic flow facility. The model was equipped with leading- and trailing-edge flaps, nose and main landing gears, and engine nacelles. Each of these components was deployed, individually and collectively, to determine their contribution to the noise field. Results are presented which show that in the clean configuration the aircraft displays a symmetric dipole directivity, whereas in the more complex landing-approach configuration the directivity peaks in the forward quadrant. It was found that the landing-approach noise was due chiefly to the landing gear, the trailing edge flaps, and the aeroacoustic interaction between the two

Preisser, J. S.↗
NASA NTRS1977

Results from an exploratory study of airframe noise on a small-scale model of a supersonic transport concept

An exploratory study of airframe noise on a small-scale model of a supersonic transport concept was made. The model was a 0.015 scale version without landing gear of Langley's Advanced Supersonic Technology configuration concept, AST-110. Noise measurements were made at positions corresponding to directly beneath the model and at 30 deg - sideline, for both cruise and the approch flaps configurations, at velocities up to 34 m/s. In general, results showed the cruise noise to be about 3dB above the background flow noise and the approach noise to be about 11 dB above. Overall sound pressure levels and spectral shapes agreed with state of the art predictive techniques.

Preisser, J. S.↗
NASA NTRS1976

An experimental study of the aeroacoustics of a subsonic jet impinging normal to a large rigid surface

This paper presents results from an experimental study of unsteady surface pressures and far-field noise produced by a subsonic jet impinging normal to a large, rigid, flat surface. The tests were performed in an anechoic room for jet Mach numbers from 0.54 to 0.85, and for jet-to-surface heights of from 5 to 10 jet diameters. Results showed that the root-mean-square surface pressure levels were proportional to jet dynamic pressure and were independent of jet height for radial distances from the stagnation point greater than 3 jet diameters. Far-field measurements indicated a significant increase in noise over that of a free jet for all cases of impingement. Cross spectral calculations between the surface and the far field suggested that at a Mach number of 0.70 and a height of 5 jet diameters the additional noise originated mainly in the outer edge of the impingement region between 1 and 3 jet diameters from the stagnation point.

Preisser, J. S.↗
NASA NTRS1975

Acoustic characteristics of a large upper-surface blown configuration with turbofan engines

This paper presents acoustic results from static and simulated low forward velocity tests of a large-scale model of an aircraft configuration with two turbofan engines in the full-scale tunnel at the Langley Research Center. The turbofan engines were integrated into the model and equipped with rectangular nozzles to provide the upper-surface blowing. Results indicate that the upper-surface-blowing noise problem can be characterized, primarily, by the unsymmetrical radiation pattern due mainly to shielding of the high-frequency engine noise and the production of low-frequency noise by jet-surface interaction. The directivity of the low-frequency noise was found to depend on the trailing-edge flap angle when the thrust levels were low. Normalized sound pressure level spectral density data showed good agreement at low Strouhal number with other small- and large-scale model data from tests using simulated wing-flap systems. Forward speed effects were undetectable at the low tunnel speeds used during the tests.

Preisser, J. S.↗
NASA NTRS1974

A method for studying near- and far-field noise characteristics of impinging jets

A new method based on cross-correlation techniques is presented for studying the near- and far-field noise characteristics of a jet impinging on a surface. Analyses show that, in near and far fields, the noise characteristics due to the contribution of fluctuating pressure on the surface and due to the combined contribution of turbulence in the impinging jet and fluctuating pressure on the surface can be determined. Both far-field noise intensities and near-field acoustic energy fluxes can be expressed in terms of appropriate cross correlations. These correlations are obtained by making microphone measurements in three different regions: on the surface, in the near field, and in the far field. The method is currently being applied to study a cold, circular, subsonic jet impinging on a large rigid surface. Some preliminary experimental data are presented on fluctuating surface pressures and narrow-band far-field noise characteristics.

Pan, Y. S.↗
NASA NTRS1972

Determination of angles of attack and sideslip from radar data and a roll-stabilized platform

Equations for angles of attack and sideslip relative to both a rolling and nonrolling body axis system are derived for a flight vehicle for which radar and gyroscopic attitude data are available. The method is limited to application where a flat, nonrotating earth may be assumed. The gyro measures attitude relative to an inertial reference in an Euler angle sequence. In particular, a pitch, yaw, and roll sequence is used as an example in the derivation. Sample calculations based on flight data are presented to illustrate the method. Results obtained with the present gyro method are compared with another technique that uses onboard camera data.

Preisser, J. S.↗