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Ian A Clark

Publications and source records attributed to Ian A Clark.

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

TPSAS-NF1676L-34754-DND

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Russell H Thomas↗
NASA NTRSDate not supplied

Fan Acoustic Flight Effects on the PAA & ASN Flight Test

Accurate and reliable prediction of noise emitted from turbofan aircraft engines is an ongoing challenge. For continued progress, it is necessary to assess the performance of the most recent prediction methods in the NASA Aircraft NOise Prediction Program (ANOPP), and to examine the effects of flight condition on fan noise. The assessment is based on an extensive acoustic dataset acquired as part of the Propulsion Airframe Aeroacoustics and Aircraft System Noise (PAA&ASN) Flight Test conducted on a Boeing 787-10 aircraft. Engine operating condition was varied to study the characteristics of fan noise in flight. In a subset of the flight test matrix, the influence of the aft duct acoustic liner was studied by covering the lined area with aluminum tape to simulate a hardwall duct. The combination of test data at different flight conditions, along with rigorous predictions of jet noise, is used in this paper to extract fan noise from the measured total aircraft noise levels. The measured fan noise levels are compared with those predicted using the latest methods for fan source noise, liner attenuation, and PAA effect prediction. Detailed analyses are undertaken to understand agreement between data and various aspects of the prediction models, including spectral shape, directivity, and response to throttle setting. An additional investigation was undertaken to study the effect of aircraft speed on fan noise, as current models do not directly account for this parameter.

Aircraft System Noise↗
NASA NTRSDate not supplied

Aircraft System Noise Assessment of the NASA Single-Aisle Over-the-Wing Nacelle Configuration

A system noise assessment of the NASA single-aisle over-wing nacelle configuration, the OWN160, is carried out to estimate the performance of the configuration relative to NASA noise goals. The vehicle was first designed during the Environmentally Responsible Aviation(ERA)project, and last analyzed in 2016.Renewed interest in the concept necessitates an updated acoustic prediction. A model for jet-trailing edge interaction noise is developed from experimental data and included in the system noise assessment and analysis. Total system noise is predicted using NASA’s research-level Aircraft Noise Prediction Program (ANOPP-Research). Results are evaluated with and without the jet-trailing edge effect and compared to prior analysis and an equivalent conventional aircraft configuration, the TW160. The jet-trailing edge interaction affects the noise source ranking and increases the total noise of the OWN160, but the concept retains an advantage for noise reduction when compared to the conventional configuration with a cumulative reduction of 7.7 EPNdB (ERA results showed a 9.7 EPNdB reduction).

Kelly M Shelts↗
NASA NTRSDate not supplied

Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Research Test: NASA Overview

Motivations and the formulation of the objectives are described for an ambitious flight research test conducted in collaboration between NASA and The Boeing Company. The Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Research Test was executed by the Boeing ecoDemonstrator Program with an Etihad Airways Boeing 787-10 aircraft. Five key technical approaches are described that were used to accomplish the more unconventional and challenging objectives of the research. In addition to the modern technology of the 787, these include evaluating multiple acoustic shielding and reflection effects using both the wing and fuselage in straight flight and banking flight paths, hardwalling the aft duct liner, and utilizing an extensive instrumentation array both on the ground and on the aircraft. The research level version of NASA’s aircraft system noise prediction capability including a new acoustic scattering method were used to confirm the technical approaches and provide guidance for the detailed design of instrumentation and flight test plans. Initial comparisons are shown of flight test data to predictions using the research level of NASA’s Aircraft Noise Prediction Program. Significant prediction challenges are revealed when compared to these high-quality data, while major progress is shown both in the measurement and the prediction of propulsion airframe aeroacoustic effects in flight. This comparison marks the first rigorous validation with modern flight test data and establishes a basis to further understand and quantify the state of NASA’s current capability and to develop improvements in the fidelity of aircraft system noise predictions. The context of multiple coordinated companion research papers is described as well as future plans for the continued analysis of this flight research data.

Propulsion Airframe Aeroacoustics↗
NASA NTRSDate not supplied

Design of an Acoustic Shielding Flap Concept with Prediction and Validation

As part of a NATO task group, NASA has designed a noise reduction technology called a Shielding Flap for application to a hybrid wing body aircraft concept. The design drivers and objectives for this technology are outlined in this paper. Design parameters are defined, and recently-developed NASA software for prediction of acoustic scattering is used to investigate the expected performance of the technology for a range of parameter values. Detailed scattering computational results are presented for several simulated noise sources and for many variations of the shielding flap concept. A selection of computational results is compared with experimental data collected in the NASA Langley Quiet Flow Facility. Overall, the results indicate that the Shielding Flap has strong potential to reduce aft-radiated noise, which was a primary design objective, by shielding sound from the simulated sources while also shielding sound that is scattered from the main airframe.

Propulsion Airframe Aeroacoustics↗
NASA NTRSDate not supplied

Refined Predictions Compared with the Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Research Test Data

In a collaboration between NASA and The Boeing Company, the Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Research Test was executed by the Boeing ecoDemonstrator Program in 2020 with an Etihad Airways Boeing 787-10 aircraft. This ambitious flight research successfully accomplished many objectives and constitutes the most comprehensive and highest quality acoustic flight data available to NASA for a modern commercial subsonic transport aircraft. One purpose of these data is to be the measure of accuracy for the aircraft system noise prediction capabilities of NASA. This research reviews the impact of the major improvements in prediction methods implemented up to this point and tested in the Research version of the NASA Aircraft Noise Prediction Program. The improvements have been to the prediction of jet source and jet-flap interaction, to both fan broadband and tone source prediction, and to the prediction of propulsion airframe aeroacoustic scattering effects. In general, over the engine power range, comparisons between prediction and flight data are within 2 EPNdB including for the intentional sideline-to-sideline asymmetries as implemented in the flight test by flying the aircraft with only one engine at power. Considerable progress has been shown here in the continuing effort to advance the fidelity of NASA aircraft noise prediction capabilities for subsonic aircraft flight acoustics, modern transport aircraft and future aircraft concepts.

aircraft system noise prediction↗
NASA NTRSDate not supplied

Noise Scattering Study for a NACA 0012 Airfoil with a Shielding Flap

Noise scattering measurements for a NACA 0012 airfoil with a flap were conducted. The effects of the flap relative placement and geometry on noise shielding are examined. This scattering test supports the development of a noise reduction concept (referred as the Shielding Flap) applicable to a NATO MULDICON vehicle. Together with the NASA PAASc scattering prediction method, the experimental study presented here was used for the initial exploration and development of the Shielding Flap concept.

noise shielding↗