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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Saturn systems holddown acoustic efficiency and normalized acoustic power spectrum.

Saturn systems field acoustic data are used to derive mid- and far-field prediction parameters for rocket engine noise. The data were obtained during Saturn vehicle launches at the Kennedy Space Center. The data base is a sorted set of acoustic data measured during the period 1961 through 1971 for Saturn system launches SA-1 through AS-509. The model assumes hemispherical radiation from a simple source located at the intersection of the longitudinal axis of each booster and the engine exit plane. The model parameters are evaluated only during vehicle holddown. The acoustic normalized power spectrum and efficiency for each system are isolated as a composite from the data using linear numerical methods. The specific definitions of each allows separation. The resulting power spectra are nondimensionalized as a function of rocket engine parameters. The nondimensional Saturn system acoustic spectrum and efficiencies are compared as a function of Strouhal number with power spectra from other systems.

Gilbert, D. W.↗
NASA NTRS1999

F-16XL and F-18 High Speed Acoustic Flight Test Databases

This report presents the recorded acoustic data and the computed narrow-band and 1/3-octave band spectra produced by F-18 and F-16XL aircraft in subsonic flight over an acoustic array. Both broadband-shock noise and turbulent mixing noise are observed in the spectra. Radar and c-band tracking systems provided the aircraft position which enabled directivity and smear angles from the aircraft to each microphone to be computed. These angles are based on source emission time and thus give some idea about the directivity of the radiated sound field due to jet noise. A follow-on static test was also conducted where acoustic and engine data were obtained. The acoustic data described in the report has application to community noise analysis, noise source characterization and validation of prediction models. A detailed description of the signal processing procedures is provided. Follow-on static tests of each aircraft were also conducted for which engine data and far-field acoustic data are presented.

Kelly, J. J.↗
NASA NTRS1984

Helicopter model rotor-blade vortex interaction impulsive noise: Scalability and parametric variations

Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scaling deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.

Splettstoesser, W. R.↗
NASA NTRS1985

Helicopter model rotor-blade vortex interaction impulsive noise - Scalability and parametric variations

Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scalig deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.

Boxwell, D. A.↗
DOE OSTI2024

DASEventNet: AI‐Based Microseismic Detection on Distributed Acoustic Sensing Data From the Utah FORGE Well 16A (78)‐32 Hydraulic Stimulation

Abstract Distributed acoustic sensing (DAS) has emerged as a promising seismic technology for monitoring microearthquakes (MEQs) with high spatial resolution. Efficient algorithms are needed for processing large DAS data volumes. This study introduces a deep learning (DL) model based on a Residual Convolutional Neural Network (ResNet) for detecting MEQs using DAS data, named as DASEventNet. The test data were collected from the Utah FORGE 16A (78)‐32 hydraulic stimulation experiments conducted in April 2022. The DASEventNet model achieves a remarkable accuracy of 100% when discriminating MEQs from noise in the raw test set of 260 examples. Surprisingly, the model identified weak MEQ signatures that have been manually categorized as noise. The decision‐making process with the model is decoded by the classic activation map, which illuminates learning features of the DASEventNet model. These features provide clear illustrations of weak MEQs and varied noise types. Finally, we apply the trained model to the entire period (∼7 days) of continuous DAS recordings and find that it discovers >5,700 new MEQs, previously unregistered in the public Silixa DAS catalog. The DASEventNet model significantly outperforms the traditional seismic method Short‐Term Average/Long‐Term Average (STA/LTA), which detected only 1,307 MEQs. The DASEventNet detection threshold is M w −1.80 compared to the minimum magnitude of M w −1.14 detected by STA/LTA. The spatiotemporal distribution of the newly identified MEQs defines an extensive stimulation zone and more accurately characterizes fracture geometry. Our results highlight the potential of DL for long‐term, real‐time microseismic monitoring that can improve enhanced geothermal systems and other activities that include subsurface hydraulic fracturing.

15 GEOTHERMAL ENERGY↗
NASA NTRS1981

Mixer nozzle aeroacoustic characteristics for the energy efficient engine

Aeroacoustic tests are conducted on scale model mixer nozzle configurations, a separate flow nozzle, and a baseline conical nozzle in an anechoic chamber free-jet facility to investigate exhaust system designs. Far-field acoustic data and exhaust jet plume aerodynamic data are obtained for various combinations of exhaust jet velocity and simulated flight speed, with corrected microphone data at a constant 12.2 m arc distance, and scaled acoustic data at a sideline distance of 457 m. It is found that jet plume aerodynamic and acoustic characteristics of lobed mixer exhaust systems are similar to those of a conical nozzle operating at the same specific thrust, although differences occur at high frequencies, where the sound pressure level of the mixer nozzle is 1-5 dB higher than that of a conical nozzle. In addition, no direct correlation is found between exit plane turbulence levels and plume development or acoustic characteristics for mixer exhaust configurations.

Gliebe, P. R.↗
NASA NTRS1973

Velocity decay and acoustic characteristics of various nozzle geometries with forward velocity.

Utilizing a static test stand, 6- by 9-foot wind tunnel and 13-inch circular free jet, aerodynamic and acoustic data were obtained with a convergent circular nozzle, bypass nozzle, 6-tube mixer nozzle, and 6-tube mixer nozzle with an ejector. The aerodynamic data consist of velocity decay surveys with and without forward velocity. The acoustic data include total sound power, directivity and frequency spectra obtained statically and with forward velocity. The relation of aerodynamic and acoustic measurements statically and in forward flight for the various nozzle configurations are discussed.

Von Glahn, U.↗
DOE OSTI2025

DESI 2024: Constraints on physics-focused aspects of dark energy using DESI DR1 BAO data

Baryon acoustic oscillation data from the first year of the Dark Energy Spectroscopic Instrument (DESI) provide near percent-level precision of cosmic distances in seven bins over the redshift range z=0.1–4.2. Here, this paper is the follow-up to the original DESI BAO cosmology paper [A. G. Adame et al. (DESI Collaboration), arXiv:2404.03002], which considered the conventional w 0 w a cold dark matter (CDM) model. We use the novel DESI data, together with other cosmic probes, to constrain the background expansion history using some well-motivated physical classes of dark energy. In particular, we explore three physics-focused behaviors of dark energy from the equation of state and energy density perspectives: the thawing class (matching many simple quintessence potentials), emergent class (where dark energy comes into being recently, as in phase transition models), and mirage class [where phenomenologically the distance to cosmic microwave background (CMB) last scattering is close to that from a cosmological constant Λ despite dark energy dynamics]. All three classes fit the data at least as well as Λ ⁢CDM, and indeed can improve on it by Δ⁢χ 2 ≈ –5 to –17 for the combination of DESI BAO with CMB and supernova data while having one more parameter. The mirage class does essentially as well as w 0 ⁢w a CDM and exhibits moderate to strong Bayesian evidence preference with respect to Λ⁢ CDM. These classes of dynamical behaviors highlight worthwhile avenues for further exploration into the nature of dark energy.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1982

Application of a computerized vibroacoustic data bank for random vibration criteria development

A computerized data bank system was developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablets, and a dry silver hard copier which are all desk top type hardware and occupy minimal space. Currently, the data bank contains data from the Saturn 5 and Titan 3 flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one third octave band plots over the frequency range from 20 to 2000 Hz. The data were stored by digitizing each spectral plot by tracing with the graphics tablet. The digitized data were statistically analyzed, and the resulting 97.5 percent confidence levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. A user's manual is included to guide potential users through the programs.

Ferebee, R. C.↗
NASA NTRS1982

Automation of vibroacoustic data bank for random vibration criteria development

A computerized data bank system was developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablet, and a dry-silver hard copier which are all desk-top type hardware and occupy minimal space. The data bank contains data from the Saturn V and Titan III flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one-third octave band plots over the frequency range from 20 to 2000 Hz. The data was stored by digitizing each spectral plot by tracing with the graphics tablet. The digitized data was statistically analyzed and the resulting 97.5% probability levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. This automated vibroacoustic data bank system greatly enhances the speed and accuracy of formulating vibration test criteria. In the future, the data bank will be expanded to include all data acquired from the space shuttle flight test program.

Ferebee, R. C.↗
NASA NTRS1987

Helicopter Model Rotor-Blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations

Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade-vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model-scale data were compared with averaged full-scale, in-flight acoustic data under similar non-dimensional test conditions using an improved data analysis technique. At low advance ratios (mu = 0.164 - 0.194), the BVI impulsive noise data scale remarkably well in level, waveform, and directivity patterns. At moderate advance ratios (mu = 0.224 - 0.270), the scaling deteriorates, suggesting that the model-scale rotor is not adequately simulating the full-scale BVI noise. Presently, no proved explanation of this discrepancy exists. Measured BVI noise radiation is highly sensitive to all of the four governing nondimensional parameters--hover tip Mach number, advance ratio, local inflow ratio, and thrust coefficient.

Boxwell, D. A.↗
NASA NTRS1986

Naval applications of a TAE-derived executive

Global Imaging introduced an interactive image processing system in 1985, featuring the Global Applications Executive (GAE) which is a modified Transportable Applications Executive (TAE) environment. The executive plus a large variety of image processing functions, known commercially as the System 9000, are designed to operate on the Hewlett-Packard as its standard desktop computer (NSDTC), the System 9000 has found easy acceptance for Naval image processing applications. The Department of Oceanography at the Naval Academy, Annapolis, Maryland, has installed an NSDTC with an image processing upgrade. This interactive digital image processing workstation is used by the midshipmen and staff for training and research in remote sensing oceanography. The turn-key system provides the capability to process imagery from commonly used Earth observation spacecraft, in conjunction with in situ data sets. The Acoustic Group at the Naval Research Laboratory, Washington, D.C. has acquired its first System 9000 to interactively process ocean acoustic data gathered by shipboard sensors. Finally, the Naval Oceanographic Facility in Bay St. Louis, Mississippi has acquired a System 9000 to provide a second generation Tactical Environmental Support System (TESS 2) prototype with image processing capabilities. This will permit merging of conventional data with polar orbiting spacecraft imagery. A brief description of these applications and the TAE-derived system is presented.

Guberek, Michael↗
NASA NTRSDate not supplied

Aeroacoustic Simulations of the High-Lift Common Research Model and Validation with Experiment

Aerodynamic and acoustic data from unsteady numerical simulations of the High-Lift Common Research Model are compared with experimental measurements from an open-jet wind tunnel test of a 10\-scale model. Time-averaged surface pressure data is in good agreement for all of the configurations evaluated during the test. Unsteady surface pressure spectra from the leading-edge slat and the nose of the main element are presented, demonstrating that the highest levels are associated with the wakes of slat brackets. At these locations the simulations and experiment match reasonably well at low enough frequencies (f < 10 kHz based on the model scale) before excessive numerical dissipation leads to a rapid roll off in the predicted frequency spectra. The agreement is inconsistent at other locations on the slat and main-element surfaces, where the pressure fluctuation levels are lower. Noise predictions using a synthetic microphone array are compared with equivalent experimental results, and the changes in levels predicted between three configurations are similar to those measured. However, some details of the noise predictions are inconsistent with the experiment, and the use of solid- instead of porous-surface data for the acoustic processing of the simulations likely contributes to the discrepancies. All of the simulations were completed before the test, and, despite some shortcomings, they provided valuable insight into the aeroacoustic performance of the model that greatly aided test planning and execution. Hence, the post-test comparisons presented here allow an assessment of the predictive methodology in the context of a realistic high-lift configuration.

High-lift↗
NASA NTRS1982

Program for narrow-band analysis of aircraft flyover noise using ensemble averaging techniques

A package of computer programs was developed for analyzing acoustic data from an aircraft flyover. The package assumes the aircraft is flying at constant altitude and constant velocity in a fixed attitude over a linear array of ground microphones. Aircraft position is provided by radar and an option exists for including the effects of the aircraft's rigid-body attitude relative to the flight path. Time synchronization between radar and acoustic recording stations permits ensemble averaging techniques to be applied to the acoustic data thereby increasing the statistical accuracy of the acoustic results. Measured layered meteorological data obtained during the flyovers are used to compute propagation effects through the atmosphere. Final results are narrow-band spectra and directivities corrected for the flight environment to an equivalent static condition at a specified radius.

Gridley, D.↗
NASA NTRS1997

Comparison of Full-Scale XV-15 Wind Tunnel and In-Flight Blade-Vortex Interaction Noise

An isolated full-scale XV-15 rotor was tested in helicopter mode in the NASA Ames 80 by 120-Foot Wind Tunnel. Extensive acoustic data were obtained to define the rotor operating condition for maximum blade-vortex interaction (BVI) noise. Additional data were obtained at operating conditions simulating flight up to 80 knots. An XV-15 aircraft was also tested under operating conditions corresponding to landing approaches for which BVI is expected to be a maximum. In-flight acoustic data were obtained using the YO-3A acoustic research aircraft. An attempt was made to closely match wind tunnel and flight test operating conditions. Details of the two tests are described and some representative acoustic results are presented. Comparisons are shown between the wind tunnel data and corresponding flight test data. Preliminary results indicate very good correlation of the BVI-related features. However, some differences between flight test and wind tunnel results exist away from the BVI event, thought to arise from differences in the two flow environments.

Kitaplioglu, Cahit↗
NASA NTRS1990

Some far-field acoustics characteristics of the XV-15 tilt-rotor aircraft

Far-field acoustics tests have been conducted on an instrumented XV-15 tilt-rotor aircraft. The purpose of these acoustic measurements was to create an encompassing, high confidence (90 percent), and accurate (-1.4/ +1/8 dB theoretical confidence interval) far-field acoustics data base to validate ROTONET and other current rotorcraft noise prediction computer codes. This paper describes the flight techniques used, with emphasis on the care taken to obtain high-quality far-field acoustic data. The quality and extensiveness of the data base collected are shown by presentation of ground acoustic contours for level flyovers for the airplane flight mode and for several forward velocities and nacelle tilts for the transition mode and helicopter flight mode. Acoustic pressure time-histories and fully analyzed ensemble averaged far-field data results (spectra) are shown for each of the ground contour cases.

Golub, Robert A.↗
NASA NTRS1986

Wind-tunnel acoustic results of two rotor models with several tip designs

A three-phase research program has been undertaken to study the acoustic signals due to the aerodynamic interaction of rotorcraft main rotors and tail rotors. During the first phase, two different rotor models with several interchangeable tips were tested in the Langley 4- by 7-Meter Tunnel on the U.S. Army rotor model system. An extensive acoustic data base was acquired, with special emphasis on blade-vortex interaction (BVI) noise. The details of the experimental procedure, acoustic data acquisition, and reduction are documented. The overall sound pressure level (OASPL) of the high-twist rotor systems is relatively insensitive to flight speed but generally increases with rotor tip-path-plane angle. The OASPL of the high-twist rotors is dominated by acoustic energy in the low-frequency harmonics. The OASPL of the low-twist rotor systems shows more dependence on flight speed than the high-twist rotors, in addition to being quite sensitive to tip-path-plane angle. An integrated band-limited sound pressure level, limited by 500 to 3000 Hz, is a useful metric to quantify the occurrence of BVI noise. The OASPL of the low-twist rotors is strongly influenced by the band-limited sound levels, indicating that the blade-vortex impulsive noise is a dominant noise source for this rotor design. The midfrequency acoustic levels for both rotors show a very strong dependence on rotor tip-path-plane angle. The tip-path-plane angle at which the maximum midfrequency sound level occurs consistently decreases with increasing flight speed. The maximum midfrequency sound level measured at a given location is constant regardless of the flight speed.

Martin, R. M.↗