Search NASA⌕ Search

SEARCH · Search NASA

Results for “Commercial Supersonics”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Basics of Mixer-Ejectors for Quiet Propulsion

A series of numerical and experimental studies were undertaken to take a fresh look at how a mixer-ejector exhaust system might provide noise reduction for the LTO operation of a commercial supersonic vehicle. Historical understandings of aero and acoustic performance were challenged and new details of noise reduction mechanisms were uncovered. New CFD-based noise prediction tools, applied to conceptual designs, predicted noise reductions of 3-5EPNdB for a few percent thrust loss. Recommendations from the study include validation of the acoustic prediction method, and using it to refine variants of practical nozzle systems for low noise exhaust systems that perform well both acoustically and aerodynamically.

jet noise↗
NASA NTRSDate not supplied

Nearfield Summary and Analysis of the Third AIAA Sonic Boom Prediction Workshop C608 Low Boom Demonstrator

A summary and statistical analysis of the nearfield Computational Fluid Dynamics (CFD)submissions for the Third AIAA Sonic Boom Prediction Workshop is provided with a focus onthe C608 Low Boom Flight Test Demonstrator. The C608 is more complex in terms of geometryand propulsion boundary conditions than previous workshop cases and is more representativeof vehicles with lower ground loudness and the potential for lower annoyance. The nearfieldsignatures submitted by the participants are propagated to the ground to compute statisticsof loudness measures over the vehicle sonic boom carpet. Principle component analysis isused to extract the primary variation modes. Context from previous sonic boom workshopsindicates that this workshop has the lowest variation even though the case is more challengingbecause it is quieter and more complex. The results documented in this summary indicate thatthe international state-of-the-art for nearfield CFD has a variation that is small enough formeaningful low-boom design and analysis. Low-boom configuration analysis methods with lowvariation are important tools to develop certification processes for addressing the prohibitionon overland supersonic commercial flight.

sonic boom CFD workshop c608↗
NASA NTRSDate not supplied

Near Field Summary and Analysis of the Third AIAA Sonic Boom Workshop Shock-Plume Interaction Case

The Third AIAA Sonic Boom Prediction Workshop was held during January 2020, on the weekend prior to the AIAA SciTech conference. The workshop had 23 participants whom represented 6 different counties and 18 unique organizations that included government, industry and academia. The workshop was attend by over 50 individuals. The motivation for the workshop stems from the goal of obtaining supersonic commercial overland flight. In order to replace the current prohibition, with a certification standard, an international effort is required to quantify the accuracy and reliability of prediction methods. The workshops also identify deficiencies in existing methods where further research should be focused. The workshop consisted of two days with the first day focused on nearfield CFD and the second day on propagation techniques. The nearfield CFD study included two configurations known as the biconvex and the C608. This paper provided a summary and comparison of the results for the shock-plume interaction case, also known as the biconvex case. Overall agreement between the participants was very good with the largest standard deviations due to a slight shift of the shock location, not the predicted strength of the shocks.

Melissa Carter↗
NASA NTRSDate not supplied

Propagation Analysis of the 3rd Sonic Boom Prediction Workshop Cases using sBOOM

The 3rd Sonic Boom Prediction Workshop was held on January 4-5, 2020 in conjunction with the AIAA SciTech conference. The workshop had 23 participants who represented 6 different countries and 18 unique organizations that included government, industry, and academia. The workshop was attended by over 50 individuals. The motivation for the workshop stems from the goal of obtaining supersonic commercial overland flight. In order to replace the current prohibition with a certification standard, an international effort is required to quantify the accuracy and reliability of prediction methods. The workshops also identify deficiencies in existing methods where further research should be focused. The workshop consisted of two days with the first day focused on near-field computational fluid dynamics (CFD) and the second day on propagation techniques. For the atmospheric propagation portion of the workshop, two required cases and one optional case were prescribed for the participants to exercise their propagation implementations. This paper presents and discusses the results that were obtained using the sonic boom propagation code sBOOM. Results show that sonic boom carpets could be much different under arbitrary atmospheric conditions as opposed to standard atmospheric conditions. Additionally, several unique features when using sBOOM are presented.

Sonic Boom↗
NASA NTRS2021

Plug20 Test Report

This report documents a test of aircraft exhaust nozzle designs applicable to commercial supersonic aircraft as envisioned in the 2025-2035 time frame. The test is primarily intended to provide data about the noise such aircraft would produce during landing and takeoff (LTO) operation, specifically the jet noise component of this noise. The tests were conducted at the NASA Glenn Research Center’s Aero-Acoustic Propulsion Laboratory in March 2020. The tests used the High-Flow Jet Exhaust Rig in the Nozzle Acoustic Test Rig which simulates the flow from a dual-stream turbofan engine in a flight stream. Seven exhaust configurations were tested with various combinations of internal mixer and external plug, and covered engine cycles having nozzle pressures from 1.5 to 2.3 at a flight speed of Mach 0.3. A few unheated flow conditions were also tested to tie results to other baseline test results. Data acquired and included in this report are 1) far-field acoustic spectra, 2) phased array measurements of noise source distributions, and 3) background-oriented schlieren of the flow near the nozzles. These data, along with the nozzle geometry in CAD format, are given as Appendices and are available online.

Jet noise↗
NASA NTRSDate not supplied

Parametric Mixer Design Methods for Acoustic Explorations of Internally Mixed Nozzles

As part of a jet noise reduction effort under the Commercial Supersonics Technology project, a process for the design and optimization of a parametric dual-stream lobe mixer is presented. The lobe mixer is fully defined from five independent parameters, including mixer length, lobe count, lobe penetration, lobe bias, and trailing edge slope. The mixers are inserted into an academic, constant-area nozzle with an external plug. The full geometry is meshed in Pointwise v18.4, and the RANS equations are solved in FUN3D v13.6. The results of a DoE study, involving ~80 different mixer designs, are presented, along with an associated parametric model for various performance response quantities. With a design space fully explored, observations and recommendations are given, and future work is discussed to further improve the design.

Dual-stream Mixer↗
NASA NTRSDate not supplied

Update on Prediction Uncertainty Reduction (PUR) Tech Challenge

NASA has taken on a Technical Challenge to reduce the uncertainty in prediction of noise from near-term commercial supersonic aircraft. To date, an assessment has been done to baseline this effort, quantifying how much more uncertainty exists when the system-level prediction methods are applied to supersonic aircraft as compared to conventional aircraft. And an assessment has been made for the uncertainty in the physics-based simulations for jets. These will be briefly demonstrated.

supersonic↗
NASA NTRS2022

NASA Analysis of Alternatives Study for Icing Research

In 2020, NASA’s Aeronautics Research Mission Directorate commissioned a study of the icing research area to provide a broad and comprehensive assessment of priority needs for NASA and enduring needs for the aviation community. Priority needs were those that supported four key focus areas for NASA Aeronautics—Transonic Truss-Braced Wing, Electrified Aircraft Propulsion, Small-Core Turbine Engine, and High-Rate Composite Manufacturing—as well as other priority areas, such as Advanced Air Mobility, Certification by Analysis, and Commercial Supersonic Technology. Enduring needs were the additional long-term capabilities and expertise identified by the aviation community as being critical for NASA to provide. This study is called an Analysis of Alternatives (AoA) because a large number of icing research needs were identified and analyzed to determine the highest priorities for NASA key focus areas and those that will endure into the future. This report offers a detailed description and results of the AoA study for icing research.

Aircraft Icing, Aircraft Icing, Rotorcraft Icing, ↗
NASA NTRSDate not supplied

Inlet Radiated Noise Predictions for the NASA Source Diagnostic Test Fan Using Physics-Based Simulations

Commercial supersonic aircraft are expected to produce considerably more noise during landing and take-off operations than existing subsonic aircraft. Establishing noise regulation is challenging because no examples of this aircraft type are currently flying. Existing aircraft noise prediction tools can be used, but the noise source models for these empirical tools are typically based on data from subsonic aircraft components. The present work documents a procedure for using physics-based computational tools to generate the propagating sound field radiating out the nacelle inlet. Although no analytical source modeling is demonstrated, these tools utilize measured data to compare the complex pressure for various propagating modes. The discrepancies found in applying the propagation tools to the subsonic inlet will be ascribed to calculations of supersonic inlets being used to update current empirical noise prediction tools.

Noise Predictions↗
NASA NTRSDate not supplied

Wall-Modeled Large-Eddy Simulations of Jet Noise in Flight Conditions

A campaign of wall-modeled large-eddy simulations (WMLES) using structured curvilinear overlapping grids has been performed with the Launch Ascent and Vehicle Aerodynamics (LAVA) computational fluid dynamics (CFD) software to predict jet noise for single-stream axisymmetric round jets. The simulations address the new Prediction Uncertainty Reduction (PUR) technical challenge within the context of NASA’s Commercial Supersonic Technology (CST) project. The focus of this effort is to generate a simulation database for single-stream axisymmetric round nozzles at several operating points both for static (no ambient co-flow), and in-flight (M ͚ =0.3 co-flow) conditions. The operating conditions range in jet exit Mach number from 0.38 to 1.1 with nozzle temperature ratios (NTR) from 0.84 to 2.7. The effect of the flight-stream on far-field noise sound spectra is assessed. Comparison of LES predictions to microphone array measurements demonstrate good agreement within the resolved frequency range. A dip in the predicted low frequency noise spectra for observers between 120° and 145° is observed. This dip is smaller for lower Mach numbers and seems to be correlated to the Mach wave radiation angle. The Mach 1.1 jet shows broadband-shock associated noise. While the onset of BBSN appears to be captured correctly in WMLES, some differences in its magnitude and the prominent frequency at which it occurs persist between the experiment and the simulations. The effect of the outer nozzle boundary layer state created by the co-flow is assessed and shows to be important for accurate comparisons with experiments. A change of 2.5dB between a slip-wall condition and a artificially thickened turbulent boundary layer was observed. In addition, simulations were performed with an alternative nozzle geometry that includes a internal plug and has twice the nozzle exit diameter. These two configurations resulted in very comparable spectra which is consistent with experimental observations. A generally stronger deviation from experimental results is observed for in-flight cases compared to static conditions. The applicability and correct usage of acoustic analogies used for far-field propagation with strong turbulent co-flows needs to be investigated more systematically using canonical problems to improve comparisons between experiments and WMLES. This is especially true for coherent noise sources seen in BBSN.

CST↗
NASA NTRSDate not supplied

Urban Air Mobility Community Noise Test Planning

The term “Advanced Air Mobility” has been adopted by NASA to describe safe, sustainable, affordable, and accessible aviation for transformational local and intraregional missions. By this definition, Advanced Air Mobility includes both “rural” and “urban” applications including cargo and passenger transport missions, and other aerial missions (e.g., infrastructure inspection). There will be a range of aircraft types performing such missions, including small and medium Unmanned Aircraft Systems (UAS), electric Conventional Takeoff and Landing (eCTOL) aircraft, and electric Vertical Takeoff and Landing (eVTOL) aircraft. Urban Air Mobility (UAM) is a challenging use case for transporting cargo and passengers in an urban environment and is a new opportunity for aviation that could revolutionize the transportation system. The National Aeronautics and Space Administration and the Noise Division of the Federal Aviation Administration Office of Environment and Energy have initiated discussions for planning UAM community noise test(s) at the end of this decade. This presentation discusses the test goals, candidate test objectives, and some of activities needed in preparation for the test(s). It also draws distinctions between the type of study envisioned (observational vs. staged), and between it and recent and planned studies on large fixed-wing transports and commercial supersonic transports.

urban air mobility↗
NASA NTRSDate not supplied

Nonnormality of Sonic Boom Loudness Metrics in the Turbulent Atmospheric Boundary Layer at Large Lateral Distances from the Flight Path

Atmospheric boundary layer (ABL) turbulence causes variability of the sonic boom waveform at the ground. Recent numerical investigations of sonic boom propagation through kinematic velocity fluctuations indicate that loudness metric distributions are positively skewed relative to a normal distribution. This skewness depends on the propagation distance and turbulence intensity. Propagation simulations of N-waves and shaped booms through inhomogeneous ABL turbulence are presented. Meteorological conditions are varied to examine different daytime ABL conditions and their effect on sonic boom loudness distributions. Two outcomes are observed: 1) the loudness metric distributions become increasingly positively skewed as the propagation distance through the ABL increases, and 2) the distributions become increasingly positively skewed at the same lateral distance from the flight path as the convection level of the daytime ABL is increased. Thus, results indicate that ground level measurements of sonic boom loudness from flight tests performed at large lateral distances from the flight path may not be normally distributed, due to turbulence present in the ABL. (This research is supported by the Commercial Supersonic Technology Project of the National Aeronautics and Space Administration under Grant No. 80NSSC19K1685.)

sonic boom↗
NASA NTRSDate not supplied

Dose-Response Data Considerations for the NASA Quesst Community Test Campaign

Key outcomes for NASA's Quesst mission are noise dose and perceptual response data to inform regulators on their decisions regarding noise certification standards for the future of overland commercial supersonic flight. Dose-response curves are commonly utilized in community noise studies to describe the annoyance of a community to a particular noise source. The X-59 aircraft utilizes shaped-boom technology to demonstrate low noise supersonic flight. For X-59 community studies, the sound level from X-59 overflights constitutes the dose, while the response is an annoyance rating selected from a verbal scale, e.g., “slightly annoyed” and “very annoyed.” Dose-response data will be collected from individual flyovers (single event dose) and an overall response to the accumulation of single events at the end of the day (cumulative dose). There are quantifiable sources of error in the noise dose due to uncertainty in microphone measurements of the sonic thumps and uncertainty in predicted noise levels at survey participant locations. Assessing and accounting for error in the noise dose is essential to obtain an accurate dose-response model. There is also a potential for error in the perceptual response. This error is due to the ability of participants to provide their response in a timely manner and participant fatigue after responding to up to one hundred surveys over the course of a month. This talk outlines various challenges in estimating noise dose and perceptual response and the methods considered in preparation for X-59 community tests.

dose-response↗
NASA NTRSDate not supplied

Diagnosing Noise Features Of Internally Mixed, External Plug Exhaust Systems

In internally mixed exhaust systems, a lobed or forced mixer is employed to mix the core and bypass streams before they exit the common nozzle. For moderate bypass-ratio engines this marginally improves thrust, and provides a significant acoustic benefit. Indeed, it has been thought that a fully mixed jet creates the lowest noise you can get from a two-stream engine. Typically, the forced mixer system produces a bit more noise than a fully mixed equivalent jet, noise that has been called “excess noise”. In recent testing, this excess noise seemed to be amplified when an external plug was employed in the exhaust system to reduce boattail drag. Identifying the mechanism of this excess noise and mitigating it is key to creating commercial supersonic vehicles that are acoustically acceptable around airports. This paper adds to that investigation, analyzing results from recent tests where far-field acoustic data were acquired on two sets of flows with matched fully mixed flow conditions. One set of flows had a heated core stream, making it a dual-stream jet. The other set had both streams heated to the same temperature, making a single-stream jet that matched the fully mixed temperature and velocity of the dual-stream jet. These flows were tested in two lobed-mixer exhaust systems with internal and external plugs. Analysis of flow and noise data from the nozzles with combinations of single- and dual-stream flows, and with and without flight streams, gives insight into how and why the noise of the dual-stream and single-stream jet differ. One additive source, present in nozzles both with and without external plugs, comes from inside the nozzle, likely the internal shear layer coming off the lobed mixer. This noise source is not impacted by a change in flight stream and has a distinctive spectral directivity that is amplified by the presence of the external plug. Finding the exact source mechanism of this new source will be key to making the internally mixed exhaust systems reach their lowest possible sound level.

Noise prediction, supersonic, jet noise↗
NASA NTRSDate not supplied

Linear Interaction Approximation for the Prediction of Noise Generated by Turbulence/Shock Interaction

In this paper we review the basic development of Linear Interaction Approximation (LIA), a linear inviscid approach to study the interaction of weak turbulence with flow discontinuities, and implement a formulation to calculate the acoustic field due to the incidence of vortical and entropic disturbances on a planar shock. The work is motivated by the observance in nozzles with internal mixers and external plugs of a shock formed by local flow accelerations, even at sub-critical pressure ratios. Exhaust systems with internally mixed/externally plugged nozzles are currently under consideration for use in commercial supersonic aircraft and it is important to have an assessment of the impact of this shock on the noise radiated by these nozzles. Numerical results are presented for the fluctuating pressure emitted by (separate) incident single-wave vorticity and entropy modes and for incident isotropic fields of turbulence and entropy. Further applications of the formulation to the flow fields in internally mixed/externally plugged nozzles, and to the modification of mixing noise sources and the scattering of internally generated noise by the shock, are discussed as future work.

: Jet noise, shock waves, aircraft noise↗
NASA NTRSDate not supplied

Jet Noise Flyover and Scale Model Tests

Renewed interest in commercial supersonic flight has rekindled the need for accurate jet-noise predictions as this source is believed to dominate at aircraft takeoff conditions. The current study compares scale-model data acquired in the NASA Aero-Acoustic Propulsion Laboratory with data obtained using a well-instrumented Learjet 25 in a flyover test completed in September 2022. The flight test included 73 flyovers with engine conditions ranging from 1.5 to 2.0 engine pressure ratios and flight Mach numbers between 0.24 and 0.27. Acoustic data were acquired with an 800-ft linear ground plate microphone array. Wind speed data were acquired up to 1000-ft altitude with a ground-based LiDAR system. Layered ambient temperature, pressure, and humidity were acquired with a weather drone. A 6% increase in the physical scale factor for the scale-model data was found to reasonably align the peak frequencies of the scale-model and flight data and resulted in peak levels for the scale model being roughly 0.7 dB above those for the flight data at NPR = 1.56 and roughly 1 dB below those for the flight data at NPR = 1.91 in the peak jet-noise direction. Comparisons with the SAE ARP876 model were poor especially at emission angles greater than, or equal to, 110° and at high frequencies.

jet noise, supersonic transport↗
NASA NTRSDate not supplied

Jet Noise Flyover and Scale Model Tests

Renewed interest in commercial supersonic flight has rekindled the need for accurate jet-noise predictions as this source is believed to dominate at aircraft takeoff conditions. The current study compares scale-model data acquired in the NASA Aero-Acoustic Propulsion Laboratory with data obtained using a well-instrumented Learjet 25D in a flyover test completed in September 2022. The flight test included 73 flyovers with engine conditions ranging from 1.5 to 2.0 engine pressure ratios and flight Mach numbers between 0.24 and 0.27. Acoustic data were acquired with an 800-ft linear ground plate microphone array. Wind speed data were acquired up to 1000-sft altitude with a ground-based LiDAR system. Layered ambient temperature, pressure, and humidity were acquired with a weather drone. A 6% increase in the physical scale factor for the scale-model data was found to reasonably align the peak frequencies of the scale-model and flight data and resulted in peak levels for the scale model being roughly 0.7 dB above those for the flight data at NPR = 1.56 and roughly 1 dB below those for the flight data at NPR = 1.91 in the peak jet-noise direction. Comparisons with the SAE ARP876 model were poor especially at emission angles greater than, or equal to, 110° and at high frequencies.

Acoustics, jet noise, supersonic transport↗
NASA NTRSDate not supplied

Linear Interaction Approximation for the Prediction of Noise Generated by Turbulence/Shock Interactions

In this paper we review the basic development of Linear Interaction Approximation (LIA), a linear inviscid approach to study the interaction of weak turbulence with flow discontinuities, and implement a formulation to calculate the acoustic field due to the incidence of vortical and entropic disturbances on a planar shock. The work is motivated by the observance in nozzles with internal mixers and external plugs of a shock formed by local flow accelerations, even at sub-critical pressure ratios. Exhaust systems with internally mixed/externally plugged nozzles are currently under consideration for use in commercial supersonic aircraft and it is important to have an assessment of the impact of this shock on the noise radiated by these nozzles. Numerical results are presented for the fluctuating pressure emitted by (separate) incident single-wave vorticity and entropy modes and for incident isotropic fields of turbulence and entropy. Further applications of the formulation to the flow fields in internally mixed/externally plugged nozzles, and to the modification of mixing noise sources and the scattering of internally generated noise by the shock, are discussed as future work.

Jet noise, shock waves, aircraft noise↗