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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Analysis and performance prediction of scramjet inlets utilizing a three-dimensional Navier-Stokes code

A series of inlet analysis codes (2-D, axisymmetric, 3-D) were developed which can analyze complicated flow through complex inlet geometries in a reasonably efficient manner. The codes were verified and are being used extensively to analyze practical inlet geometries both at Langley as well as industries. Newly installed VPS 32 computer will allow more complex configurations to be analyzed. Scalar FORTRAN versions are available to increase transportability of the codes for use on other Scalar computers and on the Cray vector processing computer.

Kumar, Ajay↗
NASA NTRS1987

A simulation study of the flight dynamics of elastic aircraft. Volume 2: Data

The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research project. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot.

Waszak, Martin R.↗
NASA NTRS1996

Evaluation of alternatives for trichlorotrifluoroethane (CFC-113) to clean and verify liquid oxygen systems

NASA Langley Research Center (LARC) investigated several alternatives to the use of tri-chloro-tri-fluoroethane(CFC-113) in oxygen cleaning and verification. Alternatives investigated include several replacement solvents, Non-Destructive Evaluation (NDE) and Total Organic Carbon (TOC) analysis. Among the solvents, 1, 1-dichloro-1-fluoroethane (HCFC 141b) and di-chloro-penta-fluoro-propane (HCFC 225) are the most suitable alternatives for cleaning and verification. However, use of HCFC 141b is restricted, HCFC 225 introduces toxicity hazards, and the NDE and TOC methods of verification are not suitable for processes at LaRC. Therefore, the interim recommendation is to sparingly use CFC-113 for the very difficult cleaning tasks where safety is critical and to use HCFC 225 to clean components in a controlled laboratory environment. Meanwhile, evaluation must continue on now solvents and procedures to find one suited to LaRCs oxygen cleaning needs.

Morris, Michelle L.↗
NASA NTRS2001

Sensitivity of the Tropical Atmospheric Energy Balance to ENSO-Related SST Changes: Comparison of Climate Model Simulations to Observed Responses

This paper focuses on how fresh water and radiative fluxes over the tropical oceans change during ENSO warm and cold events and how these changes affect the tropical energy balance. At present, ENSO remains the most prominent known mode of natural variability at interannual time scales. While this natural perturbation to climate is quite distinct from possible anthropogenic changes in climate, adjustments in the tropical water and energy budgets during ENSO may give insight into feedback processes involving water vapor and cloud feedbacks. Although great advances have been made in understanding this phenomenon and realizing prediction skill over the past decade, our ability to document the coupled water and energy changes observationally and to represent them in climate models seems far from settled (Soden, 2000 J Climate). In a companion paper we have presented observational analyses, based principally on space-based measurements which document systematic changes in rainfall, evaporation, and surface and top-of-atmosphere (TOA) radiative fluxes. Here we analyze several contemporary climate models run with observed SSTs over recent decades and compare SST-induced changes in radiation, precipitation, evaporation, and energy transport to observational results. Among these are the NASA / NCAR Finite Volume Model, the NCAR Community Climate Model, the NCEP Global Spectral Model, and the NASA NSIPP Model. Key disagreements between model and observational results noted in the recent literature are shown to be due predominantly to observational shortcomings. A reexamination of the Langley 8-Year Surface Radiation Budget data reveals errors in the SST surface longwave emission due to biased SSTs. Subsequent correction allows use of this data set along with ERBE TOA fluxes to infer net atmospheric radiative heating. Further analysis of recent rainfall algorithms provides new estimates for precipitation variability in line with interannual evaporation changes inferred from the da Silva, Young, Levitus COADS analysis. The overall results from our analysis suggest an increase (decrease) of the hydrologic cycle during ENSO warm (cold) events at the rate of about 5 W/sq m per K of SST change. Model results agree reasonably well with this estimate of sensitivity. This rate is slightly less than that which would be expected for constant relative humidity over the tropical oceans. There remain, however, significant quantitative uncertainties in cloud forcing changes in the models as compared to observations. These differences are examined in relationship to model convection and cloud parameterizations Analysis of the possible sampling and measurement errors compared to systematic model errors is also presented.

Robertson, Franklin R.↗
NASA NTRS2013

Experiment Description and Results for Arrival Operations Using Interval Management with Spacing to Parallel Dependent Runways (IMSPiDR)

The predicted increase in the number of commercial aircraft operations creates a need for improved operational efficiency. Two areas believed to offer increases in aircraft efficiency are optimized profile descents and dependent parallel runway operations. Using Flight deck Interval Management (FIM) software and procedures during these operations, flight crews can achieve by the runway threshold an interval assigned by air traffic control (ATC) behind the preceding aircraft that maximizes runway throughput while minimizing additional fuel consumption and pilot workload. This document describes an experiment where 24 pilots flew arrivals into the Dallas Fort-Worth terminal environment using one of three simulators at NASA?s Langley Research Center. Results indicate that pilots delivered their aircraft to the runway threshold within +/- 3.5 seconds of their assigned time interval, and reported low workload levels. In general, pilots found the FIM concept, procedures, speeds, and interface acceptable. Analysis of the time error and FIM speed changes as a function of arrival stream position suggest the spacing algorithm generates stable behavior while in the presence of continuous (wind) or impulse (offset) error. Concerns reported included multiple speed changes within a short time period, and an airspeed increase followed shortly by an airspeed decrease.

Baxley, Brian T.↗
NASA NTRS2026

Helicopter and Urban Air Mobility (UAM) Laboratory Comparison (HULC) Psychoacoustic Test

The Helicopter and Urban Air Mobility (UAM) Laboratory Comparison (HULC) psychoacoustic test was conducted in July 2025 to compare human annoyance responses to noise from UAM vehicles and helicopters. This document provides a literature review, describes the HULC test methodology including stimuli selection and test administration procedures, and presents results from an initial analysis using multilevel statistical modeling. The test utilized 123 sound stimuli from four helicopters and six UAM vehicles across three flight phases (departure, cruise, and approach), presented to 40 subjects in the Exterior Effects Room (EER) at NASA's Langley Research Center. Subjects rated their annoyance on a 0 to 10 scale while imagining hearing these sounds multiple times daily near their homes. Key findings revealed that, at the same A-weighted sound exposure levels, UAM vehicles and helicopters produced similar annoyance responses across all flight phases, with mean differences of only approximately 1 dB and overlapping confidence intervals. However, at equivalent observer distances, UAM vehicles had inherently quieter operations and lower mean annoyance ratings. These results suggest that UAM vehicles and helicopters may be assessed in a similar manner for community noise impact. The quieter noise characteristics of UAM vehicles may provide advantages for operating in communities and integrating into urban environments.

psychoacoustics↗
NASA NTRS1991

Finite element methods for integrated aerodynamic heating analysis

This report gives a description of the work which has been undertaken during the second year of a three year research program. The objectives of the program are to produce finite element based procedures for the solution of the large scale practical problems which are of interest to the Aerothermal Loads Branch (ALB) at NASA Langley Research Establishment. The problems of interest range from Euler simulations of full three dimensional vehicle configurations to local analyses of three dimensional viscous laminar flow. Adaptive meshes produced for both steady state and transient problems are to be considered. An important feature of the work is the provision of specialized techniques which can be used at ALB for the development of an integrated fluid/thermal/structural modeling capability.

Morgan, K.↗
NASA NTRS2005

CFD Analysis of Circulation Control Airfoils Using Fluent

In an effort to validate computational fluid dynamics procedures for calculating flows around circulation control airfoils, the commercial flow solver FLUENT was utilized to study the flow around a general aviation circulation control airfoil. The results were compared to experimental and computational fluid dynamics results conducted at the NASA Langley Research Center. The current effort was conducted in three stages: 1. A comparison of the results for free-air conditions to those from experiments. 2. A study of wind-tunnel wall effects. and 3. A study of the stagnation-point behavior.

McGowan, Gregory↗
NASA NTRS2020

Assessment of Transition Modeling Capability in OVERFLOW with Emphasis on Swept-Wing Configurations

In preparation for comparisons with data obtained from the recently concluded experiments in the National Transonic Facility at the NASA Langley Research Center on the new common research model with natural laminar flow (CRM-NLF), an assessment of the current transition modeling capability in the NASA OVERFLOW 2.2o code has been carried out. A combination of the available experimental data and linear stability analysis is used to evaluate the accuracy and robustness of these models for selected swept-wing type configurations, with significant crossflow. An additional goal for this work involves providing a comparative assessment of the relevant transition models in the context of a single flow solver and identifying model limitations as well as the potential for future improvements that would help strengthen the physical basis of such transition models. Included in this investigation is an assessment of the sensitivities of the underlying transition models to grid resolution (wall-normal, as well as streamwise and spanwise) and the values of extra input parameters such as the level of surface roughness and freestream turbulence variables. The flow configurations targeted in this assessment include the NASA NLF(2)-0415 swept-wing configuration, the sickle-shaped wing introduced by the Technical University of Braunschweig, and the wing-body configuration of the CRM model from the fourth and fifth AIAA CFD Drag Prediction Workshops.

Freestream velocity↗
NASA NTRS2019

Simulation Schiaparelli's Entry and Comparison to Aerothermal Flight Data

The European Space Agency recently flew an entry, descent, and landing demonstrator module called Schiaparelli that entered the atmosphere of Mars on the 19th of October, 2016. The instrumentation suite included heatshield and backshell pressure transducers and thermocouples (known as AMELIA - Atmospheric Mars Entry and Landing Investigations and Analysis) and backshell radiation and direct heat flux-sensing sensors (known as COMARS (Combined Aerothermal and Radiometer Sensors Instrument Package) and ICOTOM (narrow band radiometers)). Due to the failed landing of Schiaparelli, only a subset of the flight data was transmitted before and after plasma black-out. The goal of this paper is to present comparisons of the flight data with calculations from NASA simulation tools, DPLR (Data Parallel Line Relaxation) / NEQAIR (NonEQuilibrium AIr Radiation) and LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm) / HARA (High-temperature Aerothermodynamic RAdiation ). DPLR and LAURA are used to calculate the flowfield around the vehicle and surface properties, such as pressure and convective heating. The flowfield data are passed to NEQAIR and HARA to calculate the radiative heat flux. Comparisons will be made to the COMARS total heat flux, radiative heat flux and pressure measurements. Results will also be shown against the reconstructed heat flux which was calculated from an inverse analysis of the AMELIA thermocouple data performed by Astrium. Preliminary calculations are presented in this abstract.

Brandis, A. M.↗
NASA NTRSDate not supplied

High-Fidelity Analysis of Lift+Cruise VTOL Urban Air Mobility Concept Aircraft

This paper presents a high-fidelity multidisciplinary analysis for the NASA lift+cruise vertical takeoff and landing urban air mobility concept aircraft. The reported simulations couple comprehensive rotorcraft aeromechanics and high-fidelity computational fluid dynamics (CFD). Aerodynamic solutions are computed on dynamic, deforming, unstructured, overset grid systems by an unsteady CFD solver, FUN3D, developed at the NASA Langley Research Center. An integrated overset-grid assembler, Yoga, is used for communications between component grids. Two turbulence models are compared for loose-coupling simulations in hover and low-speed forward flight conditions. One model is the negative variant of the one-equation Spalart-Allmaras model (SA-neg), and the other model is the SA-neg-R model adding a simple rotation correction term to the SA-neg model. It demonstrated that the rotation correction in the SA-neg-R turbulence model significantly improves resolution of secondary vortices and wake interactions for rotorcraft simulations.

CFD↗
NASA NTRS2023

High-Fidelity Analysis of Lift+Cruise VTOL Urban Air Mobility Concept Aircraft

This paper presents a high-fidelity multidisciplinary analysis for the NASA Lift+Cruise vertical takeoff and landing urban air mobility concept aircraft. The reported simulations couple comprehensive rotorcraft aeromechanics and high-fidelity computational fluid dynamics (CFD). Aerodynamic solutions are computed on dynamic, deforming, unstructured, overset grid systems by an unsteady CFD solver, FUN3D, developed at the NASA Langley Research Center. An integrated overset-grid assembler, Yoga, is used for communications between component grids. Two turbulence models are compared for loose-coupling simulations in hover and low-speed forward flight conditions. One model is the negative variant of the one-equation Spalart-Allmaras model (SA-neg), and the other model is the SA-neg-R model adding a simple rotation correction term to the SA-neg model. It demonstrated that the rotation correction in the SA-neg-R turbulence model significantly improves resolution of secondary vortices and wake interactions for rotorcraft simulations.

CFD↗
NASA NTRS1995

Analysis of uncertainty in force balance calibration

In order to reduce errors encountered in the measurement and identification of loads using force balances, a third-order forward polynomial relation between loads and output voltages is proposed. This full third-order model represents an alternative to the second-order model currently in use at NASA Langley Research Center (LaRC) and many other installations worldwide. The new model requires the identification of 84 coefficients (including the 28 used presently) for each of the six outputs. The existing LaRC calibration loading sequence is insufficient for identification of many of these 504 coefficients because critical three-load combinations are absent. Accordingly, a new loading sequence that permits the identification of all 504 coefficients has been developed and is described fully. It is apparent from numerical tests that the new third-order model is clearly superior to second-order models in the presence of small amounts of random measurement noise, assuming that there are indeed higher-order interactions between loads. As the amount of noise increases, however, a third-order model becomes less attractive due to its ability to match the noise itself more faithfully than a second-order model. Numerical results suggest that the transition occurs when the magnitude of random noise becomes of the same order as that of the physical higher-order interactions.

Bursal, Faruk H.↗
NASA NTRS1985

Power spectral density of subsonic jet noise

The power-spectrum density (PSD) of the far-field noise of a subsonic unheated axisymmetric jet is investigated by analysis of about 80 sets of published noise spectra and of spectra obtained using 12.7 and 25.4-mm-diameter compressed-air jets at exit velocities 66 and 104 m/s and 67 and 91 m/s, respectively, in the NASA Langley anechoic flow facility. The results are presented in tables and graphs and characterized in detail. Findings reported include Strouhal-number scaling of the PSD at theta = 30 deg or more, scaling with the product of the Helmholtz number and the Doppler factor at theta less than 30 deg, best collapse at source convection Mach number 0.5, variation of PSD amplitude as U to the 6.5th at theta = 90 deg, and no sharp PSD-amplitude variation at any critical Reynolds number.

Zaman, K. B. M. Q.↗
NASA NTRS2011

Flight Simulation of ARES in the Mars Environment

A report discusses using the Aerial Regional- scale Environmental Survey (ARES) light airplane as an observation platform on Mars in order to gather data. It would have to survive insertion into the atmosphere, fly long enough to meet science objectives, and provide a stable platform. The feasibility of such a platform was tested using the Langley Standard Real- Time Simulation in C++. The unique features of LaSRS++ are: full, six-degrees- of-freedom flight simulation that can be used to evaluate the performance of the aircraft in the Martian environment; capability of flight analysis from start to finish; support of Monte Carlo analysis of aircraft performance; and accepting initial conditions from POST results for the entry and deployment of the entry body. Starting with a general aviation model, the design was tweaked to maintain a stable aircraft under expected Martian conditions. Outer mold lines were adjusted based on experience with the Martian atmosphere. Flight control was modified from a vertical acceleration control law to an angle-of-attack control law. Navigation was modified from a vertical acceleration control system to an alpha control system. In general, a pattern of starting with simple models with well-understood behaviors was selected and modified during testing.

Kenney, P. Sean↗
NASA NTRS2015

Analysis of Limit Cycle Oscillation Data from the Aeroelastic Test of the SUGAR Truss-Braced Wing Model

Research focus in recent years has been given to the design of aircraft that provide significant reductions in emissions, noise and fuel usage. Increases in fuel efficiency have also generally been attended by overall increased wing flexibility. The truss-braced wing (TBW) configuration has been forwarded as one that increases fuel efficiency. The Boeing company recently tested the Subsonic Ultra Green Aircraft Research (SUGAR) Truss-Braced Wing (TBW) wind-tunnel model in the NASA Langley Research Center Transonic Dynamics Tunnel (TDT). This test resulted in a wealth of accelerometer data. Other publications have presented details of the construction of that model, the test itself, and a few of the results of the test. This paper aims to provide a much more detailed look at what the accelerometer data says about the onset of aeroelastic instability, usually known as flutter onset. Every flight vehicle has a location in the flight envelope of flutter onset, and the TBW vehicle is not different. For the TBW model test, the flutter onset generally occurred at the conditions that the Boeing company analysis said it should. What was not known until the test is that, over a large area of the Mach number dynamic pressure map, the model displayed wing/engine nacelle aeroelastic limit cycle oscillation (LCO). This paper dissects that LCO data in order to provide additional insights into the aeroelastic behavior of the model.

Bartels, Robert E.↗
NASA NTRS1975

Results of flow-visualization investigations on a 0.015-scale modified configuration 140A/B space shuttle vehicle orbiter (model 36-0) in the Langley Research Center 8-foot transonic pressure tunnel (OA102)

The results are presented of a flow-visualization wind tunnel test of a 0.015-scale model of the Modified Configuration 140A/B Space Shuttle Vehicle Orbiter. Separation zones, flow-recirculation regions, and potential venting and contaminant-ingestion problem areas were studied by means of photographic (video tape) analysis of model-mounted tufts. The model was tested at Mach numbers of 0.60, 0.90, 1.05, and 1.20, at Reynolds numbers of 3.17, 3.98, 4.16, and 4.23, respectively. Model angle-of-attack was varied from 0 deg to 20 deg at 0 deg sideslip-angle. Three control-surface deflection combinations were tested.

Nichols, M. E.↗
NASA NTRS1976

An analysis of data related to the minimum temperatures for valid testing in cryogenic wind tunnels using nitrogen as the test gas

The minimum operating temperature which avoids adverse low temperature effects, such as condensation, has been determined at a free stream Mach number of 0.85 for flow over a 0.137 meter airfoil mounted at zero incidence in the Langley 1/3 meter transonic cryogenic tunnel. The onset of low temperature effects is established by comparing the pressure coefficient measured at a given orifice for a particular temperature with those measured at temperatures sufficiently above where low temperature effects might be expected to occur. The pressure distributions over the airfoil are presented in tabular form. In addition, the comparisons of the pressure coefficient as a function of total temperature are presented graphically for chord locations of 0, 25, 50, and 75 percent. Over the 1.2 to 4.5 atmosphere total pressure range investigated, low temperature effects are not detected until total temperatures are 2 K, or more, below free stream saturation temperatures.

Hall, R. M.↗