SEARCH · Search NASA

Results for “RESEARCH TECHNIQUE AERODYNAMICS”

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.

SourceResearch connectionFrom yearThrough year

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

At least 73 records · Page 4

All sources NASA NTRS DOE OSTI

DOE OSTI2021

FLEET velocimetry measurements in the ONR-UTA arc-jet wind tunnel

This manuscript presents and discusses the very first successful application of the Femtosecond Laser Electronic Excitation Tagging (FLEET) velocimetry technique in an arc-jet flow. Specifically, one-dimensional, quantitative, FLEET velocimetry data were obtained in the effort to characterize the 1.6 MW ONR-UTA arc-jet plasma wind tunnel, Leste, housed at the Aerodynamics Research Center of the University of Texas at Arlington. While the FLEET technique has been used in other types of high-speed wind tunnel facilities, application to flows with high background radiation, such as arc-jets, has never been demonstrated before this work. The high background emissions posed concerns on the feasibility of performing FLEET velocimetry measurements. However, this work demonstrates how these concerns were addressed and presents the first successful application of the FLEET technique in arc-jet flows. The FLEET emissions in the arc-jet plume were successfully imaged, and a significant spatio-temporal variation in the tag’s displacement was observed. For the selected operational condition in this study, the average measured gas velocity in the arc-jet plume was 1.78 km/s.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1978

Aeroacoustic research: An Army perspective

A short perspective of the Army aeroacoustic research program is presented that emphasizes rotary wing, aerodynamically generated noise. Exciting breakthroughs in experimental techniques and facilities are reviewed which are helping build a detailed understanding of helicopter external noise. Army and joint Army/NASA supported research programs in acoustics which promise to reduce the noise of future helicopters without severe performance penalties are included.

Morse, H. A.↗

NASA NTRS2011

System Identification Applied to Dynamic CFD Simulation and Wind Tunnel Data

Demanding aerodynamic modeling requirements for military and civilian aircraft have provided impetus for researchers to improve computational and experimental techniques. Model validation is a key component for these research endeavors so this study is an initial effort to extend conventional time history comparisons by comparing model parameter estimates and their standard errors using system identification methods. An aerodynamic model of an aircraft performing one-degree-of-freedom roll oscillatory motion about its body axes is developed. The model includes linear aerodynamics and deficiency function parameters characterizing an unsteady effect. For estimation of unknown parameters two techniques, harmonic analysis and two-step linear regression, were applied to roll-oscillatory wind tunnel data and to computational fluid dynamics (CFD) simulated data. The model used for this study is a highly swept wing unmanned aerial combat vehicle. Differences in response prediction, parameters estimates, and standard errors are compared and discussed

Murphy, Patrick C.↗

NASA NTRS2010

Simulation and Flight Evaluation of a Parameter Estimation Input Design Method for Hybrid-Wing-Body Aircraft

As part of an effort to improve emissions, noise, and performance of next generation aircraft, it is expected that future aircraft will make use of distributed, multi-objective control effectors in a closed-loop flight control system. Correlation challenges associated with parameter estimation will arise with this expected aircraft configuration. Research presented in this paper focuses on addressing the correlation problem with an appropriate input design technique and validating this technique through simulation and flight test of the X-48B aircraft. The X-48B aircraft is an 8.5 percent-scale hybrid wing body aircraft demonstrator designed by The Boeing Company (Chicago, Illinois, USA), built by Cranfield Aerospace Limited (Cranfield, Bedford, United Kingdom) and flight tested at the National Aeronautics and Space Administration Dryden Flight Research Center (Edwards, California, USA). Based on data from flight test maneuvers performed at Dryden Flight Research Center, aerodynamic parameter estimation was performed using linear regression and output error techniques. An input design technique that uses temporal separation for de-correlation of control surfaces is proposed, and simulation and flight test results are compared with the aerodynamic database. This paper will present a method to determine individual control surface aerodynamic derivatives.

Taylor, Brian R.↗

NASA NTRS1983

A review of preflight estimates of real-gas effects on space shuttle aerodynamic characteristics

Preflight estimates of the hypersonic aerodynamic characteristics of the Shuttle orbiter were based on a diverse series of research studies using state of the art techniques developed by basic research in the 60's and 70's. Real-gas viscous calculations on simple shapes that were used to evaluate correlation parameters indicated that real-gas effects reduce aerodynamic forces and moments. Inviscid calculations on winged lifting shapes indicated reduced forces and a slight nose-up pitch resulted because of real-gas effects. Analysis of the extensive wind tunnel data base indicated viscous correlation parameters provided the most appropriate extrapolation technique for estimating flight aerodynamics. Variations because of changes in the ratio of specific heats, which was the only available experimental tool for evaluating real-gas effects, indicated that reduced loads and nose-up pitching moments would occur at high altitudes and Mach numbers but that the values would not exceed the tolerances and variations established about the aerodynamic design data book values derived from viscous correlations. During STS-1, nose-up pitching moments exceeded the established variations.

Woods, W. C.↗

NASA NTRS1993

An improved calibration technique for wind tunnel model attitude sensors

Aerodynamic wind tunnel tests at NASA Langley Research Center (LaRC) require accurate measurement of model attitude. Inertial accelerometer packages have been the primary sensor used to measure model attitude to an accuracy of +/- 0.01 deg as required for aerodynamic research. The calibration parameters of the accelerometer package are currently obtained from a seven-point tumble test using a simplified empirical approximation. The inaccuracy due to the approximation exceeds the accuracy requirement as the misalignment angle between the package axis and the model body axis increases beyond 1.4 deg. This paper presents the exact solution derived from the coordinate transformation to eliminate inaccuracy caused by the approximation. In addition, a new calibration procedure is developed in which the data taken from the seven-point tumble test is fit to the exact solution by means of a least-squares estimation procedure. Validation tests indicate that the new calibration procedure provides +/- 0.005-deg accuracy over large package misalignments, which is not possible with the current procedure.

Tripp, John S.↗

NASA NTRS1980

National Transonic Facility: A review of the operational plan

The proposed National Transonic Facility (NTF) operational plan is reviewed. The NTF will provide an aerodynamic test capability significantly exceeding that of other transonic regime wind tunnels now available. A limited number of academic research program that might use the NTF are suggested. It is concluded that the NTF operational plan is useful for management, technical, instrumentation, and model building techniques available in the specialized field of aerodynamic analysis and simulation. It is also suggested that NASA hold an annual conference to discuss wind tunnel research results and to report on developments that will further improve the utilization and cost effectiveness of the NTF and other wind tunnels.

Liepmann, H. W.↗

NASA NTRS1991

The development of laser speckle velocimetry for the study of vortical flows

A research program was undertaken to develop a new experimental technique commonly known as particle image displacement velocity (PIVD) to measure an instantaneous two dimensional velocity field in a selected plane of flow field. This technique was successfully developed and applied to the study of several aerodynamic problems. A detailed description of the technique and a broad review of all the research activity carried out in this field are reported. A list of technical publications is also provided. The application of PIDV to unsteady flows with large scale structures is demonstrated in a study of the temporal evolution of the flow past an impulsively started circular cylinder. The instantaneous two dimensional flow in the transition region of a rectangular air jet was measured using PIDV and the details are presented. This experiment clearly demonstrates the PIDV capability in the measurement of turbulent flows. Preliminary experiments were also conducted to measure the instantaneous flow over a circular bump in a transonic flow. Several other experiments now routinely use PIDV as a non-intrustive measurement technique to obtain instantaneous two dimensional velocity fields.

Krothapalli, A.↗

NASA NTRS1993

Thermal-fluid analysis of the fill and drain operations of a cryrogenic fuel tank

The Generic Research Cryogenic Tank was designed to establish techniques for testing and analyzing the behavior of reusable fuel tank structures subjected to cryogenic fuels and aerodynamic heating. The Generic Research Cryogenic Tank tests will consist of filling a pressure vessel to a prescribed fill level, waiting for steady-state conditions, then draining the liquid while heating the external surface to simulate the thermal environment associated with hypersonic flight. Initial tests of the Generic Research Cryogenic Tank will use liquid nitrogen with future tests requiring liquid hydrogen. Two-dimensional finite-difference thermal-fluid models were developed for analyzing the behavior of the Generic Research Cryogenic Tank during fill and drain operations. The development and results of the two-dimensional fill and drain models, using liquid nitrogen, are provided, along with results and discussion on extrapolating the model results to the operation of the full-size Generic Research Cryogenic Tank. These numerical models provided a means to predict the behavior of the Generic Research Cryogenic Tank during testing and to define the requirements for the Generic Research Cryogenic Tank support systems such as vent, drain, pressurization, and instrumentation systems. In addition, the fill model provided insight into the unexpected role of circumferential conduction in cooling the Generic Research Cryogenic Tank pressure vessel during fill operations.

Stephens, Craig A.↗

NASA NTRS2002

Snapshot of Active Flow Control Research at NASA Langley

NASA Langley is aggressively investigating the potential advantages of active flow control as opposed to more traditional aerodynamic techniques. Many of these techniques will be blended with advanced materials and structures to further enhance payoff. Therefore a multi-disciplinary approach to technology development is being attempted that includes researchers from the more historical disciplines of fluid mechanics. acoustics, material science, structural mechanics, and control theory. The overall goals of the topics presented are focused on advancing the state of knowledge and understanding of controllable fundamental mechanisms in fluids rather than on specific engineering problems. An organizational view of current research activities at NASA Langley in active flow control as supported by several programs such as the Morphing Project under Breakthrough Vehicle Technologies Program (BVT). the Ultra-Efficient Engine Technology Program (UEET), and the 21st Century Aircraft Technology Program (TCAT) is presented. On-center research as well as NASA Langley funded contracts and grants are discussed at a relatively high level. The products of this research, as part of the fundamental NASA R and D (research and development) program. will be demonstrated as either bench-top experiments, wind-tunnel investigations, or in flight tests. Later they will be transferred to more applied research programs within NASA, DOD (Department of Defense), and U.S. industry.

Washburn, A. E.↗

NASA NTRS1991

Twenty-five years of aerodynamic research with IR imaging: A survey

Infrared imaging used in aerodynamic research evolved during the last 25 years into a rewarding experimental technique for investigation of body-flow viscous interactions, such as heat flux determination and boundary layer transition. The technique of infrared imaging matched well its capability to produce useful results, with the expansion of testing conditions in the entire spectrum of wind tunnels, from hypersonic high-enthalpy facilities to cryogenic transonic wind tunnels. With unique achievements credited to its past, the current trend suggests a change in attitude towards this technique: from the perception as an exotic, project-oriented tool, to the status of a routine experimental procedure.

Gartenberg, Ehud↗

NASA NTRS1990

Aerobrake aerothermodynamics

The status of aerothermodynamics research applicable to aerobrake and aeroassist vehicles is summarized. Techniques that use aerodynamic forces instead of retropropulsion to decelerate vehicles for orbit changes at Mars and upon return to earth from either the moon or Mars can reduce the initial mass required in LEO by as much as 60 percent, thus reducing the number and size of earth-to-orbit launch vehicles. However, several critical technologies must be developed in order to design aerobrakes that can withstand the aerodynamic forces and heating to which the entry vehicles will be subjected. Among these is aerothermodynamics. The ultimate goal is to develop and validate codes that can, by predicting aerobrake thermal environments, be used to select and size the thermal protection and supporting structures.

Cooper, David M.↗

NASA NTRS1991

Doppler Global Velocimeter Measurements of the Vortical Flow Above a Thin Delta Wing

A new measurement technique is being developed by NASA to measure off-surface flow fields. This method, Doppler global velocimetry, will allow quantification of complex three-dimensional flow fields at video camera rates. The entire flow field structure within a selected plane is measured simultaneously rather than by scanned, point-by-point measurements using conventional laser velocimetry. Data obtained using this technique will be used to correlate with other data sets for verification, and following verification, provide a quantified, highly detailed definition of the flow field. This will help to improve the understanding of fluid physics, supplement and broaden the database required to validate and refine computational fluid dynamics (CFD) models, and improve aircraft design methodology. To assess the capability of the technique, velocity measurements of the vortical flow field above a thin 75-degree delta wing were made in the NASA - Langley Basic Aerodynamics Research Tunnel. Preliminary comparisons of the results were made with similar measurements obtained using a three component laser velocimeter indicate that this technique is capable of describing the entire three - component velocity flow field simultaneously within a measurement plane in real time.

Usry, Jimmy W.↗

NASA NTRS1979

Composite Javelin

In the photo at right, a unique, advanced type of javelin is undergoing "flight test." The javelin was designed to meet specifications laid down by the International Amateur Athletic Federation, but it has better stability than conventional javelins, according to college athletes who tested it. Its development incorporated aerodynamic design techniques and a composite material developed by NASA's Langley Research Center for aircraft and spacecraft.

Source record↗

NASA NTRS1980

Experimental and analytical comparison of aerodynamic characteristics of a forward-control missile

Comparisons of analytical and experimental aerodynamic data for canard controlled missile configurations are presented. Recently, techniques to estimate the longitudinal, directional and lateral aerodynamic characteristics for cruciform missiles have been developed. Nielsen Engineering and Research, Inc. (NEAR, Inc.), supported by various governmental agencies, has been the originator of many of these new computational techniques. Two of these are major computer programs currently being implemented by several research organizations. Predicted data from these two programs are compared with experimental data recently obtained at the NASA Langley Research Center Unitary Plan wind tunnel facility. Comparisons cover the supersonic Mach number regime of 1.60 to 3.50, angles-of-attack from 0 to 20 degrees and roll angles of 0, 26.57 and 45 degrees. Major emphasis is on the roll characteristics due to aileron with limited longitudinal and directional characteristics addressed.

Blair, A. B.↗

NASA NTRS1992

Milestones in boundary-layer transition research with infrared imaging

Since its first use in aerodynamic testing in 1967, IR imaging techniques have made distinctive contributions to two major development programs: the configurational design of the Space Shuttle, and the laminar-flow wing program of the Advanced Technologies Testing Aircraft System (ATTAS). In the case of the Space Shuttle, IR imaging was uniquely able to generate transition and heat-transfer data while retaining full control of thermal protection tile-system surface roughness. In ATTAS, much boundary layer transition data was produced with otherwise unobtainable time- and cost-efficiency.

Gartenberg, Ehud↗

NASA NTRS1983

Special opportunities in helicopter aerodynamics

Aerodynamic research relating to modern helicopters includes the study of three dimensional, unsteady, nonlinear flow fields. A selective review is made of some of the phenomenon that hamper the development of satisfactory engineering prediction techniques, but which provides a rich source of research opportunities: flow separations, compressibility effects, complex vortical wakes, and aerodynamic interference between components. Several examples of work in progress are given, including dynamic stall alleviation, the development of computational methods for transonic flow, rotor-wake predictions, and blade-vortex interactions.

Mccroskey, W. J.↗

NASA NTRS1986

Special opportunities in helicopter aerodynamics

Mccroskey, W. J.↗