Search NASA⌕ Search

SEARCH · Search NASA

Results for “Result”

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 NTRS1979

Experimental measurements of the rotating frequencies and mode shapes of a full scale helicopter rotor in a vacuum and correlations with calculated results

This paper presents results of an experimental program conducted to obtain data which can be used for correlations of rotor blade dynamic analyses. Measurements were made of the rotating frequencies and mode shapes of a representative full-scale, two-bladed helicopter rotor in a vacuum. The blades were cantilevered to the hub. Mode shape data were obtained optically using a system of cameras developed specifically for this purpose. Excitation of the rotor was provided by vertical oscillatory motion of the hub. To compare experimental and analytical results, correlations of some experimental measurements with calculations from an existing blade modes computer program based on a Holzer-Myklestad procedure are presented, and the differences between the results are discussed. The experimental and analytical natural frequencies were generally in good agreement as were the principal components of the modal deflections for the flap and lag modes. The torsion mode shape indicated disagreement between the measured and calculated results in regard to the amount of flap and lag motions present in this mode, while the spanwise variations of the measured and calculated torsional components were in agreement.

Lee, B. L.↗
NASA NTRS1981

Numerical experiments on galaxy formation. I - Introduction and first results

The large, fully three-dimensional n-body programs designed for numerical experiments on the dynamics of galaxies have been used for investigations of protogalactic collapses. The dynamical aspects of galaxy formation dominate in this approach. The present experiments start from a large rotating gaseous mass that is made up of many gas clouds. The large mass collapses because it is out of equilibrium. Stars form as the collapse proceeds. The problem is formulated, limiting-case examples are described, and results from simple 'first cut' models are given. Results with no star formation are contrasted with results for very rapid star formation. All models with gas formed thin disklike structures; some were circular, while others were oval. The principal result from the simple models is that stars continue to form rapidly even after the gas has been depleted to unacceptably low levels (1% of the galactic mass in gas).

Miller, R. H.↗
NASA NTRS1982

Summary and recent results from the NASA advanced High Speed Propeller Research Program

Advanced high-speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. The current status of the NASA research program on high-speed propeller aerodynamics, acoustics, and aeroelastics is described. Recent wind tunnel results for five 8- to 10-blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing near-field cruise noise by dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some initial lifting line results are compared with propeller force and probe data. Some initial laser velocimeter measurements of the flow field velocities of an 8-bladed 45 deg swept propeller are shown. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller near-field noise data with linear acoustic theory indicate that the theory adequate predicts near-field noise for subsonic tip speeds but overpredicts the noise for supersonic tip speeds. Potential large gains in propeller efficiency of 7 to 11 percent at Mach 0.8 may be possible with advanced counter-rotation propellers.

Mitchell, G. A.↗
NASA NTRS1983

Ejector nozzle test results at simulated flight conditions for an advanced supersonic transport propulsion system

Results are presented of wind tunnel tests conducted to verify the performance improvements of a refined ejector nozzle design for advanced supersonic transport propulsion systems. The analysis of results obtained at simulated engine operating conditions is emphasized. Tests were conducted with models of approximately 1/10th scale which were configured to simulate nozzle operation at takeoff, subsonic cruise, transonic cruise, and supersonic cruise. Transonic cruise operation was not a consideration during the nozzle design phase, although an evaluation at this condition was later conducted. Test results, characterized by thrust and flow coefficients, are given for a range of nozzle pressure ratios, emphasizing the thrust performance at the engine operating conditions predicted for each flight Mach number. The results indicate that nozzle performance goals were met or closely approximated at takeoff and supersonic cruise, while subsonic cruise performance was within 2.3 percent of the goal with further improvement possible.

Nelson, D. P.↗
NASA NTRS1980

Results of design studies and wind tunnel tests of an advanced high lift system for an Energy Efficient Transport

The development of an advanced technology high lift system for an energy efficient transport incorporating a high aspect ratio supercritical wing is described. This development is based on the results of trade studies to select the high lift system, analysis techniques utilized to design the high lift system, and results of a wind tunnel test program. The program included the first experimental low speed, high Reynolds number wind tunnel test for this class of aircraft. The experimental results include the effects on low speed aerodynamic characteristics of various leading and trailing edge devices, nacelles and pylons, aileron, spoilers, and Mach and Reynolds numbers. Results are discussed and compared with the experimental data and the various aerodynamic characteristics are estimated.

Oliver, W. R.↗
NASA NTRS1984

First Results of Submillimeter Polarimetry

Airborne results of submillimeter polarization at one wavelength, 270 micro m for just three points in the sky are presented. Polarizations of 1.7% at each of two points in Orion are shown. A null result at 400 micro m from ground-based observations of Mars at opposition is also presented. A null result for W3(OH) is given. The Kleinmann-Low Nebula (KL) was chosen for one of the measurements because it is bright and polarization had been observed 10 micro m. Airborne results of submillimeter polarimetry indicate that: (1) Cool, dense interstellar clouds can emit polarized submillimeter radiation; (2) The direction of the magnetic field, averaged over the 90 beams, is the same for the Kleinmann-Low Nebula and the 400 micro m peak 1.5 south of the Nebula; and (3) The effectiveness of the grain alignment mechanism, averaged over the 90 beams, is the same for the Kleinmann-Low Nebula and the 400 micro m peak.

Hildebrand, R. H.↗
NASA NTRS1984

Performance test results of a low cost GPS time and frequency monitor

Final prototype and pilot production performance test results was presented on a single channel C/A code GPS receiver that was optimized for time and frequency applications. Timing accuracy and stability test results are presented, as well as position determination results. Timing accuracy, timing stability, frequency stability, position accuracy and position stability are presented in the results.

Hyatt, R. C.↗
NASA NTRS1985

Results from observations of the 15 June 1983 occultation by the Neptune system

Observations of eight Neptune occultations from six sites in the southwestern Pacific on June 15, 1983. The data were used to search for evidence of rings around Neptune down to a distance of 0.03 Neptune radii from the planetary surface, but the results were negative. An astrometric analysis of the timings yielded solution for the equatorial radius a(0) of Neptune at 1 microbar pressure and the oblatness e at this level. The results are: a(0) = 25,295 + or - 50 km; e = 0.022 + or - 0.004, from which a value for a(1) (equatorial radius at 1 bar pressure) of 24,830 + or - 100 km; and a rotation period of P = 15 h (+3, -2 h) is derived. These results are based on a recent determination of Neptune's pole position and mass quadruple moment, and are consistent with the hypothesis that Neptune and Uranus have homologous mass distributions, although the constraint on interior structure is a weak one. If the probable uncertainty of the pole position is taken into account, error bars on e and derived quantities should be increased by about 50 percent. The present determinations of Neptune atmospheric temperatures at 1 microbar are consistent with earlier results and when combined with all previous data give an average value of 156 + or - 10 K. There is only slight evidence for any latitude dependence in the temperatures. Profiles with a high signal-to-noise ratio suggest the possible presence of an absorbing layer at altitudes higher than the 1-microbar level.

Hubbard, W. B.↗
NASA NTRS1985

Vibrations of twisted cantilever plates - A comparison of theoretical results

As a result of significant differences in the published results for various methods of analysis involving the use of finite element techniques, there are now some questions regarding the adequacy of these methods to predict accurately the vibratory characteristics of highly twisted cantilever plates. In an attempt to help in a resolution of the arising problems, a joint government/industry/university research effort was initiated. The primary objective of the present paper is to summarize the theoretical methods used in the study and show samples of the obtained results. The study provided 19 sets of theoretical results which are derived from beam theory, shell theory, and finite element methods.

Kielb, R. E.↗
NASA NTRS1985

Joint research effort on vibrations of twisted plates, phase 1: Final results

The complete theoretical and experimental results of the first phase of a joint government/industry/university research study on the vibration characteristics of twisted cantilever plates are given. The study is conducted to generate an experimental data base and to compare many different theoretical methods with each other and with the experimental results. Plates with aspect ratios, thickness ratios, and twist angles representative of current gas turbine engine blading are investigated. The theoretical results are generated by numerous finite element, shell, and beam analysis methods. The experimental results are obtained by precision matching a set of twisted plates and testing them at two laboratories. The second and final phase of the study will concern the effects of rotation.

Kielb, R. E.↗
NASA NTRS1986

Initial results of the Global Thermospheric Mapping Study (GTMS)

The Global Thermospheric Mapping Study (GTMS) is a multi-technique experimental study of the thermosphere designed to map simultaneously its spatial and temporal morphology with a thoroughness and diversity of measurement techniques heretofore unachieved. The GTMS is designed around the Incoherent Scatter Radar Chain in the western hemisphere. The European incoherent scatter radars and the worldwide communities of Fabry-Perot interferometers, meteor wind radars, partial reflection drifts radars, MST radars, and satellite probes are included to extend the spatial coverage and types of measurements available. Theoretical and modeling support in the areas of thermospheric and ionospheric structure, tides, and electric fields are included to aid in program planning and data interpretation. Solar activity was low on the three observation days (F10.7 = 97, 98, 96) and magnetic conditions were unsettled to active (A = 10, 12, 20). All six incoherent scatter radar facilities collected data. Each collected F region data day and night while Saint Santin and Millstone Hill additionally collected E region data during daylight hours. Initial results from Sondrestrom and Millstone Hill are presented. Good quality Fabry Perot data were collected at Fritz Peak and San Jose dos Campos. Weather conditions produced poor results at Arequipa and Arecibo. Initial results from Fritz Peak are presented. Mesosphere/lower-thermosphere observations were conducted under the ATMAP organization. The magnetometer chains also were operational during this campaign. Initial thermospheric general circulation model predictions were made for assumed solar-geophysical conditions, and selected results are presented.

Oliver, W. L.↗
NASA NTRS1986

Results of various studies made with the NCAR Thermospheric General Circulation Model (TGCM) (invited review)

The NCAR thermospheric general circulation model (TGCM) has been used for a variety of thermospheric dynamic studies. It has also been used to compare model predictions with measurements made from various ground-based Fabry-Perot interferometer stations, incoherent scatter radar stations and the Dynamics Explorer satellites. The various input and output features of the model are described. These include the specification of solar EUV fluxes, and descriptions of empirical models to specify auroral particle precipitation, ion drag, and magnetospheric convection. Results are presented for solstice conditions giving the model perturbation temperature and circulation response to solar heating forcing alone and also with the inclusion of magnetospheric convections for two different dawn-dusk potential drops, 20 and 60 kV respectively. Results at two constant pressure levels Z =+1 at 300 km and Z= -4 at 120 km are presented for both the winter and summer polar cap regions. The circulation over the Northern Hemisphere polar cap in both the upper and lower thermosphere are presented along with a figure showing that the circulation is mainly a non-divergent irrotational flow responding to ion drag. The results of a study made on the Southern Hemisphere polar cap during October 1981 where Dynamics Explorer satellite measurements of winds, temperature and composition are compared to TGCM predictions are also presented. A diagnostic package that has been developed to analyze the balance of forces operating in the TGCM is presented next illustrating that in the F-region ion drag and pressure provide the main force balance and in the E-region ion drag, pressure and the coriolis forces provide the main balance. The TGCM prediction for the June 10, 1983 total solar eclipse are next presented showing a thermospheric disturbance following the path of totality. Finally, results are presented giving the global circulation, temperature and composition structure of the thermosphere for solar minimum conditions at equinox with 60 kV magnetospheric convection forcing at high latitudes.

Roble, R. G.↗
NASA NTRS1986

A comparison of experimental and numerical results for delta wings with vortex flaps

Computational and experimental results are presented for delta wings with vortex flaps. The wings have an undeflected leading-edge sweep of 75 deg. Flap angles of 5 deg and 10 deg, measured in the streamwise direction, are considered. The nominal angle of attack alpha is varied from 4 deg to 12 deg. Results for freestream Mach numbers of 1.7 and 2.4 are shown. Surface pressure, tuft patterns and vapor screens are given for the experimental data. Surface pressure, tuft patterns, cross-flow velocities, total pressure loss and cross-flow Mach number are given for the numerical data. C(l)-vs-alpha curves are shown for experimental and computational results. The flows are shown to be very sensitive to angle of attack, and the agreement between experimental and theoretical results is improved if the calculations are made at angles of attack slightly larger than the experimental angles of attack. The computational model correctly predicts the topology of the flow in each of the cases considered. The lift is predicted well at the higher angles of attack, but slightly overpredicted at the lower angles of attack.

Powell, K. G.↗
NASA NTRS1987

Wind tunnel test results of heavy rain effects on airfoil performance

The effects of simulated heavy rain on the aerodynamic characteristics of a NACA 64-210 airfoil section equipped with high-lift devices were investigated in the NASA Langley 14- by 22-Foot Subsonic Tunnel. The experiment was part of an on-going NASA program to determine the effect of heavy rain on airplane performance, and was directed at providing insight into scaling laws for subscale model testing of rain effects. The model used in the investigation had a chord of 2.5 feet, a span of 8.0 feet, and was mounted on the tunnel centerline between two large endplates. A water spray distribution system was located 10 chord lengths upstream of the model. The sensitivity of test results to partial-span coverage of the model in the simulated rain environment as compared to full-span coverage was also investigated. The lift and drag data obtained for the high-lift configuration show excellent repeatability of results compared to the previous data. Results obtained for various spray concentrations and tunnel speeds showed significant losses in maximum lift capability, a decrease in the angle of attack for maximum lift, and an increase in drag as the stimulated rain rate was increased. The test results also indicated that the data were not strongly affected by surface tension effects for the high-lift configuration.

Bezos, G. M.↗
NASA NTRS1987

Viscous Transonic Airfoil Workshop compendium of results

Results from the Viscous Transonic Airfoil Workshop held at the AIAA 25th Aerospace Sciences Meeting at Reno, NV in January 1987, are compared with each other and with experimental data. Test cases used in this workshop include attached and separated transonic flows for three different airfoils: the NACA 0012 airfoil, the RAE 2822 airfoil, and the Jones airfoil. A total of 23 sets of numerical results from 15 different author groups are included. The numerical methods used vary widely and include: 16 Navier-Stokes methods, 2 Euler/boundary-layer methods, and 5 full-potential/boundary-layer methods. The results indicate a high degree of sophistication among the numerical methods with generally good agreement between the various computed and experimental results for attached or moderately-separated cases. The agreement for cases with larger separation is only fair and suggests additional work is required in this area.

Holst, Terry L.↗
NASA NTRS1987

Measurements of mesospheric water vapor in 1984 and 1985 - Results and implications for middle atmospheric transport

The detailed results of ground-based mesospheric water vapor measurements obtained by microwave spectroscopy at the Jet Propulsion Laboratory (JPL) from December 1984 to April 1985 (JPL 1984/85), and an overview of results obtained the previous year from April to June 1984 are presented. The JPL 1984/85 spectral data appeared to contain an instrumental baseline curvature which was bracketed and removed. In general, the JPL 1984/85 results are in good agreement with those of previous measurements. They indicate water vapor mixing ratios between 6 and 8 ppmv at 60 or 65 km and falling off steeply with height above this point to values of less than 2 ppmv at 80 km. In addition, there is a large amount of day-to-day variability indicated in the data. A major result of the study is that it is found that both the observed vertical gradient of water vapor mixing ratio and its seasonal variation are consistent with the hypothesis that vertical transport time scales are smaller, perhaps by an order of magnitude, than values currently used in both one- and two-dimensional photochemical/dynamical models.

Bevilacqua, Richard M.↗
NASA NTRS1988

Computational fluid dynamics drag prediction: Results from the Viscous Transonic Airfoil Workshop

Results from the Viscous Transonic Airfoil Workshop are compared with each other and with experimental data. Test cases used include attached and separated transonic flows for the NACA 0012 airfoil. A total of 23 sets of numerical results from 15 different author groups are included. The numerical method used vary widely and include: 16 Navier-Stokes methods, 2 Euler boundary layer methods, and 5 potential boundary layer methods. The results indicate a high degree of sophistication among the numerical methods with generally good agreement between the various computed and experimental results for attached or moderately separated cases. The agreement for cases with larger separation is only fair and suggests additional work is required in this area.

Holst, Terry L.↗
NASA NTRS1988

Comparison of compliance results for the wedge-loaded compact specimen

Results of the ratio of stress intensity factor to crack-mouth displacement as a function of crack length are presented for the wedge-loaded compact specimen. Comparisons are made between experimental compliance results, numerical results from collocation methods, and deep-crack limit-solution results. Applications are for crack-arrest and stress-corrosion-cracking tests for metals and other materials under predominantly linear elastic conditions.

Underwood, J. H.↗