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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Analysis of airfoil leading edge separation bubbles

A local inviscid-viscous interaction technique was developed for the analysis of low speed airfoil leading edge transitional separation bubbles. In this analysis an inverse boundary layer finite difference analysis is solved iteratively with a Cauchy integral representation of the inviscid flow which is assumed to be a linear perturbation to a known global viscous airfoil analysis. Favorable comparisons with data indicate the overall validity of the present localized interaction approach. In addition numerical tests were performed to test the sensitivity of the computed results to the mesh size, limits on the Cauchy integral, and the location of the transition region.

Carter, J. E.↗
NASA NTRS1982

Testing of the Eagle-Picher nickel-iron, the Globe ISOA lead-acid, and the Westinghouse nickel-iron battery subsystems in an electric-vehicle environment

Three full size developmental batteries were tested with electric vehicles; two nickel-iron batteries and a lead-acid battery. Constant speed and driving schedule tests were done on a chassis dynamometer. Several aspects of battery performance were evaluated for capacity, recharge efficiency, voltage response, and self discharge. Each of these three batteries exhibited some strengths and some weaknesses.

Hewitt, R.↗
NASA NTRS1983

Pressure investigation of NASA leading edge vortex flaps on a 60 deg Delta wing

Pressure distributions on a 60 deg Delta Wing with NASA designed leading edge vortex flaps (LEVF) were found in order to provide more pressure data for LEVF and to help verify NASA computer codes used in designing these flaps. These flaps were intended to be optimized designs based on these computer codes. However, the pressure distributions show that the flaps wre not optimum for the size and deflection specified. A second drag-producing vortex forming over the wing indicated that the flap was too large for the specified deflection. Also, it became apparent that flap thickness has a possible effect on the reattachment location of the vortex. Research is continuing to determine proper flap size and deflection relationships that provide well-behaved flowfields and acceptable hinge-moment characteristics.

Marchman, J. F., III↗
NASA NTRS1983

A method of predicting flow rates required to achieve anti-icing performance with a porous leading edge ice protection system

A proposed method of analytically predicting the minimum fluid flow rate required to provide anti-ice protection with a porous leading edge system on a wing under a given set of flight conditions is presented. Results of the proposed method are compared with the actual results of an icing test of a real wing section in the NASA Lewis Icing Research Tunnel.

Kohlman, D. L.↗
NASA NTRS1983

Augmentation of Fighter-Aircraft Performance by Spanwise Blowing over the Wing Leading Edge

Spanwise blowing over the wing and canard of a 1:35 model of a close-coupled-canard fighter airplane configuration (similar to the Kfir-C2) was investigated experimentally in low-speed flow. Tests were conducted at airspeeds of 30 m/sec (Reynolds number of 1.8 x 10 to the 5th power based on mean aerodynamic chord) with angle-of-attack sweeps from -8 to 60 deg, and yaw-angle sweeps from -8 to 36 deg at fixed angles of attack 0, 10, 20, 25, 30, and 35 deg. Significant improvement in lift-curve slope, maximum lift, drag polar and lateral/directional stability was found, enlarging the flight envelope beyond its previous low-speed/maximum-lift limit. In spite of the highly swept (60 deg) leading edge, the efficiency of the lift augmentation by blowing was relatively high and was found to increase with increasing blowing momentum on the close-coupled-canard configuration. Interesting possibilities of obtaining much higher efficiencies with swirling jets were indicated.

Seginer, A.↗
NASA NTRS1983

The structure of separated flow regions occurring near the leading edge of airfoils, including transition

Data was obtained for the NACA 663-018 airfoil in order to assess the advantages of tripping the boundary layer very near the leading edge for chord Reynolds numbers between 40,000 and 200,000. Single element trips were made from tape 2.5 mm wide and 0.15 mm thick. The unmodified tape trip in five thicknesses was placed across the span at 1.1% chord and the results of lift and drag measurements compared with the smooth airfoil case. Saw tooth geometry trips were also cut from tape and studied using five thicknesses. The saw tooth trips were placed across the span with the sharp points facing upstream at 1.1% chord and with the valley of the teeth at the 2.5% chord position. A large number of bumps and wiggles were produced in the lift coefficient versus angle of attack curves with various combinations of Reynolds number, thickness, and type of trips. The main result in the drag coefficient was an increase in C sub d min with increase in trip thickness.

Mueller, T. J.↗
NASA NTRS1983

An experimental study of pressures on 60 deg Delta wings with leading edge vortex flaps

An experimental study was conducted in the Virginia Tech Stability Wind Tunnel to determine surface pressures over a 60 deg sweep delta wing with three vortex flap designs. Extensive pressure data was collected to provide a base data set for comparison with computational design codes and to allow a better understanding of the flow over vortex flaps. The results indicated that vortex flaps can be designed which will contain the leading edge vortex with no spillage onto the wing upper surface. However, the tests also showed that flaps designed without accounting for flap thickness will not be optimum and the result can be oversized flaps, early flap vortex reattachment and a second separation and vortex at the wing/flap hinge line.

Marchman, J. F., III↗
NASA NTRS1983

A method of predicting flow rates required to achieve anti-icing performance with a porous leading edge ice protection system

An analytical method was developed for predicting minimum flow rates required to provide anti-ice protection with a porous leading edge fluid ice protection system. The predicted flow rates compare with an average error of less than 10 percent to six experimentally determined flow rates from tests in the NASA Icing Research Tunnel on a general aviation wing section.

Kohlman, D. L.↗
NASA NTRS1983

Space Shuttle Orbiter Leading Edge Structural Subsystem development

The development of the Space Shuttle Orbiter Leading Edge Structural Subsystem (LESS) is traced from concept definition, through technical development, to final design, qualification testing and flight performance. A detailed description of the LESS is presented to support a discussion of the design, material development and thermal/structural integration. Extensive development/qualification tests and analytical studies were performed to verify the thermal/structural system performance and to certify the LESS for flight. Flight data and detailed post-flight inspection results are presented which support the conclusion that the LESS system performance has been outstanding.

Curry, D. M.↗
NASA NTRS1983

Numerical simulation of the leading-edge separation vortex for a wing and strake-wing configuration

In the present investigation, the 'thin layer' Navier-Stokes equations are used to compute the flow about a delta wing and a strake-delta wing configuration. Both configurations possess blunt noses and rounded leading edges. The computational grid about these configurations is generated using a newly developed three-dimensional grid-generation code which solves a set of Poisson equations with spherical coordinate variables using an alternating direction implicit (ADI) scheme. Computational results are obtained for an isolated wing with 60 deg sweep and a strake-wing configuration with 80-60 deg sweep. Computations for angles of attack in the range from 6 to 30 deg are presented. Attention is given to the effect of the angle of attack, the Mach number, and the Reynolds number. Theoretical results are compared with experimental data.

Fujii, K.↗
NASA NTRS1982

Low gravity solidification structures in the tin-15 wt pct lead and tin-3 wt pct bismuth alloys

The tin-15 wt pct lead and tin-3 wt pct bismuth alloys have been solidified in the low-gravity environment provided by the Space Processing Applications Rocket (SPAR), on the KC-135 airplane, and at high 'g' levels in a centrifuge furnace. In each case the resultant cast structure was significantly different from that obtained in ground based experiments. Earlier low-gravity studies with the metal-model system NH4Cl-H2O presaged these results. This paper presents and discusses the influence of changes in the gravity force on the grain structure of these materials.

Johnston, M. H.↗
NASA NTRS1985

Selecting Flatpack Lead-Forming Dies

Optical instrument accurately records unformed lead offset for each flatpack and provides better fit of flatpack to printed wiring board.

Choate, E. L.↗
NASA NTRS1983

Space shuttle wing leading edge heating environment prediction derived from development flight data

An analytical program is in progress at Rockwell International to revise wing leading edge heating predictions in order to improve correlation with STS-1 to -5 flight radiometer data. This paper discusses the methods that have been used to improve agreement between prediction and flight and summarizes the aerodynamic correlations which, when updated, will be used to analyze future orbiter missions.

Cunningham, J. A.↗
NASA NTRS1983

Augmentation of fighter-aircraft performance by spanwise blowing over the wing leading edge

Spanwise blowing over the wing and canard of a 1:35 model of a close-coupled-canard fighter-airplane configuration (similar to the Kfir-C2) was investigated experimentally in low-speed flow. Tests were conducted at airspeeds of 30 m/sec (Reynolds number of 1.8 x 10 to the 5th power based on mean aerodynamic chord) with angle-of-attack sweeps from -8 deg to 60 deg, and yaw-angle sweeps from -8 deg to 36 deg at fixed angles of attack 0 deg, 10 deg, 20 deg, 25 deg, 30 deg, and 35 deg. Significant improvement in lift-curve slope, maximum lift, drag polar and lateral/directional stability was found, enlarging the flight envelope beyond its previous low-speed/maximum-lift limit. In spite of the highly swept (60 deg) leading edge, the efficiency of the lift augmentation by blowing was relatively high and was found to increase with increasing blowing momentum on the close-coupled-canard configuration. Interesting possibilities of obtaining much higher efficiencies with swirling jets were indicated.

Seginer, A.↗
NASA NTRS1984

Ablation effects in oxygen-lead fragmentation at 2.1 GeV/nucleon

The mechanism of particle evaporation was used to examine ablation effects in the fragmentation of 2.1 GeV/nucleon oxygen nuclei by lead targets. Following the initial abrasion process, the excited projectile prefragment is assumed to statistically decay in a manner analogous to that of a compound nucleus. The decay probabilities for the various particle emission channels are calculated by using the EVAP-4 Monte Carlo computer program. The input excitation energy spectrum for the prefragment is estimated from the geometric ""clean cut'' abrasion-ablation model. Isotope production cross sections are calculated and compared with experimental data and with the predictions from the standard geometric abrasion-ablation fragmentation model.

Townsend, L. W.↗
NASA NTRS1984

Low-speed investigation of effects of wing leading- and trailing-edge flap deflections and canard incidence on a fighter configuration equipped with a forward-swept wing

An advanced fighter configuration with a forward-swept wing of aspect ratio 3.28 is tested in the Langley 7 by 10 Foot High Speed Tunnel at a Mach number of 0.3. The wing has 29.5 degrees of forward sweep of the quarter chord line and is equipped with 15 percent chord leading edge and 30 percent chord trailing edge flaps. The canard is sweptback 45 degrees. Tests were made through a range of angle of attack from about -2 degrees to 22 degrees. Deflecting the flaps significantly improves the lift drag characteristics at the higher angles of attack. The canard is able to trim the configurations with different flap deflections over most of the range of angle of attack. The penalty in maximum lift coefficient due to trimming is about 0.10.

Gainer, T. G.↗
NASA NTRS1984

Lead salt diode lasers and development of tunable solid state lasers for remote sensing

Extensive studies of the output characteristics of single quantum well lead-telluride lasers developed at the General Motors Research Laboratories were carried out. Threshold currents, output powers and line structures were measured as a function of temperature. Very low-current lasing thresholds, record high operating temperatures and over 30% tuning ranges were achieved. Excellent reproducibilities, good far-field patterns and reasonable linewidths (approx. 500 kHz) were found.

Freed, C.↗
NASA NTRS1984

Use of a discontinuous wing leading-edge modification to enhance spin resistance for general aviation airplanes

Spin resistance of two typical general aviation airplanes has been studied. Improvement in spin resistance due to an outboard wing leading-edge modification was evaluated through wind-tunnel and flight tests. The basic airplanes would readily enter a spin; however, with the wing modification the airplanes were highly spin resistant. Spin resistance has been related to the angle of attack of the outer wing panel and the yaw rate as a step toward development of guidelines for design of more spin resistant airplanes.

Dicarlo, D. J.↗