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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Nacelle-wing integration

The Aerodynamics Division at NASA ARC is participating in the propulsion airframe integration phase of the High Speed Research Program. The two areas of research being pursued include an experimental program and analysis using computational fluid dynamics. The applied Aerodynamics Branch is conducting the experimental program, which will involve a nacelle airframe model that was tested in the Ames 11- by 11-Foot Transonic Wind Tunnel in 1973. This branch will also assess various Euler codes in predicting nacelle airframe interference effects. The goal is to provide the industry with the necessary data and tools to design a high speed civil transport with favorable propulsion airframe interference.

Cappuccio, Gelsomina↗
NASA NTRS1959

The Static Longitudinal Stability and Control Characteristics in the Presence of the Ground of a Model Having a Triangular Wing and Canard

A wind-tunnel investigation was made of the low-speed characteristics of a canard configuration having triangular wing and canard surfaces with an aspect ratio of 2. The exposed area of the canard was 6.9 percent of the total wing area. The canard hinge line was located at 0.35 of its mean aerodynamic chord and was 0.5 wing mean aerodynamic chord lengths forward of the wing apex. The ground effects, which made the lift more positive and the -Pitching moment more negative at a given angle of attack, were unaffected by the canard. The stability of the model at a constant canard hinge-moment coefficient decreased to 0 near a lift coefficient of 1.0. In addition, the maximum lift coefficient at which the canard could provide balance was decreased by ground effects to less than 1.0 if the moment center was as far forward as 0.21 of the wing mean aerodynamic chord. The relative magnitude of interference effects between the canard and the wing and body is presented.

Buell, Donald A.↗
NASA NTRS1959

The Stabilizing Effectiveness of Conical Flares on Bodies with Conical Noses

An analysis is presented of published results of force tests on 80 cone-cylinder-flare configurations at Mach numbers of 2.18, 2.81, and 4.04. The contributions, excluding interference effects, of the cone-cylinder bodies to the over-all normal force derivatives have been removed by means of the second-order shock-expansion method, and the normal force derivatives at zero angle of attack due to the flares alone are shown. The results from a wide variety of configurations are correlated by plotting ratios of the normal force derivatives of the flares to the normal force derivatives of cones having the same included angle. Comparisons are made of the experimental normal force results with the normal force derivatives obtained by assuming conical flow over the flares and with those obtained by use of the second-order shock-expansion method. The comparisons show that use of the second-order shock-expansion method is generally the superior of the two, and in most cases gives values of the normal force derivatives of the flares which agree very well with the experimental results. Centers of pressure of the flares are presented and comparisons are made with results obtained from the theories mentioned. In general, the comparisons show that the assumption of conical flow over the flares is comparable to use of the second-order shock-expansion method in determining the centers of pressure, and in many cases both methods give values which agree closely with the experimental results.

Kirk, Donn B.↗
NASA NTRS1951

Effect of Ground Interference on the Aerodynamic Characteristics of a 42 Degrees Sweptback Wing

The effects of ground interference on the aerodynamic characteristics of a 42 degrees sweptback wing have been determined at distances above the ground 0.68 and 0.92 of the mean aerodynamic chord (measured from the 0.25 mean aerodynamic chord). The wing was tested without flaps and with inboard trailing-edge split and outboard leading-edge flaps deflected. The wing had an aspect ratio of 4, a taper ratio of 0.625, and NACA 641-112 airfoil sections perpendicular to the 0.273 chord line. The results are, in general, comparable to those reported for unswept wings. The longitudinal stability at the stall was not materially affected at the ground heights of the present tests.

RESEARCH TECHNIQUE, AERODYNAMICS↗
NASA NTRS1973

Space Shuttle response to atmospheric turbulence.

A fully reusable Space Shuttle configuration has been analyzed during ascent flight to determine its response to atmospheric turbulence. Propellant sloshing, gust penetration, and automatic control system effects were included. The steady-state aerodynamic method of Woodward was used to derive the generalized aerodynamic forces, using the standard quasi-steady assumption. Aerodynamic interference effects between adjacent wings and bodies were found to be significant, with symmetric responses generally higher than antisymmetric. The stability augmentation system tended to lower booster response while increasing orbiter response. Loads due to 9 m/s quasi-square-wave gusts were considerably higher than the 3 sigma random turbulence loads. The elastic portion of the response accounted for about 15% of the total wing load in the discrete gust analysis, while in the random case the elastic effect was small.

Huntington, R. G.↗
NASA NTRS1979

The role of wind tunnels in predicting sounding rocket aerodynamics

The aerodynamic characteristics of sounding rockets, in some cases, may be adequately determined by various estimating procedures, however, there are cases where these procedures fail and wind tunnel studies become necessary. The present paper deals with configurations of the latter type, for which the problems of concern include mismatched diameters between stages, mutual fin interference effects, fin alignment and orientation, body deflections between stages, boundary layer growth, and stability changes that occur as stages are dropped. Some characteristics related to separated flow, interference flow fields, and Reynolds number are examined.

Spearman, M. L.↗
NASA NTRS2019

Interference Drag Associated with Engine Locations for Multidisciplinary Design Optimization

This research aims to quantify the interference drag for various engine locations on a traditional “tube and wing,” 150-passenger commercial aircraft flying at 35,000 ft and Mach 0.8. Engine locations are varied in the chord wise, span wise, and vertical directions near the wing, both under and above the wing, as well as along the fuselage. Euler simulations are performed with representative powered modern engines. The results are intended to supplement empirical drag estimates suitable for multidisciplinary design environments. Large interference drag increases, as compared to the isolated air frame and engine geometry, are found to occur when the engine is placed directly above or below the wing. Interference effects are significantly reduced, and in some instances result in benefits compared to the isolated bodies, when the engines are placed fore or aft of the wing. Interference drag increases are partially explained by flow channels leading to choked flow and shock interactions between bodies.

Blaesser, Nathaniel J.↗
NASA NTRS1991

Collisional effects in laser detection of tropospheric OH

The use of laser-induced fluorescence to measure OH in the troposphere is discussed. It is noted that quantitative laser detection of OH requires knowledge of collisional processes affecting the measurements and interference effects due to OH generated by laser photolytic processes. Collisions induce quenching of the excited A-state, as well as vibrational and rotational energy transfer in the excited and ground states. It is noted that the state-specific nature of these processes is important, especially the rotational level dependence of quenching and vibrational transfer in excited OH. Also important is the temperature dependence according to which quenching cross sections sharply increase with decreasing temperature. Laboratory experiments studying these collisional processes are described, and their implications for laser detection of tropospheric OH are examined.

Crosley, David R.↗
NASA NTRS1978

Theoretical and experimental aerodynamics of strake-wing interactions up to high angles-of-attack

This paper reports on an experimental investigation where the longitudinal aerodynamic characteristics were determined up to high angles-of-attack for configurations employing parametric variations in strake span and wing sweep and includes correlations with theory. The investigation included both component and complete configuration studies to provide information for the analysis of interaction effects. Comparisons between strake-wing and high canard-wing configurations demonstrate the strake-wing to develop higher lift coefficients than did the canard-wing due to enhanced interference effects. Correlations with theory demonstrate the suction analogy to be a useful method for estimating the effects of vortex flow aerodynamics on both component and total forces and moments.

Luckring, J. M.↗
NASA NTRS2003

Interferometer for Measuring Displacement to Within 20 pm

An optical heterodyne interferometer that can be used to measure linear displacements with an error <=20 pm has been developed. The remarkable accuracy of this interferometer is achieved through a design that includes (1) a wavefront split that reduces (relative to amplitude splits used in other interferometers) self interference and (2) a common-optical-path configuration that affords common-mode cancellation of the interference effects of thermal-expansion changes in optical-path lengths. The most popular method of displacement- measuring interferometry involves two beams, the polarizations of which are meant to be kept orthogonal upstream of the final interference location, where the difference between the phases of the two beams is measured. Polarization leakages (deviations from the desired perfect orthogonality) contaminate the phase measurement with periodic nonlinear errors. In commercial interferometers, these phase-measurement errors result in displacement errors in the approximate range of 1 to 10 nm. Moreover, because prior interferometers lack compensation for thermal-expansion changes in optical-path lengths, they are subject to additional displacement errors characterized by a temperature sensitivity of about 100 nm/K. Because the present interferometer does not utilize polarization in the separation and combination of the two interfering beams and because of the common-mode cancellation of thermal-expansion effects, the periodic nonlinear errors and the sensitivity to temperature changes are much smaller than in other interferometers

Zhao, Feng↗
NASA NTRS1976

A submerged singularity method for calculating potential flow velocities at arbitrary near-field points

A discrete singularity method has been developed for calculating the potential flow around two-dimensional airfoils. The objective was to calculate velocities at any arbitrary point in the flow field, including points that approach the airfoil surface. That objective was achieved and is demonstrated here on a Joukowski airfoil. The method used combined vortices and sources ''submerged'' a small distance below the airfoil surface and incorporated a near-field subvortex technique developed earlier. When a velocity calculation point approached the airfoil surface, the number of discrete singularities effectively increased (but only locally) to keep the point just outside the error region of the submerged singularity discretization. The method could be extended to three dimensions, and should improve nonlinear methods, which calculate interference effects between multiple wings, and which include the effects of force-free trailing vortex sheets. The capability demonstrated here would extend the scope of such calculations to allow the close approach of wings and vortex sheets (or vortices).

Maskew, B.↗
NASA NTRS1937

Spinning Characteristics of Wings III : a Rectangular and Tapered Clark Y Monoplane Wing with Rounded Tips

An investigation was made to determine the spinning characteristics of Clark Y monoplane wings with different plan forms. A rectangular wing and a wing tapered 5:2, both with rounded tips, were tested on the N.A.C.A. spinning balance in the 5-foot vertical wind tunnel. The aerodynamic characteristics of the models and a prediction of the angles of sideslip for steady spins are given. Also included is an estimate of the yawning moment that must be furnished by the parts of the airplane to balance the inertia couples and wing yawing moment for spinning equilibrium. The effects on the spin of changes in plan form and of variations of some of the important parameters are discussed and the results are compared with those for a rectangular wing with square tips. It is concluded that for a conventional monoplane using Clark Y wing the sideslip will be algebraically larger for the wing with the rounded tip than for the wing with the square tip and will be largest for the tapered wing. The effect of plan form on the spin will vary with the type of airplane; and the provision of a yawing-moment coefficient of -0.025 (i.e., opposing the spin) by the tail, fuselage, and interference effects will insure against the attainment of equilibrium on a steady spin for any of the plan forms tested and for any of the parameters used in the analysis.

Bamber, M J↗
NASA NTRS2005

Cumulative Interference to Aircraft Radios from Multiple Portable Electronic Devices

Cumulative interference effects from portable electronic devices (PEDs) located inside a passenger cabin are conservatively estimated for aircraft radio receivers. PEDs' emission powers in an aircraft radio frequency band are first scaled according to their locations' interference path loss (IPL) values, and the results are summed to determine the total interference power. The multiple-equipment-factor (MEF) is determined by normalizing the result against the worst case contribution from a single device. Conservative assumptions were made and MEF calculations were performed for Boeing 737's Localizer, Glide-slope, Traffic Collision Avoidance System, and Very High Frequency Communication radio systems where full-aircraft IPL data were available. The results show MEF for the systems to vary between 10 and 14 dB. The same process was also used on the more popular window/door IPL data, and the comparison show the multiple-equipment-factor results came within one decibel (dB) of each other.

Nguyen, Truong X.↗
NASA NTRS1959

An Investigation of the Pitching-Moment Contribution of a High Horizontal Tail on an Unswept-Wing and Body Combination at Mach Numbers from 0.80 to 1.40

An investigation has been conducted to determine the effects of a high positioned horizontal tail on a wing-body configuration having a thin unswept wing of aspect ratio 3.09. Lift and pitching-moment coefficients were obtained for Mach numbers from 0.80 to 1.40 at Reynolds numbers of 1.0 and 1.5 million and for angles of attack to 20 deg. An experimental study of the pitching-moment contribution of the horizontal tail indicated that the marked destabilizing effect of the horizontal tail at high angles of attack for Mach numbers of 0.80 to 1.00 was associated with the formation of completely separated flow on the upper surface of the wing. Computations of the interference effects of the wing-body combination on the tail for Mach numbers of 0.80 and 0.94 and high angles of attack confirmed this conclusion. For a Mach number of 1.40, and high angles of attack, computations disclosed that the destabilizing effect primarily resulted from the trailing vortices of the wing. Two modifications to the basic wing plan form, which consisted of chord extensions, were generally unsuccessful in reducing the destabilizing contributions of the horizontal tail at high angles of attack.

Lippmann, Garth W.↗
NASA NTRS1985

Wind-tunnel evaluation of a 21-percent-scale powered model of a prototype advanced scout helicopter

An exploratory wind tunnel investigation of a 21 percent scale powered model of a prototype advanced scout helicopter was conducted in the Langley 4 by 7 Meter Tunnel. The investigation was conducted to define the overall aerodynamic characteristics of the Army Helicopter Improvement Program (AHIP), to determine the effects of the rotor on the aerodynamic characteristics and to evaluate the effect of a mast mounted sight on the aircraft stability characteristics. Tests covered a range of thrust coefficients, advance ratios, angles of attack and angles of sideslip and were run for both rotor on and rotor off configurations. Results of the investigation showed that the prototype configuration was longitudinally unstable with angle of attack for all configurations tested. The instability was due to unfavorable interference effects between the horizontal tail and the wake shed from the engine pylon and rotor hub, which caused a loss of horizontal tail effectiveness. The addition of the mast mounted sight had little effect on the stability of the model, but it caused an alteration in the rotor lift distribution that resulted in substantial interference drag for the sight.

Phelps, A. E., III↗
NASA NTRS1959

Experimental and Theoretical Studies of Axisymmetric Free Jets

Some experimental and theoretical studies have been made of axisymmetric free jets exhausting from sonic and supersonic nozzles into still air and into supersonic streams with a view toward problems associated with propulsive jets and the investigation of these problems. For jets exhausting into still air, consideration is given to the effects of jet Mach number, nozzle divergence angle, and jet static pressure ratio upon jet structure, jet wavelength, and the shape and curvature of the jet boundary. Studies of the effects of the ratio of specific heats of the jets are included are observations pertaining to jet noise and jet simulation. For jets exhausting into supersonic streams, an attempt has been made to present primarily theoretical certain jet interference effects and in formulating experimental studies. The primary variables considered are jet Mach number, free stream Mach number, jet static pressure ratio, ratio of specific heats of the jet, nozzle exit angle, and boattail angle. The simulation problem and the case of a hypothetical hypersonic vehicle are examined, A few experimental observations are included.

Love, Eugene S.↗
NASA NTRS1972

Radiation sensitivity of silicon imaging sensors on missions to the outer planets.

Review of the results of an investigation of the magnitude of the degradation effects of radiation on the operating characteristics of camera tubes using silicon diode arrays in the space environment, and discussion of the radiation damage mechanisms concerned. The effects produced by bombardment of bare-silicon-diode arrays or vidicon tubes with 85-kV X rays, Cobalt 60 gamma rays, 1 MeV and 11 MeV electrons, 3 MeV and 142 MeV protons, and reactor neutrons are presented. Interference effects produced by radiation bombardment during operation of television tubes are investigated, and limiting fluxes of electrons and protons are given.

Brucker, G. J.↗