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  • Other Sources  (512)
  • AERODYNAMICS  (366)
  • MECHANICAL ENGINEERING  (146)
  • Animals
  • 1980-1984  (512)
  • 1925-1929
  • 1981  (512)
  • 1
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    Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives (1981)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.
    Keywords: AERODYNAMICS
    Type: AGARD Dyn. Stability Parameters; 13 p
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  • 2
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    A clamp mechanism for deployable three-ton payloads (1981)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The requirements, capabilities, and unique design features of the instrument payload subsystem payload clamp assembly (PCA) are presented. The PCA is designed to have the flexibility to accommodate a wide payload range varying from 0.5 m to 3 m in diameter and from 500 kg to 3000 kg mass. This is achieved by modular clamp design in connection with replaceable struts. The design features include clamping of payload in a statically determined way and actuation of clamp latches by means of single linear actuator via ropes. The vibration and TV environmental conditions for the mechanism are extremely severe. A structural and prototype model was built. Test results of the operating characteristic are presented. In addition, problems of tribology are highlighted.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 375-390
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  • 3
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    An antenna pointing mechanism for large reflector antennas (1981)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: An antenna pointing mechanism for large reflector antennas on direct broadcasting communication satellites was built and tested. After listing the requirements and constraints for this equipment the model is described, and performance figures are given. Futhermore, results of the qualification level tests, including functional, vibrational, thermovacuum, and accelerated life tests are reported. These tests were completed successfully.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 253-261
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  • 4
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    A drive unit for the instrument pointing system (1981)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The requirements, capabilities, and unique design features of the instrument pointing system drive units (DU) are presented. The DU's are identical for all three gimbal axes (elevation, cross elevation, and azimuth) and provide alternating rotation of shaft versus the housing of + or - 180 deg. The design features include: two ball bearing cartridges using cemented carbide balls coated with TiC a layer; redundant brushless torque motors and resolvers; a load by-pass mechanism driven by a dc torque motor to off-load the bearings during ascent/descent, ground transportation, and to provide an emergency breaking capability; and cabling over each gimbal axis by means of cable follow-up consisting of 13 signal and 15 power flat band cable loops. Test results of disturbance torque characteristics are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 263-278
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  • 5
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    An antenna fine pointing mechanism (1981)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: SOFA, a device designed for the highly accurate 2 axis pointing of antenna or any feature installed on a spacecraft is described. The major characteristic of this system is complete freedom from friction and wear out, resulting in numerous advantages, such as outstanding precision, virtually endless service life, high simplicity, and reliability. The sizing method is described and performances are analyzed. The results from analogue simulations are presented. A functional model of the electrical and mechanical parts was built and subjected to on ground tests using a 2 axis platform simulating the spacecraft's motions. The results obtained are thoroughly in keeping with the predictions and simulations. Various possible applications of the SOFA system are mentioned.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 235-252
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  • 6
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    A mechanical drive for retractable telescopic masts (1981)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Test results on the mechanical drive have indicated that the system is capable of deploying a typical telescopic mast under ambient conditions. The design can be considered for a wide range of space applications since, in theory, there is no limit to the number of tubes that can be deployed. The mechanical system offers a number of advantages over a gas driven system, such as the ability to retract and also provide a significant mass saving.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 205-217
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  • 7
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    Tribology experiment (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: A two-dimensional concept for Spacelab rack 7 was developed to study the interaction of liquid lubricants and surfaces under static and dynamic conditions in a low-gravity environment fluid wetting and spreading experiments of a journal bearing experiments, and means to accurately measure and record the low-gravity environment during experimentation are planned. The wetting and spreading process of selected commercial lubricants on representative surface are to the observes in a near-zero gravity environment.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 58-60
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  • 8
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    An analytic solution to the classical two-body problem with drag (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The two body problem was analyzed with a specific drag model. The model treats drag as a force proportional to the vector velocity and inversely proportional to the distance to the center of attraction. The solution is expressed in terms of known functions and is of a simple and compact form. The time of flight is expressed as a quadrature in the true anomaly. The results are: (1) development of a vector differential equation which allows analysis of an infinite number of gravitational and drag models; and (2) obtaining the solution of a linear differential equation using the inverse method of laplace transforms.
    Keywords: AERODYNAMICS
    Type: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 22 p
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  • 9
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    Langley high-lift research on a high-aspect-ratio supercritical wing configuration (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: To determine the low speed performance characteristics of a representative high aspect ratio supercritical wing, two low speed jet transport models were fabricated. A 12-ft. span model was used for low Reynolds number tests in the Langley 4- by 7-Meter Tunnel and the second, a 7.5-ft. span model, was used for high Reynolds number tests in the Ames 12-foot Pressure Tunnel. A brief summary of the results of the tests of these two models is presented and comparisons are made between the data obtained on these two models and other similar models. Follow-on two and three dimensional research efforts related to the EET high-lift configurations are also presented and discussed.
    Keywords: AERODYNAMICS
    Type: Advan. Aerodyn.: Selected NASA Res.; p 55-77
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  • 10
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    Measured transonic unsteady pressures on an energy efficient transport wing with oscillating control surfaces (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Highlight results are presented from subsonic and transonic pressure measurement studies conducted in the Langley Transonic Dynamics Tunnel on a supercritical wing model representative of an energy efficient transport design. Steady- and unsteady-pressure data were acquired on the upper and lower wing surface at an off-design Mach number of 0.60 and at the design Mach number of 0.78, for a Reynolds number of 2.2 x 10(6) (based on the wing average chord). The model configuration consisted of a sidewall-Mounted half-body fuselage and a semi-span wing with an aspect ratio of 10.76, a leading-edge sweepback angle of 28.8 degrees, and supercritical airfoil sections. The wing is instrumented with 252 static pressure orifices and 164 dynamic pressure gages. Model test variables included wing angle of attack, control-surface mean deflection angle, control-surface oscillating deflection angle and frequency, and phasing between oscillating leading-edge and trailing-edge controls when used together.
    Keywords: AERODYNAMICS
    Type: Advan. Aerodyn.: Selected NASA Res.; p 21-36
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  • 11
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    Vortex-flow aerodynamics - An emerging design capability (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Promising current theoretical and simulational developments in the field of leading edge vortex-generating delta, arrow ogival wings are reported, along with the history of theory and experiment leading to them. The effects of wing slenderness, leading edge nose radius, Mach number and incidence variations, and planform on the onset of vortex generation and redistribution of aerodynamic loads are considered. The range of design possibilities in this field are consequential for the future development of strategic aircraft, supersonic transports and commercial cargo aircraft which will possess low-speed, high-lift capability by virtue of leading edge vortex generation and control without recourse to heavy and expensive leading edge high-lift devices and compound airfoils. Attention is given to interactive graphics simulation devices recently developed.
    Keywords: AERODYNAMICS
    Type: Astronautics and Aeronautics; 19; May 1981
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  • 12
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    Longitudinal grooves for bluff body drag reduction (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Wind tunnel test results are presented for four axisymmetric bluff body configurations in order to determine their effect on form and pressure drag. It was found that drag reductions on the order of 40% are obtainable with an afterbody incorporating four longitudinal 'V' grooves. Although this effect may be due to the functioning of the grooves as longitudinal, continuous vortex generators, it is concluded that further research is needed to elucidate the physical basis of the test results. Optimization of the effect will be useful in base drag reduction for such vehicles as automobiles and cargo aircraft with sharply upswept afterbodies.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Apr. 198
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  • 13
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    Vectored injection into compressible laminar and turbulent boundary layers (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A fundamental analysis of two-dimensional supersonic boundary layer flow, both laminar and turbulent, is presented for a wide range of normal and nonnormal mass-transfer velocities. The analysis is based on the numerical solution of the Navier-Stokes equations, and results are compared with available theoretical and experimental data. Certain cases of practical importance, for which results are not presently available, are referred to.
    Keywords: AERODYNAMICS
    Type: Computer Methods in Applied Mechanics and Engineering; 25; Jan. 198
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  • 14
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    Report of the panel on theoretical aerodynamics (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Interactions between theoretical aerodynamics and the NTF are discussed. The development and validation of computational fluid dynamics computer codes, the determination of Reynolds number scaling laws, and extension of the data bases of entrainment type turbulence models to include high Reynolds number data are recommended areas of study. The major benefit theoretical aerodynamics could have on the NTF is in the quantitative description of wind tunnel wall interference effects.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 277-286
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  • 15
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    High Reynolds number research requirements for space vehicle design (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Requirements of entry vehicle design requiring high Reynolds number wind tunnel testing are discussed. The space shuttle orbiter, development of future space transportation systems, and planetary entry data analysis are considered.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 265-274
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  • 16
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    Report of the panel on aeroelasticity and unsteady aerodynamics (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The status of recommended areas of study for the NTF are reviewed. Transonic and control surface unsteady aerodynamics, and buffet onset and loads are considered. Testing of dynamically scaled flutter models is discussed.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 237-246
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  • 17
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    Model experience in the Langley 0.3-m transonic cryogenic tunnel (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The model building, development, and testing experience gained during 8 years of operation of the 0.3-m Transonic Cryogenic Tunnel (TCT) is summarized. The summary is divided into four portions: (1) models tested in the 0.3-m TCT's original octagonal test section; (2) models tested in the present two dimensional test section; (3) models tested as a part of tunnel calibration and the development of advanced technology airfoils; and (4) development of a new way to construct two dimensional airfoil models. Design requirements imposed on the models by high Reynolds number testing at cryogenic temperatures are reviewed.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 53-73
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  • 18
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    Effectiveness of leading-edge vortex flaps on 60 and 75 degree delta wings (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A series of wind tunnel tests were run on 60 and 75 deg sweep delta wings to examine the effectiveness of leading-edge vortex flaps. Tests results showed that leading-edge vortex flaps are effective in giving large increases in lift-to-drag ratio and decreases in drag over a wide range of angle of attack. Tests on inverted flaps on the 60 deg delta wing showed substantial increases in lift and drag and may indicate a possibility of using inverted flaps on delta wings in the landing portion of flight. The 60 deg data were compared with that for a 75 deg sweep delta wing confirming that leading-edge vortex flap effectiveness is stronger as sweep is increased. Pitching moment effects due to vortex flaps use were also examined.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Apr. 198
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  • 19
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    The transfer of polytetrafluoroethylene studied by X-ray photoelectron spectroscopy (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A polytetrafluoroethylene (PTFE) sphere of radius 4.8 mm was rubbed against nickel and S-Monel at speeds from 0.94 to 94 mm/s and at loads from 0.19 to 3.9 N. The transfer film of PTFE on the metal was examined with X-ray photoelectron spectroscopy. In all cases the film was found to be indistinguishable from bulk PTFE. A trace of metal fluoride was observed whether the rubbing took place on oxidized or atomically clean metal. The film was of the order of a molecule thick for the entire range of loads and did not increase with repeated passes over the same rubbed area. An erratic increase in thickness at rubbing speeds above 10 mm/s was taken as evidence of random transfer of bulk material.
    Keywords: MECHANICAL ENGINEERING
    Type: Wear; 66; Feb. 16
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  • 20
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    Partially confined multiple jet mixing (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results of hot-wire measurements in an incompressible partially confined jet issuing from an array of rectangular nozzles, equally spaced with their small dimensions aligned are presented. The quantities measured include mean velocity and the Reynolds stress in the two central planes of the jet at stations covering up to 115 widths (small dimension of a nozzle) downstream of the nozzle exit. For downstream distances greater than 60 widths, the flowfield is observed to be nearly homogenous and the turbulence appears to be quite similar to that of a grid generated turbulence.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 21
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    Unsteady Newton-Busemann flow theory. I - Airfoils (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Newtonian flow theory for unsteady flow at very high Mach numbers is completed by the addition of a centrifugal force correction to the impact pressures. The correction term is the unsteady counterpart of Busemann's centrifugal force correction to impact pressures in steady flow. For airfoils of arbitary shape, exact formulas for the unsteady pressure and stiffness and damping-in-pitch derivatives are obtained in closed form, which require only numerical quadratures of terms involving the airfoil shape. They are applicable to airfoils of arbitrary thickness having sharp or blunt leading edges. For wedges and thin airfoils these formulas are greatly simplified, and it is proved that the pitching motions of thin airfoils of convex shape and of wedges of arbitrary thickness are always dynamically stable according to Newton-Busemann theory. Leading-edge bluntness is shown to have a favorable effect on the dynamic stability; on the other hand, airfoils of concave shape tend toward dynamic instability over a range of axis positions if the surface curvature exceeds a certain limit. As a byproduct, it is also shown that a pressure formula recently given by Barron and Mandl for unsteady Newtonian flow over a pitching power-law shaped airfoil is erroneous and that their conclusion regarding the effect of pivot position on the dynamic stability is misleading.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 22
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    Evidence of imbedded vortices in a three-dimensional shear flow (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Vortex phenomena encountered in an investigation of the streamwise development of the three-dimensional wake region behind the tip of a three-dimensional wedge model are reported. Pressure profiles were measured by pitot probes downstream of a tip with a nearly constant surface pressure level and a nearly continuous surface curvature in a blowdown air tunnel operating at Mach 6. Rather than the simple three-dimensional quasi-parallel shear flow expected, the measurements indicated the presence of a flow with large deficits in longitudinal pitot pressure, which are usually associated with the core region of quasi-steady longitudinal vortices. Vapor screen flow visualizations also support the presence of longitudinal vortices located primarily in the tip region and evidently forming in the vicinity of the wake neck. An increase in overall wake thickness by 100% is also observed. The origin of the vortices as quasi-steady Taylor-Gortler vortices generated in the concavely curved shear layer near the wake neck is considered. It is pointed out that the existence of longitudinal vortexes suggests that three-dimensional turbulence modeling may be much more difficult than previously supposed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 23
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    Proposed aeroelastic and flutter tests for the National Transonic Facility (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Tests that can exploit the capability of the NTF and the transonic cryogenic tunnel, or lead to improvements that could enhance testing in the NTF are discussed. Shock induced oscillation, supersonic single degree control surface flutter, and transonic flutter speed as a function of the Reynolds number are considered. Honeycombs versus screens to smooth the tunnel flow and a rapid tunnel dynamic pressure reducer are recommended to improve tunnel performance.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 153-161
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  • 24
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    Report of the wind tunnel/flight correlation panel (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Basic calibration of the tunnel prior to conducting any tests, the areas requiring wind tunnel/flight test correlation for validating the NTF, and recommendations for achieving validation of the NTF are discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 249-262
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  • 25
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    High lift technology (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The NASA Langley high lift technology program is reviewed and elements of the program which are considered Reynolds number sensitive are discussed. The Energy Efficient Transport (EET) and Supersonic Cruise Research (SCR) models proposed for high lift studies in the National Transonic Facility (NTF) are described. Recommendations regarding the NTF facility and test techniques are presented.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 197-213
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  • 26
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    Wall interference effects: Status review (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interference technology incorporated into the NTF design (hardware) and the emerging transonic wall interference assessment correction procedures (software) to be employed when the NTF becomes operational was reviewed. It is anticipated that the early experiments will provide data relevant to wall interference effects.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 123-241
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  • 27
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    Configuration aerodynamics (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Static aerodynamic research related to aircraft configurations in their cruise or combat modes is discussed. Subsonic transport aircraft, transonic tactical aircraft, and slender wing aircraft are considered. The status and plans of Langley's NTF configuration research program are reviewed. Recommendations for near term configuration research are made.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 217-234
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  • 28
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    Comments on Reynolds number effects and the role of NTF in the development of air vehicles (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The National Transonic Facility (NTF) capability to match the full scale Reynolds numbers of all but the largest airplanes is discussed. Conversion factors to enable calculation of Sl-unit equivalents for all U.S. units are listed. Using data from several facilities, analytic methods, and flight test data, a competetive aircraft in the relatively low Reynolds number was developed. The NTF offers the capability to obtain data at full scale Reynolds numbers in the cruise condition for most of the products, and will be much closer than previous tunnels to full scale Reynolds number for the operating envelopes. It is primarily on the operating envelope that Reynolds number effects are most important and least predictable.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 143-148
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  • 29
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    Solution of the transonic full potential equation in conservative form using an implicit algorithm (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper presents numerical solutions of the full potential equation in conservative form. The iteration scheme used is a fully implicit approximate factorization technique and provides a significant improvement in convergence speed relative to standard successive line overrelaxation algorithms. The spatial differencing algorithm is centrally differenced in both subsonic and supersonic regions to maintain stability. This effectively approximates rotated differencing, thereby greatly improving the reliability of the algorithm.
    Keywords: AERODYNAMICS
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  • 30
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    Computation of airfoil buffet boundaries (1981)
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    Publication Date: 2011-08-18
    Description: The ILLIAC IV computer has been programmed with an implicit, finite-difference code for solving the thin layer compressible Navier-Stokes equation. Results presented for the case of the buffet boundaries of a conventional and a supercritical airfoil section at high Reynolds numbers are found to be in agreement with experimentally determined buffet boundaries, especially at the higher freestream Mach numbers and lower lift coefficients where the onset of unsteady flows is associated with shock wave-induced boundary layer separation.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Nov. 198
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  • 31
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    Ball bearing lubrication: The elastohydrodynamics of elliptical contacts (1981)
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    Publication Date: 2011-08-18
    Description: The history of ball bearings is examined, taking into account rollers and the wheel in the early civilizations, the development of early forms of rolling-element bearings in the classical civilizations, the Middle Ages, the Industrial Revolution, the emergence of the precision ball bearing, scientific studies of contact mechanics and rolling friction, and the past fifty years. An introduction to ball bearings is presented, and aspects of ball bearing mechanics are explored. Basic characteristics of lubrication are considered along with lubrication equations, the lubrication of rigid ellipsoidal solids, and elastohydrodynamic lubrication theory. Attention is given to the theoretical results for fully flooded elliptical hydrodynamic contacts, the theoretical results for starved elliptical contacts, experimental investigations, the elastohydrodynamics of elliptical contacts for materials of low elastic modulus, the film thickness for different regimes of fluid-film lubrication, and applications.
    Keywords: MECHANICAL ENGINEERING
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  • 32
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    Application of unsteady airfoil theory to rotary wings (1981)
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    Publication Date: 2011-08-18
    Description: A clarification is presented on recent work concerning the application of unsteady airfoil theory to rotary wings. The application of this theory may be seen as consisting of four steps: (1) the selection of an appropriate unsteady airfoil theory; (2) the resolution of that velocity which is the resultant of aerodynamic and dynamic velocities at a point on the elastic axis into radial, tangential and perpendicular components, and the angular velocity of a blade section about the deformed axis; (3) the expression of lift and pitching moments in terms of the three components; and (4) the derivation of explicit expressions for the components in terms of flight velocity, induced flow, rotor rotational speed, blade motion variables, etc.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; July 198
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    The coupling between flow instabilities and incident disturbances at a leading edge (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is now generally agreed that an external disturbance field, such as an incident acoustic wave, can effectively couple to instabilities of a flow past a trailing edge. One purpose of the present paper is to show that there are situations where a similar coupling can occur at a leading edge. The process is analyzed and the effects of experimentally controllable parameters are assessed. It is important to account for such phenomena when evaluating the effect of external disturbances on transition.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 104; Mar. 198
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  • 34
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    A discrete vortex method for the non-steady separated flow over an airfoil (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A discrete vortex method was used to analyze the separated non-steady flow about a cambered airfoil. The foil flow modelling is based on the thin lifting-surface approach, where the chordwise location of the separation point is assumed to be known from experiments or flow-visualization data. Calculated results provided good agreement when compared with the post-stall aerodynamic data of two airfoils. Those airfoil sections differed in the extent of travel of the separation point with increasing angle of attack. Furthermore, the periodic wake shedding was analyzed and its time-dependent influence on the airfoil was investigated.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 102; Jan. 198
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  • 35
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    Pathfinder model program for the National Transonic Facility (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An overview of the Pathfinder Models Program is presented. The Pathfinder program is a major research and development activity in support of the National Transonic Facility Activation Plan. The program scope, models design approach, and Pathfinder model configurations are presented along with a discussion of major supportive program activities. The anticipated design criteria for NTF models are presented.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 37-52
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  • 36
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    Development of a polymetric grout for the hydrostatic bearing at DSS 14 (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Results of an investigation into the causes of the deterioration and premature failure of the grout under the hydrostatic bearing runner at DSS 14 are reported. Generic types of materials were screened and tested to find a grout material more resistive to the causes of grout failure. Emphasis was placed on the physical properties, strength, modulus of elasticity, and resistance to erosion and chemical attack by oil and unique requirements imposed by each material for mixing, placing, compacting, and cooling. The polymetric grout developed to replace the dry grout is described.
    Keywords: MECHANICAL ENGINEERING
    Type: The Telecommun. and Data Acquisition; p 115-148
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  • 37
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    Trailing edge noise prediction using Amiet's method (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Amiet's (1976, 1978) solution to the problem of airfoil trailing edge noise prediction is discussed in light of the results of evanescent wave theory's application to the measured surface pressure behavior near the trailing edge of an airfoil with a turbulent boundary layer. The method employed by Amiet has the advantage of incorporating the effect of finite chord in its solution. The assumed form of the pressure distribution is examined as well as the constant turbulent boundary layer convection assumption, which is found to be unnecessarily restrictive.
    Keywords: AERODYNAMICS
    Type: Journal of Sound and Vibration; 77; Aug. 8
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  • 38
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    Forebody drag reduction (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is shown that the mechanisms of forebody drag reduction by means of either a spike or a forward-facing jet are similar, with the maximum achievable drag reduction being of the same order. Because the jet may be a relatively cool gas, however, the forward facing jet has the additional capability of reducing the aerodynamic heating that is so severe at high Mach numbers. By means of the correlation presented, jet ejection parameters may be chosen to achieve maximum permissible forebody drag reduction. The correlation method uses a momentum coefficient that characterizes jet efflux and freestream conditions.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Oct. 198
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  • 39
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    Unsteady Newton-Busemann flow theory. II - Bodies of revolution (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A complete Newtonian flow theory is presented for unsteady flow past oscillating bodies of revolution of general shape at very high Mach numbers, consideration being given to a centrifugal force correction to the impact pressures. Expressions are obtained for the unsteady pressure and the stability derivatives are presented in closed form. It is stressed that the correction for the centrifugal force, which arises because of the curved trajectories that fluid particles follow along the surface subsequent to their impact, must not be neglected. If the correction is included, the theory is shown to be in excellent agreement with experimental results for relatively sharp cones. Theoretical results are in poor agreement with experimental results in air for bodies having moderate or large-nose bluntness.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Oct. 198
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  • 40
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    Torque characteristics of a 122-centimeter butterfly valve with a hydro/pneumatic actuator (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Actuating torque data from field testing of a 122-centimeter (48 in.) butterfly valve with a hydro/pneumatic actuator is presented. The hydraulic cylinder functions as either a forward or a reverse brake. Its resistance torque increases when the valve speeds up and decreases when the valve slows down. A reduction of flow resistance in the hydraulic flow path from one end of the hydraulic cylinder to the other will effectively reduce the hydraulic resistance torque and hence increase the actuating torque. The sum of hydrodynamic and friction torques (combined resistance torque) of a butterfly valve is a function of valve opening time. An increase in the pneumatic actuating pressure will result in a decrease in both the combined resistance torque and the actuator opening torque; however, it does shorten the valve opening time. As the pneumatic pressure increases, the valve opening time for a given configuration approaches an asymptotical value.
    Keywords: MECHANICAL ENGINEERING
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  • 41
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    Hostile environmental conditions facing candidate alloys for the automotive Stirling engine (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The materials research program in support of the Automotive Stirling Engine Project focuses on the hot heater head of the engine including the heater head tubes, cylinders, and regenerator housings, which are considered to be the most critical components from a materials viewpoint. The specific areas of investigation in the program involve hydrogen permeability testing, doping of the hydrogen working fluid to reduce permeability rates, oxidation/corrosion studies, creep-rupture evaluation, and assessing effects of hydrogen environment on mechanical properties. Emphasis is placed on the materials challenges that result from the use of hydrogen as the working fluid. Previously announced in STAR as N81-26236
    Keywords: MECHANICAL ENGINEERING
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  • 42
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    Top-mounted inlet system feasibility for transonic-subsonic fighter aircraft applications (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: To inlet flow field and engine inlet performance data for an advanced fighter aircraft configuration were obtained over the Mach 0.6 to 2.0 range. The studies not only provided extensive data for the baseline arrangement, but also evaluated the effects of key aircraft configuration variables (inlet location, canopy-dorsal integration, wing leading-edge extension planform area, and variable incidence canards) on top inlet performance. In order to set these data in the context of practical aircraft systems top inlet performance is compared with that of more conventional inlet/airframe integrations. The results of these evaluations show that, for the top inlet configuration tested, relatively good inlet performance and compatibility characteristics are maintained during subsonic and transonic maneuver. However, at supersonic speeds, flow expansion over the forebody and wings causes an increase in local inlet Mach number subsequently reduces inlet performance levels. These characteristics infer that although top inlets many not pose a viable design option for aircraft requiring a high degree of supersonic maneuverability, they have distinct promise for vehicles with subsonic and transonic maneuver capabilities.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Power Plant Installation; 17 p
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  • 43
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    Impact of high-alpha aerodynamics on dynamic stability parameters of aircraft and missiles (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The aerodynamic phenomena associated with high angles of attack and their effects on the dynamic stability characteristics of airplane and missile configurations are examined. Information on dynamic effects is limited. Steady flow phenomena and their effects on the forces and moments are reviewed. The effects of asymmetric vortices and of vortex bursting on the dynamic response of flight vehicles are reviewed with respect to their influence on: (1) nonlinearity of aerodynamic coefficients with attitude, rates, and accelerations; (2) cross coupling between longitudinal and lateral directional models of motion; (3) time dependence and hysteresis effects; (4) configuration dependencey; and (5) mathematical modeling of the aerodynamics.
    Keywords: AERODYNAMICS
    Type: AGARD Dyn. Stability Parameters; 18 p
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  • 44
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    An assessment of theoretical models for viscous and transonic flow (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Topics discussed include shear flow models, simplified models for treating separation, classical linear theory, a local linearization theory, a transonic linear theory, a transonic nonlinear theory, the experiment of Davis, and the experiment of Tijdeman. It is concluded that shear flow models, which have proven very accurate in taking into account boundary layer effects for panel flutter, are likely to be less so for lifting surface flutter. For many applications in transonic flow, transonic linear theory will be adequate.
    Keywords: AERODYNAMICS
    Type: AGARD Boundary Layer Effects on Unsteady Airloads; 28 p
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  • 45
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    Experimental studies of scale effects on oscillating airfoils at transonic speeds (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Scale effects are discussed with reference to a conventional airfoil (NACA 64A010) and a supercritical airfoil (NLR 7301) at mean flow conditions that support both weak and strong shock waves. During the experiment the Reynolds number was varied from 3 x 10 to the sixth power at time history data are presented over the range of reduced frequencies that are important in aeroelastic applications. The experimental data show that viscous effects are important in the case of the supercritical airfoil at all flow conditions and in the case of the conventional airfoil under strong shock wave conditions. Some frequency dependent viscous effects were also observed.
    Keywords: AERODYNAMICS
    Type: AGARD Boundary Layer Effects on Unsteady Airfoils; 13 p
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  • 46
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    Natural laminar flow data from full-scale flight and wind-tunnel experiments (1981)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: Experimental results obtained at NASA Langley during studies of natural laminar flow (NLF) over commercially produced aircraft surfaces are reported. The general aviation aircraft examined were light aircraft, yet displayed NLF extents close to the maximum available and equivalent to high performance business aircraft flying envelopes. Sublimating chemicals and acoustic detection techniques were employed to measure the boundary layer transition. Theoretical predictions of boundary layer stability were found to match well with the experimental data, with consideration given to both swept wings and the amplitudes of allowable waves on the airfoil surfaces. The presence of the NLF on the airfoil surfaces confirmed the benefits available from use of composite materials for airfoil surfaces.
    Keywords: AERODYNAMICS
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  • 47
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    Natural Laminar Flow Flight Experiment (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A supercritical airfoil section was designed with favorable pressure gradients on both the upper and lower surfaces. Wind tunnel tests were conducted in the Langley 8 Foot Transonic Pressure Tunnel. The outer wing panels of the F-111 TACT airplane were modified to incorporate partial span test gloves having the natural laminar, flow profile. Instrumentation was installed to provide surface pressure data as well as to determine transition location and boundary layer characteristics. The flight experiment encompassed 19 flights conducted with and without transition fixed at several locations for wing leading edge sweep angles which varied from 10 to 26 at Mach numbers from 0.80 to 0.85 and altitudes of 7620 meters and 9144 meters. Preliminary results indicate that a large portion of the test chord experienced laminar flow.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center Advan. Aerodyn. and Active Controls; p 135-144
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  • 48
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    Aerodynamic drag reduction tests on a box-shaped vehicle (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The intent of the present experiment is to define a near optimum value of drag coefficient for a high volume type of vehicle through the use of a boattail, on a vehicle already having rounded front corners and an underbody seal, or fairing. The results of these tests will constitute a baseline for later follow-on studies to evaluate candidate methods of obtaining afterbody drag coefficients approaching the boattail values, but without resorting to such impractical afterbody extensions. The current modifications to the box-shaped vehicle consisted of a full and truncated boattail in conjunction with the faired and sealed underbody. Drag results from these configurations are compared with corresponding wind tunnel results of a 1/10 scale model. Test velocities ranged up to 96.6 km/h (60 mph) and the corresponding Reynolds numbers ranged up to 1.3 x 10 to the 7th power based on the vehicles length which includes the boattail. A simple coast-down technique was used to define drag.
    Keywords: AERODYNAMICS
    Type: NASA-CR-176982 , NAS 1.26:176982
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  • 49
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    Design aspects of a solar array drive for spot, with a high platform stability objective (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A solar array drive mechanism (MEGS) for the SPOT platform, which is a prototype of a multimission platform, is described. High-resolution cameras and other optical instruments are carried by the platform, requiring excellent platform stability in order to obtain high-quality pictures. Therefore, a severe requirement for the MEGS is the low level of disturbing torques it may generate considering the 0.6 times 10 to the minus 3 power deg/sec stability required. The mechanical design aspects aiming at reducing the mean friction torque, and therefore its fluctuations, are described as well as the method of compensation of the motor imperfections. It was concluded, however, that this is not sufficient to reach the stability requirement.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Kennedy Space Center The 16th Aerospace Mech. Symp.; p 143-157
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  • 50
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    Why use case studies rather than simulation-gaming techniques or library research? (1981)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: Method which present a student with a more challenging and true to life situation of needing to conduct research in a problem solving context--and not thinking about organization of format until research and thinking are complete are investigated. Simulation-gaming techniques which attempt to teach initiative and creativity that library research are used for this purpose. However, it is shown case studies provide the greatest opportunities to engage the students in problem solving situations in which they develop skills as researchers and writers.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center Tech. Commun., Pt. 1; p 99-103
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  • 51
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    The phenomenon of dynamic stall (1981)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Dynamic stall and its consequences which are important to aircraft design and operation are discussed. A certain degree of unsteadyness always accompanies the flow over streamlined bodies at high angle of attack, however, the stall of lifting surface undergoing unsteady motion is more complex than static stall. Dynamic stall remains a major unsolved problem with a variety of applications in aeronautics, hydrodynamics and wind engineering.
    Keywords: AERODYNAMICS
    Type: Von Karman Inst. for Fluid Dynamics Unsteady Airloads and Aeroelastic Probl. in Separated and Transonic Flow; 28 p
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  • 52
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    Prediction of blade vortex interaction noise from measured blade pressure (1981)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The impulsive nature of noise due to the interaction of a rotor blade with a tip vortex is studied. The time signature of this noise is calculated theoretically based on the measured blade surface pressure fluctuation of an operational load survey rotor in slow descending flight and is compared with the simultaneous microphone measurement. Particularly, the physical understanding of the characteristic features of a waveform is extensively studied in order to understand the generating mechanism and to identify the important parameters. The interaction trajectory of a tip vortex on an acoustic planform is shown to be a very important parameter for the impulsive shape of the noise. The unsteady nature of the pressure distribution at the very leading edge is also important to the pulse shape. The theoretical model using noncompact linear acoustics predicts the general shape of interaction impulse pretty well except for peak amplitude which requires more continuous pressure information along the span at the leading edge.
    Keywords: AERODYNAMICS
    Type: DGLR Seventh European Rotorcraft and Powered Lift Aircraft Forum; 20 p
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  • 53
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    Two-dimensional aerodynamic characteristics of an airfoil designed for two (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An airfoil designed for helicopter rotor application is investigated. The airfoil is designed to increase maximum normal force coefficient while maintaining favorable drag divergence and pitching moment characteristics. Two modifications are also tested. Maximum normal force coefficient varies from 1.14 to 0.90 at Mach numbers from about 0.35 to 0.65. Both modifications decreased drag coefficient at zero normal force coefficient for Mach numbers near drag divergence, but were less beneficial at a normal force coefficient of -0.2.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1965 , L-14825 , NAS 1.60:1965 , AVRADCOM-TR-81-B-6
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  • 54
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    Selected advanced aerodynamic and active control concepts development (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A task for the Energy Efficient Transport program conducted: (1) The design and wind tunnel development of high-aspect-ratio supercritical wings, investigating the cruise speed regime and also high-lift. (2) The preliminary design and evaluation of an aircraft combining a high-aspect-ratio supercritical wing with a winglet. (3) Active Controls: The determination of criteria, configuration, and flying qualities associated with augmented longitudinal stability of a level likely to be acceptable for the next generation transport; and the design of a practical augmentation system. The baseline against which the work was performed and evaluated was the Douglas DC-X-200 twin engine derivative of the DC-10 transport. The supercritical wing development showed that the cruise and buffet requirements could be achieved and that the wing could be designed to realize a sizable advantage over today's technology. Important advances in high lift performance were shown. The design study of an aircraft with supercritical wing and winglet suggested advantages in weight and fuel economy could be realized. The study of augmented stability, conducted with the aid of a motion base simulator, concluded that a negative static margin was acceptable for the baseline unaugmented aircraft.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3469 , NAS 1.26:3469
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  • 55
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    Subsonic and transonic pressure measurements on a high-aspect-ratio supercritical-wing model with oscillating control surfaces (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Data from the present test (this is the second in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60 and 0.78 and are presented in tabular form.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83201 , L-14831 , NAS 1.15:83201
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  • 56
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    An extended model for determining dynamic loads in spur gearing (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In this study a large scale digitized approach is used for an uninterrupted static and dynamic analysis of spur gearing. An interactive method was developed to calculate directly the variable gear mesh stiffness as a function of transmitted load, gear profile errors, gear tooth deflections and gear hub torsional deformation, and position of contacting profile points. The developed methods are applicable to both the normal and high contact ratio gearing. Certain types of simulated sinusoidal profile errors and pitting can cause interruptions of the normal gear mesh stiffness function and, thus, increase the dynamic loads in gearing.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 80-C2/DET-90
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  • 57
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    Low thermal conductance rigidizer for reducing torsional oscillations in cryogenic Dewars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A rigidizer, which provides greater rigidity against torsional oscillations, is highly resistant to radial motions, and has low thermal conductivity, has been developed to decrease vibrational levels affecting infrared detectors operated in cryostats (e.g., HD-3L Dewar) in aircraft such as NASA's Kuiper Airborne Observatory. The rigidizer is composed of two triangular elements and an intermediate support structure which joins them at the centers of their sides. The reentrant design provides a long heat path, while the triangular truss structure provides high rigidity in the horizontal plane. The structure is relatively compliant in the vertical direction, a desirable feature since the internal structure of the Dewar contracts as it cools. Rigidity in the vertical direction is provided by the neck tube. The support structure is quite compact. Several variants of the rigidizer have been fabricated, using flat sheets of G-10 fiberglass epoxy in thicknesses between 0.75-1.5 mm for the upper and lower truss assemblies, and either G-10 or stainless steel for the intermediate structure.
    Keywords: MECHANICAL ENGINEERING
    Type: Review of Scientific Instruments; 52; Mar. 198
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  • 58
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    Unpowered Aerodynamic Characteristics of a 15-Percent Scale Model of a Twin-Engine Commuter Aircraft (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the Ames 12-Foot Pressure Wind Tunnel to determine the unpowered aerodynamic characteristics of a 15-percent-scale model of a twin-engine commuter aircraft. Model longitudinal aerodynamic characteristics were examined at discrete flap deflections for various angle-of-attack and wind-tunnel-velocity ranges with the empennage on and off. Data are presented for the basic model configuration consisting of the fuselage, wing, basic wing leading edge, double slotted flaps, midengine nacelles, and empennage. Other configurations tested include a particle-span drooped leading edge (dropped outboard of the engine nacelles), a full-span drooped leading edge, low- and high-mounted engine nacelles, and a single-slotted flap. An evaluation was made of the model mounting system by comparing data obtained with the model mounted conventionally on the wind-tunnel model-support struts and the model inverted.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81284 , A-8552
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  • 59
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    The influence of unsteady aerodynamics on hingeless rotor ground resonance (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Calculations of the model frequency and damping for a hingeless rotor on a gimballed support in hover are compared with measured results for two configurations (differing in blade flap stiffness). Good correlation is obtaned when an inflow dynamics model is used to account for the influence of the unsteady aerodynamics. The effect of the unsteady aerodynamics is significant for this rotor system. The inflow dynamics model introduces additional states corresponding to perturbations of the wake-induced velocity at the rotor disk. The calculations confirm the experimental observation that the inflow mode introduced by these additional states is measurable for one configuration but not for the other.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81302 , A-8635 , USAAVRADCOM-TR-81-B-16
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  • 60
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    Cold-air performance of compressor-drive turbine of Department of Energy upgraded automobile gas turbine engine. 1: Volute-manifold and stator performance (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The aerodynamic performance of the inlet manifold and stator assembly of the compressor drive turbine was experimentally determined with cold air as the working fluid. The investigation included measurements of mass flow and stator-exit fluid torque as well as radial surveys of total pressure and flow angle at the stator inlet and annulus surveys of total pressure and flow angle at the stator exit. The stator-exit aftermixed flow conditions and overall stator efficiency were obtained and compared with their design values and the experimental results from three other stators. In addition, an analysis was made to determine the constituent aerodynamic losses that made up the stator kinetic energy loss.
    Keywords: AERODYNAMICS
    Type: NASA-TM-82682 , DOE/NASA/1011-34 , E-572 , AVRADCOM-TR-80-C-20
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  • 61
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    Terminal guidance sensor system (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A system is described for guiding a claw to the proper distance and into the proper orientation in yaw and pitch, to engage a grappling fixture. The system includes four proximity sensors on the claw, that are arranged at corners of an imaginary square, which sense the distance to the top surface of the grappling fixture. If a pair of sensors at opposite corners of the square sense a different distance to the top surface of the grappling fixture, then it is known that the claw is rotated about a corresponding axis with respect to the plane of the grappling fixture.
    Keywords: MECHANICAL ENGINEERING
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  • 62
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    An experimental investigation of the aerodynamics and cooling of a horizontally-opposed air-cooled aircraft engine installation (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A flight-test based research program was performed to investigate the aerodynamics and cooling of a horizontally-opposed engine installation. Specific areas investigated were the internal aerodynamics and cooling mechanics of the installation, inlet aerodynamics, and exit aerodynamics. The applicable theory and current state of the art are discussed for each area. Flight-test and ground-test techniques for the development of the cooling installation and the solution of cooling problems are presented. The results show that much of the internal aerodynamics and cooling technology developed for radial engines are applicable to horizontally opposed engines. Correlation is established between engine manufacturer's cooling design data and flight measurements of the particular installation. Also, a flight-test method for the development of cooling requirements in terms of easily measurable parameters is presented. The impact of inlet and exit design on cooling and cooling drag is shown to be of major significance.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3405
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    An experimental and analytical investigation of the aerodynamics of a hypersonic vehicle at free stream Mach 6 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The goal of this research is the assessment of the validity of existing three dimensional numerical programs in the prediction of the flow fields about general three dimensional hypersonic bodies. A detailed experimental research program was performed in which surface and flow field pressures were mapped. The results of the experimental work were compared with existing inviscid programs. Improvements were made on the existing numerical methods to include angle of attack. A summary of this work is presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-164133
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  • 64
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    Aerodynamic preliminary analysis system 2. Part 2: User's manuals (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An aerodynamic analysis system based on potential theory at subsonic/supersonic speeds and impact type finite element solutions at hypersonic conditions is described. Three dimensional configurations having multiple nonplanar surfaces of arbitrary planform and bodies of noncircular contour may be analyzed. Static, rotary, and control longitudinal and lateral directional chracteristics may be generated. The analysis has been implemented on a time sharing system in conjunction with an input tablet digitizer and an interactive graphics input/output display and editing terminal to maximize its responsiveness to the preliminary analysis problem. Typical simulation indicates that program provides an efficient analysis for systematically performing various aerodynamic configuration tradeoff and evaluation studies.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165628 , NA-80-374-PT-2
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  • 65
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    Aerodynamic prediction techniques for hypersonic configuration design (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation of approximate theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at moderate hypersonic speeds was performed. Emphasis was placed on approaches that would be responsive to preliminary configuration design level of effort. Potential theory was examined in detail to meet this objective. Numerical pilot codes were developed for relatively simple three dimensional geometries to evaluate the capability of the approximate equations of motion considered. Results from the computations indicate good agreement with higher order solutions and experimental results for a variety of wing, body, and wing-body shapes for values of the hypersonic similarity parameter M delta approaching one.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165651 , NA-80-611
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  • 66
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    The phenomenon of dynamic stall (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The general features of dynamic stall on oscillating airfoils are explained in terms of the vortex shedding phenomenon, and the important differences between static stall, light dynamic stall, and deep stall are described. An overview of experimentation and prediction techniques is given.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81264 , A-8464
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  • 67
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    Method of cold welding using ion beam technology (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A method for cold welding metal joints is described. In order to remove the contamination layer on the surface of the metal, an ion beam generator is used in a vacuum environment. A gas, such as xenon or argon, is ionized and accelerated toward the metal surface. The beam of gas effectively sputters away the surface oxides and contamination layer so that clean underlying metal is exposed in the area to be welded. The use of this method allows cold welding with minimal deformation. Both similar and dissimilar metals can be cold welded with this method.
    Keywords: MECHANICAL ENGINEERING
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  • 68
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    Performance of jet- and inner-ring-lubricated 35 millimeter bore ball bearings operating to 2.5 million DN (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Parametric tests were conducted with a 35 millimeter bore, angular contact ball bearing having a single outer land guided cage. Lubrication was achieved by flowing oil through axial grooves and radial holes machined in the inner ring of the bearing. Test conditions were a thrust load of 667 N (150 lb), shaft speeds from 48,000 to 72,000 rpm, and an oil inlet temperature of 394 K (250 F). Data from tests where the distribution of the total oil supplied to the inner ring was 50 percent for bearing lubrication and 50 percent for bearing inner ring cooling were compared with those where the distribution pattern was 25 percent lubrication and 75 percent cooling. Successful operation was experienced with both the 50-50 and 25-75 percent flow distribution patterns to 2.5 million DN. The 50-50 percent flow pattern provided the cooler bearing operation of the two inner ring lubricated bearings. The jet lubricated bearing had lower outer ring and higher inner ring temperatures than the inner ring lubricated bearings. Maximum power loss of 2.8 kW (3.7 hp) was experienced with the 25-75 percent flow distribution, and maximum percent cage slip of 7.0 occurred at 72,300 rpm with the 50-50 percent flow distribution.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-1808 , E-515
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  • 69
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    Aeropropulsive characteristics of twin nonaxisymmetric vectoring nozzles installed with forward-swept and aft-swept wings (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation was conducted in the Langley 16 Foot Transonic Tunnel to determine the aeropropulsive characteristics of a single expansion ramp nozzle (SERN) and a two dimensional convergent divergent nozzle (2-D C-D) installed with both an aft swept and a forward swept wing. The SERN was tested in both an upright and an inverted position. The effects of thrust vectoring at nozzle vector angles from -5 deg to 20 deg were studied. This investigation was conducted at Mach numbers from 0.40 to 1.20 and angles of attack from -2.0 deg to 16 deg. Nozzle pressure ratio was varied from 1.0 (jet off) to about 9.0. Reynolds number based on the wing mean geometric chord varied from about 3 million to 4.8 million, depending upon free stream number.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1778 , L-13902
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  • 70
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    Transient dynamic analysis of high-speed lightly loaded cylindrical roller bearings. 2: Computer program and results (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The governing differential equations of motion for a high speed cylindrical roller bearing are programmed for numerical solution and plotted output. This computer program has the capability of performing a two dimensional or three dimensional simulation. Two numerical solutions of the governing differential equations were obtained to simulate the motion of a roller bearing, one for the two dimensional equations of motion and one for the three dimensional equations of motion. Computer generated plots were obtained and present such data as roller/cage interaction forces, roller/race traction forces, roller/race relative slip velocities and cage angular speed over a nondimensional time equivalent to 1.2 revolutions of the inner race. Roller axial displacement, roller skew angle, and skew moment are also plotted for the three dimensional solution. The trajectory of the cage center is plotted for both the two dimensional and three dimensional solutions.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-3335
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  • 71
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    History of ball bearings (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The familiar precision rolling-element bearings of the twentieth century are products of exacting technology and sophisticated science. Their very effectiveness and basic simplicity of form may discourage further interest in their history and development. Yet the full story covers a large portion of recorded history and surprising evidence of an early recognition of the advantages of rolling motion over sliding action and progress toward the development of rolling-element bearings. The development of rolling-element bearings is followed from the earliest civilizations to the end of the eighteenth century. The influence of general technological developments, particularly those concerned with the movement of large building blocks, road transportation, instruments, water-raising equipment, and windmills are discussed, together with the emergence of studies of the nature of rolling friction and the impact of economic factors. By 1800 the essential features of ball and rolling-element bearings had emerged and it only remained for precision manufacture and mass production to confirm the value of these fascinating machine elements.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-81689 , E-209
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  • 72
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    Experimental investigation of vortices shed by various wing fin configurations (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Forty-six different fins, which were members of twelve plan-form families, were tested. A two dimensional Boeing single element airfoil at an angle of attack of eight degrees and a sweepback angle of thirty-two was used to simulate a portion of the wing of a generator aircraft. Various free stream velocities were used to test any individual fin at its particular angle of attack. While the fin itself was mounted on the upper surface of the generator model, the angle of attack of each fin was varied until stall was reached and/or passed. The relative fin vortex strengths were measured in two ways. First, the maximum angular velocity of a four blade rotor placed in the fin vortex center was measured with the use of a stroboscope. Second, the maximum rolling moment on a following wing model placed in the fin vortex center was measured by a force balance.
    Keywords: AERODYNAMICS
    Type: NASA-CR-163874 , ISU-ERI-AMES-81112
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  • 73
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    Steady and nonsteady supersonic turbulent afterbody flow (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of the specific heat ratio gamma of the incoming ideal gas on the flow properties, especially on pressure distributions along the base and sting surfaces and on reattachment distance, was investigated. The specific heat ratios considered were gamma = 1.2, 1.4, and 1.667. Also, effects of other major parameters, such as eddy-viscosity coefficient (or effective Reynolds number) and Mach number, on the afterbody pressure and reattachment distance were studied and are discussed. Evolution of shock induced flow and stabilization time were examined and are discussed for a transient problem. The important influence of the flow-field geometry, pressure distributions, and reattachment distance on the aerodynamics radiative heat transfer for an atmosphere entry probe in high speed flight are briefly described.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1769 , A-8271
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  • 74
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    Prediction of laminar and turbulent primary and secondary flows in strongly curved ducts (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The analysis is based on a primary secondary velocity decomposition in a given coordinate system, and leads to approximate governing equations which correct an a priori inviscid solution for viscous effects, secondary flows, total pressure distortion, heat transfer, and internal flow blockage and losses. Solution of the correction equations is accomplished as an initial value problem in space using an implicit forward marching technique. The overall solution procedure requires significantly less computational effort than Navier-Stokes algorithms. The solution procedure is effective even with the extreme local mesh resolution which is necessary to solve near wall sublayer regions in turbulent flow calculations. Computed solutions for both laminar and turbulent flow compared very favorably with available analytical and experimental results. The overall method appears very promising as an economical procedure for making detailed predictions of viscous primary and secondary flows in highly curved passages.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3388 , R80-900007-12
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  • 75
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    A new solution-adaptive grid generation method for transonic airfoil flow calculations (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The clustering algorithm is controlled by a second-order, ordinary differential equation which uses the airfoil surface density gradient as a forcing function. The solution to this differential equation produces a surface grid distribution which is automatically clustered in regions with large gradients. The interior grid points are established from this surface distribution by using an interpolation scheme which is fast and retains the desirable properties of the original grid generated from the standard elliptic equation approach.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81330 , A-8733
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  • 76
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    Effect of leading-edge vortex flaps on aerodynamic performance of delta wings (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effect of leading-edge vortex flaps on the aerodynamic characteristics of highly swept-back wings is analytically investigated, using the free vortex sheet method. The method, based on a three-dimensional inviscid flow model, is an advanced panel type employing quadratic doublet distributions to represent the wing surface, rolled-up vortex sheet and wake and is capable of computing forces, moments and surface pressures.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Sept
    Format: text
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  • 77
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    Instability and transition in rotating disk flow (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The stability of three-dimensional rotating disk flow is investigated, including the effects of Coriolis forces and streamline curvature. The numerical results show that the critical Reynolds number for establishment of stationary vortex flow is 287. These vortices spiral outward at an angle of about 11.2 deg, and transition to turbulence occurs when their total amplification is about e to the 11th. New experimental results are also reported on the spatial growth rates of the stationary vortices. It is shown that the analysis gives growth rates that compare much better with the experimental results than do results obtained using the Orr-Sommerfeld equation. The experimental results tend to support the numerical prediction that the number of stationary vortices varies directly with the Reynolds number. The calculations also indicate the existence of weakly unstable propagating (type II) modes at low Reynolds numbers (Critical Reynolds Number being approximately equal to 49).
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Sept
    Format: text
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  • 78
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    Effect of sweep angles on aerodynamic performance of double arrow wing - An analytical study (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Hybrid wing planforms are studied for adoption on supersonic transport and fighter aircraft. The free vortex sheet method is used to determine effects of the leading-edge sweep angles on the aerodynamic performance of a double arrow wing with a strake. Results show lift and drag increase with the increase of the inboard and outboard leading-edge sweep angles. However, the lift-to-drag ratio is little influenced by the changes in these sweep angles. Spanwise surface pressure distributions on the aft region are influenced by the inboard sweep angle while the outboard sweep angle has no effect on these pressures. Finally, the experimental data and predicted results are compared to show good agreement.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Aug. 198
    Format: text
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  • 79
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    Stability and control characteristics of a three-surface advanced fighter configuration at angles of attack up to 45 deg (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The tests were conducted at Mach numbers from 0.40 to 0.90, at angles of attack up to 45 deg for the lower Mach numbers, and at angles of sideslip up to 15 deg. The model variations under study included adding a canard surface and deflecting horizontal tails, ailerons, and rudders.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83171 , L-14433
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  • 80
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    Reciprocating engines (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An intake valve arrangement for positively controlling the opening and closing of the poppet valve in a hot gas cylinder in a hydrazine powered engine is described. The poppet valve is operated by the piston and gas pressure only. The poppet valve uses a pneumatic spring which holds the poppet valve against the piston while the valve is opened and closed. To accomplish this, a poppet valve is slidably mounted in a pneumatic spring chamber which reaches a pressure approaching the gas supply pressure and, during the opening of the valve, the spring chamber retains enough pressure to hold the poppet valve onto the piston. In addition, the bottom of the poppet valve can have a suction cup type configuration to hold the poppet valve on the piston during the down stroke.
    Keywords: MECHANICAL ENGINEERING
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  • 81
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    Development of an unsteady aerodynamic analysis for finite-deflection subsonic cascades (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An unsteady potential flow analysis, which accounts for the effects of blade geometry and steady turning, was developed to predict aerodynamic forces and moments associated with free vibration or flutter phenomena in the fan, compressor, or turbine stages of modern jet engines. Based on the assumption of small amplitude blade motions, the unsteady flow is governed by linear equations with variable coefficients which depend on the underlying steady low. These equations were approximated using difference expressions determined from an implicit least squares development and applicable on arbitrary grids. The resulting linear system of algebraic equations is block tridiagonal, which permits an efficient, direct (i.e., noniterative) solution. The solution procedure was extended to treat blades with rounded or blunt edges at incidence relative to the inlet flow.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3455 , R81-914777-7
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  • 82
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    Effect of sweep and aspect ratio on the longitudinal aerodynamics of a spanloader wing in and out of ground effect (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A wind tunnel investigation was conducted in the Langley 4 by 7 meter tunnel to determine the effects of leading edge sweep, aspect ratio, flap deflection, and elevon deflection on the longitudinal aerodynamic characteristics of a span distributed load advanced cargo aircraft (spanloader). Model configurations consisted of leading edge sweeps of 0, 15, 30 and 45 deg and aspect ratios of approximately 2, 4, 6, and 8. Data were obtained for angles of attack of -8 to 18 deg out of ground effect and at angles of attack of -2, 0, and 2 deg in ground effect at Mach number equal 0.14. Flap and elevon deflections ranged from -20 to 20 deg. The data are represented in tabulated form.
    Keywords: AERODYNAMICS
    Type: NASA-TM-80199
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  • 83
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    Historical background and design evolution of the transonic aircraft technology supercritical wing (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two dimensional wind tunnel test results obtained for supercritical airfoils indicated that substantial improvements in aircraft performance at high subsonic speeds could be achieved by shaping the airfoil to improve the supercritical flow above the upper surface. Significant increases in the drag divergence Mach number, the maximum lift coefficient for buffer onset, and the Mach number for buffet onset at a given lift coefficient were demonstrated for the supercritical airfoil, as compared with a NACA 6 series airfoil of comparable thickness. These trends were corroborated by results from three dimensional wind tunnel and flight tests. Because these indicated extensions of the buffet boundaries could provide significant improvements in the maneuverability of a fighter airplane, an exploratory wind tunnel investigation was initiated which demonstrated that significant aerodynamic improvements could be achieved from the direct substitution of a supercritical airfoil on a variable wing sweep multimission airplane model.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81356 , H-1148
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  • 84
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    Surrogate-equation technique for simulation of steady inviscid flow (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A numerical procedure for the iterative solution of inviscid flow problems is described, and its utility for the calculation of steady subsonic and transonic flow fields is demonstrated. Application of the surrogate equation technique defined herein allows the formulation of stable, fully conservative, type dependent finite difference equations for use in obtaining numerical solutions to systems of first order partial differential equations, such as the steady state Euler equations. Steady, two dimensional solutions to the Euler equations for both subsonic, rotational flow and supersonic flow and to the small disturbance equations for transonic flow are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1866 , E-583
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  • 85
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    Development of the triplet singularity for the analysis of wings and bodies in supersonic flow (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A supersonic triplet singularity was developed which eliminates internal waves generated by panels having supersonic edges. The triplet is a linear combination of source and vortex distributions which gives directional properties to the perturbation flow field surrounding the panel. The theoretical development of the triplet singularity is described together with its application to the calculation of surface pressures on wings and bodies. Examples are presented comparing the results of the new method with other supersonic methods and with experimental data.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3466 , AMI-8104
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  • 86
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    GRID3O: Computer program for fast generation of multilevel, three-dimensional boundary-conforming O-type computational grids (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A fast algorithm was developed for accurately generating boundary-conforming, three-dimensional, consecutively refined computational grids applicable to arbitrary wing-body and axial turbomachinery geometries. The method is based on using an analytic function to generate two-dimensional grids on a number of coaxial axisymmetric surfaces positioned between the centerbody and the outer radial boundary. These grids are of the O-type and are characterized by quasi-orthogonality, geometric periodicity, and an adequate resolution throughout the flow field. Because the built-in nonorthogonal coordinate stretching and shearing cause the grid lines leaving the blade or wing trailing edge to end at downstream infinity, the numerical treatment of the three-dimensional trailing vortex sheets is simplified.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1920 , E-590
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  • 87
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    Preliminary results of buffet tests in a cryogenic wind tunnel (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Buffet tests of two wings with different leading-edge sweep show that it is feasible to use the standards wing root bending moment technique in a cryogenic wing tunnel. The results for the 65 deg sweep delta wing indicate the importance of matching the reduced frequency parameter in model tests for planforms which are sensitive to reduced frequency parameter if quantitative buffet measurements are required. The unique ability of a pressurized cryogenic wind tunnel to separate the effects of Reynolds number and of aeroelastic distortion by variations in the tunnel stagnation temperature and pressure was demonstrated.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81923
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  • 88
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    The 34-meter antenna drive control system (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Detailed definitions of the baseline antenna drive and control/instrumentation equipment for 34 meter antennas included in Network Consolidation Program of the Deep Space Network are presented. The overall antenna control and monitor system and its interfaces with other higher level control and monitor equipment is described. Explicit descriptions of the antenna axis drive motors and motor controllers, the axis angle encoding systems, and miscellaneous antenna located components are presented, and related to system functional and performance requirements. Some potential alternates to the baseline system configuration are described and discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-164683 , WDL-TR9153 , JPL-9950584
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  • 89
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    Wing-alone aerodynamic characteristics for high angles of attack of supersonic speeds (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experiment was conducted to determine wing-alone supersonic aerodynamic characteristics at high angles of attack. The wings tested varied in aspect ratio from 0.5 to 4.0 and in taper ratio from 0 to 1.0. The wings were tested at angles of attack ranging rom -5 deg to 60 deg and at Mach number from 1.60 to 4.60. The aerodynamic characteristics were obtained by integrating local pressures measured over the wing surfaces. Presented and discussed are results showing the effects of aspect ratio, taper ratio, Mach number, and angle of attack on force and moment coefficients and center of pressure locations. Also included are tabulations of the pressure measurements.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1889 , L-14546
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  • 90
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    Effect of simulated in-flight thrust reversing on vertical-tail loads of F-18 and F-15 airplane models (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Investigations were conducted in the Langley 16-Foot Transonic Tunnel to provide data on a 0.10-scale model of the prototype F-18 airplane and a 0.047-scale model of the F-15 three-surface configuration (canard, wing, and horizontal tails). Test data were obtained at static conditions and at Mach numbers from 0.6 to 1.2 over an angle-of-attack range from 2 deg to 15 deg. Nozzle pressure ratio was varied from jet off to about 8.0.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1890 , L-14531
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  • 91
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    Computer analysis of flow perturbations generated by placement of choke bumps in a wind tunnel (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An inviscid analytical study was conducted to determine the upstream flow perturbations caused by placing choke bumps in a wind tunnel. A computer program based on the stream-tube curvature method was used to calculate the resulting flow fields for a nominal free-stream Mach number range of 0.6 to 0.9. The choke bump geometry was also varied to investigate the effect of bump shape on the disturbance produced. Results from the study indicate that a region of significant variation from the free-stream conditions exists upstream of the throat of the tunnel. The extent of the disturbance region was, as a rule, dependent on Mach number and the geometry of the choke bump. In general, the upstream disturbance distance decreased for increasing nominal free-stream Mach number and for decreasing length-to-height ratio of the bump. A polynomial-curve choke bump usually produced less of a disturbance than did a circular-arc bump and going to an axisymmetric configuration (modeling choke bumps on all the tunnel walls) generally resulted in a lower disturbance than with the corresponding two dimensional case.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1892 , L-14415
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  • 92
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    Analysis of Mach number 0.8 turboprop slipstream wing/nacelle interactions (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Data from wind tunnel tests of a powered propeller and nacelle mounted on a supercritical wing are analyzed. Installation of the nacelle significantly affected the wing flow and the flow on the upper surface of the wing is separated near the leading edge under powered conditions. Comparisons of various theories with the data indicated that the Neumann surface panel solution and the Jameson transonic solution gave results adequate for design purposes. A modified wing design was developed (Mod 3) which reduces the wing upper surface pressure coefficients and section lift coefficients at powered conditions to levels below those of the original wing without nacelle or power. A contoured over the wing nacelle that can be installed on the original wing without any appreciable interference to the wing upper surface pressure is described.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166214 , ACEE-25-FR-1564
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 93
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    An investigation of engine influence on inlet performance (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The performance of a conventional engine/inlet installation, in which inlet and engine flow field interaction occurs, was compared to the performance of the same inlet remote coupled to the engine. The remote coupled inlet configuration decouples the influence of the engine on the inlet flow field and simulates current small scale inlet test techniques in which inlet airflow is provided by a vacuum source or coupled engine. The investigation was conducted in the NASA-Ames 40- by 80-foot wind tunnel using a General Electric TF-34 turbofan engine and a subsonic inlet having an average inlet contraction ratio of 1.26. Test results indicated that engine interaction allows the inlet to operate with lower distortion levels at and beyond the separation angle-of-attack experienced without engine interaction.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166136 , D6-49228
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 94
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    Experimental aerodynamic characteristics of two V/STOL fighter/attack aircraft configurations at Mach numbers from 1.6 to 2.0 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tests were conducted in the Ames 9 by 7 ft supersonic wind tunnel to measure the aerodynamic characteristics of two horizontal attitude takeoff and landing V/STOL fighter/attack aircraft concepts. One concept featured a jet diffuser ejector for its vertical lift system and the other employed a remote augmentation lift system (RALS). Test results for Mach numbers from 1.6 to 2.0 are reported. Effects of varying the angle of attack (-4 deg to +17 deg), angle of sideslip (-4 deg to +8 deg) Mach number, and configuration building were investigated. The effects of wing trailing edge flap deflections, canard incidence, and vertical tail deflections were also explored as well as the effects of varying the canard longitudinal location and shapes of the inboard nacelle body strakes.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81286 , A-8559
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 95
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    Comparisons of AEROX computer program predictions of lift and induced drag with flight test data (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The AEROX aerodynamic computer program which provides accurate predictions of induced drag and trim drag for the full angle of attack range and for Mach numbers from 0.4 to 3.0 is described. This capability is demonstrated comparing flight test data and AEROX predictions for 17 different tactical aircraft. Values of minimum (skin friction, pressure, and zero lift wave) drag coefficients and lift coefficient offset due to camber (when required) were input from the flight test data to produce total lift and drag curves. The comparisons of trimmed lift drag polars show excellent agreement between the AEROX predictions and the in flight measurements.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81237 , A-8344
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 96
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    Development of high-speed balancing technology (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation into laser material removal showed that laser burns act in a manner typical of mechanical stress raisers causing a reduction in fatigue strength; the fatigue strength is lowered relative to the smooth specimen fatigue strength. Laser-burn zones were studied for four materials: Alloy Steel 4340, Stainless Steel 17-4 PH, Inconel 718, and Aluminum Alloy 6061-T6. Calculations were made of stress concentration factors K, for laser-burn grooves of each material type. A comparison was then made to experimentally determine the fatigue strength reduction factor. These calculations and comparisons indicated that, except for the 17-4 PH material, good agreement (a ratio of close to 1.0) existed between Kt and Kf. The performance of the 17-4 PH material has been attributed to early crack initiation due to the lower fatigue resistance of the soft, unaged laser-affected zone. Also covered in this report is the development, implementation, and testing of an influence coefficient approach to balancing a long, slender shaft under applied-torque conditions. Excellent correlation existed between the analytically predicted results and those data obtained from testing.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-165314 , MTI-81TR8
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 97
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    Calculation of vortex lift effect for cambered wings by the suction analogy (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An improved version of Woodward's chord plane aerodynamic panel method for subsonic and supersonic flow is developed for cambered wings exhibiting edge separated vortex flow, including those with leading edge vortex flaps. The exact relation between leading edge thrust and suction force in potential flow is derived. Instead of assuming the rotated suction force to be normal to wing surface at the leading edge, new orientation for the rotated suction force is determined through consideration of the momentum principle. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semi-empirical method. Comparisons of predicted results with available data in subsonic and supersonic flow are presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3449 , CRINC/FRL-426-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 98
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    Aerodynamic tests and analysis of a turbojet-boosted launch vehicle concept (spacejet) over a Mach number range of 1.50 to 2.86 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results from analytical and experimental studies of the aerodynamic characteristics of a turbojet-boosted launch vehicle concept through a Mach number range of 1.50 to 2.86 are presented. The vehicle consists of a winged orbiter utilizing an area-ruled axisymmetric body and two winged turbojet boosters mounted underneath the orbiter wing. Drag characteristics near zero lift were of prime interest. Force measurements and flow visualization techniques were employed. Estimates from wave drag theory, supersonic lifting surface theory, and impact theory are compared with data and indicate the ability of these theories to adequately predict the aerodynamic characteristics of the vehicle. Despite the existence of multiple wings and bodies in close proximity to each other, no large scale effects of boundary layer separation on drag or lift could be discerned. Total drag levels were, however, sensitive to booster locations.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1888 , L-14509
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 99
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    Additional testing of the inlets designed for a tandem fan V/STOL nacelle (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The wind tunnel testing of a scale model of a tandem fan nacelle designed for a type (subsonic cruise) V/STOL aircraft configuration is discussed. The performance for the isolated front inlet and for the combined front and aft inlets is reported. Model variables include front and aft inlets with aft inlet variations of short and long aft inlet cowls, with a shaft simulator and diffuser vortex generators, cowl lip fillets, and nacelle strakes. Inlet pressure recovery, distortion, and inlet angle-to-attack separation limits were evaluated at tunnel velocity from 0 to 240 knots, angles-of-attack from -10 to +40 degrees and inlet flow rates corresponding to throat Mach number from 0.0 to 0.6. Combined nacelle pitch and yaw runs up to 30 deg. were also made.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165310 , TR-2-53020/IR-52726
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 100
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    A direct inverse technique for low speed high lift airfoil flowfield analysis (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A direct inverse method is presented for computing the flow about low speed airfoils under high lift massive separation conditions. On the lower surface the flowfield is determined using an iterative inviscid relaxation technique coupled to a laminar turbulent momentum integral boundary layer scheme direct boundary conditions. On the upper surface, the flowfield is also computed directly with viscous interaction up to the separation point, with the separation point and separated pressure level determined as part of the solution. Downstream of separation, inverse boundary conditions are utilized; and the flowfield and displacement surface are calculated. Typical results and comparisons with experimental data for GA(W)-2 and NACA 4412 airfoils are presented, including pressure distributions, lift, and drag coefficients versus angle of attack.
    Keywords: AERODYNAMICS
    Type: AGARD Computation of Viscous-Inviscid Interactions; 10 p
    Format: text
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    NASA TECHNICAL REPORTS
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