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  • AERODYNAMICS
  • 1970-1974  (1,256)
  • 1
    Publication Date: 2018-06-11
    Description: The rotor blade-vortex interaction problem and the resulting impulsive airloads which generate undesirable noise levels are discussed. A numerical lifting surface method to predict unsteady aerodynamic forces induced on a finite aspect ratio rectangular wing by a straight, free vortex placed at an arbitrary angle in a subsonic incompressible free stream is developed first. Using a rigid wake assumption, the wake vortices are assumed to move downsteam with the free steam velocity. Unsteady load distributions are obtained which compare favorably with the results of planar lifting surface theory. The vortex lattice method has been extended to a single bladed rotor operating at high advance ratios and encountering a free vortex from a fixed wing upstream of the rotor. The predicted unsteady load distributions on the model rotor blade are generally in agreement with the experimental results. This method has also been extended to full scale rotor flight cases in which vortex induced loads near the tip of a rotor blade were indicated. In both the model and the full scale rotor blade airload calculations a flat planar wake was assumed which is a good approximation at large advance ratios because the downwash is small in comparison to the free stream at large advance ratios. The large fluctuations in the measured airloads near the tip of the rotor blade on the advance side is predicted closely by the vortex lattice method.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2421
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  • 2
    Publication Date: 2013-08-31
    Description: A lifting airfoil theoretically designed for shockless supercritical flow utilizing a complex hodograph method has been evaluated in the Langley 8-foot transonic pressure tunnel at design and off-design conditions. The experimental results are presented and compared with those of an experimentally designed supercritical airfoil which were obtained in the same tunnel.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3082 , NAS 1.15:X-3082 , L-9548
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  • 3
    Publication Date: 2013-08-31
    Description: A general theory for indicial-potential-compressible aerodynamics around complex configurations is presented. The motion is assumed to consist of constant subsonic or supersonic speed (steady state) and small perturbations around the steady state. Using the finite-element method to discretize the space problem, a set of differential-difference equations in time relating the potential to its normal derivative on the surface of the body was obtained. The aerodynamics transfer function was derived by using standard method of operational calculus.
    Keywords: AERODYNAMICS
    Type: NASA-CR-142818 , TN-74-01
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  • 4
    Publication Date: 2013-08-31
    Description: A program plan for system evaluation of the two-dimensional Scanning Laser Doppler System (SLDS) is presented. In order to meet system evaluation and optimization objectives the following tests were conducted: (1) noise tests; (2) wind tests; (3) blower flowfield tests; (4) single unit (1-D) flyby tests; and (5) dual unit (2-D) flyby tests. Test results are reported. The final phase of the program included logistics preparation, equipment interface checkouts, and data processing. It is concluded that the SLDS is capable of accurately tracking aircraft wake vortices from small or large aircraft, and in any type of weather.
    Keywords: AERODYNAMICS
    Type: NASA-CR-120600 , LMSC-HREC-TR-D390470
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  • 5
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.
    Keywords: AERODYNAMICS
    Type: NASA-CR-137553 , ASRL-TR-174-2
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  • 6
    Publication Date: 2013-08-31
    Description: Wind tunnel experiments were conducted on four small-scale flow-direction vanes for the determination of aerodynamic response. The tests were further extended to include a standard sized low-inertia vane currently employed in aircraft flight testing. The four test vanes had different aspect ratios and were about 35 percent of the surface area of the standard vane. The test results indicate satisfactory damping and frequency response for all vanes tested and compare favorably with the standard design.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132545
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  • 7
    Publication Date: 2013-08-31
    Description: A numerical solution precedure of a simplified unsteady transonic equation which is fast, reasonably accurate, and takes into account many of the effects of the steady flow field is described. The numeric solution of this equation is accurate and is accomplished on an IBM 360/65 computer. Arbitrary planform shape is accommodated and variable local Mach number effects from the steady flow are easily handled.
    Keywords: AERODYNAMICS
    Type: NASA-CR-141114
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  • 8
    Publication Date: 2013-08-31
    Description: The model tested was a general research model of a swept-wing, jet-powered STOL transport with externally blown flaps. The model was tested with four engine simulators mounted on pylons under the wing. Tests were conducted in the V/STOL tunnel over an angle of attack range of 0 deg to 16 deg and a thrust coefficient range from 0 to approximately 4 at a Reynolds number of 0.461 x 1 million based on the wing reference chord. The results of this investigation are presented primarily as plots of the individual velocity vectors obtained from the wake survey. These data are used to extend an earlier analysis to isolate the effects of the engine thrust on the behavior of the flow at the flap trailing edge. Results of a comparison with a jet-flap theory are also shown.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3079 , L-9665
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  • 9
    Publication Date: 2013-08-31
    Description: The aerodynamic roll damping and the yawing moment due to roll rate for a model of a T-tail transport with aft-mounted engines were measured by means of a small-amplitude forced-oscillation mechanism. The tests were made for Mach numbers between 0.21 and 0.80 over a range of angles of attack from about minus 4 deg to 22 deg. The basic configuration had positive damping in roll at low angles of attack with regions of low positive and negative damping for angles of attack above 8 deg to 10 deg. There was good agreement between the theoretical estimates of the roll damping for the wing alone and the experimental results at an angle of attack of 0 deg for Mach numbers of 0.60 and less. The T-tail configuration and the engine nacelles mounted aft on the fuselage did not significantly affect either the damping in roll or the yawing moment due to roll rate.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3115 , L-9378
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  • 10
    Publication Date: 2013-08-31
    Description: Wing models were tested in the high-speed section of the Langley Unitary Plan wind tunnel to study the effects of the leading-edge sweep angle and the design lift coefficient on aerodynamic performance and efficiency. The models had leading-edge sweep angles of 69.44 deg, 72.65 deg, and 75.96 deg which correspond to values of the design Mach-number-sweep-angle parameter (beta cotangent A) sub DES of 0.6, 0.75, and 0.9, respectively. For each sweep angle, camber surfaces having design lift coefficients of 0,0.08, and 0.12 at a design Mach number of 2.6 were generated. The wind-tunnel tests were conducted at Mach numbers of 2.3, 2.6, and 2.96 with a stagnation temperature of 338.7 K (150 F) and a Reynolds number per meter of 9.843 times 10 to the 6th power. The results of the tests showed that only a moderate sweeping of the wing leading edge aft of the Mach line along with a small-to-moderate amount of camber and twist was needed to significantly improve the zero-lift (flat camber surface) wing performance and efficiency.
    Keywords: AERODYNAMICS
    Type: L-9446 , NASA-TN-D-7753
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  • 11
    Publication Date: 2013-08-31
    Description: A study was made of the effect of increasing the fan rotor-to-stator spacing on the noise level of a full-scale, single-stage, 1.6-pressure-ratio fan. Noise data were obtained with axial spacing of 1.14, 1.65, and 2.27 rotor chord lengths. Over this spacing range, data indicate a reduction of 1.5 PNdb. Apparently, rotor-alone noise at the frequency at which the rotor-stator interaction noise was cut off limited the noise reduction for the QF-5 fan. It seems, however, that the reduction in sound power level with increases in spacing is potentially about 6 db over the range of spacing tested.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3103 , E-7879
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  • 12
    Publication Date: 2013-08-31
    Description: An experimental investigation has been conducted to investigate the broadband noise generated by a rotating-blade system. Tests were made with circular and NACA 0012 rotor-blade sections. The blades were operated only with zero lift at each radial station. Tests were made both with zero axial velocity, so that the blades operated in their own turbulent wake, and with a small axial velocity imposed by the wind tunnel to blow the wake of one blade away before the passage of the next blade. The rotor with cylindrical blades generally radiated more noise throughout the noise spectrum than did the rotor with airfoil blades. Blowing the blade wake away from the rotor with cylindrical blades did not have any appreciable effect on the amplitude frequency spectrum, and the predominant noise was broadband, either with tunnel wind on or off. For the rotor with airfoil blades, however, blowing the blade wake away changed the character of the noise spectrum completely in that broadband noise was eliminated or diminished to such an extent as to be indistinguishable. The broadband noise of the airfoil-bladed rotor with zero axial velocity is apparently caused by lift fluctuations due to velocity components of the turbulence normal to the plane of rotation.
    Keywords: AERODYNAMICS
    Type: L-9349 , NASA-TN-D-7623
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  • 13
    Publication Date: 2013-08-31
    Description: Low-speed wind-tunnel tests were conducted to determine the two-dimensional aerodynamic characteristics of 6-, 12-, and 18-percent-thick airfoil sections with rounded trailing edges in both forward and reverse flow. The shapes incorporated camber with both the leading and trailing edges rounded to provide reasonable aerodynamic performance with either edge directed toward the free-stream flow. The tests were conducted with the airfoils in both normal and reverse orientations relative to the free stream. The Mach number was varied from 0.16 to 0.36 and the angle of attack was varied from minus 10 to 24 million. Reynolds number, based on the airfoil chord, was varied from about 1.0 to 12.0 million.
    Keywords: AERODYNAMICS
    Type: L-9327 , NASA-TM-X-3060
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  • 14
    Publication Date: 2013-08-31
    Description: A computer program has been developed to account approximately for the effects of finite wing thickness in the transonic potential flow over an oscillating wing of finite span. The program is based on the original sonic-box program of Rodemich and Andrew, and accounts for the nonuniform flow caused by finite thickness by application of the local linearization concept. A brief description of each subroutine is given, and the method of input is shown in detail. A sample problem as well as a complete listing of the computer program are presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132477
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  • 15
    Publication Date: 2013-08-31
    Description: Surface pressure and heat transfer, flow separation, flow field, and oil flow patterns on the leeward side of a space shuttle orbiter model are investigated at a free stream Mach number of 6. The free stream Reynolds numbers are between 1.64 times 10 to the 7th power and 1.31 times 10 to the 8th power per meter, and the angle of attack is varied between 0 deg and 40 deg for the present experiments. The stagnation temperatures for the tests are approximately 500 K and the wall temperature is maintained at 290 K. Existing numerical methods of three-dimensional inviscid supersonic flow theory and compressible boundary layer theory are used to predict the present experimental measurements. Results of the present tests indicate two distinct types of flow separation and surface peak heating depending on the angle of attack.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132501
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  • 16
    Publication Date: 2013-08-31
    Description: The application of a kernel function lifting surface method to three dimensional, thin wing theory is discussed. A technique for determining the influence functions is presented. The technique is shown to require fewer quadrature points, while still calculating the influence functions accurately enough to guarantee convergence with an increasing number of spanwise quadrature points. The method also treats control points on the wing leading and trailing edges. The report introduces and employs an aspect of the kernel function method which apparently has never been used before and which significantly enhances the efficiency of the kernel function approach.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-62327
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  • 17
    Publication Date: 2013-08-31
    Description: The boundary-layer transition on a short plate was studied by means of the china-clay visual technique. The plate model was mounted in a wind tunnel so that it was subjected to small simultaneous spanwise and chordwise pressure gradients. Results of the experimental study, which was performed at three subsonic velocities, indicated that the transition pattern was appreciably curved in the spanwise direction but quite smooth and well behaved. Reasonable comparisons between predictions of transition and experiment were obtained from two finite-difference two-dimensional boundary-layer calculation methods which incorporated transition models based on the concept of a transition intermittency factor.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3107 , E-7979
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  • 18
    Publication Date: 2013-08-31
    Description: A computer program was developed to produce the ordinates for airfoils of any thickness, thickness distribution, or camber in the NACA 6- and 6A-series. For the 6-series and for all but the leading edge of the 6A-series, agreement between the ordinates obtained from the new program and previously published values is generally within .00005 chord. Near the leading edge of the 6A-series airfoils, differences up to .00035 chord are found.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3069 , L-9558
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  • 19
    Publication Date: 2013-08-31
    Description: Investigations have been conducted in the Langley 8-foot transonic pressure tunnel and the Langley Unitary Plan wind tunnel at Mach numbers from 0.20 to 4.63 to determine the stability and control characteristics of a cruciform air-to-air missile with triangular canard controls and a trapezoidal wing. The results indicate that canards are effective in producing pitching moment throughout most of the test angle-of-attack and Mach number range and that the variations of pitching moment with lift for trim conditions are relatively linear. There is a decrease in canard effectiveness with an increase in angle of attack up to about Mach 2.50 as evidenced by the beginning of coalescence of the pitching-moment curves. At a Mach number above 2.50, there is an increase in effectiveness at moderate to high angles of attack. Simulated launch straps have little effect on the lift and pitch characteristics but do cause an increase in drag, and this increase in drag induces a rolling moment at a zero roll attitude where the straps cause an asymmetric geometric shape. The canards are not suitable devices for roll control and, at some Mach numbers and roll attitudes, are not effective in producing pure yawing moments.
    Keywords: AERODYNAMICS
    Type: L-9577 , NASA-TM-X-3070
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  • 20
    Publication Date: 2013-08-31
    Description: A wind-tunnel investigation was conducted in the Langley V/STOL tunnel and in a scaled version of the Ames 40- by 80-foot tunnel test section installed as a liner in the Langley V/STOL tunnel to determine the effect of test-section size on aerodynamic characteristics of the model. The model investigated was a swept-wing, jet-powered, externally blown flap (EBF) STOL transport configuration with a leading-edge slat and triple-slotted flaps. The model was an 0.1645-scale model of a 11.58-meter (38.0-ft) span model designed for tests in a 40- by 80-foot tunnel. The data compare the aerodynamic characteristics of the model with and without the tunnel liner installed. Data are presented as a function of thrust coefficient over an angle-of-attack range of 0 deg to 25 deg. A thrust-coefficient range up to approximately 4.0 was simulated, most ot the tests being conducted at a free-stream dynamic pressure of 814 Newtons/sq m (17 lb sq ft). The data are presented with a minimum of analysis.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3009
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  • 21
    Publication Date: 2013-08-31
    Description: Magnitudes of lags in the pneumatic angle-of-attack and angle-of-sideslip sensor systems of the YF-12A airplane were determined for a variety of flight conditions by analyzing stability and control data. The three analysis techniques used are described. An apparent trend with Mach number for measurements from both of the differential-pressure sensors showed that the lag ranged from approximately 0.15 second at subsonic speed to 0.4 second at Mach 3. Because Mach number was closely related to altitude for the available flight data, the individual effects of Mach number and altitude on the lag could not be separated clearly. However, the results indicated the influence of factors other than simple pneumatic lag.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-7819 , H-767
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  • 22
    Publication Date: 2013-08-31
    Description: An investigation of a four-engine externally blown flap (EBF) powered-lift transport was conducted in the Langley V/STOL tunnel to determine the effect of different engine configurations on the longitudinal aerodynamic characteristics. The different engine configurations were simulated by five different sets of propulsion simulators on a single aircraft model. Longitudinal aerodynamic data were obtained for each simulator on each flap deflection corresponding to cruise, take-off, and landing at a range of angles of attack and various thrust coefficients. The bypass ratio (BPR) 6.2 engine simulator provided the best lift and drag characteristics of the five simulators tested in the take-off and landing configurations. The poor performance of the BPR 10.0 and 3.2 engine simulators can be attributed to a mismatch of engine-model sizes or poor engine location and orientation. Isolated engine wake surveys indicated that a reasonable assessment of the aerodynamic characteristics of an engine-wing-flap configuration could be made if qualitative information were available which defined the engine wake characteristics. All configurations could be trimmed easily with relatively small horizontal-tail incidence angles; however, the take-off landing configurations required a high-lift tail.
    Keywords: AERODYNAMICS
    Type: L-9538 , NASA-TN-D-7670
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  • 23
    Publication Date: 2013-08-31
    Description: A method for determining the lift, drag, and pitching moment for wings which have separated flow at the leading and side edges with subsequently reattached flow downstream and inboard is presented. Limiting values of the contribution to lift of the side-edge reattached flow are determined for rectangular wings. The general behavior of this contribution is computed for rectangular, cropped-delta, cropped-diamond, and cropped-arrow wings. Comparisons of the results of the method and experiment indicate reasonably good correlation of the lift, drag, and pitching moment for a wide planform range. The agreement of the method with experiment was as good as, or better than, that obtained by other methods. The procedure is computerized and is available from COSMIC as NASA Langley computer program A0313.
    Keywords: AERODYNAMICS
    Type: L-9460 , NASA-TR-R-428
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  • 24
    Publication Date: 2013-08-31
    Description: Qualitative and quantitative spectral analyses are presented that give the broadband-noise, discrete-tone, and multiple-tone properties of the noise generated by a full-scale high-bypass single-stage axial-flow transonic fan (fan B, NASA Quiet Engine Program). The noise components were obtained from narrow-band spectra in conjunction with 1/3-octave-band spectra. Variations in the pressure levels of the noise components with fan speed, forward-quadrant azimuth angle, and frequency are presented and compared. The study shows that much of the apparent broadband noise on 1/3-octave-band plots consists of a complex system of shaft-order tones. The analyses also indicate the difficulties in determining or defining noise components, especially the broadband level under the discrete tones. The sources which may be associated with the noise components are discussed.
    Keywords: AERODYNAMICS
    Type: E-7989 , NASA-TN-D-7788
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  • 25
    Publication Date: 2013-08-31
    Description: Control laws were developed to investigate methods of alleviating the response of a STOL transport to gusty air. The transport considered in the study had triple-slotted, externally blown jet flaps and a large T-tail. The control devices used were the elevator, spoilers, and flaps. A hybrid computing system was used to simulate linearized longitudinal dynamics of the aircraft and to implement a conjugate gradient optimal search algorithm. The aircraft was simulated in the low-speed approach condition only. Feedback control matrices were found which minimized the average of a quadratic functional involving passenger compartment accelerations, pitch angle and rate, flight path angle and speed variations. The optimization was performed for artificially designed gust inputs in the form of predetermined rectangular waveforms. Results were obtained for elevator, spoilers, and flaps acting singly and in combination. Additional results were obtained for unit sinusoidal gust inputs by using the gain matrices computed for the artificial test gusts. Various sensor configurations were also investigated.
    Keywords: AERODYNAMICS
    Type: L-9250 , NASA-TN-D-7559
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  • 26
    Publication Date: 2013-08-31
    Description: An experimental study was devised to determine the profile drag on a subsonic wind tunnel model partially covered with various compliant surface materials. The model consisted of a large section of constant thickness bounded fore and aft by symmetric airfoil fairings. A flat rigid plate, the control surface, could be exchanged for four contiguous complaint panels. The flexible media generally consisted of thin polyvinylchloride membranes stretched to various tensions over trapped fluid cavities of air, water, or polyethelene oxide solution, or over dry or flooded open-celled polyurethane foams. On the basis of very accurate direct-force cell measurements, all configurations were found to yield profile drags equal to or slightly higher than that obtained for the conventional rigid surface case. The results indicate that the potential for practical drag-reducing applications will be limited to either high-density or high-speed flows where more sensible pressure perturbations occur.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3119 , A-5596
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  • 27
    Publication Date: 2013-08-31
    Description: A circular-arc - conic boattail nozzle, typical of those used on a twin engine fighter, was tested on an underwing nacelle mounted on an F-106B aircraft. The boattail had a radius ratio r/r sub c of 0.41 and a terminal boattail angle of approximately 19 deg. The gas generator was a J85-GE-13 turbojet engine. The effects of Reynolds number and angle of attack on boattail pressure drag and boattail pressure profiles were investigated. Increasing Reynolds number resulted in reduced boattail drag at both Mach numbers of 0.6 and 0.9.
    Keywords: AERODYNAMICS
    Type: E-7997 , NASA-TM-X-3121
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  • 28
    Publication Date: 2013-08-31
    Description: The potential-flow velocity distributions on several splitter geometries in an engine inlet and their variation with different splitter leading-edge shapes and distances from the inlet highlight were analyzed. The velocity distributions on the inner and outer surfaces of the splitters are presented for low-speed and cruise conditions. At zero incidence angle, the splitter with the 4-to-1 elliptical leading edge had lower peak velocities and velocity gradients than the splitter with the 2-to-1 elliptical leading edge. The velocity gradients decreased as the distance from the inlet highlight to the splitter leading edge was increased. For a given distance, the peak velocity on the splitter inner surface increased with increasing inlet incidence angle. At an incidence angle of 50 deg, the velocity level and gradients on the inner surface of the splitter in the forward position were sufficiently severe to suggest local separation.
    Keywords: AERODYNAMICS
    Type: E-8001 , NASA-TM-X-3114
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  • 29
    Publication Date: 2013-08-31
    Description: Aerodynamic design parameters and overall and blade-element performances of a 1.25-pressure-ratio fan stage are reported. Detailed radial surveys were made over the stable operating flow range at rotative speeds from 70 to 120 percent of design speed. At design speed, the measured stage peak efficiency of 0.872 occurred at a weight flow of 34.92 kilograms per second and a pressure ratio of 1.242. Stage stall margin is about 20 percent based on the peak efficiency and stall conditions. The overall peak efficiency for the rotor was 0.911. The overall stage performance showed no significant change when the stators were positioned at 1, 2, or 4 chords downstream of the rotor.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3083 , E-7800
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  • 30
    Publication Date: 2013-08-31
    Description: A box-shaped ground vehicle was used to simulate the aerodynamic drag of high volume transports, that is, delivery vans, trucks, or motor homes. The coast-down technique was used to define the drag of the original vehicle, having all square corners, and several modifications of the vehicle. Test velocities ranged up to 65 miles per hour, which provided maximum Reynolds numbers of 1 times 10 to the 7th power based on vehicle length. One combination of modifications produced a reduction in aerodynamic drag of 61 percent as compared with the original square-cornered vehicle.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-56027
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  • 31
    Publication Date: 2013-08-31
    Description: The recent energy crisis and subsequent substantial increase in fuel prices have provided increased incentive to reduce the fuel consumption of civil transport aircraft. At the present time many changes in operational procedures have been introduced to decrease fuel consumption of the existing fleet. In the future, however, it may become desirable or even necessary to introduce new fuel-conservative aircraft designs. This paper reports the results of a preliminary study of new near-term fuel conservative aircraft. A parametric study was made to determine the effects of cruise Mach number and fuel cost on the optimum configuration characteristics and on economic performance. For each design, the wing geometry was optimized to give maximum return on investment at a particular fuel cost. Based on the results of the parametric study, a nominal reduced energy configuration was selected. Compared with existing transport designs, the reduced energy design has a higher aspect ratio wing with lower sweep, and cruises at a lower Mach number. It has about 30% less fuel consumption on a seat-mile basis.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-62383
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  • 32
    Publication Date: 2013-08-31
    Description: An experimental aerodynamic investigation was conducted in the NASA/MSFC 14-inch Trisonic Wind Tunnel on a 0.00736 scale model of Titan 3 C Solid Rocket Motor (SRM). Static stability and drag data were obtained for Mach numbers of 0.6 to 4.96, angles of attack of minus 10 deg to 190 deg, and roll angles of 0 to 360 deg. The resulting data will be used to predict the dynamic motions of the SRM during entry which will then be compared to flight data. This comparison will improve and lend credibility to methods for predicting the entry dynamics of the space shuttle Solid Rocket Booster (SRB), which is needed for recovery studies and design of the parachute recovery system.
    Keywords: AERODYNAMICS
    Type: NASA-CR-134402 , DMS-DR-2142
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  • 33
    Publication Date: 2013-08-31
    Description: The program input and output are described, and the program listing is presented. A sample program output for an infinite swept wing calculation is shown.
    Keywords: AERODYNAMICS
    Type: NASA-CR-137550 , REPT-20
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  • 34
    Publication Date: 2013-08-31
    Description: A method has recently been developed for calculating the flow over a subsonic nacelle at zero angle of attack. The method makes use of annular wing theory and boundary-layer theory and has shown good agreement with both experimental data and more complex theoretical solutions. The method permits variation of the mass flow by changing the size of a center body.
    Keywords: AERODYNAMICS
    Type: L-9274 , NASA-TN-D-7630
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  • 35
    Publication Date: 2013-08-31
    Description: An investigation has been conducted to determine the effects of canard, canard location, vertical tails, and vertical-tail location on the aerodynamic characteristics of a model having a 59 deg sweptback wing. The investigation was conducted at a Mach number of 0.30, at angles of attack up to 22 deg and at sideslip angles of 0 deg and plus or minus 5 deg. The results of the study indicate that adding the canard to the model had only a slight effect on the lift at the lower angles of attack. At the higher angles of attack there is a significant effect of canard height on lift, canard in the high location (above the wing chord plane) resulting in the highest lifts. The lift drag characteristics are predicted well for the configuration with the mid or high canard locations by combining a potential flow solution on the canard with a potential plus vortex solution on the wing. Variations in the height significantly affect the pitching-moment characteristics of the configuration; the configuration with the low or mid canard location exhibits an increase in stability at the higher lift coefficients, whereas the configuration with the high canard exhibits pitch-up. Adding the vertical tails in the outboard location caused a significant loss in lift at the higher angles of attack; this lift loss was eliminated by moving the vertical tails inboard.
    Keywords: AERODYNAMICS
    Type: L-9662 , NASA-TM-X-3088
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  • 36
    Publication Date: 2013-08-31
    Description: A method of calculating the pressure distributions on boattails is proposed. This method accounts for viscous effects including the presence of a separated region for base flows by combining an inviscid analysis with a boundary layer analysis in an iterative calculation. Details of the reversed flow region are not considered. Some preliminary results have been obtained for boattails at subsonic free stream Mach number with turbulent boundary layers separating at the boattail base. In some cases convergence could not be obtained using the present computer program. It is possible, in principle, to extend this method to the calculation of boattail flows with pressure gradient induced separation on the boattail.
    Keywords: AERODYNAMICS
    Type: E-7811 , NASA-TM-X-3109
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  • 37
    Publication Date: 2013-08-31
    Description: A two-stage axial-flow fan with a tip speed of 1450 ft/sec (442 m/sec) and an overall pressure ratio of 2.8 was designed, built, and tested. At design speed and pressure ratio, the measured flow matched the design value of 184.2 lbm/sec (83.55kg/sec). The adiabatic efficiency at the design operating point was 85.7 percent. The stall margin at design speed was 10 percent. A first-bending-mode flutter of the second-stage rotor blades was encountered near stall at speeds between 77 and 93 percent of design, and also at high pressure ratios at speeds above 105 percent of design. A 5 deg closed reset of the first-stage stator eliminated second-stage flutter for all but a narrow speed range near 90 percent of design.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3076 , E-7851
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  • 38
    Publication Date: 2013-08-31
    Description: Slender sharp-edge wings having leading-edge sweep angles of 74 deg have been studied at Mach numbers from 0.60 to 2.80, at angles of attack from about minus 4 deg to 22 deg, and at angles of sideslip from 0 deg to 5 deg. The wings had delta, arrow, and diamond planforms. The experimental tests were made in the Langley 8-foot transonic pressure tunnel and the Langley Unitary Plan wind tunnel test section number 1. The theoretical predictions were made using the theories of NASA TN D-3767 and NASA TN D-6243. The results of the study indicated that the lift and drag characteristics as affected by planform and Mach number could be reasonably well predicted for the delta wing in the subsonic and transonic Mach number range. In the supersonic range, the delta and diamond wings were about equally good in the degree of agreement between experiment and theory. In making drag-due-to-lift predictions the vortex lift effects must be taken into account if reasonable results are to be obtained at moderate or high lift coefficients.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-7631 , L-9433
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  • 39
    Publication Date: 2013-08-31
    Description: An investigation has been made in the Mach number range from 0.20 to 2.16 to determine the longitudinal aerodynamic characteristics of a fighter airplane concept. The configuration concept employs a single fixed geometry inlet, a 50 deg leading-edge-angle clipped-arrow wing, a single large vertical tail, and low horizontal tails. The wing camber surface was optimized in drag due to lift and was designed to be self-trimming at Mach 1.40 and at a lift coefficient of 0.20. An uncambered or flat wing of the same planform and thickness ratio was also tested. However, for the present investigation, the fuselage was not cambered. Further tests should be made on a cambered fuselage version, which attempts to preserve the optimum wing loading on that part of the theoretical wing enclosed by the fuselage.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3078 , L-9463
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  • 40
    Publication Date: 2013-08-31
    Description: A procedure has been developed for calculating the effects of blowing two jets over a swept tapered wing at low subsonic speeds. The algorithm used is based on a vortex-lattice representation of the wing lifting surface and a line sink-source distribution to simulate the effects of the jet exhaust on the wing lift and drag. The method is limited to those cases in which the jet exhaust does not intersect or wash the wing. The predictions of this relatively simple procedure are in remarkably good agreement with experimentally measured interference lift and interference induced drag.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-7754 , L-9683
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  • 41
    Publication Date: 2013-08-31
    Description: Detailed pressure measurements were made on a flat semispan swept wing with a rounded leading edge at Mach number 2.2 through a range of Reynolds numbers. Pressure orifices were distributed in the streamwise direction at five spanwise stations on the leading edge and on the upper and lower surfaces. No significant amount of leading-edge suction was found, but the pressures and integrated normal forces on the upper and lower surfaces indicate the presence of a vortex lift.
    Keywords: AERODYNAMICS
    Type: L-9185 , NASA-TN-D-7506
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  • 42
    Publication Date: 2013-08-31
    Description: The effects of active controls on the suppression of flutter and gust alleviation of two different types of subsonic aircraft (the Arava, twin turboprop STOL transport, and the Westwind twin-jet business transport) are investigated. The active controls are introduced in pairs which include, in any chosen wing strip, a leading-edge (LE) control and a trailing-edge (TE) control. Each control surface is allowed to be driven by a combined linear-rotational sensor system, located on the activated strip. The control law, which translates the sensor signals into control surface rotations, is based on the concept of aerodynamic energy. The results indicate the extreme effectiveness of the active systems in controlling flutter. A single system spanning 10% of the wing semispan made the Arava flutter-free, and a similar active system, for the Westwind aircraft, yielded a reduction of 75% in the maximum bending moment of the wing and a reduction of 90% in the acceleration of the cg of the aircraft. Results for simultaneous activation of several LE - TE systems are presented. Further work needed to bring the investigation to completion is also discussed.
    Keywords: AERODYNAMICS
    Type: TAE-198 , NASA-CR-138658
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  • 43
    Publication Date: 2013-08-31
    Description: Several technical areas were encompassed in providing support for booster thermal environment test work. These areas included: (1) cavity flow heating, (2) rarefied flow heating, and (3) impulse operated model research and testing. Cavity flow heating problems were studied with respect to the proposed altitude control motors for the space shuttle. Available literature on this subject was reviewed and analytical predictive methods were summarized for use in planning testing work. Rarefied flow heating data was reviewed and correlated. The study showed the importance of considering rarefied flow conditions in launch thermal environment prediction. Impulse operated model research and testing was conducted to provide a basis for understanding and designing such models for booster thermal environment testing.
    Keywords: AERODYNAMICS
    Type: NASA-CR-120234 , RTR-008-4
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  • 44
    Publication Date: 2013-08-31
    Description: The dynamic stall phenomenon was examined in detail by analyzing an existing set of unsteady pressure data obtained on an airfoil oscillating in pitch. Most of the data were for sinusoidal oscillations which penetrated the stall region in varying degrees, and here the effort was concentrated on the chordwise propagation of pressure waves associated with the dynamic stall. It was found that this phenomenon could be quantified in terms of a pressure wave velocity which is consistently much less than free-stream velocity, and which varies directly with frequency. It was also found that even when the stall region has been deeply penetrated and a substantial dynamic stall occurs during the downstroke, stall recovery near minimum incidence will occur, followed by a potential flow behavior up to stall inception.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2394
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  • 45
    Publication Date: 2013-08-31
    Description: A FORTRAN-IV computer program, MERIDL, has been developed that obtains a subsonic or shock-free transonic flow solution on the hub-shroud mid-channel flow surface of a turbomachine. The blade row may be fixed or rotating and may be twisted and leaned. Flow may be axial or mixed, up to 45 deg from axial. Upstream and downstream flow variables can vary from hub to shroud, and provision is made to correct for loss of stagnation pressure. The results include velocities, streamlines, and flow angles on the flow surface and approximate blade surface velocities. Subsonic solutions are obtained by a finite-difference stream-function solution. Transonic solutions are obtained by a velocity-gradient method, using information from a finite-difference stream-function solution at a reduced mass flow.
    Keywords: AERODYNAMICS
    Type: E-7516 , NASA-TN-D-7344
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  • 46
    Publication Date: 2013-08-31
    Description: Low speed flow angularity results are presented showing flow direction at the nacelle locations on the Boeing 727-200. Flow angle probes (yawheads) were used for measurements at side and center inlet positions on the aft fuselage. A range of flap settings were tested with flap angles of 0 deg, 15 deg, and 40 deg selected for investigation.
    Keywords: AERODYNAMICS
    Type: NASA-CR-134630 , D6-43098
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  • 47
    Publication Date: 2013-08-31
    Description: Water-table flow tests were conducted for proposed heat-transfer tunnels which were designed to provide uniform flow into their respective test sections of a single core engine turbine vane and a full annular ring of helicopter turbine vanes. Water-table tests were also performed for the single-vane test section of the core engine tunnel. The flow in the heat-transfer tunnels was shown to be acceptable.
    Keywords: AERODYNAMICS
    Type: E-7870 , NASA-TM-X-3073
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  • 48
    Publication Date: 2013-08-31
    Description: A contoured boattail nozzle typical of those used on a twin-engine fighter was tested on an underwing nacelle mounted on an F-106B aircraft. The gas generator was a J85-GE-13 turbojet engine. The effects of Reynolds number, Mach number, and angle of attack on boattail drag and boattail pressure profiles were investigated. Increasing Reynolds number caused a slight reduction in boattail drag at both Mach 0.7 and 0.9. The nozzle had relatively low boattail drag even though the flow was separated over a large portion of the boattail.
    Keywords: AERODYNAMICS
    Type: E-7818 , NASA-TM-X-3053
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  • 49
    Publication Date: 2013-08-31
    Description: An investigation was conducted in the Langley 16-foot transonic tunnel to determine the performance of seven inlets having NACA 1-series contours and one inlet having an elliptical contour over a range of mass-flow ratios and at angle of attack. The inlet diameter ratio varied from 0.81 to 0.89; inlet length ratio varied from 0.75 to 1.25; and internal contraction ratio varied from 1.009 to 1.093. Reynolds number based on inlet maximum diameter varied from 3.4 million at a Mach number of 0.4 to 5.6 million at a Mach number of 1.29.
    Keywords: AERODYNAMICS
    Type: L-8588 , NASA-TM-X-2917
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  • 50
    Publication Date: 2013-08-31
    Description: The investigation was conducted to evaluate the static turning performance and the pressure and temperature environment of an upper-surface-blown wing and flap utilizing a small turbofan engine. The tests involved modifications of the engine primary nozzle designed to alleviate high temperature problems on the wing and flaps and yet provide acceptable static turning performance over the desired range of flap deflections and thrust conditions.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-71931
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  • 51
    Publication Date: 2013-08-31
    Description: Flight tests have been conducted to evaluate the effectiveness of a wingtip vortex attenuating device, referred to as a spline. Vortex penetrations were made with a PA-28 behind a C-54 aircraft with and without wingtip splines attached and the resultant rolling acceleration was measured and related to the roll acceleration capability of the PA-28. Tests were conducted over a range of separation distances from about 5 nautical miles (n. mi.) to less than 1 n. mi. Preliminary results indicate that, with the splines installed, there was a significant reduction in the vortex induced roll acceleration experienced by the PA-28 probe aircraft, and the distance at which the PA-28 roll control became ineffective was reduced from 2.5 n. mi. to 0.6 n. mi., or less. There was a slight increase in approach noise (approximately 4 db) with the splines installed due primarily to the higher engine power used during approach. Although splines significantly reduced the C-54 rate of climb, the rates available with four engines were acceptable for this test program. Splines did not introduce any noticeable change in the handling qualities of the C-54.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-71928
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  • 52
    Publication Date: 2013-08-31
    Description: Three sting-mounted winged-body models with tunnel blockages of 0.1, 1.0, and 2.0 percent were tested in the Lewis Research Center's 8- by 6- Foot Supersonic Wind Tunnel. Fuselage pressures were obtained over a Mach number range of 0.6 to 1.0 at angles of attack from 0 deg to 4 deg. Two other types of model support were investigated, which included simulated wing-tip and fuselage support-strut mountings. The effects of tunnel porosity and sidewall geometry were also investigated. Model blockage effects were small up to M sub 0 = 0.95. At higher speeds the major blockage effect observed was a displacement of the local transonic terminal shocks on the model. The effects of the wing-tip type of model support were small up to M sub 0 = 0.95, but disturbances were observed on the fuselage at higher speeds. Changes in local tunnel porosity were effective in reducing the disturbances up to M sub 0 = 0.975, but a change in sidewall geometry was not.
    Keywords: AERODYNAMICS
    Type: E-7596 , NASA-TM-X-3011
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  • 53
    Publication Date: 2013-08-31
    Description: The aerodynamic performance of a solid vane was experimentally determined in a full-annular cascade, where three-dimensional effects could be obtained. This vane was of the same size and profile as the cooled vanes to be subsequently tested. The vanes were tested over a pressure ratio range that corresponded to mean-radius ideal aftermixed critical velocity ratios of 0.71 to 0.89. Overall vane aftermixed efficiencies were obtained over this range of critical velocity ratios and compared with results from a four-vane annular-sector cascade. The variation in vane aftermixed conditions and vane aftermixed efficiency with radius were also obtained and compared with design values. Vane surface static-pressure distributions were measured and compared with theory and with the results obtained in the four-vane cascade.
    Keywords: AERODYNAMICS
    Type: E-7699 , NASA-TM-X-3006
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  • 54
    Publication Date: 2013-08-31
    Description: An experimental investigation was conducted to systematically explore the effects of inter-blade spatial relationships and pitch variations on rotor performance and wake geometry. Variable-geometry rotors consisting of various combinations of blade length, axial spacing, azimuth spacing, and collective pitch were tested at model scale in hover and forward flight. In addition, a hover test of a model rotor with an ogee blade tip design was conducted to determine its performance and wake characteristics. The results of this investigation indicate that properly selected variable geometry rotor configurations can offer substantial improvements in hover performance without adversely affecting forward flight performance. Axial spacing of alternate blades was found to provide the greatest performance benefit, and further improvements were achieved by combining azimuth spacing with axial spacing. The performance benefit appears to be related to the relief of local adverse aerodynamic phenomena produced by vortex interference. The ogee tip design was found to substantially reduce the concentrated core intensity of the tip vortex, and could thus prove beneficial for the relief of blade-vortex interaction problems. However, the ogee tip was found to reduce hover performance at model scale.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2275
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  • 55
    Publication Date: 2013-08-31
    Description: A solid, half-scale model of a 50.8-cm (20-in) research turbine designed for a high temperature core engine application was investigated over a range of speeds and pressure ratios. The results of this test are presented. The effect of rotor blade twist was also investigated. At the design equivalent speed and specific work output, the total efficiency of the turbine with untwisted rotor blades was 87.1 percent; at the same pressure ratio the efficiency of the turbine with twisted rotor blades was 88.0 percent.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-7557 , E-7592
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  • 56
    Publication Date: 2013-08-31
    Description: A simulator study of STOL airworthiness criteria was conducted using a model of an augmentor wing transport. The approach, flare and landing, go-around, and takeoff phases of flight were investigated. The results are summarized and possible implications with regard to airworthiness criteria are discussed. The results provide a data base for future STOL airworthiness requirements and a preliminary indication of potential problem areas. The results are also compared to the results from an earlier simulation of the Breguet 941S. Where possible, airworthiness criteria are proposed for consideration.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-62395 , A-5797-VOL-1 , AD-A005878 , FAA-RD-74-179-VOL-1
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  • 57
    Publication Date: 2013-08-31
    Description: The characteristics of the plateau region in the vortex system which trails from a lifting wing are discussed. The decay of the vortex due to viscous or turbulent shear is very slow in the plateau so that the maximum tangential speed in the vortices remains nearly constant for some distance downstream of roll-up and then begins to decrease, becoming inversely proportional to the square root of the distance downstream. Mathematical models are developed to analyze the structure of the plateau area. Solutions are obtained for both constant and variable eddy viscosity models.
    Keywords: AERODYNAMICS
    Type: NASA-CR-142298 , ISU-ERI-AMES-74241
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  • 58
    facet.materialart.
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The development of a three axis stabilized balloon platform capable of being operated in three modes of increasing accuracy is discussed. The system relies on angular motion sensing for primary feedback with linear accelerometers, magnetometers, and a star sensor for positional information. When under primary control the system will acquire and stabilize on any accessible part of the celestial sphere. A video verification system is included to provide pointing confirmation. Under improved accuracy control, the star sensor is used to lock onto a target star.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 284-293
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  • 59
    Publication Date: 2016-05-14
    Description: The air and ground resonance instabilities of hingeless rotor helicopters are examined on a relatively broad parametric basis including the effects of blade tuning, virtual hinge locations, and blade hysteresis damping, as well as size and scale effects in the gross weight range from 5,000 to 48,000 pounds. A special case of a 72,000 pound helicopter air resonance instability is also included. The study shows that nominal to moderate and readily achieved levels of blade inertial hysteresis damping in conjunction with a variety of tuning and/or feedback conditions are highly effective in dealing with these instabilities. Tip weights and reductions in pre-coning angles are also shown to be effective means for improving the air resonance instability.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 205-218
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  • 60
    Publication Date: 2016-06-07
    Description: The establishment and functions of the AFCRL balloon operations facility are discussed. The types of research work conducted by the facility are defined. The facilities which support the balloon programs are described. The free balloon and tethered balloon capabilities are analyzed.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 160-164
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  • 61
    Publication Date: 2016-06-07
    Description: A configuration has been developed for a long-life balloon platform to carry pointing telescopes weighing as much as 80 pounds (36 kg) to point at selected celestial targets. A platform of this configuration weighs about 375 pounds (170 kg) gross and can be suspended from a high altitude super pressure balloon for a lifetime of several months. The balloon platform contains a solar array and storage batteries for electrical power, up and down link communications equipment, and navigational and attitude control systems for orienting the scientific instrument. A biaxial controller maintains the telescope attitude in response to look-angle data stored in an on-board computer memory which is updated periodically by ground command. Gimbal angles are computed by using location data derived by an on-board navigational receiver.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 136-144
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  • 62
    Publication Date: 2016-06-07
    Description: A system capable of pointing a balloon-borne telescope at selected celestial objects to an accuracy of approximately 10 arc minutes for an extended period (weeks to months) without reliance on telemetry is described. A unique combination of a sun/star tracker, an on-board computer, and a gyrocompass is utilized for navigation, source acquisition and tracking, and data compression and recording. The possibilities for intelligent activities by the computer are also discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Telescope Systems for Balloon-Borne Res.; p 71-80
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  • 63
    Publication Date: 2016-06-07
    Description: An overview of an experimental and analytical research program underway for studying the aeroelastic and dynamic characteristics of tilt-rotor VTOL aircraft is presented. Selected results from several investigations of scaled models in the transonic dynamics tunnel, as well as some results from a test of a flight-worthy proprotor in the full-scale wind tunnel are shown and discussed with a view toward delineating various aspects of dynamic behavior peculiar to proprotor aircraft. Included are such items as proprotor/pylon stability, whirl flutter, gust response, and blade flapping. Theoretical predictions are shown to be in agreement with the measured stability and response behavior.
    Keywords: AERODYNAMICS
    Type: Its Rotorcraft Dyn.; p 171-184
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  • 64
    Publication Date: 2016-06-07
    Description: A nine degrees-of-freedom theoretical model was developed for investigations of the dynamics of a proprotor operating in high inflow axial flight on a cantilever wing. The theory is described, and the results of the analysis are presented for two proprotor configurations: a gimballed, stiff-inplane rotor, and a hingeless, soft-inplane rotor. The influence of various elements of the theory are discussed, including the modeling used for the blade and wing aerodynamics, and the influence of the rotor lag degree of freedom. The results from full-scale tests of the two proprotors are presented and compared with the theoretical results.
    Keywords: AERODYNAMICS
    Type: Its Rotorcraft Dyn.; p 159-169
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  • 65
    Publication Date: 2017-06-24
    Description: The Theodorsen theory of airfoil design for incompressible flow can be used with the modifications proposed in this paper to design airfoils that satisfy a much wider variety of pressure variations than are permitted by the original Theodorsen procedure. Several examples illustrating this method are computed and discussed.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-7741 , L-9578
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  • 66
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: An extensive wind-tunnel test of a round turbulent jet directed normally through a flat plate into a subsonic cross flow has been conducted. The results of the velocity field measurements are presented in a concise and usable form through the use of simple models to relate the velocity field to empirical values for the strength and location of the pair of contrarotating vortices associated with the jet.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Dec. 197
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  • 67
    Publication Date: 2011-08-16
    Description: The artificial viscosity method of Kuwahara and Takami (1973) is used to calculate the roll-up of trailing vortices behind a number of practical aerodynamic configurations. Where possible, the results are compared for core location with available experimental data.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 11; Nov. 197
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  • 68
    Publication Date: 2011-08-16
    Description: Two methods for determining the virtual origin of turbulent boundary layers in hypersonic flow are evaluated. The results of the analyses are restricted to wind-tunnel models having sharp-edged surfaces with zero or small pressure gradients. Virtual origin and skin friction estimates from these two methods are compared with values from a base method for which the virtual origin is calculated from the measured momentum thickness at a station downstream of boundary layer transition.
    Keywords: AERODYNAMICS
    Type: ASME PAPER 74-APM-V
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  • 69
    Publication Date: 2011-08-16
    Description: The techniques of Galilean-Lorentz transformation and matched asymptotic expansions are used to simplify the procedure of calculating the lift and pressure distribution induced on an infinite-span thin wing interacting with an oblique sinusoidal gust in subsonic flow. This technique requires that the product of the flow Mach number and the reduced frequency be small. Under this condition, the inner region of the transformed space behaves as an incompressible flow, so that existing incompressible flow theories can be used as a basis to construct closed-form solutions for the airload induced on the wing. This approach is an extension of the GASP approximation developed by Amiet and Sears (1970). Results are obtained for both the magnitude and the phase of the unsteady lift due to interaction with gust. These results are compared with available numerical results. Some discrepancies are noted and discussed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Sept
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  • 70
    Publication Date: 2011-08-16
    Description: A general equation governing aerodynamic sound generation in the presence of solid boundaries is derived. It is shown that all the theories in the literature appear as special cases of this general equation. Derived special equations for propeller and fan noise are likewise shown to be more general than the conventional equations in that they make allowance for variation in retarded time over the blade surfaces.
    Keywords: AERODYNAMICS
    Type: Acoustical Society of America; vol. 56
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  • 71
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: Discussion of the method of parametric differentiation in application to predictions of farfield noise propagation in both lossless and dissipative media. It is shown that, in the lossless medium, the governing equation, transformed to parameter space, reduces to a wave equation in the farfield. In the dissipative medium, the system of nonlinear partial differential equations, transformed to parameter space, reduces to a linear partial differential equation of the propagating type which contains a third-order derivative as well as the wave operator.
    Keywords: AERODYNAMICS
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  • 72
    facet.materialart.
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: A scanning laser Doppler velocimeter was used to measure the axial velocity defect in the cores of trailing vortices behind a lifting airfoil of rectangular planform. Data were obtained at several different angles of attack and downstream distances ranging from 30 to 1000 chord lengths. The test was designed to obtain continuous data from the near field into the far field while removing uncertainties associated with the interpretation of data obtained by the hydrogen bubble technique. The measured velocities of V sub x/U sub infinity are compared with those predicted. The agreement is remarkably good over the entire range of downstream distances, which supports the credibility of calculating axial velocities using the results of Moore and Saffman (1973).
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Aug. 197
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  • 73
    Publication Date: 2011-08-16
    Description: Some results of the application of a unified theory of small disturbances in nonuniform high-speed boundary layers to the small-step problem for the case of supersonic laminar nonadiabatic flow are described. Comparisons with experimental data are given which show good agreement in a variety of physical features, including useful new base pressure and heat-transfer correlation relations. Using a small perturbation approach, an analytical theory is developed that predicts the steady-state pressure, temperature, and heat-transfer disturbance fields including suction or blowing through the step. Particular emphasis is placed on the important effects of the highly nonuniform flow across the boundary layer, lateral pressure gradients, and the upstream influence associated with viscous-inviscid interaction. Approximate analytical expressions for the wall pressure, skin friction, and heat-transfer perturbations and upstream influence distance are derived by a Fourier transformation approach.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Aug. 197
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  • 74
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    Publication Date: 2011-08-16
    Description: The flowfield associated with the underexpanded axisymmetric nozzle freejet flow including the appearance of a Mach disk has been studied. It is shown that the location and size of the Mach disk are governed by the appearance of a triple-point shock configuration and the condition that the central core flow will reach a state of 'choking at a throat'. It is recognized that coalescence of waves requires special attention and the reflected wave, as well as the vorticity generated from these wave interactions, have to be taken accurately into account. The theoretical results obtained agreed well with the experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Aug. 197
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  • 75
    Publication Date: 2011-08-16
    Description: A numerical generalized-capacity-matrix technique is developed for application to aerodynamic flow computations. This technique allows the very fast direct (noniterative) numerical elliptic solvers to be used in problems with arbitrary internal boundaries and with a wide class of boundary conditions, including numerical application of the Kutta condition on an airfoil without iteration. Accuracy, speed, and usefulness of the technique are demonstrated with linear problems for potential flows over airfoil shapes. The method's main advantages, however, can be exploited within iterative procedures for a variety of complex flow problems governed by systems of equations not necessarily elliptic or linear.
    Keywords: AERODYNAMICS
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  • 76
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    Publication Date: 2011-08-16
    Description: The steady flow of an ideal gas past a conical body is investigated by the method of matched asymptotic expansions, with particular emphasis on the flow near the singular ray occurring in linearized theory. The first-order problem governing the flow in this region is formulated, leading to the equation of Kuo, and an approximate solution is obtained in the case of compressive flow behind the main front. This solution is compared with the results of previous investigations with a view to assessing the applicability of the Lighthill-Whitham theories.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 63; Apr. 29
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  • 77
    Publication Date: 2011-08-16
    Description: Some results are described for a lifting rectangular wing centrally located on a circular-cylindrical body. This simple configuration has been utilized in order to assess the merits of a mapping technique for wing-body configurations. The procedure employed makes use of a coordinate transformation to simplify specification of the surface boundary condition in the computation of the flow about the wing. The method can be extended to incorporate wing sweep, finite length body of noncircular cross section, and arbitrary wing placement; however, these extensions involve a considerable increase in complexity of the problem.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 11; Apr. 197
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  • 78
    Publication Date: 2011-08-16
    Description: Discussion of the local heating effect on the lee-side control flaps of supersonic configurations due to the interaction between vortices and leeward control surfaces at an angle of attack. Considerations are given for an appropriate positioning of control flaps to alleviate such interactions and the resulting thermal effect. Tests are carried out on a sharp right circular cone with two types of flap configurations in a study of oil flow patterns about the cone at selected angles of attack. Splitting of flaps and moving them to positions away from the symmetry plane did reduce the heating but also reduced the average flap pressure and increased flow complexity.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 11; Mar. 197
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  • 79
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    Publication Date: 2011-08-16
    Description: Presented data on vortex-induced heating in a cone-cylinder body at Mach 6 show that the most severe heating need not occur as a result of the interaction of the primary vortices with the lee surface, even though this interaction produces a large, well-defined featherline oil smear. It is pointed out that the severity of vortex-induced heating is extremely sensitive to Reynolds number and geometry and that there exists a 'threshold Reynolds number' below which vortex-induced heating decreases abruptly.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 11; Feb. 197
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  • 80
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    Publication Date: 2011-08-16
    Description: A proposed method for calculating three-dimensional incompressible laminar and turbulent boundary layers is investigated with respect to its applicability to incompressible attachment line flow on an infinite swept wing. The calculation results obtained exhibit satisfactory agreement with experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Feb. 197
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  • 81
    Publication Date: 2011-08-16
    Description: A general theory of subsonic potential aerodynamic flow around a lifting body having arbitrary shape and motion is presented. By using the Green function method, an integral representation for the velocity potential is obtained for both supersonic and subsonic flow. Under the small perturbation assumption, the potential at any point in the field depends only upon the values of the potential and its normal derivative on the surface of the body. On the surface of the body, this representation reduces to an integro-differential equation relating the potential and its normal derivative (which is known from the boundary conditions) on the surface. The theory is applied to finite-thickness wings in subsonic steady and oscillatory flows.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Feb. 197
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  • 82
    Publication Date: 2011-08-16
    Description: Description of a procedure for predicting the flowfields that develop when successive interactions between oblique shock waves and a turbulent boundary layer occur. Such interactions may occur, for example, in engine inlets for supersonic aircraft. A control volume analysis is used to predict changes in the flow field across the interactions. Two bleed flow models are considered. The predicted results are compared with measured results and are shown to be in good agreement when the bleed flow rate is low, or when there is no bleed. Shortcomings of the bleed flow models at higher bleed flow rates are discussed.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 11; Jan. 197
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  • 83
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    Publication Date: 2011-08-16
    Description: A mathematical model of the vortex flow over a slender sharp-edged delta wing is proposed, and is shown to provide good agreement with the experiment. Although the technique requires experimental data in the form of the vortex core locations, it does account for the previously ignored mass entrainment of the vortex core.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 12; Jan. 197
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  • 84
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    Publication Date: 2011-08-16
    Description: The criterion that is proposed is an expected value of the mean square response error as an alternative to testing a model against new data. Modeling with respect to this new criterion does not change the estimate for a given model format from a maximum likelihood estimate or mean square response error estimate. The new criterion does, however, provide a means of comparing models with different formats and varying complexity. A numerical example is used to illustrate the application of the proposed criteria and the problem of searching for the best model. For all but the most trivial system identification problems, it is shown that a prohibitive number of combinations of terms of the model must be investigated to ensure the final model is best.
    Keywords: AERODYNAMICS
    Type: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 291-313
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  • 85
    Publication Date: 2011-08-16
    Description: Results are presented of a procedure for estimating stability and control parameters from flight data, by using maximum likelihood methods employing an interactive computer system, which was established at the NASA Langley Research Center. Problems encountered are discussed.
    Keywords: AERODYNAMICS
    Type: Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 49-76
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  • 86
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    Publication Date: 2011-08-16
    Description: The growth of the field of system identification is discussed along with changes in methodology which have taken place in recent years. The similarity between pattern recognition and system identification is pointed out, involving the modelling in the latter and the feature selection problem in the former. It is stated that once a model is formulated, including the disturbances and measurement errors, the parameter finding can be formulated as a statistical estimation problem. The various techniques and their application are discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Flight Res. Center Parameter Estimation Tech. and Appl. in Aircraft Flight Testing; p 381-385
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  • 87
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