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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Estimation of leading-edge thrust for supersonic wings of arbitrary planform

A numerical method for the estimation of leading edge thrust for supersonic wings of arbitrary planform was developed and was programmed as an extension to an existing high speed digital computer method for prediction of wing pressure distributions. The accuracy of the method was assessed by comparison with linearized theory results for a series of flat delta wings. Application of the method to wings of arbitrary planform, both flat and cambered, is illustrated in several examples.

Carlson, H. W.↗
NASA NTRS1989

A natural flow wing design employing 3-D nonlinear analysis applied at supersonic speeds

A wing-design study has been conducted on a 65-deg-swept leading-edge delta wing in which a near-conical geometry was employed to take advantage of the naturally occurring conical flow which arises over such a wing in a supersonic flow field. Three-dimensional nonlinear analysis methods were used in the study. In preliminary design, wing planform, design conditions, and near-conical concept were derived and a baseline standard wing (conventional airfoil distribution) and a baseline near-conical wing were chosen. During the initial analysis, a full-potential solver was employed to determine the aerodynamic characteristics of the baseline standard delta wing and the near-conical delta wing. Modifications due to airfoil thickness, leading-edge radius, and camber were then applied to the baseline near-conical wing. The final design employed a Euler solver to analyze the best wing configurations found in the initial design, and to extend this study to develop a more refined wing. Benefits due to each modification are discussed, and a final natural flow wing geometry is chosen and its aerodynamic characteristics are compared with the baseline wings.

Bauer, Steven X. S.↗
NASA NTRS1974

Effect of canard position and wing leading-edge flap deflection on wing buffet at transonic speeds

A generalized wind-tunnel model, with canard and wing planform typical of highly maneuverable aircraft, was tested. The addition of a canard above the wing chord plane, for the configuration with leading-edge flaps undeflected, produced substantially higher total configuration lift coefficients before buffet onset than the configuration with the canard off and leading-edge flaps undeflected. The wing buffet intensity was substantially lower for the canard-wing configuration than the wing-alone configuration. The low-canard configuration generally displayed the poorest buffet characteristics. Deflecting the wing leading-edge flaps substantially improved the wing buffet characteristics for canard-off configurations. The addition of the high canard did not appear to substantially improve the wing buffet characteristics of the wing with leading-edge flaps deflected.

Gloss, B. B.↗
NASA NTRS1982

Dynamic load measurements with delta wings undergoing self-induced roll-oscillations

The aerodynamic forces acting on a delta wing, mounted on a free-to-roll sting-balance apparatus, were measured. Two wing planforms having leading edge sweeps of 76 and 80 deg were tested, but only the wing with the 80 deg sweep would undergo periodic self-induced roll oscillation. The time dependent forces and roll angles for this wing were then recorded for various test conditions. In these tests a considerable drop in the average normal force of the free-to-roll wing was measured, relative to the normal force obtained in the static tests. Also, the helium-bubble flow visualization technique was used to gain some insight into the periodic motion of the separated leading edge vortices.

Levin, D.↗
NASA NTRS1990

Application of laminar flow control to supersonic transport configurations

The feasibility and impact of implementing a laminar flow control system on a supersonic transport configuration were investigated. A hybrid laminar flow control scheme consisting of suction controlled and natural laminar flow was developed for a double-delta type wing planform. The required suction flow rates were determined from boundary layer stability analyses using representative wing pressure distributions. A preliminary design of structural modifications needed to accommodate suction through a perforated titanium skin was carried out together with the ducting and systems needed to collect, compress and discharge the suction air. The benefits of reduced aerodynamic drag were weighed against the weight, volume and power requirement penalties of suction system installation in a mission performance and sizing program to assess the net benefits. The study showed a feasibility of achieving significant laminarization of the wing surface by use of a hybrid scheme, leading to an 8.2 percent reduction in the cruise drag. This resulted in an 8.5 percent reduction in the maximum takeoff weight and a 12 percent reduction in the fuel burn after the inclusion of the LFC system installation penalties. Several research needs were identified for a resolution of aerodynamics, structural and systems issues before these potential benefits could be realized in a practical system.

Parikh, P. G.↗
NASA NTRS1990

Simulation and analysis of a delta planform with multiple jets in ground effect

The three-dimensional, thin-layer Navier-Stokes equations on a body-conforming, overset, multiple-grid topology are solved in the present numerical simulations of the flow around a 60-deg delta-planform wing equipped with two thrust-reverser jets in ground-effect conditions. Such experimentally flow-visualized features as jet-deformation and ground vertex-formation are captured by these simulations; the loss of wing-borne lift due to the 'suck-down' phenomenon, which arises as the delta planform flies at low speeds in close proximity to the ground, is also well simulated.

Chawla, K.↗
NASA NTRS2004

Avian Wings

This paper describes the avian wing geometry (Seagull, Merganser, Teal and Owl) extracted from non-contact surface measurements using a three-dimensional laser scanner. The geometric quantities, including the camber line and thickness distribution of airfoil, wing planform, chord distribution, and twist distribution, are given in convenient analytical expressions. Thus, the avian wing surfaces can be generated and the wing kinematics can be simulated. The aerodynamic characteristics of avian airfoils in steady inviscid flows are briefly discussed. The avian wing kinematics is recovered from videos of three level-flying birds (Crane, Seagull and Goose) based on a two-jointed arm model. A flapping seagull wing in the 3D physical space is re-constructed from the extracted wing geometry and kinematics.

Liu, Tianshu↗
NASA NTRS1990

Integrated Aerodynamic and Control System Design of Oblique Wing Aircraft

An efficient high speed aircraft design must achieve a high lift to drag ratio at transonic and supersonic speeds. In 1952 Dr. R. T. Jones proved that for any flight Mach number minimum drag at a fixed lift is achieved by an elliptic wing planform with an appropriate oblique sweep angle. Since then, wind tunnel tests and numerical flow models have confirmed that the compressibility drag of oblique wing aircraft is lower than similar symmetrical sweep designs. At oblique sweep angles above thirty degrees the highly asymmetric planform gives rise to aerodynamic and inertia couplings which affect stability and degrade the aircraft's handling qualities. In the case of the NASA-Rockwell Oblique Wing Research Aircraft, attempts to improve the handling qualities by implementing a stability augmentation system have produced unsatisfactory results because of an inherent lack of controllability in the proposed design. The present work focuses on improving the handling qualities of oblique wing aircraft by including aerodynamic configuration parameters as variables in the control system synthesis to provide additional degrees of freedom with which to further decouple the aircraft's response. Handling qualities are measured using a quadratic cost function identical to that considered in optimal control problems, but the controller architecture is not restricted to full state feedback. An optimization procedure is used to simultaneously solve for the aircraft configuration and control gains which maximize a handling qualities measure, while meeting imposed constraints on trim. In some designs wing flexibility is also modeled and reduced order controllers are implemented. Oblique wing aircraft synthesized by this integrated design method show significant improvement in handling qualities when compared to the originally proposed closed loop aircraft. The integrated design synthesis method is then extended to show how handling qualities may be traded for other types of mission performance (drag, weight, etc.). Examples are presented which show how performance can be maximized while maintaining a desired level of handling quality.

Morris, Stephen James↗
NASA NTRS1986

Computational wing design studies relating to natural laminar flow

Two research studies are described which directly relate to the application of natural laminar flow (NLF) technology to transonic transport-type wing planforms. Each involved using state-of-the-art computational methods to design three-dimensional wing contours which generate significant runs of favorable pressure gradients. The first study supported the Variable Sweep Transition Flight Experiment and involves design of a full-span glove which extends from the leading edge to the spoiler hinge line on the upper surface of an F-14 outer wing panel. A wing was designed computationally for a corporate transport aircraft in the second study. The resulting wing design generated favorable pressure gradients from the leading edge aft to the mid-chord on both upper and lower surfaces at the cruise design point. Detailed descriptions of the computational design approach are presented along with the various constraints imposed on each of the designs.

Waggoner, Edgar G.↗
NASA NTRS1988

High performance forward swept wing aircraft

A high performance aircraft capable of subsonic, transonic and supersonic speeds employs a forward swept wing planform and at least one first and second solution ejector located on the inboard section of the wing. A high degree of flow control on the inboard sections of the wing is achieved along with improved maneuverability and control of pitch, roll and yaw. Lift loss is delayed to higher angles of attack than in conventional aircraft. In one embodiment the ejectors may be advantageously positioned spanwise on the wing while the ductwork is kept to a minimum.

Koenig, David G.↗
NASA NTRS1974

Effect of canard location and size on canard-wing interference and aerodynamic center shift related to maneuvering aircraft at transonic speeds

A generalized wind-tunnel model, typical of highly maneuverable aircraft, was tested in the Langley 8-foot transonic pressure tunnel at Mach numbers from 0.70 to 1.20 to determine the effects of canard location and size on canard-wing interference effects and aerodynamic center shift at transonic speeds. The canards had exposed areas of 16.0 and 28.0 percent of the wing reference area and were located in the chord plane of the wing or in a position 18.5 percent of the wing mean geometric chord above or below the wing chord plane. Two different wing planforms were tested, one with leading-edge sweep of 60 deg and the other 44 deg; both wings had the same reference area and span. The results indicated that the largest benefits in lift and drag were obtained with the canard above the wing chord plane for both wings tested. The low canard configuration for the 60 deg swept wing proved to be more stable and produced a more linear pitching-moment curve than the high and coplanar canard configurations for the subsonic test Mach numbers.

Gloss, B. B.↗
NASA NTRS1988

Optimization of slender wings for center-of-pressure shift due to change in Mach number

It is observed that the center of pressure on a wing shifts as the Mach number is changed. Such shifts are in general undesirable and are sometimes compensated for by actively shifting the center of gravity of the aircraft or by using active stability controls. To avoid this complication, it is desirable to design the wings of a high speed aircraft so as to minimize the extent of the center-of-pressure shifts. This, together with a desire to minimize the center-of-pressure shifts in missile control surfaces, provides the motivation for this project. There are many design parameters which affect center-of-pressure shifts, but it is expected that the largest effects are due to the wing planform. Thus, for the sake of simplicity, this study is confined to an investigation of thin, flat, (i.e., no camber or twist), relatively slender, pointed wings flying at a small angle of attack. Once the dependence of the center of pressure on planform and Mach number is understood, we can expect to investigate the sensitivity of the center-of-pressure shifts to various other parameters.

Andersen, Carl M.↗
NASA NTRS1989

Hypersonic 3-D flow past winged bodies

The hypersonic flow past winged bodies is calculated using the 3D Navier-Stokes equations in both a space- and time-marching finite difference code. The bodies are a blunt ogive-cylinder with a delta wing planform and an elliptical body referred to as the allbody configuration. Laminar flow solutions for the ogive-cylinder-wing body and for the allbody configuration are presented. It is shown that the present technique has an excellent shock-capturing capability for all speed regimes. An axial zonal capability is incorporated to make the procedure more versatile. The grid system is created offline using an efficient hyperbolic grid generator which can handle the rapid variations in the body cross sections.

Chaussee, Denny S.↗
NASA NTRS1990

A closer look at the induced drag of crescent-shaped wings

Recent interest in the induced drag characteristics of crescent-shaped wings has led to a closer look at the methods used for determination of induced drag from computational aerodynamic methods. Induced drag may be computed by integration of surface pressure, or by evaluation of a contour integral in the Trefftz plane. A high-order panel method was used to study the induced drag of crescent and elliptical wings using both techniques. Induced drag computations using surface-pressure integration were strongly affected by panel density and angle of attack. Accurate drag computations for the crescent wing were obtained only when the spanwise as well as chordwise panel density was extremely high. Trefftz-plane results for the two wing planforms do not show this sensitivity to panel density or angle of attack. Span efficiencies of 0.994 for the crescent wing and 0.987 for the elliptical wing were computed by the Trefftz-plane technique. Substitution of a force-free, rolled-up wake geometry on the crescent wing did not change the pressure-integrated drag significantly. The slightly higher span efficiency of the crescent wing is attributed to a more nearly elliptical spanwise lift distribution. The chord distribution of the elliptical wing was modified to produce an elliptical span-loading on a wing with an unswept quarter-chord line. This wing demonstrated a span efficiency equal to that of the crescent wing.

Smith, Stephen C.↗
NASA NTRS1979

Recent theoretical developments and experimental studies pertinent to vortex flow aerodynamics, with a view towards design

Recent progress in a research program directed toward an improved vortex flow technology base was reviewed. Analysis methods for conical flow and analysis and design methods for nonconical flows are presented. Applications are made for a variety of planar, nonplanar, and interferring lifting surfaces. Several methods are shown to provide reasonable estimates of over-all forces and moments for simple wing planforms with the suction analogy method currently offering the most versatility for arbitrary configuration applications. For the prediction of surface loadings the free vortex sheet method being developed by Boeing is shown to have considerable promise and further development of this type of method is encouraged. A data base for ogee strake-wing configurations is summarized with an emphasis on the requirements for maximizing the interference lift. A strake planform design procedure is discussed and a first solution (gothic in planview) is integrated with a wing body. The data show the strake to exhibit expected stable vortex characteristics. It was found that, apart from increasing sweep, conically cambered delta wings developed drag levels approaching that of attached flow with increasing either the lift or the wing camber height, lastly, an approximate vortex flow design method, based on the suction analogy, is outlined and an example is given.

Lamar, J. E.↗
NASA NTRS1989

An experimental and analytical investigation of the effect of spanwise curvature on wing flutter at Mach number of 0.7

An experimental and analytical study was conducted at Mach 0.7 to investigate the effects of spanwise curvature on flutter. Two series of rectangular planform wings of aspect ration 1.5 and curvature ranging from zero (uncurved) to 1.04/ft were flutter tested in the NASA Langley Transonic Dynamics Tunnel (TDT). One series consisted of models with a NACA 65 A010 airfoil section and the other of flat plate cross section models. Flutter analyses were conducted for correlation with the experimental results by using structural finite element methods to perform vibration analysis and two aerodynamic theories to obtain unsteady aerodynamic load calculations. The experimental results showed that for one series of models the flutter dynamic pressure increased significantly with curvature while for the other series of models the flutter dynamic pressure decreased with curvature. The flutter analyses, which generally predicted the experimental results, indicated that the difference in behavior of the two series of models was primarily due to differences in their structural properties.

Rivera, Jose A., Jr.↗