Showing papers on "Wing root published in 1989"

Sheared Wing-Tip Aerodynamics: Wind-Tunnel and Computational Investigation

Abstract: Computational and experimental performance benefits are presented for a high-aspect-ratio unswept wing configuration with sheared tips. The sheared tip is a highly swept and highly tapered surface located in the same plane as the inboard wing panel to which it is attached. The compuational results were obtained with an inviscid surface panel method that models the nonlinear influence of the trailing wake. Both wind-tunnel and calculated results were obtained for a 12-ft span wing model with various wing-tip configurations. The computational and experimental data are in fair agreement and demonstrate that sheared wing tips can reduce induced drag at cruise and climb lift coefficients. The drag reduction is the result of wake deformation effects and changes in spanwise load distribution. Wind-tunnel measured longitudinal and lateral directional stability characteristics are also presented for the various wing-tip layouts.

Accomplished Insect Fliers

Abstract: The flight characteristics of dragonflies, and to a lesser extent hawk moths, have been summarized. Wing kinematics, aerodynamic force generation and flow-wing interactions are presented. It is clear that these insects generate and use unsteady separated flow structures to support flight. Prominent vortex-wing interactions are routinely documented in conjunction with significant force generation. The wing geometry and kinematics dictate optimal unsteady flow generation as long as the wingbeat frequencies are maintained within prescribed ranges. The dragonfly appears able to readily switch between the use of unsteady flows and the use of more conventional steady state aerodynamics. The latter is used for gliding, a major element of dragonfly territoriality defense as seen in patrolling. The hawk moth appears to use similar unsteady flow strategies but doesn’t exploit gliding. What we believe we have observed is (1) a mechanistic, self-correcting device for creating unsteady flows, (2) a set of devices for using these flows and (3) a set of principles for unsteady flow exploitation by other biological flight systems.

Analysis of wings with flow separation

Abstract: An interactive viscous/inviscid procedure has been developed combining a three-dimensional panel method with an inverse finite-difference boundary-layer method. The scheme incorporates both a two-dimensional and a quasi-three-dimensional boundary-layer scheme. The resulting method has been applied to the calculation of the flow over three-dimensional wings and wing/body configurations and it has been shown that the procedure can compute flows with significant regions of boundary-layer separation.

Transonic region of high dynamic response encountered on an elastic supercritical wing

Abstract: Unsteady aerodynamic data were measured on a 10.3 aspect-ratio elastic supercritical wing while undergoing high dynamic response above a Mach number of 0.90. These tests were conducted in the NASA Langley Transonic Dynamics Tunnel. A previous test of this wing predicted an unusual instability boundary based upon subcritical response data. During the present test, no instability was found, but an angle-of-attack dependent narrow Mach number region of high dynamic wing response was observed over a wide range of dynamic pressures. The effect on dynamic wing response of wing angle of attack, static outboard control surface deflection and a lower surface spanwise fence located near the 60% local chordline was investigated. The driving mechanism of the dynamic wing response appears to be related to chordwise shock movement in conjunction with flow separation and reattachment on both the upper and lower surfaces.

Multigrid transonic computations about arbitrary aircraft configurations

Abstract: A three-dimensio nal full-potential code that is able to handle arbitrary aircraft configurations is described. This code is based on the use of Cartesian grids, local refinement, and multigrid calculations. The configuration is treated as an assembly of elements (bodies, wings, pylons, etc.). The algorithm incorporates the body boundary condition implementation for nonaligned grids. Multigrid treatment of local refinement and grid overlapping is described. Three application cases are discussed. First, a fighter configuration including body, wing, fairing, and canard; this example shows the importance of the grid-to-shock alignment. Second, a fighter configuration including body, wing, fairing, canard, and external fuel tank; the analysis shows an unexpectedly strong interference between body, wing, and fuel tank. Third, a civil aircraft configuration with different wing root fairings.

Flutter of a Low-Aspect-Ratio Rectangular Wing

Abstract: A flutter test of a low-aspect-ratio rectangular wing was conducted in the Langley Transonic Dynamics Tunnel (TDT). The model used in this flutter test consisted of a rigid wing mounted to the wind-tunnel wall by a flexible, rectangular beam. The flexible support shaft was connected to the wing root and was cantilever mounted to the wind-tunnel wall. The wing had an aspect ratio of 1.5 based on the wing semispan and an NACA 64A010 airfoil shape. The flutter boundary of the model was determined for a Mach number range of 0.5 to 0.97. The shape of the transonic flutter boundary was determined. Actual flutter points were obtained on both the subsonic and supersonic sides of the flutter bucket. The model exhibited a deep transonic flutter bucket over a narrow range of Mach number. At some Mach numbers, the flutter conditions were extrapolated using a subcritical response technique. In addition to the basic configuration, modifications were made to the model structure such that the first bending frequency was changed without significantly affecting the first torsion frequency. The experiment showed that increasing the bending stiffness of the model support shaft through these modifications lowered the flutter dynamic pressure. Flutter analysis was conducted for the basic model as a comparison with the experimental results. This flutter analysis was conducted with subsonic lifting-surface (kernel function) aerodynamics using the k method for the flutter solution.

Nonlinear Aerodynamics of a Delta Wing in Combined Pitch and Roll

Abstract: This paper presents an experimental study on the effects of roll on the loading and rolling moment of a 60 deg swept delta wing. The parameters studied were the incidence angle (including those in which vortex breakdown was present), roll angle, and ground proximity. Results indicate that when vortex breakdown is not present, the effects of roll on the wing loading and rolling moment are in reasonable agreement with predictions. When vortex breakdown is present, the magnitude of the rolling moment coefficient is reduced considerably and its sign can even be altered. The changes in the rolling moment characteristics due to vortex breakdown can be attributed to the roll-induced spanwise displacement of the leading-edge vortices. Effects of ground proximity on roll characteristics were shown to be small.

Drive extension/retraction mechanism for 2-engined aircraft in weight classes (civil) G, I, K and corresponding military aircraft

Abstract: The invention relates to 2-engined aircraft, such as those for which a patent was applied for by the applicant in 1977, for shrouded fan engines. The present invention relates to the use of engines having free propellers, which automatically fold up after the engines have been stopped. The propeller engines, when unfolded, are located in the triangle between the fuselage and wings (low-wing monoplane) and thus project less from the aircraft structure than in the case of known retractable engines. In the retracted state, the engines with the propeller are located - without any detrimental aerodynamic effect - in the fuselage, which allows economical gliding. The engines can be extended/retracted independently of one another. Slow cruising flight is thus also possible, using only one engine. The retraction mechanism is simple. Motor-driven or hand-driven spindles act on the so-called pylons whose rotation points are arranged close to the wing root. In the extended state, the force-fitting cups in the region of the fuselage outer wall increase the static strength of the engine mounting.