Effects Of Wing Sweep Research Articles

Performance Enhancement by Wing Sweep for High-Speed Dynamic Soaring

Dynamic soaring is a flight mode that uniquely enables high speeds without an engine. This is possible in a horizontal shear wind that comprises a thin layer and a large wind speed. It is shown that the speeds reachable by modern gliders approach the upper subsonic Mach number region where compressibility effects become significant, with the result that the compressibility-related drag rise yields a limitation for the achievable maximum speed. To overcome this limitation, wing sweep is considered an appropriate means. The effect of wing sweep on the relevant aerodynamic characteristics for glider type wings is addressed. A 3-degrees-of-freedom dynamics model and an energy-based model of the vehicle are developed in order to solve the maximum-speed problem with regard to the effect of the compressibility-related drag rise. Analytic solutions are derived so that generally valid results are achieved concerning the effects of wing sweep on the speed performance. Thus, it is shown that the maximum speed achievable with swept wing configurations can be increased. The improvement is small for sweep angles up to around 15 deg and shows a progressive increase thereafter. As a result, wing sweep has potential for enhancing the maximum-speed performance in high-speed dynamic soaring.

Experimental study on the effects of wing sweep on Gurney flap performance

The effect of wing sweep on the aerodynamic characteristics of Gurney flaps is examined. Wind tunnel models incorporating un-tapered 2.1 aspect ratio wings with sweeps of 0, 45 and 60 deg were designed and manufactured. Flap heights of 1% and 3% of the chord were evaluated. Testing was undertaken at Reynold's numbers of 100,000 and 150,000. The overarching result was that sweep attenuates the lift modulating ability of the flap, resulting from the effects of spanwise flow and reduced base suction behind the flap. Aerodynamic parameters were found to show a strong dependence on the cosine of the leading edge sweep angle as well as the square root of the flap height.

Undergraduate Aeroelasticity: The Typical Section Idealization Re-Examined

A simple typical section approach to aircraft wing bending-torsion divergence and flutter is presented. The approach can be used to illustrate the significant effects of wing sweep and material orthotropy in response to either steady or a simplified unsteady aerodynamic loading. This paper proposes that the typical section model, despite its well known deficiencies as a predictive tool, is appropriate as a learning device at the undergraduate level. The influences of wing sweep, material orthotropy and aerodynamic damping can be sequentially introduced with the aid of a single model. Indeed, the typical section approach outlined herein can be the unifying model that complements existing textbook presentations. Divergence and flutter velocities for a graphite-epoxy wing configuration are shown; the solution spans all angles of sweep and fiber orientations. Further, the approach is implemented in an MS Excel spreadsheet. The graphical user interface uses a notional wing geometry to aid in illustration and visualization during class or during individual study. The velocity root locus is plotted in real time based on 13 user inputs.

Open rotor tone scattering

This paper describes a method for calculating the scattering of open rotor tones by an adjacent surface such as the aircraft fuselage or wing. This is of practical importance because shielding by these structures could be used to significantly reduce community noise levels. In the first part of this paper the propeller is modelled as a rotating point source and the effect of propeller translation is neglected. The scattering of sound from this rotating point source by either a rigid circular cylinder or a rigid half-plane is calculated and the reflection/shielding effect is clearly demonstrated. In the second part of this paper, the point source/stationary medium model is extended to include the effect of distributed sources and a moving medium. The extended model is then applied to calculate the effect of scattering of rotor-alone tones by a wing (which is modelled as an infinite half-plane). The effect of wing sweep and the application of the Kutta-condition at the trailing edge is investigated. An approximate method for quickly calculating open rotor tone scattering is also developed and validated.

Infrared thermography investigations in transitional supersonic boundary layers

The study of boundary-layer transition in supersonic flows is conducted employing infrared thermography (IRT). Several models of swept wings are tested in a blow-down facility at Mach number 2.4. The effects of wing sweep and other parameters (angle of attack, leading-edge contour, presence/absence of surface roughness) are successfully observed. The transition front is clearly identified, demonstrating the utility of IRT for this type of study. The technique is particularly indicated for flows that are sensitive to surface alterations (roughness), such as transitional boundary layers, because it does not require interaction with the model or the flow under investigation. The additional advantage of no need for special apparatus, except for the infrared camera, makes IRT well suited for both wind-tunnel and in-flight testing. Practical problems and limitations encountered when dealing with IRT in high-speed flows are also discussed.

Some Recent Aerodynamic Advances in STOL Aircraft

16 Connors, J. W., Pfenninger, W., Smith, D. B., systems for laminar flow aircraft/ IAS Paper 61-52 (January 1961). 17 Fresenius, R., The principle of interaction between ship hull and propeller, Schiffbau (December 1921). 18 Pfenninger, W., Status of the X-21 nights, Northrop Norair Memo. 3850-63-356 (June 24, 1963); unpublished. 19 Gray, W. E., The effect of wing sweep on laminar flow, Royal Aircraft Establishment, Farnborough, England, Tech. Memo. 255 (1953). 20 Gregory, N., Transition and the spread of turbulence on a 60° swept-back wing, J. Roy. Aeronaut. Soc. 64, 562 (September 1960). 21 Pfenninger, W., about the spanwise turbulent contamination of swept low drag suction wings, Northrop Norair Intern. Note (July 17,1963); unpublished. 22 Sears, W. R., The boundary layer of yawed cylinders, J. Aeronaut. Sci. 15, 49-52 (January 1948). 23 Wild, J. M., The boundary layer of yawed infinite wings, J. Aeronaut. Sci. 16, 41-45 (January 1949). 24 Pfenninger, W., about a hypothesis of the instability of the laminar boundary layer in the leading edge region of a swept wing, Northrop Norair Intern. Note (March 3, 1964); unpublished. 25 Pfenninger, W., Further investigations of local suction regions at the leading edge of swept laminar suction wings, Northrop Norair Memo. 3850-395 (December 6, 1963); unpublished. 26 Bacon, J. W., Jr., Wind tunnel tests of 45° swept wing model with leading edge suction, Northrop Norair Memo. 3850-428 (May 20, 1964); unpublished. 27 Jones, R. T. and Cohen, D., Aerodynamic components of aircraft at high speeds, High Speed Aerodynamics and Jet Propulsion (Princeton University Press, N. J., 1957), Vol. VII, Chap. A 7, p. 81.