Pitching moment

About: Pitching moment is a research topic. Over the lifetime, 3213 publications have been published within this topic receiving 38721 citations.

Control of Flow Separation Using Self-Supplying Air-Jet Vortex Generators

Abstract: Wind-tunnel experimental investigations were conducted to investigate the use of conventional outsupplying and proposed self-supplying air-jet vortex generators to delay flow separation over an NACA 0012 airfoil. The conventional air-jet vortex generators were supplied with the air from an external compressor, and proposed self-supplying generators got the air from the overpressure region situated in the nose part of the airfoil lower surface. The lift, drag, and pitching moment for the smooth airfoil equipped with air-jet vortex generators were determined based on the pressure distribution measurements. The experimental tests were carried out in both the low-speed wind tunnel (M=0.05-0.1) with the airfoil model of 0.5-m chord length and the high-speed wind tunnel (M = 0.1-0.85) with the airfoil model of 0.18-m chord length. In the high-speed wind tunnel, the influence of using only the self-supplying air-jet vortex generators was tested. It was found that using both types of air vortex generators can delay the flow separation on the airfoil, which leads to the increase of both the lift coefficient and the critical angle of attack.

Wind-tunnel Investigation of Ground Effect on Wings with Flaps

Abstract: An investigation was conducted in the N.A.C.A. 7- by 10-foot wind tunnel to determine the effect of ground proximity on the aerodynamic characteristics of wings equipped with high-lift devices. A rectangular and a tapered wing were tested without flaps, with a split flap, and with a slotted flap. The ground was represented by a flat plate, completely spanning the tunnel and extending a considerable distance ahead and back of the model. The position of the plate was varied from one-half to three chord lengths below the wing. The results are presented in the form of curves of absolute coefficients, showing the effect of the ground on each wing arrangement. The effect of the ground on lift, drag, and pitching moment is discussed. An appendix gives equations for calculating tunnel-wall corrections to be applied to ground-effect tests conducted in rectangular tunnels when a plate is used to represent the ground. The tests indicated that the ground effect on wings with flaps is a marked decrease in drag, a decrease in diving moment, and a substantial reduction in maximum lift.

Pitch-up characteristics for hsct class planforms: survey and estimation

Abstract: Low aspect ratio, highly-swept cranked delta and arrow wing planforms are often proposed for high-speed civil transports. These wing planforms offer low supersonic drag without suffering greatly from low liftldrag ratios in low-speed flight. They can, however, suffer from pitch-up at modest angles of attack (as low as 5' angle of attack) during low-speed flight due to leading edge vortex influence, flow separation and vortex breakdown. This paper describes an investigation conducted to study past research on the longitudinal aerodynamic characteristics of highlyswept cranked wing planforms and a new method to estimate pitch-up. The survey of past research placed emphasis on 1) understanding the problem of pitch-up, and 2) ascertaining the effects of leading and trailing edge flaps. The estimation method uses a vortex lattice method to calculate the inviscid flow solution. Then, the results are adjusted to account for flow separation on the outboard wing section by imposing a limit on the equivalent 2-D sectional lift coefficient. The method offers a means of making low cost estimates of the non-linear pitching moment characteristics of slender, cranked arrow wing configurations. Numerous comparisons with data are included.

The aerodynamic interference between tanker and receiver aircraft during air-to-air refuelling

Abstract: Wind tunnel data from a tanker wing and receiver aircraft model at varying vertical separation have been compared with theoretical results. In the aerodynamic model the tanker wing is represented by a horseshoe vortex while the aerodynamic loads on the receiver are determined by the vortex lattice method and lifting-line theory, although an approximate method is used to determine the side force on the fin. In the longitudinal case data were obtained for low, mid and high tailplane positions and, with the exception of the pitching moment results, fairly good agreement is obtained between theory and experiment. The relatively small differences are due mainly to the wind tunnel boundary interference effect which could not be quantified for the pitching moment measurements. The lateral aerodynamic interference was determined by banking the tanker wing and displacing it sideways and by yawing the receiver model. Fairly good agreement is obtained between the theory and experiment for the most significant terms which are the rolling moments due to bank and sideways displacement. The effect of the sidewash due to the tanker wake on the receiver in yaw is found to be relatively insignificant. Over the range of bank, yaw and sideways displacements tested the results are almost linear.