scispace - formally typeset
Search or ask a question
Topic

Airfoil

About: Airfoil is a research topic. Over the lifetime, 24696 publications have been published within this topic receiving 337709 citations. The topic is also known as: aerofoil & wing section.


Papers
More filters
01 Apr 1976
TL;DR: In this paper, the stability of elastic flap bending, lead-lag bending, and torsion of uniform, untwisted, cantilever rotor blades without chordwise offsets between the elastic, mass, tension, and areodynamic center axes is investigated for the hovering flight condition.
Abstract: The stability of elastic flap bending, lead-lag bending, and torsion of uniform, untwisted, cantilever rotor blades without chordwise offsets between the elastic, mass, tension, and areodynamic center axes is investigated for the hovering flight condition. The equations of motion are obtained by simplifying the general, nonlinear, partial differential equations of motion of an elastic rotating cantilever blade. The equations are adapted for a linearized stability analysis in the hovering flight condition by prescribing aerodynamic forces, applying Galerkin's method, and linearizing the resulting ordinary differential equations about the equilibrium operating condition. The aerodynamic forces are obtained from strip theory based on a quasi-steady approximation of two-dimensional unsteady airfoil theory. Six coupled mode shapes, calculated from free vibration about the equilibrium operating condition, are used in the linearized stability analysis. The study emphasizes the effects of two types of structural coupling that strongly influence the stability of hingeless rotor blades. The first structural coupling is the linear coupling between flap and lead-lag bending of the rotor blade. The second structural coupling is a nonlinear coupling between flap bending, lead-lag bending, and torsion deflections. Results are obtained for a wide variety of hingeless rotor configurations and operating conditions in order to provide a reasonably complete picture of hingeless rotor blade stability characteristics.

124 citations

Journal ArticleDOI
TL;DR: In this article, a comparison of various approaches with each other and with alternative computational approaches yields insight into both the methodologies and the solutions of both the solution and the results of these approaches.

124 citations

Journal ArticleDOI
TL;DR: In this paper, the aerodynamic properties of dynamic stall penetration at constant pitch rate and high Reynolds number were studied in an attempt to model more accurately conditions during aircraft poststall maneuvers and during helicopter high-speed forward flight.
Abstract: An experiment has been performed to study the aerodynamics of dynamic stall penetration at constant pitch rate and high Reynolds number, in an attempt to model more accurately conditions during aircraft poststall maneuvers and during helicopter high-speed forward flight. An airfoil was oscillated at pitch rates, A = ac/2U between 0.001 and 0.020, Mach numbers between 0.2 and 0.4, and Reynolds numbers between 2-4 x 10. Surface pressures were measured using 72 miniature transducers, and the locations of transition and separation were determined using 8 surface hot-film gages. The results demonstrate the influence of the leading-edge vorticity on the unsteady aerodynamic response during and after stall. The vortex is strengthened by increasing the pitch rate and is weakened by increasing the Mach number and by starting the motion close to the steady-state stall angle. A periodic pressure oscillation occurred after stall at high pitch angle and moderate Reynolds number; the oscillation frequency was close to that predicted for a von Karman vortex street. A small supersonic zone near the leading edge at M = 0.4 was found to reduce significantly the peak suction pressures and the unsteady increments to the airloads. These results provide the first known data base of constant-pitch-rate aerodynamic information at realistic combinations of Reynolds and Mach numbers.

124 citations

Journal ArticleDOI
TL;DR: The canard airfoil from the Voyager aircraft was tested in Ohio State University's subsonic wind tunnel as discussed by the authors, where a set of properly designed vortex generators were found to increase the lift and reduce the drag of the contaminated canard.
Abstract: The canard airfoil from the Voyager aircraft was tested in Ohio State University's subsonic wind tunnel. This highly optimized laminar flow section had good clean airfoil performance, but suffered severe lift and drag penalties with early boundary-layer transition. These performance penalties resulted from a midchord boundary-layer separation. An experimental program was conducted to document this problem and then to design and test vortex generators in order to improve the tripped airfoil performance while having the least effect on the clean airfoil. A set of properly designed vortex generators were found to increase the lift and reduce the drag of the contaminated airfoil. A brief study documented a significant drag rise due to a rough surface in the turbulent boundary-layer region.

123 citations

Journal ArticleDOI
TL;DR: In this article, three-dimensional bumps have been developed and investigated on transonic wings, aiming to fulfill two major objectives of shock-wave/boundary-layer interaction control, that is, drag reduction and buffet delay.
Abstract: Three-dimensional bumps have been developed and investigated on transonic wings, aiming to fulfill two major objectives of shock-wave/boundary-layer interaction control, that is, drag reduction and buffet delay. An experimental investigation has been conducted for a rounded bump in channel flow at the University of Cambridge and a computational study has been performed for a spanwise series of rounded bumps mounted on a transonic aerofoil at the University of Stuttgart. In both cases wave drag reduction and mild control effects on the boundary layer have been observed. Control effectiveness has been assessed for various bump configurations. A double configuration of narrow rounded bumps has been found to perform best, considerably reducing wave drag by means of a well-established X-shock structure with little viscous penalty and thus achieving a maximum overall drag reduction of about 30%, especially when significant wave drag is present. Counter-rotating streamwise vortex pairs have been produced by some configurations as a result of local flow separation. On the whole a large potential of three-dimensional control with discrete rounded bumps has been demonstrated both experimentally and numerically.

123 citations


Network Information
Related Topics (5)
Reynolds number
68.4K papers, 1.6M citations
80% related
Boundary layer
64.9K papers, 1.4M citations
77% related
Laminar flow
56K papers, 1.2M citations
76% related
Rotor (electric)
179.9K papers, 1.2M citations
75% related
Vortex
72.3K papers, 1.3M citations
75% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,083
20221,871
2021923
2020979
20191,097
20181,002