Journal of Applied Mechanics · 1963 · 99 citations · 0 references
AeroacousticsAeronauticsEngineeringFlexible AirfoilsAerospace EngineeringMechanicsFluid MechanicsMechanical EngineeringAirfoil AerodynamicsAeroelasticityAerodynamicsUnstable Airfoil ShapesThin-airfoil TheoryAircraft Design ProcessStructural MechanicsAerostructureFlexible Aerodynamic Surfaces
The study combines thin‑airfoil theory and quasi‑two‑dimensional experiments to compute camber line shapes as functions of angle of attack and excess material length, and to measure lift, drag, and moment for flexible airfoils. The analysis shows that specific eigenvalues of a nondimensional chordwise tension parameter produce stagnation‑point‑free shapes, with eigenmodes delineating stable and unstable regimes, and that lift, center of pressure, shape, and pressure distributions vary across the practical angle‑of‑attack range; experimentally, many aerodynamic characteristics match theory, but discrepancies arise mainly from fabric porosity and boundary‑layer separation.
A theoretical and experimental investigation has been made of the two-dimensional, aerodynamic characteristics of flexible airfoils or sails with no thickness. Thin-airfoil theory has been used to calculate the shapes of the camber lines as a function of angle of attack and excess length of material over the chord length. It is found that for specific eigenvalues of a nondimensional chordwise tension parameter, specific shapes arise for which there is no stagnation point. Some eigenmodes also correspond to boundaries between stable and unstable airfoil shapes. Lift, center of pressure, shapes, and pressure distributions are determined for the entire practical range of angle of attack. An experimental investigation of the lift, drag, and moment of quasi-two-dimensional flexible airfoils has been made, and the measurements have been compared with theory. Certain of the aerodynamic characteristics are in good accord with theory, but certain others are not, principally because of fabric porosity and boundary-layer separation.