An upper wing surface of a laminar-flow airfoil for decreasing an undesirable head-lowering pitching moment around an aerodynamic center of the airfoil. The upper wing surface includes: a convex front profile portion extending from a leading edge to a largest-thickness point located corresponding to
An upper wing surface of a laminar-flow airfoil for decreasing an undesirable head-lowering pitching moment around an aerodynamic center of the airfoil. The upper wing surface includes: a convex front profile portion extending from a leading edge to a largest-thickness point located corresponding to 38% of a wing chord length. A convex central profile portion extends from the largest-thickness point to a position corresponding to 90% of the wing chord length at which a value obtained by dividing a thicknesswise difference between the position and the largest-thickness point by a distance in a direction of the wing chord from the largest-thickness point is equal to or smaller than 0.12. A concave rear profile portion extends from a position corresponding to 95% of the wing chord length to the trailing edge. The rear profile portion forms a pressure gradient is steeper than that formed by the central profile portion.
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What is claimed is: 1. A laminar-flow airfoil comprising: an upper wing surface, a lower wing surface, a leading edge and a trailing edge, wherein said upper wing surface includes: a front profile portion which has a positive curvature radius, and which is provided to extend from the leading edge t
What is claimed is: 1. A laminar-flow airfoil comprising: an upper wing surface, a lower wing surface, a leading edge and a trailing edge, wherein said upper wing surface includes: a front profile portion which has a positive curvature radius, and which is provided to extend from the leading edge to a largest-thickness point located in a range of 30% to 50% of a wing chord length, the front profile portion forming a laminar-flow boundary layer; a central profile portion which has a positive curvature radius, and which is provided to extend from the largest-thickness point to the vicinity of a position corresponding to approximately 90% of the wing chord length at which a value obtained by dividing a thicknesswise difference between the position and the largest-thickness point by a distance in a direction of a wing chord from the largest-thickness point is equal to or smaller than 0.12, the central profile portion forming a gentle pressure gradient to suppress separation of the boundary layer; and a rear profile portion which is curved concavely outwards, and which is provided to extend from the vicinity of a position corresponding to approximately 95% of the wing chord length to the trailing edge, the rear profile portion forming a pressure gradient steeper than that formed by the central profile portion to induce slight separation of the boundary layer, whereby a head-lowering pitching moment about an aerodynamic center is decreased. 2. The laminar-flow airfoil according to claim 1, wherein the largest-thickness point is approximately 38% of the wing chord length. 3. The laminar-flow airfoil according to claim 1, and further including a transition point at which the laminar-flow boundary layer region changes to a turbulent-flow boundary layer region. 4. The laminar-flow airfoil according to claim 3, wherein the transition point is approximately 42% of the wing chord length. 5. The laminar-flow airfoil according to claim 1, and further including a largest-thickness position disposed on the lower wing surface for forming a laminar-flow boundary layer region. 6. The laminar-flow airfoil according to claim 5, wherein the largest-thickness position disposed on the lower wing surface is approximately 49% of the wing chord length. 7. The laminar-flow airfoil according to claim 5, and further including a transition point disposed on the lower wing surface at which the laminar-flow boundary layer region changes to a turbulent-flow boundary layer regions. 8. The laminar-flow airfoil according to claim 7, wherein the transition point disposed on the lower wing surface is approximately 63% of the wing chord length. 9. A laminar-flow airfoil comprising: an upper wing surface, a lower wing surface, a leading edge and a trailing edge, wherein said upper wing surface includes: a front profile portion which has a positive curvature radius, and which is provided to extend from the leading edge to a largest-thickness point located in a range of 30% to 50% of a wing chord length, the front profile portion forming a laminar-flow boundary layer; a central profile portion which has a positive curvature radius, and which is provided to extend from the largest-thickness point to the vicinity of a position corresponding to approximately 90% of the wing chord length at which a value obtained by dividing a thicknesswise difference between the position and the largest-thickness point by a distance in a direction of a wing chord from the largest-thickness point is equal to or smaller than 0.12, the central profile portion forming a gentle pressure gradient to suppress separation of the boundary layer; and a rear profile portion which is rectilinear in shape, and which is provided to extend from the vicinity of a position corresponding to approximately 95% of the wing chord length to the trailing edge, the rear profile portion forming a pressure gradient steeper than that formed by the central profile portion to induce slight separation of the boundary layer, whereby a head-lowering pitching moment about an aerodynamic center is decreased. 10. The laminar-flow airfoil according to claim 9, wherein the largest-thickness point is approximately 38% of the wing chord length. 11. The laminar-flow airfoil according to claim 9, and further including a transition point at which the laminar-flow boundary layer region changes to a turbulent-flow boundary layer region. 12. The laminar-flow airfoil according to claim 11, wherein the transition point is approximately 42% of the wing chord length. 13. The laminar-flow airfoil according to claim 9, and further including a largest-thickness position disposed on the lower wing surface for forming a laminar-flow boundary layer region. 14. The laminar-flow airfoil according to claim 13, wherein the largest-thickness position disposed on the lower wing surface is approximately 49% of the wing chord length. 15. The laminar-flow airfoil according to claim 13, and further including a transition point disposed on the lower wing surface at which the laminar-flow boundary layer region changes to a turbulent-flow boundary layer regions. 16. The laminar-flow airfoil according to claim 15, wherein the transition point disposed on the lower wing surface is approximately 63% of the wing chord length. 17. A laminar-flow airfoil comprising: an upper wing surface, a lower wing surface, a leading edge and a trailing edge, wherein said upper wing surface includes: a front profile portion which has a positive curvature radius, and which is provided to extend from the leading edge to a largest-thickness point located in a range of 30% to 50% of a wing chord length, the front profile portion forming a laminar-flow boundary layer; a central profile portion which has a positive curvature radius, and which is provided to extend from the largest-thickness point to the trailing edge of the wing chord length at which a value obtained by dividing a thicknesswise difference (Δt) between the position and the largest-thickness point by a distance in a direction of a wing chord from the largest-thickness point is equal to or smaller than a predetermined number, the central profile portion forming a gentle pressure gradient to suppress separation of the boundary layer; and a rear profile portion which is curved concavely outwards, and which is provided to extend from the vicinity of a position adjacent to the trailing edge of the wing chord length to the trailing edge, the rear profile portion forming a pressure gradient steeper than that formed by the central profile portion to induce slight separation of the boundary layer, whereby a head-lowering pitching moment about an aerodynamic center is decreased, wherein a thickness between an upper wing surface and a lower wing surface at the largest-thickness point of the airfoil being substantially 15% of the wing chord length. 18. The laminar-flow airfoil according to claim 17, wherein the value obtained by dividing is equal to or smaller than 0.12. 19. The laminar-flow airfoil according to claim 17, wherein the central profile portion extends to the vicinity of a position corresponding to approximately 90% of the wing chord length. 20. The laminar-flow airfoil according to claim 17, wherein the rear profile portion extends to a position corresponding to approximately 95% of the wing chord length. 21. The laminar-flow airfoil according to claim 17, wherein the aerodynamic center is located at a position substantially corresponding to 25% of the wing chord length. 22. A laminar-flow airfoil comprising: an upper wing surface, a lower wing surface, a leading edge and a trailing edge, wherein said upper wing surface includes: a front profile portion which has a positive curvature radius, and which is provided to extend from the leading edge to a largest-thickness point located in a range of 30% to 50% of a wing chord length, the front profile portion forming a laminar-flow boundary layer; a central profile portion which has a positive curvature radius, and which is provided to extend from the largest-thickness point to the trailing edge of the wing chord length at which a value obtained by dividing a thicknesswise difference (Δt) between the position and the largest-thickness point by a distance in a direction of a wing chord from the largest-thickness point is equal to or smaller than a predetermined number, the central profile portion forming a gentle pressure gradient to suppress separation of the boundary layer; and a rear profile portion which is curved concavely outwards, and which is provided to extend from the vicinity of a position adjacent to the trailing edge of the wing chord length to the trailing edge, the rear profile portion forming a pressure gradient steeper than that formed by the central profile portion to induce slight separation of the boundary layer, whereby a head-lowering pitching moment about an aerodynamic center is decreased, wherein the rear profile portion extends to a position corresponding to approximately 95% of the wing chord length.
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이 특허에 인용된 특허 (11)
Bousquet Jean (Blagnac FRX), Airfoil shape for aircraft.
Thibert Jean-Jacques (Verrieres le Buisson FRX) Rodde Anne-Marie (Verrieres le Buisson FRX) Pouradier Jean-Marc E. (Port-Saint-Louis-du-Rhone FRX), Blade section for rotating wings of an aircraft.
Ashill Patrick R. (Bromham GBX) Pierce Donald (Crookham Village GBX) Treadgold Desmond A. (Farnborough GBX) Fulker John L. (Sharnbrook GBX), Manoeuverable supercritical wing section.
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