Hydrofoils and airfoils
First Claim
1. In apparatus characterized as a foil having cambered surface extending from the leading edge to the trailing edge of said foil, between the cambered surface and a fluid of which relative movement can occur, the improvement which comprisesan area completely smooth, without indentations and devoid of projections located between the leading edge of the foil and the area of maximum camber, anda plurality of surface indentations disposed in a row spanwise on maximum camber which is devoid of projections and, except for the presence of said indentations is smooth, and sufficient to produce a low level boundary level turbulence and cause the fluid stream to attach and cling to the cambered surface in the area of said low level turbulence to postpone trailing edge separation of the stream to reduce noise level and improve the performance and efficiency of the foil as contrasted with a foil otherwise similar except that it contains no indentations on maximum camber, or contains indentations or projections, or both, in the area between the leading edge of the foil and maximum camber.
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Accused Products
Abstract
A low turbulence cambered surface foil, hydrofoil or airfoil, which contains indentations located on maximum camber across which a fluid can be flowed. The indentations create turbulence in the boundary layer downstream of the indentations, changing the characteristics of the flowing fluid to a turbulent boundary layer ahead of the normal point of separation of the fluid from the foil, this causing the fluid to cling close to the surface of the foil and postpone or delay trailing edge separation of the fluid stream from the foil. The noise level is reduced, the performance and efficiency of the foil is improved, or both the noise level is reduced and the performance and efficiency of the foil is improved.
90 Citations
24 Claims
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1. In apparatus characterized as a foil having cambered surface extending from the leading edge to the trailing edge of said foil, between the cambered surface and a fluid of which relative movement can occur, the improvement which comprises
an area completely smooth, without indentations and devoid of projections located between the leading edge of the foil and the area of maximum camber, and a plurality of surface indentations disposed in a row spanwise on maximum camber which is devoid of projections and, except for the presence of said indentations is smooth, and sufficient to produce a low level boundary level turbulence and cause the fluid stream to attach and cling to the cambered surface in the area of said low level turbulence to postpone trailing edge separation of the stream to reduce noise level and improve the performance and efficiency of the foil as contrasted with a foil otherwise similar except that it contains no indentations on maximum camber, or contains indentations or projections, or both, in the area between the leading edge of the foil and maximum camber.
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13. An airfoil having a cambered surface extending from the leading edge to the trailing edge of said airfoil designed to control the stability, direction, lift, thrust or propulsion capabilities of an aircraft moving in air of which said airfoil is a component, the improvement which comprises
an area completely smooth, without indentations and devoid of projections located between the leading edge of the foil and the area of maximum camber, and a plurality of surface indentations disposed in a row spanwise on maximum camber which is devoid of projections and, except for the presence of said indentations is smooth, and sufficient to produce a low level boundary level turbulence and cause the stream of air to attach and cling to the cambered surface in the area of said low level turbulence to postpone trailing edge separation of the stream of air to reduce the noise level and improve the performance and efficiency of the airfoil as contrasted with a foil otherwise similar except that it contains no indentations on maximum camber, or contains indentations or projections, or both, in the area between the leading edge of the foil and maximum camber.
- 18. In a process for producing a foil having a cambered surface extending from the leading edge to the trailing edge of said foil, between the cambered surface and a fluid of which relative movement can occur, the improvement which comprises locating an area completely smooth, without indentations and devoid of projections between the leading edge of the foil and the area of maximum camber, and a plurality of surface indentations disposed in a row spanwise on maximum camber which is devoid of projections and, except for the presence of said indentations is smooth, and sufficient to produce a low level boundary level turbulence which causes the fluid stream to attach and cling to the cambered surface in the area of said low level turbulence to postpone trailing edge separation of the stream to reduce noise level and improve the performance and efficiency of the foil as contrasted with a foil otherwise similar except that it contains no indentations on maximum camber, or contains indentations or projections, or both, in the area between the leading edge of the foil and maximum camber.
Specification