Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Patent
1996-06-24
1999-01-19
Mojica, V. Lissi
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
244204, 244130, B64C 138, B64C 2100, B64C 2110
Patent
active
058606262
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a surface of a body exposed to circumfluent fluid with elevations protruding from the base surface.
2. Description of the Related Art
It is already known that bodies exposed to circumfluent flows such as the external skin of airplanes are provided with fine waves, that is with corresponding relativly small elevations protruding from the base surface. In this way, a surface with an overall more favorable flow is obtained.
On the other hand, it is known, for example from the German utility model DE 90 13 099 U, that rotors can be provided in wave form to absorb energy from a flowing medium or to release energy to a flowing medium. The corresponding undulation of the rotor can substantially improve its efficiency.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a surface of a body exposed to circumfluent fluid with small elevations protruding from the base surface for an improved favorable flow.
This object is achieved in accordance with the present invention in that where a surface with elevations protruding from the base surface, in a view looking down on the surface the elevations are bordered in each case by two boundary lines of which one boundary line is longer and possesses a greater curvature than the other boundary line so that the cross-sectional area of an aerofoil is produced. The flow skimming over the surface therefore covers a longer path on the one side of the elevation than on the other side.
The elevations can now be arranged with respect to each other in such a way that in each case a boundary line with a larger curvature of an elevation is positioned next to a boundary line with a smaller curvature of a following elevation. In this way a channel is created which, on the one hand, is bordered by the comparatively longer and more curved boundary surface of an elevation and, on the other hand, by the shorter boundary surface with a smaller curvature of an adjacent elevation. In this way, an interference effect is obtained within the boundary layer of the fluid flowing round the body. The interference effect can be influenced dependency on the orientation of the curvature of the respective elevations to one another. The amount of curvature, and in particular the differences in curvature, between the respective boundary lines, also influences this effect.
In accordance with one embodiment of the present invention, several elevations can be arranged in rows with one behind the other, and several rows of elevations can be positioned next to each other.
In the rows formed by the elevations, the respective boundary lines of the elevations with a larger curvature can be aligned in one direction.
The boundary lines of the elevations with the larger curvature can point alternately in opposite directions in a row. The height of the elevations in the event of rows of elevations being positioned next to each other may vary. Furthermore, the height of the elevations positioned one behind the other in a row may vary.
The elevations may also be curved in the direction of their end pointing away from the base surface.
The surface of the elevations lying opposite the base surface can be parallel to the base surface or be aligned diagonally to the base surface while the lateral boundary surfaces of the elevations are aligned perpendicularly to the base surface in each case.
Furthermore, the surface may possess first, comparatively high elevations which form a macrostructure, and on this macrostructure in turn comparatively low elevations can be created which form a microstructure.
These surfaces can be applied to the body exposed to circumfluent fluid subsequently as an external skin. In principle, however, it is possible that the body exposed to circumfluent fluid can be formed with the surface in accordance with the present invention right from the start.
In principle, the surface in accordance with the present invention can be used preferentially with all bodies exposed to circumfluent flows. Thus,
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Walsh, M.J.; et al.: AIAA Paper 84-0347, Jan. 1984, S.1-10.
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