Boundary layer devices

Details Boundary layer devices Boundary layer devices

1988-02-19

1989-09-05

Barefoot, Galen L.

Aeronautics and astronautics

Aircraft sustentation

Sustaining airfoils

244130, B64C 2100

Patent

active

048631213

ABSTRACT:
An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprise flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.

REFERENCES:
patent: 4650138 (1987-03-01), Grose
patent: 4706910 (1987-11-01), Walsh
patent: 4736912 (1988-04-01), Loebert
AIAA-83-0230-An Experimental Study of Changes in the Structure of a Turbulent Boundary Layer Due to Surface Geometry Changes; Hooshmand et al., Jan. 1983.
AIAA 12th Aerospace Sciences Meeting-Turbulent Boundary Layer Drag Reduction Using Riblets; Walsh, Jan. 1982.
AIAA 22nd Aerospace Sciences Meeting-Optimization and Application of Riblets for Turbulent Drag Reduction; Walsh et al., Jan. 1984.
ICAS '86-Paper No. 86-1.8.3-Drag Reduction Mechanisms Derived from Shark Skin; Bechert et al.; Sep. 1986.
AIAA'83-AIAA-83-0227, Turbulent Drag Reduction for External Flows, D. M. Bushnell, p. 6, lines 16-64.
Mechanical Engineering, vol. 103, No. 3, Mar. 1981, p. 71, Grooves Reduce Aircraft Drag.
European Search Report 9/87.
NASA Tech. Brief, vol. 5, No. 2, Summer 1980.
NASA TM X-2643; Soderman, Aerodynamic Effects of Leading-Edge Serrations on a Two-Dimensional Airfoil, Sep. 1972, p. 11.

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