GB718498A - Improvements in and relating to solid/fluid boundary surfaces - Google Patents

Abstract

718,498. Controlling boundary layer flow. STEPHENS, A. V. Oct. 23, 1951 [Oct. 24, 1950]. No. 25886/50. Class 4 A substantially impervious boundary surface relative to which when in use a fluid medium moves, is provided with a conformation for dividing up the boundary layer of the medium into side by side sections and diverting alternate sections away from the surface, thereby to project them into the medium some distance away from the boundary surface itself, while allowing the remaining sections to expand laterally into the spaces adjacent the boundary surfaces from which the first mentioned sections have been diverted. A plurality of excrescences 2 of generally triangular plan-form are arranged in one or more rows transverse to the direction of fluid flow. Their bases 3 face the direction of flow 4 and their apices 5 are raised above the level of the boundary surface 1, and they are spaced apart so that the distance 8 between each pair is a fraction, and preferably one-sixth, of the width of the base 3. The sides 6 may be curved in substantially S-form and the excrescences may be solid with the apices forming a knife-edge or they may comprise a plate surface supported by a central web. The portions of the boundary layer that flow over the surfaces of the excrescences 2 are deflected away from the boundary surface 1 the remaining portions that pass between the excrescences 2 being free to expand laterally with a corresponding reduction in thickness. The rows of excrescences may be positioned on an aircraft along the leading edge of a wing or ahead of a control surface such as a flap or an aileron or on the fuselage adjacent the roots of the wings. The excrescences may be hinged along their bases 3 so that the height 7 of the apices may be adjusted and when they are associated with control surfaces this adjustment may be operatively connected to the surface control mechanism. In an aileron, the leading edge thereof may be serrated and the trailing edge of the wing adjacent thereto formed with corresponding serrations so that when the aileron is deflected excrescences as shown in Fig. 1 may be formed. Other applications to motor vehicles, diffusers, ships hulls and propellers for ships and aircraft are described.