Flow Studies in the Vicinity of a Modified Flat-Plate Rectangular Wing of Aspect Ration 0.25

摘要

An investigation was made in order to study the characteristics of the flow in the vicinity of a rectangular wing of aspect ratio 0.25 with a modified flat-plate airfoil section. The investigation was conducted by means of photographs of a tuft grid located at a number of chordwise positions along the airfoil and behind the trailing edge of the airfoil. Supplementary measurements of the vorticity distribution in the wake were made with a yaw-head pitot-tube installation. The results indicate that there is a rapid rolling-up of the trailing vorticity along the chord of the wing and that at the higher angles of attack there is a distinct vortex visible at the first chordwise station behind the leading edge considered (12.5 percent chord). The trailing vortex sheet is apparently immediately rolled up into the vortex cores. The vertical locations of the vortex cores appear to leave the wing at approximately the 12.5-percent- chord position with an initial slope somewhat less than the angle of attack of the wing. The slope is approximately equal to one-half the angle of attack at the trailing edge and decreases somewhat behind the trailing edge. The slopes of the vertical locations of the vortex cores are predicted very well by the theory of Bollay. The photographs used in the present study show no clearly defined lateral movement of the cores with increasing angle of attack. The chordwise growth of lift calculated from the trailing-vortex strengths shows that the lift increases fairly rapidly across the forward part of the chord with approximately 70 to 85 percent of the total wing lift present forward of the midchord position. The total lift calculated from the tuft-grid photographs showed good agreement with the lift measured on the balance system.