Effects of wing-tip strakes on a sheared-tip wing

An experimental investigation was conducted to evaluate the ability of plan ar and nonplanar wing tip strakes to improve the performance of a 4.18-aspe ct-ratio rectangular wing with a sheared tip. Strake leading-edge sweep, pl anform, and anhedral were varied. Force balance measurements, as well as su rface-pressure measurement and off-surface smoke flow visualization were un dertaken. The results show that planar strakes exhibit a minimal drag penal ty compared with the basic wing at low lift coefficients, while recording i mprovements in efficiency up to 12.8 %, Nonplanar strakes can significantly improve the wing efficiency at the expense of a substantial increase in th e minimum drag coefficient. Plow visualization showed that the wing-tip vor tex system consists of four vortices, two on the strake and two above the w ing tip, The forward progression of breakdown of the strake vortices with a ngle of attack is shown to be slower than would be expected for a delta win g.