Aerodynamic Characteristics of Semi-spiroid Winglets at Subsonic Speed

In recent years, owing to the improving global socio-economic conditions, the number of air passengers grows rapidly. Despite the phenomenal increase in the passenger growth, the airline fuel cost continues to dominate with 27% of the total airline operating cost. Induced drag due to the pressure differential induced between the wings being the major contributor accounts for 25% of total drag at cruise to around 60% during take-off. With a view to overcome this, end plates were introduced in the 1980s to reduce the wingtip vortices. Several studies have been performed by researchers over various configurations and found that the angle at which the winglets are inclined greatly influences the strength of the wingtip vortices shed away from the winglets. In order to understand the effect of eccentricity on aerodynamic performance, a baseline swept wing with vertical winglets and seven different modified models featuring curved winglets with different eccentricities were computationally investigated for various angles of attack at Re = 4.0 × 10⁶. Results reveal that the curved semi-spiroid winglet with eccentricity e (0.2) outperforms clean wing showing a 9.85% increment in the aerodynamic efficiency over the pre-stall regions.