Today the construction of planes, especially of sailplanes, is complex since a modern sailplane performs as a high-tech sports equipment. In the past a sailplane was built as a wooden construction. Today a sailplane is manufactured in composite material such as glass fiber or carbon fiber. On the one hand side this transformation in the manufacturing technology ensures a great advantage in the structural stability of the sailplanes and on the other hand side it enables new edges in aerodynamics. Due to the use of composites the construction achieves a production accuracy, which allows the use of aerodynamic laminar airfoils. The interaction of the complexity of structural mechanics and aerodynamic construction challenges the development engineers of the sailplane manufacturer. Especially the fundamental aerodynamic development of a sailplane is challenging. It is important to calculate and predict the aerodynamic performance accurately before a porotype is built.In this work a 15-meter-standard-class sailplane was designed. The preliminary aerodynamic design was made with the freeware software XFLR5, which is based on XFOIL, in combination with numerical simulations with the commercial Navier-Stokes-Solver Siemens STAR CCM+.A winglet is an aerodynamic component of an aircraft. The winglet extends the wingtip upwards. Because of the lower pressure on upper surface of the wing and the higher pressure on the lower wing surface, the flow generates vortices on the wing tip. A winglet separates the vortex in two parts. One main part of the vortex is formed on the transition from the main wing to the winglet and the other main part of the vortex is generated on the tip of the winglet.To investigate the aerodynamic impact and performance of winglets first isolated wings with winglets were designed and investigated with CFD and compared to the wings without winglets, showing the fundamental working principle and effectiveness of winglets. Then the complete sailplane was designed with an integrated inviscid flow method with XFLR5 combined with Navier-Stokes CFD computations with Siemens PLM STAR CCM+. In such a way a modern sailplane was designed for operation with winglets. Using this modern sailplane design the impact of winglets on sailplanes was investigated in detail. This modern sailplane was simulated with CFD in the configurations without winglets and with two modern advanced winglets. The aerodynamic characteristics and the performance of the sailplane without and with these two winglets was investigated. The difference of the aerodynamic performance of wings alone with and without winglets and the full sailplane with and without winglets were also compared. All aerodynamic results are analyzed and shown in detail.

Aerodynamic Performance Analysis of Winglets of Modern Sailplanes

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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