| Summary: | 碩士 === 淡江大學 === 航空太空工程學系碩士班 === 93 === Drag reduction is one of the main objectives of the transport aircraft manufacturers. The drag breakdown of a transport aircraft at cruise shows that the skin frictional drag and the lift-induced drag constitute the two main sources of drag. The vortices produced in the wing tip are unavoidable products by the presence of lift. Generation of tip vortices requires energy, and transfer of this energy from wing to air is induced drag. Large induced drag will reduce airplane endurance while cruising, and also increase the fuel consumption.
Furthermore, wing tip vortices on large aircraft can be so powerful as to endanger smaller aircraft flying behind them. For large airplanes such as Boeing 747, these tip vortices can be powerful enough to cause small airplanes following too closely to be out of control. The energy of the vortices can be modified through displacement and reduction. These modifications can potentially be achieved by the use of wing tip devices such as winglets.
In this paper, use computational method, and regard FLUENT software as flow solver. Investigating wings with different shapes of winglet, the situation of the flow field near the wing tip. The objective of this work is to gain a greater understanding of how the wing tip device modifies the vortex structure. Use ATR-72 wing as the datum, and add different types of winglet shape, at Mach number equal to 0.2 and 0.41, with different angles of attack, to compare the differences in CL and CD. It is including a new winglet appearance－spiroid winglet. I also design different kinds of spiroid winglet, including spiroid winglets with different cant angles, different sprial radius, and different spiroid winglet airfoil section, hope to find a optimize shape which can reduce the drag most, and then achieve the aerodynamic performance and fuel-efficient goals.
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