Aerodynamics of Forward and Backward Swept Wings with an Over-Wing-Nacelle

Kurzfassung

In this thesis the impact of ultra-high bypass ratio over-wing-nacelle installation on aerodynamic wing characteristics is investigated on the basis of two aircraft configurations. The engine was placed above the wing trailing edge. For cruise flight conditions, at a Mach number of 0.78, different aspects are evaluated to build up a fundamental and generalized understanding of the associated installation effects. The investigation is accomplished with the aid of numerical simulations. At first, a comparison of wing-body and wing-body-engine-pylon configuration for a swept-back wing enables the identification of basic installation effects. The variation of the engine power setting provides a further detailing of the aerodynamic interaction between wing and OWN. The investigations reveal a significant effect on the upper wing pressure distribution due to the installation of an OWN-UHBR engine, while the lower wing is almost unaffected. The upper wing surface pressure is influenced on the one hand by the presence of the engine and on the other hand the engine power setting, whereby the sphere of influence in upstream and sideways direction is within the order of the engine diameter, leading to an upstream shift of the wing shock position in front of the engine. Moreover, flow disturbances originating from the OWN, are induced along the wing span, especially in the direction of the wing sweep, resulting in additional regions of supersonic flow and shock induced flow separations. The impact of an engine position variation in vertical and horizontal direction enables insight and assessment of the causes resulting in e.g. shock position variation or flow separations and their associated impact on aerodynamic coefficients. In this regard, the aerodynamic coefficients are evaluated with the aid of surface- and volume-based approaches to identify the type of generated drag component as well as the place of origin. The vertical engine position affects mainly the subsonic rear wing pressure level and thus has solely an impact on the wing lift coefficient, while the horizontal engine position is dominant with respect to the overall drag and affects the wing shock position. The investigation of OWN installation on a backward and forward swept wing planform offers an examination of the installation effects and accompanied aerodynamic characteristics on an additional configuration to derive on the one hand the impact of forward sweep and on the other hand achieve an extended and more general evaluation. The OWN installation on the forward swept wing configuration reveals similar interactions, as observed for the backward swept wing, whereby the main area of interference switches for the negative sweep angle from outer to inner wing segment.