Search

The potential of airfoil optimisation for the specific requirements of airborne wind energy (AWE) systems is investigated. Experimental and numerical investigations were conducted at high Reynolds numbers for the S1223 airfoil and an optimised airfoil with thin slat. The optimised geometry was generated using the NSGA-II optimisation algorithm in conjunction with 2D-RANS simulations. The results showed that simultaneous optimisation of the slat and airfoil is the most promising approach. Furthermore, the choice of turbulence model was found to be crucial, requiring appropriate transition modeling to reproduce experimental data. The k- ω - S S T - γ - R e θ model proved to be most suitable for the geometries investigated. Wind tunnel experiments were conducted with high aspect ratio model airfoils, using a novel structural design, relying mostly on 3D-printed airfoil segments. The optimised airfoil and slat geometry showed significantly improved maximum lift and a shift of the maximum power factor to higher angles of attack, indicating good potential for use in AWE systems, especially at higher Reynolds numbers. The combined numerical and experimental approach proved to be very successful and the overall process a promising starting point for future optimisation and investigation of airfoils for AWE systems. [ABSTRACT FROM AUTHOR]

Aerodynamic performance of aircraft wings vary with flight path conditions and depend on efficiency of high lift systems. In this work, a study on high lift devices and mechanisms that aim to increase maximum lift coefficient and reduce drag on commercial aircraft wings is discussed. Typically, such extensions are provided to main airfoil along span wise direction of wing and can increase lift coefficient by more than 100% during operation. Increasing the no of trailing edge flaps in chord wise direction could result in 100% increment in lift coefficient at a given angle of attack but leading edge slats improve lift by delaying the flow separation near stall angle of attack. Different combinations of trailing edge flaps used by Airbus, Boeing and McDonnel Douglas manufacturers are explained along with kinematic mechanisms to deploy them. The surface pressure distribution for 30P30N airfoil is evaluated using 2D vortex panel method and effects of chord wise boundary layer flow transitions on aerodynamic lift generation is discussed. The results showed better agreements with experiment data for high Reynolds number (9 million) flow conditions near stall angle of attack. [ABSTRACT FROM AUTHOR]

An immersed boundary method on unstructured meshes is used in serial eddy-resolving simulations of turbulent flows over individual bodies with a changeable configuration and position. The corresponding numerical technique is based on mesh deformation and dynamic adaptation of a moving mesh without changing its topology. The described approach makes it possible to substantially reduce the computational costs of serial computations with variations in geometric parameters aimed at optimizing the shapes of airfoil elements. The performance of the technique is demonstrated by simulating the aeroacoustic properties of a two-element airfoil segment involving a leading-edge slat with changeable geometry. [ABSTRACT FROM AUTHOR]

A new undergraduate laboratory exercise is described which explores the generation of lift over an aerofoil with and without a leading-edge slat. The experiment emphasises a fundamental understanding of the fluid-dynamic boundary layer and supports a second-year lecture course in fluid mechanics. A NACA 2415 aerofoil is used by the undergraduates in a simple open-return circuit wind tunnel at a Reynolds number of 2 × 105. Measurements of inviscid and viscous aerodynamic characteristics of the aerofoil are validated against cambered aerofoil theory and published NACA data. Oil surface-shear flow visualisation and the differences in the pressure distribution around the NACA 2415 with and without the leading-edge slat demonstrate the governing influence of the boundary layer on aerodynamic stall and the lift generated by the aerofoil. The new laboratory format was introduced to the undergraduates in 2007 and the response from student evaluation questionnaires confirmed that their understanding of basic fluid dynamics was greatly enhanced by the wind tunnel experiment. [ABSTRACT FROM AUTHOR]