An Investigation of the Non-Linear 3D Flow Effects Relevant for Leading Edge Inflatable Kites

The kite power group at TU Delft is currently researching the use of leading edge inflatable (LEI) kites for use in power generation. A thorough understanding of the aeroelastics of these kites is paramount to the development of system simulation models and optimum kite and system designs. The current lack of understanding is therefore seen as a roadblock to the development of a commercially viable kite power system. The aeroelastics of LEI kites are complicated by three main challenges. \u95 There is a high degree of coupling between the flexible kite and the aerodynamic loading. This means that a fluid-structure interaction approach is typically needed to produce accurate simulation results. \u95 The low aspect ratio and large anhedral of the kite means that 3D effects are significant. \u95 During normal power production it is desirable to fly the kite at high angles of attack where significant non-linear viscous phenomena (e.g. flow seperation) are known to occur. In order to model correctly the 3D viscous aerodynamic phenomena present in LEI kite flight a computational approach utilizing a steady-state Reynolds-Average-Navier-Stokes (RANS) solver has been suggested. This work presents a review of relevant literature, outlines the computational approach taken, and discusses the limitations and computational costs of the approach. It was found that the RANS approach is able to model the kite’s flow environment up to angles of attack of 24?. At angles larger than this significant flow separation from the suction surface of the kite precludes the use of a steady-state solver. At angles as low as 18? significant non-linear effects begin to take effect, decreasing lift and increasing drag. It was also found that at lower angles of attack separation from behind the leading edge tube serves to decrease effective camber and therefore lift. The computational cost of the approach is heavily influenced by the quality of the mesh generated, in particular the presence of non-orthogonal cells. It is concluded that the RANS approach is capable of quantifying well the non-linear flow effects of LEI kites at moderately high angles of attack. The challenge of this method in the future will be to decrease it’s significant computational costs so that it may be used in the context of systems modeling, optimization, or fluid-structure interaction.European Wind Energy MasterWind EnergyAerospace Engineerin