Accurate modeling of large wind turbine blades is an extremely challenging problem. This is due to their tremendous geometric complexity and the turbulent and unpredictable conditions in which they operate. In this paper, a continuum based three dimensional finite element model of an elastic wind turbine blade is derived using the absolute nodal coordinates formulation (ANCF). This formulation is very suitable for modeling of largedeformation, large-rotation structures like wind turbine blades. An efficient model of six thin plate elements is proposed for such blades with non-uniform, and twisted nature. Furthermore, a mapping procedure to construct the ANCF model of NACA (National Advisory Committee for Aeronautics) wind turbine blades airfoils is established to mesh the geometry of a real turbine blade. The complex shape of such blades is approximated using an absolute nodal coordinate thin plate element, to take the blades tapering and twist into account. Three numerical examples are presented to show the transient response of the wind turbine blades due to gravitational/aerodynamics forces. The simulation results are compared with those obtained using ANSYS code with a good agreement.

This paper describes the use of the Absolute Nodal Coordinate Formulation (ANCF) in modeling large-size wind turbine blades. An efficient procedure is developed for mapping NACA airfoil wind-turbine blades into ANCF thin plate models. The procedure concerns the wind turbine blade with non-uniform, twisted nature. As a result, the slope discontinuity problem arises and presents numerical errors in the dynamic simulation. This investigation illustrates a method for modeling slope discontinuity resulting from the variations of the cross sectional layouts across the blade. A method is developed and applied for the gradient-deficient thin plate element in order to account for structural discontinuity. The numerical results show a numerical convergence and satisfy the principle of work and energy in dynamics. The simulation results are compared with those obtained using ANSYS code with a good agreement.

We consider the problem of selecting among different computational models of various fidelity for evaluating the objective and constraint functions in numerical design optimization. Typically, higher-fidelity models are associated with higher computational cost. Therefore, it is desirable to employ them only when necessary. We introduce a reference error formulation that aims at determining whether lower-fidelity models (that are computationally cheaper) can be used in certain areas of the design space as the latter is being explored during the optimization process. The proposed approach is implemented using an existing trust region model management framework. We demonstrate the link between feasibility and fidelity and the key features of the proposed approach using the design example of a cantilever flexible beam subject to high accelerations.

In this paper, the Blade Element Momentum (BEM) theory is used to design the horizontal wind turbine blades. The design procedure concerns the main parameters of the axial/angular induction factors, chord length, twist/attack angles, and local power/thrust coefficients. These factors in turns affect the blade aerodynamics characteristics and efficiency at the corresponding nominal speed. NACA 4-digits airfoil geometry is obtained, using BEM theory, to achieve the maximum lift to drag ratios. The optimization of the power coefficient and its distribution versus different speeds is carried out by modifying the twist angle and chord length distribution along the blade span. The dynamic characteristics of both the original and optimized design are examined through forward dynamic simulation of the blade model. Since large-size wind turbine blade is considered, the dynamic model is established using the Absolute Nodal Coordinate Formulation (ANCF), which is suitable for large-rotation large-deformation problems. Finally, in order to verify the dynamic enhancements in the Aerodynamic/Structural properties, the fluid-solid interaction simulation for both the original and optimized model is performed using ANSYS code. The obtained results show a good rank of the proposed optimization procedure for a practical case of wind data upon Gulf of Suez-Egypt.

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