A Simplified Model for Fatigue Load Calculations of Small Wind- Turbines with Vertical Axis of Rotation

Wind Turbines with a vertical axis of rotation (VAWT) recently regained new interest. In this paper we summarize results from [2] in which our new aerodynamic model [1] was applied to an existing 50 kW machine. The presentation is organized as follows: First we present our simplified model which was formulated in closest analogy along the rules from IEC 61400-2 used for horizontal axis wind-turbines including some rigid-body extensions. Second we shortly discuss the only to us known aeroelastic code for VAWT, GAROS. Finally we present our results for fatigue loads from application to an 50 kW (140 m² swept area) prototype from both computations. As a main result we see that the differences between our simplified model (rigid body model with most equations coming from engineering mechanics) and a full aeroelastic modelling seems to be largest for the beam system supporting the blades on the shaf

Comparison of 3D transitional CFD simulations for rotating wind turbine wings with measurements:Paper

Since the investigation of van Ingen et al., attempts were undertaken to search for laminar parts within the boundary layer of wind turbines operating in the lower atmosphere with much higher turbulence levels than seen in wind tunnels or at higher altitudes where airplanes usually fly. Based on the results of the DAN-Aero experiment and the Aerodynamic Glove project, a special work package Boundary Layer Transition was embedded in IAEwind Task 29 MexNext 3rd phase (MN3). Here, we report on the results of the application of various CFD tools to predict transition on the MEXICO blade. In addition, recent results from a comparison of thermographic pictures (aimed at detecting transition) with 3D transitional CFD are included as well. The MEXICO (2006) and NEW MEXICO (2014) wind tunnel experiments on a turbine equipped with three 2.5 m blades have been described extensively in the literature. In addition, during MN3, high-frequency Kulite data from experiments were used to detect traces of transitional effects. Complementary, the following set of codes were applied to cases 1.1 and 1.2 (axial inflow with 10 m/s and 15 m/s respectively) – elsA, CFX, OpenFOAM (with 2 different turbulence/transitional models), Ellipsys, (with 2 different turbulence models and eN transition prediction tool), FLOWer and TAU – to search for detection of laminar parts by means of simulation. Obviously, the flow around a rotating blade is much more complicated than around a simple 2D section. Therefore, results for even integrated quantities like thrust and torque are varying strongly. Nevertheless, visible differences between fully turbulent and transitional set-ups are present. We discuss our findings, especially with respect to turbulence and transition models used

Synthetic turbulence models for wind turbine applications

Wind energy converters such as wind turbines permanently work in the atmospheric boundary layer. For the modelling of the dynamics and for the optimisation of design and material of wind turbines synthetic models for atmospheric turbulence are applied already for a long time. The main purpose of these models is to provide fast and efficient methods for numerical simulation of random fields, that show some characteristic features of atmospheric turbulence. Typically they only have a partial connection to the fundamental equations of fluid dynamics. After a short overview summarizing widespread models by Veers and Mann, that are based on the simulation of random fields in the Fourier domain, advanced models for the simulation of velocity fields are discussed

Experimental Analysis of a Wind-Turbine Rotor Blade Airfoil by means of Temperature-Sensitive Paint

Knowledge on the boundary-layer transition location at large chord Reynolds numbers (Re ≥ 3 million) is essential to evaluate the performance of airfoils designed for modern wind-turbine rotor blades, which rotor diameters can be of the order of hundred meters. In the present work, a temperature-sensitive paint (TSP) was used to systematically study boundary-layer transition on the suction side of a DU 91-W2-250 airfoil. The experiments were performed in the High-Pressure Wind Tunnel Göttingen at chord Reynolds numbers up to Re = 12 million and angles-of-attack from -14° to 20°. The coefficients of airfoil lift, drag, and pitching moment were also obtained after integration of the pressure distributions measured on the wind-tunnel model surface and in the model wake. The surface data obtained by means of TSP enabled not only to analyze the evolution of the transition location with varying angle-of-attack and chord Reynolds number, but also to provide an explanation for the evolution of the aerodynamic coefficients measured at stall and post-stall conditions. The stability of the laminar boundary layers investigated in the experiments was analyzed according to linear stability theory. The results of the stability computations supported the experimentally observed variations in the transition location. The amplification factors of boundary-layer disturbances at transition were also determined by correlating the experimental and numerical results

IEA Wind TCP Task 29, Phase IV:: Detailed Aerodynamics of Wind Turbines

This report describes the results of the fourth phase of IEA TCP Wind Task 29 on wind turbine aerodynamics