Numerical Analysis of Horizontal-Axis Wind Turbine Characteristics in Yawed Conditions

Masami Suzuki

Department of Mechanical Systems Engineering, University of the Ryukyus, Okinawa, Japan.

DOI: 10.4236/ojfd.2012.24A041                

Abstract

Computational fluid dynamics (CFD) modeling and experiments have both advantages and disadvantages. Doing both can be complementary, and we can expect more effective understanding of the phenomenon. It is useful to utilize CFD as an efficient tool for the turbomachinery and can complement uncertain experimental results. However the CFD simulation takes a long time for a design in generally. It is need to reduce the calculation time for many design condi- tions. In this paper, it is attempted to obtain the more accurate characteristics of a wind turbine in yawed flow condi- tions for a short time, using a few grid points. It is discussed for the reliability of the experimental results and the CFD results.

Keywords

Wind Turbine; Yawed Flow; CFD; Unsteady Rotor Aerodynamics; Performance

1. Introduction

Computational fluid dynamics (CFD) modeling and experiments have both advantages and disadvantages. Doing both can be complementary, and we can expect more effective understanding of the phenomenon. Although CFD has more advantages than experiments for the prediction where experiments are difficult to carry out, generally when compared with experimental results, it is difficult to obtain reliable results for a large domain by using CFD. However, it is possible to obtain useful CFD results based on verification by the experimental results. Moreover, experiments cannot deliver correct results for any arbitrary condition due to limitations to experimental equipment, measurement errors and problems with measurement systems. It is useful to utilize CFD as an efficient tool for the turbomachinery and can complement uncertain experimental results. However the CFD simulation takes a long calculation time for a design in generally. It is need to reduce the calculation time for many design conditions. In this paper, it is attempted to solve the more accurate characteristics of a wind turbine for a short time even a personal computer, using coarse grid [1]. In this paper the wind turbine characteristics of the yawed condition are discussed including the reliability of the experimental results and the CFD results.

2. Numerical Method

The in-house code used is an incompressible finite volume Navier-Stokes solver which is developed originally. The solver is based on structured grids and the use of curve-linear boundary fitted coordinates. The grid arrangement is collocated (Perić et al. [2]) and the Rhie and Chow interpolation method [3] is used. The SIMPLE algorithm (Patankar [4]) is used for pressure-velocity coupling. The convection term is calculated using the QUICK scheme (Leonard [5]) and the other terms in space are calculated using the 2^nd order difference schemes. It is well known that sophisticated turbulence models do not always produce better results than the very simple models. For practical applications that are computationally expensive it is often wiser to use a simple approach. Therefore the proven and computationally efficient Launder-Sharma low-Reynolds-number k-e turbulence model [6] is used in this report.

3. Wind Turbine and Aerodynamic Force Acting to Blade

Figure 1 shows a schematic view of experimental apparatus for a wind turbine carried out by Vermeer [7]. A two bladed wind turbine is situated in front of the wind turbine. The wind turbine has diameter of 1.2 m and the blades consist of NACA 0012 airfoil and the chord length of 0.08 m. The experiment is conducted at wind velocity of 5 m/s, and the measured data are the wind velocity, the number of rotation, the torque, and the thrust. Moreover, Haans et al. [8,9] measure with the same experiment equipment about the thrust according to a yawed wind (0˚, ±15˚, ±30˚, ±45˚) of 5.5 m/s in speed

Conflicts of Interest

The authors declare no conflicts of interest.

References

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