New Evaluation Technique for WTG Design Wind Speed Using a CFD‐Model‐Based Unsteady Flow Simulation with Wind Direction Changes

Takanori Uchida,Yuji Ohya,Takashi Maruyama

doi:10.1155/2011/941870

Abstract

Because a significant portion of the topography in Japan is characterized by steep, complex terrain, which results in a complex spatial distribution of wind speed, great care is necessary for selecting a site for the construction of wind turbine generators (WTG). We have developed a CFD model for unsteady flow called RIAM‐COMPACT (Research Institute for Applied Mechanics, Kyushu University, computational prediction of airflow over complex terrain). The RIAM‐COMPACT CFD model is based on large eddy simulation (LES). The computational domain of RIAM‐COMPACT can extend from several meters to several kilometers, and RIAM‐COMPACT can predict airflow and gas diffusion over complex terrain with high accuracy. The present paper proposes a technique for evaluating the deployment location of a WTG. The proposed technique employs the RIAM‐COMPACT CFD model and simulates a continuous wind direction change over 360 degrees.

Highlights

With the implementation of the revised Building Standard Law of Japan in June 2007, all structures which exceed a height of 60 m are subject to a performance assessment by a designated institution and the approval of the Minister of Land, Infrastructure, Transport, and Tourism
The evaluation is made for a wind farm which consists of ten wind turbines with rotor diameters of 62 m (Figure 3)
In order to ensure that the wind direction change has little influence on the statistical values calculated over approximately 10minute intervals, the number of time steps required for the rotation of the wind profile over 360 degrees is set to an appropriate value

Summary

Introduction

With the implementation of the revised Building Standard Law of Japan in June 2007, all structures which exceed a height of 60 m are subject to a performance assessment by a designated institution and the approval of the Minister of Land, Infrastructure, Transport, and Tourism. The ratio of the wind speed at the hubheight subject to topographical effects to the wind speed at the hubheight free of topographical effects (fractional increase of hubheight wind speed), hereafter, needs to be evaluated by taking topographical factors into consideration Given this background, the “Guidelines for the Design of Wind Turbine Support Structures/Commentary” [1] were published by the Japan. Modelling and Simulation in Engineering on the occurrence of high wind speed is evaluated from the analysis with the mesoscale meteorological model. A technique is proposed which resolves the above-mentioned drawbacks of the use of a mesoscale meteorological model This technique utilizes the strengths of a CFD model, which is able to simulate unsteady turbulence fields, and the wind speed for the wind-resistant design of wind turbines is evaluated for all wind directions using a calculation in which the wind direction is varied continuously in time

Numerical Computation Method

An Example of Design Wind Speed Evaluation

Summary