Abstract
The aerodynamic analysis of a wind turbine represents a very complex task since it involves an unsteady three‐dimensional viscous flow. In most existing performance‐analysis methods, wind turbines are considered isolated so that interference effects caused by other rotors or by the site topology are neglected. Studying these effects in order to optimize the arrangement and the positioning of Horizontal‐Axis Wind Turbines (HAWTs) on a wind farm is one of the research activities of the Bombardier Aeronautical Chair. As a preliminary step in the progress of this project, a method that includes some of the essential ingredients for the analysis of wind farms has been developed and is presented in the paper. In this proposed method, the flow field around isolated HAWTs is predicted by solving the steady‐state, incompressible, two‐dimensional axisymmetric Navier‐Stokes equations. The turbine is represented by a distribution of momentum sources. The resulting governing equations are solved using a Control‐Volume Finite Element Method (CVFEM). This axisymmetric implementation efficiently illustrates the applicability and viability of the proposed methodology, by using a formulation that necessitates a minimum of computer resources. The axisymmetric method produces performance predictions for isolated machines with the same level of accuracy than the well‐known momentum‐strip theory. It can therefore be considered to be a useful tool for the design of HAWTs. Its main advantage, however, is its capacity to predict the flow in the wake which constitutes one of the essential features needed for the performance predictions of wind farms of dense cluster arrangements.
Highlights
After some unsuccessful attempts at constructing and operating very-large-scale isolated wind turbines, the recent tendency is to construct wind farms of medium-size machines (500 kW)
The pressure is assumed to be uniform and given while the three velocity components are computed from the discretised momentum equations obtained using the outflow treatment of Patankar [980]
The results presented are aimed at demonstrating the capacity of the proposed methodology to accurately predict the performances of isolated Horizontal-Axis Wind Turbines (HAWTs), and to analyse wind farms
Summary
After some unsuccessful attempts at constructing and operating very-large-scale isolated wind turbines, the recent tendency is to construct wind farms of medium-size machines (500 kW). The strategy currently used during the conception of such wind farms consists in installing the turbines far from each other in order to minimize the interference effects. This practice results in very sparse wind farms where the wind energy potential of a site is inefficiently used. A relatively dense but staggered arrangement of the turbines is expected to produce an increase in the performance of the downstream turbines with respect to the isolated-turbine situation This is due to the beneficial venturi effects that occur between two adjacent turbine wakes. Some of the construction expenses, such as the grading and electric infrastructure costs, will be reduced
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