ECN publication
AWSM - Ground and wind shear effects in aerodynamic analysis
Published by: Publication date:
ECN Wind Energy 28-3-2011
ECN report number: Document type:
ECN-E--10-016 ECN publication
Number of pages: Full text:
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In order to design more advanced and efficient wind turbines, more accurate results coming from numerical predictions are mandatory. This need became more and more important in the last years due to the growth of wind turbines, especially for offshore scenarios. The diameter of a modern MW class wind turbine can easily be greater than 100m, on which the effect of wind shear and incoherent atmospheric structures on blade loads play a much more significant role. Most of the available codes are based on Blade Element Momentum (BEM) theory. The main advantage of this class of codes is the fact that they are very fast to calculate the loads and performance of a wind turbine. This makes BEM codes very convenient especially in the very extensive wind turbine design and load calculations, but due to all the hypotheses of the theory, there are several restrictions for BEM codes usage. By using full Navier-Stokes based codes, for example, there are no limitations about the geometry and no restrictive hypotheses related with the aerodynamics, so it is possible to perform both detailed fluid-dynamics studies and general performance-oriented analyses in very general conditions. The drawback is the big demand in terms of computational resources, computational time and expertise. A code, named Aerodynamic Windturbine Simulation Module (AWSM), has been developed at Energy research Centre of the Netherlands (ECN) by van Garrel [1]. The main scope was to keep the advantages of BEM codes in terms of calculation time and ease of use, but to obtain a superior quality, especially concerning wake and time dependent wake-related phenomena. The presence of the ground during the analyses, as well as the presence of a non uniform wind introduce sensitive effects in the numerical predictions. These effects regard both the response of the blade and the evolution of the wake. During UpWind project, part of the research was focused on these two effects and their inclusion in the calculations. The aim of the present report is to illustrate these two extensions and their implementation in AWSM code. Two separated sections are dedicated to describe these additions in terms of implementation, usage and numerical examples.

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