The performance of a 0.9 m diameter model wind turbine using the National Renewable Energy Laboratory S826 airfoil profile has been investigated both experimentally and numerically. The geometry was laid out using blade element momentum (BEM) theory, and a detailed description of the geometry is given here. The design was tested experimentally and gave a peak power coefficient of C P D 0:448 at the design tip speed ratio of D 6. After the model tests had been undertaken, numerical calculations were performed by means of fully three-dimensional computational fluid dynamics (CFD) simulations using a k ! turbulence model. It was found that the BEM correctly predicts the shape of the power and thrust coefficient curves, with the efficiency coefficient virtually identical to the measurements at the design conditions. At higher tip speed ratios, the performance is over-predicted. The estimated thrust was, however, consistently too low by a shift of the order of C T 0:1 in the normal operating tip speed range. The high-resolution CFD predictions (using about 3:5 10 6 grid points) reproduced the model thrust coefficient almost perfectly, and the predicted power coefficients were also very close to the measurements, although the agreement with the measurements at high tip speed ratios were only marginally better than those from the BEM method. At the design tip speed ratio, the CFD over-predicted the power coefficient by merely 2%. The good agreement between the measured and computed performance at model scale assures that accurate predictions of turbine performance at full-scale conditions are also possible with high-resolution CFD.
a bs t r ac t Drawing upon Bernard Stiegler's and Jacques Rancière's conceptions of medium as a milieu this article seeks to address the question of the political aspects of the aesthetic in relation to the notion of medium. Based on the analysis of this theoretical question the article interprets and discusses artistic endeavors to re-appropriate and reconfigure conservative symbolic orders and media milieus that have become dissociated in relation to works of art by Alfredo Jaar and Thomas Hirschhorn. k e y wor ds Medium, re-appropriation,
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