Performance of non-uniform tidal turbine arrays in uniform flow

Theoretical models suggest that in order to maximise their collective power out put, tidal turbines should be arranged in a single cross-stream row and optimally spaced to exploit local blockage effects. However, because it is assumed that the turbines within these arrays are identical, such models do not consider the possibility of enhanced power production through the exploitation of spanwise variations in local blockage and resistance. In this paper, we use depth-averaged numerical simulations to investigate whether the performance of a tidal turbine array can be further enhanced by varying solely the local blockage, solely the local resistance, or both local blockage and resistance together, across the array width. Our results suggest that for an initially uniform flow field, the optimal tidal turbine array is also uniform, that is to say that it comprises turbines of equal size, spacing, and resistance. This finding is encouraging because it is more cost-effective and much simpler to design each turbine to be the same and to operate in the same way. Together with earlier findings, these results also suggest a more general, and perhaps unsurprising, conclusion that tidal turbine arrays perform best when designed to match site-specific natural flow conditions

Some exact and numerical results for plane steady sheared flow of an incompressible inviscid fluid

Analytical and numerical solutions are presented for the steady flow of an inviscid fluid about symmetric lifting profiles at an angle of attack in a plane sheared onset flow for which conformal mapping plays a critical role. For uniform shear (i.e. the onset flow speed varies linearly with position) in two dimensions, the disturbance field is potential and hence a solution based on the conformal transformation technique may be constructed. The Moriya transformation, which employs a leading-term transformation coefficient that stretches and rotates the field at great distances from the foil (as distinct from other classical transformations which leave the far field unchanged) is used and, with a limited number of terms selected for the transformation, a simple elegant solution is obtained that may be easily evaluated at arbitrary points on the foil contour. An additional investigation is reported for the field solution -- involving a locally similar but globally non-uniform sheared onset flow -- about one of the foils for which a simple O-type grid is analytically generated from the mapping function. These data indicate that the uniform-shear solution overpredicts the lift and surface speed on the suction side of the foil relative to the more realistic onset flow: the numerical solution predicts surface speeds that generally lie between those for the uniform flow and the uniformly sheared flow solutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29989/1/0000356.pd

Topographie et géologie du bassin du Petit-Lac (partie occidentale du Léman)

Joukowsky Étienne. Topographie et géologie du bassin du Petit-Lac (partie occidentale du Léman). In: Le Globe. Revue genevoise de géographie, tome 59, 1920. pp. 15-31

La carte du canton de Genève à l'échelle de 1 : 12500, équidistance 4 mètres, par le général Dufour

Joukowsky Étienne. La carte du canton de Genève à l'échelle de 1 : 12500, équidistance 4 mètres, par le général Dufour. In: Le Globe. Revue genevoise de géographie, tome 60, 1921. p. 28

Élude géologique de la région de la Dole. Matériaux pour la carte géologique de la Suisse N. S. livr. XLVI avec carte géologique de la région de St-Cergue-La Dôle, carte spéciale n° 88. par H. Lagotala

Joukowsky Étienne. Élude géologique de la région de la Dole. Matériaux pour la carte géologique de la Suisse N. S. livr. XLVI avec carte géologique de la région de St-Cergue-La Dôle, carte spéciale n° 88. par H. Lagotala. In: Le Globe. Revue genevoise de géographie, tome 60, 1921. pp. 46-47

Sur les éclogites des Aiguilles Rouges

Pas de résumé disponible.</p