The ornamental design for a windturbine, as shown and described.
FIG. 1 is a perspective view of a wind turbine showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a left side elevational view thereof, the right side elevational view being a mirror image thereof;
FIG. 5 is a front elevational view thereof, shown with the diffuser removed to show portions of the design that are not clearly visible when combined;
FIG. 6 is a left side elevational view thereof; and,
FIG. 7 is a top plan view thereof.
The surface shading is used to shade FIGS. 1-7 to show clearly the character and contour of all surfaces of the 3-dimensional aspects of the design and form a part of the design sought to be protected.
In the drawings, the broken lines illustrate portions of the article which form no part of the claimed design.