The ornamental design for a windturbine, as shown and described.
FIG. 1 is a top perspective view of a wind turbine showing my new design;
FIG. 2 is a bottom perspective view of the wind turbine of FIG. 1;
FIG. 3 is a view in front elevation of the wind turbine of FIG. 1 with the views in left, right, and rear elevation being mirror images thereof;
FIG. 4 is a top plan view of the wind turbine of FIG. 1;
FIG. 5 is a bottom plan view of the wind turbine of FIG. 1;
FIG. 6 is a perspective view of the rotor assembly separated from the wind turbine for ease of illustration; and,
FIG. 7 is a view in front elevation of the rotor assembly separated from the wind turbine for ease of illustration, with the views in left, right, and rear elevation being mirror images thereof.