This invention relates to a noise reducing device, a wind turbine blade comprises such a noise reducing device, a method of retrofitted a noise reducing device, and a method of manufacturing such a noise reducing device. The noise reducing device comprises first noise reducing elements projecting from a base part having a third surface towards a second end. Second noise reducing elements are attached to the third surface and projects along the first noise reducing elements towards the second end. The first noise reducing elements are preferably serrations while the second noise reducing elements are bristles. The bristles projects at least into the gaps formed between adjacent serrations.

A fluid dynamic body having a trailing edge with a pattern formed thereon, the pattern can include a plurality of smoothly surfaced adjacent members with respective interstices therebetween, wherein at least one of the interstices completely contains a porous barrier. In some embodiments, the porous barrier can obstruct fluid flow through the respective interstice between a first surface of the fluid dynamic body on a first side of the trailing edge and a second surface of the fluid dynamic body on a second side of the trailing edge. This helps to reduce noise produced at the trailing edge. In some embodiments, the fluid dynamic body is a wind turbine blade or an air-engine blade.

A vane body of a guide vane includes a leading edge, and a trailing edge which is located closer to a runner than the leading edge, when located radially outside the runner. A projection extending in a direction from the trailing edge toward the leading edge is provided on an internal-diameter side blade face of the vane body, at least in any one of one side area of the internal-diameter side blade face and the other side area thereof in an axial direction of a guide vane rotation shaft, the internal-diameter side blade face being disposed on a side of the runner. The projection has a projection rear end of an arcuate shape, which projection rear end is formed to extend along a rotation trajectory which is drawn by the trailing edge when the vane body is rotated about the guide vane rotation shaft.

A foil, such as an aerofoil, having a leading edge and a trailing edge, of which at least a portion of one or both of the leading edge and trailing edge has a serrated profile comprising a plurality of adjoining teeth, each tooth having a tip point that represents a local maximum chord-wise extent of the tooth and, on each side span-wise of the tip point, a root point that represents a local minimum chord-wise extent of the tooth and at which the tooth adjoins a respective adjacent tooth, wherein the tooth edge profile varies with an ogee-like curve between tip point and root point such that the tooth is sharper in the neighbourhood of the tip point and in the neighbourhood of the root point than at locations in between.

A method is provided for forming an add-on component for an aerofoil which enable the structure of the aerofoil to be tuned in order to reduce the amplitude of sound produced at frequency f.sub.peak when air flows in a flow direction from the leading edge over the trailing edge of an aerofoil. The method applies both to add-on components having a slitted formation and a Double-Rooted Trailing Edge Serration (abbreviated to “DRooTES”).

A foil, such as an aerofoil, having a leading edge and a trailing edge, of which at least a portion of one or both of the leading edge and trailing edge has a serrated profile comprising a plurality of adjoining teeth, each tooth having a tip point that represents a local maximum chord-wise extent of the tooth and, on each side span-wise of the tip point, a root point that represents a local minimum chord-wise extent of the tooth and at which the tooth adjoins a respective adjacent tooth, wherein the tooth edge profile varies with an ogee-like curve between tip point and root point such that the tooth is sharper in the neighbourhood of the tip point and in the neighbourhood of the root point than at locations in between.

A wind turbine blade apparatus at least includes a wind turbine blade body, wherein a serration portion is disposed on at least on a part of a trailing edge of the wind turbine blade body, the serration portion having a saw-teeth shape where a mountain portion and a valley portion are arranged alternately in a blade longitudinal direction, and wherein a chord-directional cross section of the wind turbine blade body along a chord direction is formed to have an airfoil shape at any position in a region from the mountain portion to the valley portion.

A method is provided for forming an add-on component for an aerofoil which enable the structure of the aerofoil to be tuned in order to reduce the amplitude of sound produced at frequency f.sub.peak when air flows in a flow direction from the leading edge over the trailing edge of an aerofoil. The method applies both to add-on components having a slitted formation and a Double-Rooted Trailing Edge Serration (abbreviated to “DRooTES”).

To provide a wind power generation device that can be suitably increased in size while increasing the electricity generation efficiency. A wind power generation device (10) is characterized by being provided with: a first wind turbine unit (12) comprising multiple wind turbines (30a to 30d) aligned in one line; a pair of blade units (16), each of the blade units being disposed adjacent to the first wind turbine unit (12) and having an inner-side shape extending along the circumferences of circles defined by rotation of the wind turbines (30a to 30d) to enhance collection of wind by the rotation; and a conversion unit for converting energy obtained by the rotation of the first wind turbine unit (12) to electricity.

A wind turbine blade apparatus at least includes a wind turbine blade body, wherein a serration portion is disposed on at least on a part of a trailing edge of the wind turbine blade body, the serration portion having a saw-teeth shape where a mountain portion and a valley portion are arranged alternately in a blade longitudinal direction, and wherein a chord-directional cross section of the wind turbine blade body along a chord direction is formed to have an airfoil shape at any position in a region from the mountain portion to the valley portion.