FLUID MACHINE UTILIZING UNSTEADY FLOW, WINDMILL, AND METHOD FOR INCREASING VELOCITY OF INTERNAL FLOW OF FLUID MACHINE

An object is to provide a fluid machine, a wind turbine, and a method for increasing velocity of an internal flow, utilizing an unsteady flow, according to which a casing can be designed and produced easily, a vortex street flow is formed by virtue of the shape of the casing, and a strong negative pressure region is realized on the outlet side so that the velocity of the internal flow is increased. The present invention is primarily characterized in that a basic shape of the casing 2 has a cycloid curve connecting the front edge 2b and the rear edge 2b and having a convex portion at a position axially corresponding to the throat section 2a between the front and rear edges. The throat section 2a and a vortex generating face 2c disposed downstream of the throat section to generate the negative pressure region are formed on an inner circumferential face 201 of the casing 2. A first outflow gradient is formed on an outer circumferential face 202 of the casing 2 and at the rear edge 2d. A second outflow gradient is formed on a boundary of a throat-side adjacent face adjacent to the vortex generating portion to separate the internal flow. The negative pressure region of high vorticity is generated behind the vortex generating face 2c by virtue of the non-streamline shaped casing to increase the velocity of the internal flow.