Guide vane and fluid machine

A guide vane provided on an outer circumferential side of a runner of a fluid machine to control a flow rate of water into the runner by rotating about a guide vane rotation axis,

• wherein, where in a section perpendicular to the guide vane rotation axis, a curvature of a contour line forming a runner side vane surface of the guide vane is referred to as a positive curvature when the contour line is formed to be convex, while the curvature of the contour line forming the runner side vane surface of the guide vane is referred to as a negative curvature when the contour line is formed to be concave, a negative curvature portion where the curvature of the contour line becomes negative is provided on the runner side vane surface, and
• wherein the negative curvature portion is formed from an upper end portion to a lower end portion of the runner side vane surface,
• wherein an inlet non-negative curvature portion where the curvature of the contour line becomes positive or zero is provided at a portion lying closer to an inlet end than the negative curvature portion, and
• wherein an outlet non-negative curvature portion where the curvature of the contour line becomes positive is provided at a portion lying closer to an outlet end than the negative curvature portion,
• wherein when L0 denotes a length of the negative curvature position along the contour line which extends from the inlet end to the outlet end and L denotes a length from the inlet end to an arbitrary position along the contour line, the negative curvature portion is formed on at least part of a range of L which satisfies L/L0≤0.8, and the outlet non-negative curvature portion is formed on a range of L which satisfies 0.8<L/L0.