BUTTERFLY VALVE

A valve having improved inherent flow characteristics and improved dynamic torque characteristics is provided. The valve includes a disk for controllin g fluid flow inside the valve. The disk has at least a sealing surface for sealing with a valve seal when the disk is in a closed position. The sealing surface includes a contour and creates a flow clearance with the valve seal as the disk pivots from a closed position toward an open position. A radius of curvature of the contour defines a size of the flow clearance at predetermin ed disk positions to characterize flow through the valve. The valve can further include an upstream indentation for dynamic torque reduction and/or an indentation for dynamic torque reduction in case of a fluid flow reversal.