Gate for controlling upstream water level

For controlling flow-induced level changes in the upstream reach of a channel with a flowing fluid, a level-controlling gate, comprising:

• (a) a face for controlling said flowing fluid, said face incorporating an upper gate face section which forms an arc with a center of curvature at a pivot axis, and with a predetermined radius, and a lower gate face section which forms an arc with a center of curvature at said pivot axis, and with a radius that is a predetermined amount less than said radius of said upper gate face section,
• (b) said face incorporating a hydraulic thrust surface connecting the lower edge of said upper gate face section to the upper edge of said lower gate face section, said hydraulic thrust surface providing a variable opening torque about said pivot axis,
• (c) a counterweight system, comprising one or more masses mounted to provide a variable closing torque about said pivot axis, and
• (d) members for rigidly connecting said face to said counterweight system and also to a horizontal pivot shaft mounted coaxially to said pivot axis, downstream from said face, across said channel, in such a manner that said face will pivot in said channel, to a position in which said variable opening torque and said variable opening closing torque are in balance,
• whereby said flowing fluid passes through the opening below said face, and
• whereby, in the .presence of said flow-induced level changes, said face will be driven more open or closed by said combination of said variable opening torque and said variable closing torque, such that said flow-induced level changes are mitigated, and
• whereby said opening torque produced by said hydraulic thrust surface is zero when said fluid is not flowing.