Flap gate

The flap gate is a hydraulic facility that achieves automatic water level regulation through the balance of hydraulic force and self-weight. It is primarily used in reservoirs, rivers, and other locations to block or discharge water flow. Its core principle involves lever balance and a rotational mechanism, where the gate’s tilt angle is controlled by changes in the moment of hydrodynamic pressure and gate weight. The structure includes components such as the faceplate, legs, and piers, enabling automatic opening and closing to maintain a set water level range.
Core Principle
The flap gate utilizes the interaction between water pressure and gravity. When the upstream water level rises, the moment of hydrodynamic pressure on the pivot exceeds that of the gate weight and damping, causing the gate to gradually open around the horizontal axis to release flow. As the water level drops, it automatically closes to retain water. For example, the roller-linkage type gate reduces vibration through a dual-pivot structure and, combined with a trapezoidal practical weir, improves the discharge coefficient for more precise regulation.