【Daily Discussion】Public Utilities – Water Resources and Hydropower – 20210410

Jet dissipator energy reduction works by using a nose weir to throw the high-speed water flowing downward into the air, causing the water to spread and mix with a large amount of air. Once it falls back onto the downstream riverbed, it creates intense swirling movements that erode the riverbed and form pits. As these pits deepen, the layer of water on the riverbed becomes thicker; most of the energy is consumed in the friction caused by these swirling movements, and the pits gradually reach a state of stability. Flow break structures are simple and economical, but localized erosion downstream is inevitable; they are generally suitable for high or medium dams with relatively solid bedrock. Bottom flow energy dissipation involves installing energy dissipation basins or weirs downstream of the dam toe to induce water jumps within a defined area, thereby dissipating energy through turbulence, friction, aeration, and impact within the flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.

Common energy dissipation methods for spillways: tip discharge energy dissipation and underflow energy dissipation. Principle and applicable conditions of bottom flow energy dissipation: Bottom flow energy dissipation involves the installation of energy dissipation tanks or weirs downstream of the dam foot, to induce water jumps within a defined area; energy is then dissipated through swirling, friction, aeration, and impact within the water flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.

Common energy dissipation methods for overflow dams: spillway energy dissipation and underflow energy dissipation. Principle of energy dissipation and applicable conditions for bottom flow energy dissipation: Bottom flow energy dissipation involves the installation of energy dissipation tanks or weirs downstream of the dam foot, which facilitate the formation of water jumps within a defined area; energy is then dissipated through swirling, friction, aeration, and impact within the flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.

Common energy dissipation methods for spillways: tip discharge energy dissipation and underflow energy dissipation. Principle and applicable conditions of bottom flow energy dissipation: Bottom flow energy dissipation involves the installation of energy dissipation tanks or weirs downstream of the dam foot, to induce water jumps within a defined area; energy is then dissipated through swirling, friction, aeration, and impact within the water flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.

Principle and applicable conditions of bottom flow energy dissipation: Bottom flow energy dissipation involves the installation of energy dissipation tanks or weirs downstream of the dam foot, to induce water jumps within a defined area; energy is then dissipated through swirling, friction, aeration, and impact within the water flow. Bottom flow energy dissipation is suitable for medium and low dams or river channels with weak bedrock.

Common energy dissipation methods for spillways: tip discharge energy dissipation and underflow energy dissipation. Principle and applicable conditions of bottom flow energy dissipation: Bottom flow energy dissipation involves the installation of energy dissipation tanks or weirs downstream of the dam foot, to induce water jumps within a defined area; energy is then dissipated through swirling, friction, aeration, and impact within the water flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.

Bottom flow energy dissipation involves installing energy dissipation basins or weirs downstream of the dam toe to induce water jumps within a defined area, thereby dissipating energy through turbulence, friction, aeration, and impact within the flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.

The working principle of bottom flow energy dissipation involves the installation of a stilling basin and a stilling wall downstream of the dam site, which cause the water flow to generate a hydraulic jump within a defined area; energy is then dissipated through internal friction in the water flow, air entrainment, and impact. A concrete apron of a certain length is installed downstream of the dam site; as the water flowing over the dam encounters this apron, it undergoes a shock wave, resulting in turbulence. This process helps to dissipate some of the water’s energy through air entrainment, collisions between water molecules, and friction, thereby reducing or preventing severe erosion downstream. Bottom flow energy dissipation is reliable, but requires a large amount of work; it is commonly used in overflow gravity dams with low head and high flow rates.

Stream disruption for energy dissipation involves using a nose weir to throw the high-speed water flowing downward into the air, causing the water to spread out and mix with a large amount of air. After falling back onto the downstream riverbed, this water forms intense vortices that erode the riverbed and create pits. As these pits deepen, the layer of water above them becomes thicker; most of the energy is consumed in the friction caused by these vortices, and eventually the pits stabilize. Flow-guiding energy dissipators are relatively simple and economical, but localized erosion downstream is inevitable; they are generally suitable for high or medium dams with relatively solid bedrock. Bottom flow energy dissipation involves installing energy dissipation chambers or weirs downstream of the dam toe to induce water jumps within a defined area, thereby dissipating energy through turbulence, friction, aeration, and impact within the water flow. Bottom flow energy dissipation is suitable for medium and low dams or river channels with weak bedrock.

Common energy dissipation methods for spillways: tip discharge energy dissipation and underflow energy dissipation. Principle and applicable conditions of bottom flow energy dissipation: Bottom flow energy dissipation involves the installation of energy dissipation tanks or weirs downstream of the dam foot, to induce water jumps within a defined area; energy is then dissipated through swirling, friction, aeration, and impact within the water flow. Bottom flow energy dissipation is suitable for medium and low dams or rivers with weak bedrock.