Flow Field Numerical Simulation Of Colliding Energy Dissipation Of The Diversion Tunnel Of Baihetan

In order to improve rate of jet collision energy dissipation of the diversion tunnel of Baihetan hydropower, downstream flow smooth, scour hole at the central river, both slopes of downstream export without scouring,in this paper, use numerical simulation of the whole cavern groups calculate the diversion tunnel of Baihetan flow characteristics of the six-hole program. Simulation conditions: five flow within the total discharge capacity 19000 ~ 30000m3/s, and there are two types of downstream water level conditions of backwater effects Xiluodu or not; computational grid: two mesh systems about fine grid of the total number of 900,000 and coarse grid of 250,000. To ensure accuracy, rate the number of numerical simulation parameters strictly, and use the roughness perturbation method test simulation results of the loss along diversion tunnel.The overall characteristics of the six-hole program. Reach conclusion as follow the diversion tunnels of the discharge capacity in various studies conditions, the relationship between the total discharge capacity with water level, and the discharge capacity of the left and right bank; the head loss of the diversion tunnels, total energy head and pressure's variation along the way, and the head loss distribution of the flow area.Friction of diversion tunnel playe a decisive role in the discharge capacity of non-symmetry of both sides.Flow characteristics of the original design under the conditions of flooding are normal, there is no severe vicious flow. However, there are two types of bad flow: the reverse flow occurred in the flow area into upstream river, water flow into part of the diversion tunnels on the contrary; The intersection of the axis of flow conductance channels of # 1 and # 6 diversion tunnel inclined to right side too much, point of jet collision is close to the slope of right bank, a great impact.River flow and jet collision. Inlet of diversion tunnel flow smoothly, There is no large-scale circulation in river upstream, loss of inlet take up about 7.5% of total losses. Funnel vortex of inlet is not strong, flow near the upstream cofferdam is safer, Water level rises less than 0.2m. Water flow into #1 and #6 diversion channel smoothly, but water flow into #4, and #3, #5 diversion channel on the contrary, entrances of diversion channel are prone to flow separation. Downstream due to swirl control the lower channel is extremely complicated: two jets splashing that the collision produced and vertical vortex flow controls water flow regime, energy dissipation effect and adjustment of velocity profile along the way. Isolated standing wave that amplitude is 1.3 ~ 3.8m can be formed on the surface of the water outflow area, water level of the two banks rise; all levels of jets collision is stable, but the collision point deflect to the right bank step by step; a range of 500m of downstream of the collision zone is energy dissipation area ; a large scale horizontal vortex occurs in the water surface of outside lower exports diversion holes, cause velocity and water level fluctuation.Near cofferdam of downstream water flow smoothly, the flow rate is small, scouring force is not strong; flow regime of downstream river is stability, the mainstream adjoin the right bank, maximum flow velocity at a cross-section is high, scouring force is strong.Suggestion of design improvement. The flow direction of the axis of lead pipes should be change, in order to maintain all levels of the jets collision point in the center the river, reduce the jet's impact on the river bank; river flow velocity of downstream is high, the appropriate bank protection measures are necessary; reverse flow in inhalant region should be seek to eliminate or mitigate, avoid water flow into the diversion tunnels on the contrary.