Numerical Simulation Study Of Combined Energy Dissipation In Small Hydropower Plants

Small hydropower stations in mountainous areas face problems such as large singlewidth flow and heavy task of energy dissipation during flood discharge due to the narrow river channel,relatively small reservoir capacity,steep rise and fall of flood,and large peak flow in a short period of time.Tangir hydropower station is a typical small hydropower station in mountainous areas,with a large single-wide flow and a heavy task of discharging and dissipating energy during its flooding.In this thesis,the hydraulic physical model and the 3D water flow mathematical model of Tangir hydropower station were established to study the discharge capacity,water flow characteristics,and energy dissipation effect of different energy dissipation arrangement schemes of Tangir hydropower station.Firstly,based on the gravity similarity criterion,the physical model of Tangir hydropower project was established with a geometric scale of 1:30.The hydraulic characteristics such as discharge capacity,flow velocity and water level of two energy dissipation schemes,namely,dissipation pool + step and dissipation pool + step + energy dissipation pier,were investigated.The results of the analysis concluded that the discharge capacity of the flow under these two schemes meets the requirements.Compared with the natural riverbed flow rate,the flow rate at the end of sea manga and the downstream channel is lower than the natural riverbed flow rate after the completion of the first hub.The flow velocity decreases even more when the dissipation pool + step+ energy dissipation pier is deployed to dissipate energy.After that,a three-dimensional water flow mathematical model with the same arrangement of dissipation pool + ladder + energy dissipation pier in the physical model was established,and the calculation results of the numerical simulation were compared with the test results of the physical model to verify the simulation results.Finally,based on the above three-dimensional water flow mathematical model combined with available information and theoretical analysis,four energy dissipation schemes were combined,namely;dissipation pool energy dissipation,dissipation pool +step energy dissipation,dissipation pool + energy dissipation pier energy dissipation and dissipation pool + step + energy dissipation pier energy dissipation.Then the GAMBIT software was used to dissect the grid of the numerical simulation area,and then the standard k-ε turbulence model combined with VOF method was used to establish the numerical simulation model of four combined energy dissipation schemes using FLUENT software,and the three-dimensional numerical simulation of the Tangir hydropower project by non-constant flow was carried out.After comparing and analyzing the simulated water surface line,pressure distribution,energy dissipation rate,dissipation rate and flow velocity distribution data,it was concluded that: the combination of dissipation pool + step energy dissipation + energy dissipation pier energy dissipation scheme produces obvious water leap in the dissipation pool,the maximum turbulent energy consumption,the minimum flow velocity out of the pool,and the maximum energy dissipation rate can reach 74%,so this thesis recommends the combination of dissipation pool + step + energy dissipation pier energy dissipation scheme.