Baihetan Dam is sited on the lower reaches of the Jinsha River in the southwest of China between the boarders of Sichuan and Yunnan province. The dam is scheduled to be taken into operation in the year of 2020 with an installed generation capacity of 14 GW which will put Baihetan Dam on the map as the third largest hydropower station in the world considering installed power output. In comparison, the world’s biggest dam Three Gorges has an installed generation capacity of 22,5 GW. To ensure a sufficient safety evaluation in terms of erosion (scour) formation at the bottom of the plunge pool, pressure simulations in the plunge pool floor in an experimental model at the Department of Hydraulic Engineering in Tsinghua University, Beijing, China has been performed. Data from two experiments with two different outflow configurations has been obtained and analyzed together with three earlier performed experiments on the same experimental model. The results from outflow configuration one had an incomplete data set and could not be compared to the other experiments. The results retrieved from the other experiments however showed the importance of a spillway design with nappe splitters and nappe blocks implemented and the value of a sufficient water cushion in the plunge pool. All four outflow configurations with nappe splitters or nappe blocks implemented held a hydrodynamic pressure below the recommended maximum pressure value of 15 cm water head (experimental model scale) stated by the East Asian Investigation and Design Institute, whilst the one configuration with no nappe splitters or nappe blocks exceeded the value. The design of outflow configuration two is four nappe splitters implemented in two spillways and two nappe blocks in two spillways. In this thesis, this configuration has proven to be the most suitable one in terms of maximum pressure minimization and pressure distribution at the plunge pool floor.

The hydrodynamic characteristics of the Baihetan Plunge pool and the impact of changing the secondarydam’s top elevation was investigated. Quantities such as the velocity distribution, turbulencedissipation rate, water surface profile and the probability of a submerged jump forming in the plungepool was studied.The numerical model showed in general good agreement with data gathered from an experimentalstudy conducted in 2012. The only exception was the maximum pressure in the plunge pool, whichwas 16.91 % higher for the simulation using a top elevation of 604 MASL for the secondary dam. Theuse of a grid convergence index (GCI) showed that the result was closer to being mesh independentin the plunge pool (GCIplunge = 4:5 %), but not in the jet body (GCIjet = 16:9 %).The results indicated that no significant improvement was given for changing the top elevationof the secondary dam to 604 or 606 MASL (original height is 602 MASL) since all cases displayflow pattern indicating that a submerged jump will occur. Moreover most of the turbulence wasconcentrated near the jet for all the cases, indicating that the plunge pool is properly designed forthe purpose it is intended to do, i.e. dissipating the energy of the jets in the plunge pool and notdownstream to the unprotected riverbanks.The main conclusion is that the original design is to prefer since no advantages is given byheightening the secondary dam, and will only increase the cost of construction.

Recently it has become more common in the construction of large dams to reuse diversion tunnels as flood discharge tunnels in the final structure. These tunnels handle large flows with the characteristics of open channel flow. When such large hydrological forces act upon a structure there are several problems to be expected. One of these is the occurrence of cavitation, which could have potential hazardous erosion as a consequence. Cavitation is the formation and collapse of bubbles that create a shockwave strong enough to erode the underlying material. The Baihetan dam is one of the largest hydro power projects in China at present. It has three discharge tunnels that all run the risk of developing cavitation damages. By modelling one of the tunnels using Computational Fluid Dynamics (CFD) it is possible to investigate where in the tunnel structure cavitation is likely to occur. This degree project assesses the risk of cavitation erosion in the Baihetan tunnel using the static pressure distribution, the velocity distribution and modern cavitation theory. Several modifications of the tunnel – including alterations in the gradient and construction parameters – are simulated in order to investigate if changes in the design can mitigate the cavitation problem. None of the analysed modifications completely eliminate the problem and aeration is recommended to counteract the problem. This study indicates where cavitation might be a problem in the Baihetan tunnel and can be used as a basis for further research.