| Along with the importance to environmental protection, and due to the obvious character of temperature-stratified phenomena in large reservoir, a Multi-Level Intake Structure (MLIS) has been gradually introducing in heavy hydropower station. The purpose of MLIS is to stretch selectively the surface warmer water, and reduce the negative effect of releasing cold water on downstream environment. However, the flow conditions in MLIS are very complex, and there has been without one engineering example which adopted MILS in China. Therefore, the study should be done on the hydraulic characteristics of MLIS.Taking one heavy hydropower station as an example in this paper, the hydraulic characteristics of the MLIS is studied by the model test and numerical simulation. The main conclusions are summarized as follows:(1)The head losses, approach velocity distributions, minimum operating level, time-average pressure and fluctuating pressure in the MLIS are studied experimentally. The head loss of intake is 0.307 when the lower intake works, while the head loss is 1.470 when the upper intake works. Velocity distribution at the MLIS is uniform, and the maximum velocity is about 1.0m/s. Harmful vortex does not occur when the lowest operating level is above 798.0m for the upper intake and is above 765.0m for the lower intake. There is no negative pressure zone on the lower working gate and the upper working gate when the intake works normally.(2)The hydraulic characteristics during the process of switching the working gates of lower intake and upper intake was studied experimentally. The results show that the flow state in MLIS is stable during the process of switching the working gates.(3)The head loss calculated is consistent with that experimented, and the error is less 4.2%.(4)The velocity distribution calculated at the intake accords with that obtained by the model test. The flow characteristics in the MLIS are simulated numerically.
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