The present paper discusses the basic principles of hydraulic turbines, with special emphasis on the use of computational fluid dynamics (CFD) as a tool which is being increasingly applied to gain insight into the complex three-dimensional (3D) phenomena occurring in these types of fluid machinery. The basic fluid mechanics is briefly treated for the three main types of hydraulic turbine: Pelton, Francis and axial turbines. From the vast number of applications where CFD has proven to be an important help to the design engineer, two examples have been chosen for a detailed discussion. The first example gives a comparison of experimental data and 3D Euler and 3D Navier-Stokes results for the flow in a Francis runner. The second example highlights the state-of-the-art of predicting the performance of an entire Francis turbine by means of numerical simulation.

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Abstract. A full stage simulation method is used to calculate the first numerically predicted hill chart of a high specific speed Francis turbine. The numerical method simulates rotating and non-rotating components and their mutual interactions within a single computation. An efficiency hill chart is determined numerically and compared to experimental results from a model test whereby good agreement is obtained.