Modelagem Computacional de Escoamentos em Turbinas Francis Usando a Plataforma OpenFOAM

Abstract

This work presents the modeling and numerical simulation of incompressible turbulent flow in a Francis turbine with a real geometry, based on the unit installed at the Foz do Chapecó Hydropower Plant, using the OpenFOAM software. A representative physical model of the machine is developed, the mathematical model is formulated from the Navier--Stokes equations in the URANS form with the k–ε turbulence model. From the simulations, pressure and velocity fields are qualitatively analyzed, showing behavior consistent with that expected for Francis turbines and with reference results from the literature. Then, two approaches are used to estimate the shaft power: one based on the First Law of Thermodynamics, using averaged quantities at the inlet and outlet sections, and another based on the rotor moment computed by the forces function of OpenFOAM. Powers of approximately 170.61 MW and 107 MW are obtained, respectively, both lower than the design power of the unit 212 MW, which is discussed in terms of geometric simplifications, boundary conditions and turbulence modeling limitations. The results demonstrate the potential of Computational Fluid Dynamics as an analysis tool for hydraulic turbines, while highlighting the importance of careful modeling to achieve quantitative predictions closer to the real behavior.