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Steady-state Capabilities for Hydroturbines with OpenFOAM

The availability of a high quality open source CFD simulation platform like OpenFOAM offers new R&D opportunities by providing direct access to models and solver implementation details. Efforts have been made by Hydro-Qubec to adapt OpenFOAM to hydroturbines for the development of steady-state capabilities. This paper describes the developments that have been made to implement new turbomachinery related capabilities: multiple frames of reference solver, domain coupling interfaces (GGI, cyclicGGI and mixing plane) and specialized boundary conditions. Practical use of the new turbomachinery capabilities are demonstrated for the analysis of a 195-MW Francis turbine.

Steady-state capabilities for hydroturbines with OpenFOAM

The availability of a high quality Open Source CFD simulation platform like OpenFOAM offers new R&D opportunities by providing direct access to models and solver implementation details. Efforts have been made by Hydro-Quebec to adapt OpenFOAM to hydroturbines for the development of steady-state capabilities. The paper describes the developments that have been made to implement new turbomachinery related capabilities: Multiple Frame of Reference solver, domain coupling interfaces (GGI, cyclicGGI and mixing plane) and specialized boundary conditions. Practical use of the new turbomachinery capabilities are demonstrated for the analysis of a 195-MW Francis hydroturbine.

Imposition of slip boundary conditions without the explicit computation of consistent normals

Computational fluid dynamics simulations often require the imposition of slip boundary conditions: zero-normal velocity. When the geometry is complex, the imposition of this type of boundary condition is not trivial since the current implementations require the computation of consistent normals. The slip boundary condition can be viewed as a constraint to the solution. Hence in the framework of the Lagrange multiplier approach, we present an accurate general implementation of consistent normals. With this new approach, these consistent normals are not computed explicitly at the expense of adding new unknowns - the Lagrange multipliers of the constraint - which can be interpreted as normal forces on the flow

Evaluation of an improved mixing plane interface for OpenFOAM

A mixing plane interface provides a circumferentially averaging rotor-stator coupling interface, which is extremely useful in practical turbomachinery simulations. It allows fundamentally transient problems to be studied in steady-state, using simplified mesh components having periodic properties, and with the help of a multiple reference frames (MRF) approach. An improved version of the mixing plane interface for the community-driven version of OpenFOAM is presented. This new version of the mixing plane introduces a perfield, user-selectable mixing option for the flow fields at the interface, including the possibility to use a mass-flow averaging algorithm for the velocity field. We show that the quality of the mass-flow transfer can be improved by a proper selection of the mixing options at the interface. This paper focuses on the evaluation of the improved mixing plane interface for various steady-state simulations of incompressible flows, applied to a simple 2D validation test case, and to more complex 3D turbomachinery cases.