Evaluation of Numerical Simulation Strategies Applied to Hydraulic Turbomachinery

Abstract

The design of hydraulic turbomachines operating at the so-called design point has advanced to a stage where further improvements can only be achieved through a detailed understanding of the internal flow behavior. As an alternative to physical experimentation, numerical methods have become a powerful tool for predicting internal flow characteristics. However, these predictions involve several complex challenges, including the rotating reference frame, the three-dimensional geometry of the impeller, the unsteady and turbulent nature of the flow, and fluid–structure interactions, especially under off-design conditions, where strong interactions between the impeller and the stator or casing occur. These simulations are often computationally demanding due to the fine mesh resolution required and the inclusion of various sub-models, such as moving reference frames, turbulence modeling, and, in some cases, cavitation models when operating away from the design point. This work focuses on evaluating the interplay among different modeling strategies, particularly sub-models related to rotating frames and turbulence. Various combinations of these models are tested to achieve accurate predictions of the mean flow behavior in a radial pump, accounting for some of their important geometrical characteristics. Both open-source and commercial CFD solvers are employed. The simulation results are compared against a standard experimental dataset defined for benchmarking studies.