Unsteady CFD analysis and shape optimization of a hydraulic turbine

Abstract

This paper presents the CFD-based constrained shape optimization of the runner of a hydraulic turbine for minimum pressure pulsations between the guide vanes and the runner. The GPU-accelerated flow solver PUMA, which solves the (U)RANS equations coupled with the Spalart-Allmaras turbulence model and a free-form deformation tool based on volumetric NURBS are used. A control lattice encapsulates the runner's blade and the coordinates of (some of) its control points are the design variables; this results in 180 design variables. The optimization is carried out by means of an evolutionary algorithm assisted by surrogate evaluation models and the principal component analysis, in order to minimize the computational cost. During the one-and two-operating point optimizations, all CFD simulations rely on the mixing plane model; however, at the end, the so-optimized solution is re-evaluated using the sliding plane technique.