Influence of Numerical Dissipation on Draft Tube Flows

Abstract

Hydro-turbines are operated at loads above or below the best efficiency point (over- or part-load), where turbulent flow structures are formed in the draft tube. The goal of the project is to investigate turbulent flows present in the draft tube through a thorough numerical investigation. In the context of numerical simulations, a focus is made on the numerical scheme. Steady and unsteady simulations with the k-ωom SST turbulence model are applied with a novel eddy-preserving limiter scheme for draft tube flows. The application of the eddy-preserving limiter scheme allows to better resolve the flow field. Numerical results are validated through a comparison to experimental data.