Numerical investigation of draft tube flows using a hybrid RANS-LES turbulence model and a low-dissipation scheme

[摘要] 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 complex turbulent structures present in the draft tube through a thorough numerical investigation. In the context of numerical simulations, a focus is made on the turbulence model and the numerical scheme. Transient simulations with the k-ω SST and SAS (Scale Adaptive Simulation)-SST turbulence models are applied with a novel eddy-preserving limiter scheme for draft tube flows. The application of both the SAS-SST turbulence model and the eddy-preserving limiter scheme allows for the resolution of more turbulent structures. The impact of the inlet modification is also studied. Numerical results are validated through a comparison to experimental data for the BulbT test case.

[发布机构] McGill University, 817 Sherbrooke Street West, Montreal; QC; H3A 0C3, Canada^1

[关键词] Adaptive simulation;Best efficiency point;Low dissipations;Numerical investigations;Numerical results;SST turbulence models;Transient simulation;Turbulent structures