The turbulent flow, with the Reynolds number of 5.9× 105, in the strongly 3-D skew blade passage of a true Francis hydro turbine was simulated by the Large Eddy Simulation (LES) approach to investigate the spatial and temporal distributions of the fully developed turbulence in the passage with strongly 3-D complex geometry. The simulations show that the strong three-dimensionality of the passage has a great amplification effect on the turbulence in the passage, and the distributions of the turbulence are diversely nonuniform, for instance, the rise of turbulent kinetic energy in the lower 1/3 region of the passage is more than 45%, whereas its rise in the upper 1/3 region is less than 1%. With the LES approach, the details of the flow structures at the near-wall surfaces of the blades could be obtained. Several turbulent spots were captured.
Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation (LES) to investigate the spatial and temporal distributions of the turbulence when strongly distorted wakes in the inflow sweep over the passage. In a suitable consideration of the energy exchanging mechanism between the large and small scales in the complicated passage with a strong 3-D curvature,one-coefficient dynamic Sub-Grid-Scale (SGS) stress model was used in this article. The simulations show that the strong wakes in the inflow lead to a flow separation at the leading zone of the passage,and to form a primary vortex in the span-wise direction. The primary span-wise vortex evolves and splits into smaller vortex pairs due to the constraint of no-slip wall condition,which triggers losing stability of the flow in the passage. The computed pressures on the pressure and suction sides agree with the measured data for a working test turbine model.
