Effects of inlet boundary conditions on spiral casing simulation

The results of numerical simulations of threedimensional turbulent viscous flow through the spiral casing and distributor of the Hölleforsen hydraulic turbine (Turbine-99 test case) are presented. Two CAD geometries, with and without the penstock, are analyzed in details to determine the effects of the upstream geometry, i.e. the inlet boundary conditions to the spiral casing. Conservation of mass and momentum equations of the flow are analysed using finite volume methods with the commercial software ANSYS CFX10.0. Standard k-ε with scalable wall function and SST k-ω based turbulence models are applied to study the flow characteristics. Comparisons are made between the numerical simulations with and without the penstock and available experimental results. The numerical results are found to more closely match with the experimental results when the penstock is included in the simulation. Therefore, detailed inlet boundary conditions are necessary to simulate accurately the spiral casing flows if the penstock is not included in the simulation. The numerical simulations also seem to show little sensitivity to the turbulence model.Godkänd; 2007; 20071030 (cervante