Vortex ropes in draft tube of a laboratory Kaplan hydro turbine at low load

Application Area 6: Turbomachinery Internal Flow

Application Challenge AC6-15

CFD Simulations

Solution Strategy

The computations reported here were performed with the ANSYS-FLUENT (Manual ANSYS Fluent v.17.1) code using the two built-in popular linear eddy-viscosity models (k-?-SST and realizable k-?), the Re-stress LRR model (Launder, Reece, & Rodi, 1975) with the linear pressure strain and wall-echo terms, and a DES (based on Menter?s k?? SST model). In parallel, for reference, LES with the WALE subgrid-scale viscosity model (Nicoud & Ducros, 1999) was carried out on finer grids.

The high-Re-number realizable k-? model and the basic RSM were solved using the standard wall functions. A test with the enhanced wall treatment and the non-equilibrium wall function available in the FLUENT code produced no significant differences in the results. For the k?? SST model we used the enhanced-wall-treatment ?-equation model (EWT-?) (ANSYS Fluent v.17.1 Theory Guide).

Contributed by: A. Minakov [1,2], D. Platonov [1,2], I. Litvinov [2], S. Shtork [2], K. Hanjalić [3] —

[1] Institute of Thermophysics SB RAS, Novosibirsk, Russia,

[2] Siberian Federal University, Krasnoyarsk, Russia,

[3] Delft University of Technology, Chem. Eng. Dept., Holland.