Computer simulation of flow at part load in a laboratory model of Kaplan hydroturbine by RANS, des and les

We presents some results of numerical simulation of flow in a 60:1 scaled-down laboratory model of a Kaplan hydroturbine at a part load of about 40% nominal flow rate, using several RANS models (realizable k-ϵ k-ω SST EVMs and LRR RSM), DES (all on 2 mill cells) and LES (on 6 mill cells). Unlike the linear eddy viscosity models, the RSM, DES and LES all reproduced well the available mean velocity axial and tangential components and the rsm of their fluctuations in the draft tube diffusor. Despite a relatively coarse mesh that did not resolve well the near-wall region, LES, DES and RSM reproduced well the intrinsic flow unsteadiness and the dominant flow structures, all capturing a double rope pattern in the cone behind the turbine runner.