Flow analyses in a high-pressure axial ventilation fan with a non-linear eddy-viscosity closure

The axial fan studied represents a challenge for simulation because of the presence of large three-dimensional interblade flow structures and strong leakage effects. The potential improvement of non-isotropic closures has been assessed with respect to a classical linear k-ε model. The comparative analyses aimed at the prediction of flow structure within the blades and close to the rotor tip clearance. The rotor design point and near-pressure-peak operating conditions have been simulated. The non-linear model is shown to provide a better base-line for non-equilibrium effects simulation with respect to the standard one. The authors adopt a parallel multi-grid algorithm developed for a highly accurate Petrov-Galerkin finite element method, here applied on equal-order Q1-Q1 as well as mixed Q2-Q1 element pairs. The parallel solution algorithm for Reynolds Averaged Navier-Stokes modelling exploits an overlapping domain decomposition technique based on an “inexact explicit non-linear Schwarz method”.