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

Abstract

A computational study is presented which investigates the predictive performance of a non-linear turbulence closure in simulating the flow physics pertinent to a high-pressure axial ventilation fan. The studied employed a cubic k– ε model which is considered as a promising closure for improving the state-of-the-art of industrial CFD by accounting for non-equilibrium effects. 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”.