Numerical investigation of the flow within a turbofan lobed mixer

Abstract

A computational procedure is described for the calculation of the flowfield within a multilobed turbofan mixer. The predictions have been obtained by using a finite-volume solution procedure for the three-dimensional elliptic equations of fluid flow extended to allow the modeling of flows within complex geometries. Turbulence is modeled using the two equation k-e eddy viscosity model. Previous experimental investigations have shown that large scale secondary flows at exit from the lobes play a dominant role in the mixing process downstream of the lobe exit plane. The present work demonstrates the capability of the current method to predict the flow characteristics within the lobes and hence the formation of these secondary velocities. Finally, parametric studies of the effect of changes in the fan-side geometry are reported to investigate how these influence the flow structure, in particular the generation and amplification of the secondary flow patterns. The calculations provide useful information on the nature of the secondary flows and demonstrate how the procedure may be used to examine the likelihood of flow separation and the influence of the thickening of upstream boundary layers.