Towards a high order throughflow. Part I: Investigating the effectiveness of a harmonic reconstruction for 3D flows
The computation time and the extraction of useful information remain severe drawbacks to systematic use of modern three-dimensional Navier-Stokes codes in a design procedure of multistage turbomachines. That explains why throughflow simulation is still widely used at industrial scale. The main limitation of throughflow is however the need for empirical models to reproduce blade-flow interactions and major 3D flow features. The purpose of this work is to investigate the degree to which empiricism could be reduced by using the averaged-passage equations of Adamczyk, combined with a harmonic closure strategy. To that aim, results of a computation performed with a steady three-dimensional Navier-Stokes code are used to calculate some of the additional terms of the circumferentially-averaged equations, the so-called circumferential stresses. The importance of the latter to bring back the mean effect of circumferential non-uniformities, linked to 3D phenomena, is illustrated by injecting them into a throughfow simulation. Then the ability of truncated Fourier series to reproduce the level of non-uniformity in the core flow and near the walls is detailed. It is finally shown that the harmonic approximated stresses can lead to a good reproduction of local 3D flow features in throughflow simulation and to a better accuracy. © 2010 by ASME.