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research-article

TWO-SCALE METHODOLOGY FOR URANS / LES SOLUTIONS OF UNSTEADY TURBOMACHINERY FLOWS

[+] Author and Article Information
Li He

Department of Engineering Science, University of Oxford Oxford OX2 0ES, UK
Li.He@eng.ox.ac.uk

Junsok Yi

Department of Engineering Science, University of Oxford Oxford OX2 0ES, UK
Junsok.Yi@eng.ox.ac.uk

1Corresponding author.

ASME doi:10.1115/1.4036765 History: Received January 03, 2017; Revised April 28, 2017

Abstract

A general issue in turbomachinery flow computations is how to capture and resolve two kinds of unsteadiness efficiently and accurately: a) deterministic disturbances with temporal and spatial periodicities linked to blade count and rotational speed, and b) non-deterministic disturbances including turbulence and self-excited coherent patterns (e.g. vortex shedding, shear layer instabilities, etc.) with temporal and spatial wave lengths unrelated to blade count and rotational speed. In particular, the high cost of large eddy simulations (LES) is further compounded by the need to capture the deterministic unsteadiness of bladerow interactions in computational domains with large number of blade passages. The present work addresses this challenge by developing a multi-scale solution approach. The framework is based on an ensemble-averaging to split deterministic and nondeterministic disturbances. The two types of disturbances can be solved in suitably selected computational domains and solvers respectively. The local fine mesh is used for non-deterministic turbulence eddies and vortex shedding, while the global coarse mesh is for deterministic unsteadiness. A key enabler is that the unsteady stress terms of the non-deterministic disturbances are obtained only in a small set of blade passages and propagated to the whole domain with many more passages by a block spectral mapping. This distinctive multi-scale treatment makes it possible to achieve a high resolution URANS/LES solution in a multi-passage/whole annulus domain very efficiently. The method description will be followed by test cases demonstrating the validity and potential of the proposed methodology.

Copyright (c) 2017 by ASME
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