Prediction of external intermittency using RANS-based turbulence modelling and a transported PDF approach

Abstract

Article:Olivieri, DA, Fairweather, M and Falle, SAEG (2011) Prediction of external intermittency using RANS-based turbulence modelling and a transported PDF approach. Computers and Fluids, 47 (1 ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Prediction of External ______________________________________________________________ AbstractThis paper investigates the modelling of external intermittency in turbulent round jets using a RANS approach coupled to solutions of the transported probability density function (PDF) equation for scalar variables. Solutions to the descriptive equations are obtained using a finite-volume method, combined with an adaptive mesh refinement algorithm, applied in both physical and compositional space. The effects of intermittency on the flow field are accommodated using intermittency-modified eddy viscosity and second-moment turbulence closures, as well as through modifications to the mixing model embodied within the transported PDF equation. Predictions of the model are validated against data on the velocity and scalar fields in jets, as well as against measurements of scalar PDFs and intermittency profiles, with reasonable agreement obtained. From the cases examined, predictions of the second-moment closure are superior, although both approaches provide realistic predictions of the bimodal features to the measured PDFs.

External Intermittency Simulation in Turbulent Round Jets

“…Tests were performed to ensure that the resolution used in the DNS calculations was sufficient to capture the local conditions employed were as for the low Reynolds number case, although inlet conditions for this jet were generated using a separate inflow turbulence generator based on digital filters [50]. This technique generates turbulence structures, correlated in time and space, with specified turbulence length and time scales, and was applied together with time-averaged inlet profiles obtained from experimental data [13] and RANS calculations [51].…”