Instantaneous transport of a passive scalar in a turbulent separated flow

Ouro, P. ORCID: https://orcid.org/0000-0001-6411-8241, Fraga, B., Viti, N., Angeloudis, A. ORCID: https://orcid.org/0000-0001-5021-3643, Stoesser, T. ORCID: https://orcid.org/0000-0001-8874-9793 and Gualtieri, C. 2018. Instantaneous transport of a passive scalar in a turbulent separated flow. Environmental Fluid Mechanics 18 (2) , pp. 487-513. 10.1007/s10652-017-9567-3

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Abstract

The results of large-eddy simulations of flow and transient solute transport over a backward facing step and through a 180° bend are presented. The simulations are validated successfully in terms of hydrodynamics and tracer transport with experimental velocity data and measured residence time distribution curves confirming the accuracy of the method. The hydrodynamics are characterised by flow separation and subsequent recirculation in vertical and horizontal directions and the solute dispersion process is a direct response to the significant unsteadiness and turbulence in the flow. The turbulence in the system is analysed and quantified in terms of power density spectra and covariance of velocity fluctuations. The injection of an instantaneous passive tracer and its dispersion through the system is simulated. Large-eddy simulations enable the resolution of the instantaneous flow field and it is demonstrated that the instabilities of intermittent large-scale structures play a distinguished role in the solute transport. The advection and diffusion of the scalar is governed by the severe unsteadiness of the flow and this is visualised and quantified. The analysis of the scalar mass transport budget quantifies the mechanisms controlling the turbulent mixing and reveals that the mass flux is dominated by advection.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Advanced Research Computing @ Cardiff (ARCCA) Engineering
Additional Information:	This article is distributed under the terms of the Creative Commons Attribution 4.0 International License.
Publisher:	Springer Verlag
ISSN:	1567-7419
Date of First Compliant Deposit:	2 January 2018
Date of Acceptance:	4 December 2017
Last Modified:	22 May 2023 18:48
URI:	https://orca.cardiff.ac.uk/id/eprint/107771

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