Instantaneous transport of a passive scalar in a turbulent separated flow

P. Ouro, B. Fraga, N. Viti, A. Angeloudis, T. Stoesser*, C. Gualtieri

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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.

Original languageEnglish
Pages (from-to)487-513
Number of pages27
JournalEnvironmental Fluid Mechanics
Volume18
Issue number2
Early online date18 Dec 2017
DOIs
Publication statusPublished - 1 Apr 2018

Keywords / Materials (for Non-textual outputs)

  • Backward facing step
  • Large eddy simulation
  • Separation flows
  • Solute dispersion
  • Turbulence

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