Recent developments in multiscale forcing for enhanced mixing

Bernard J. Geurts*, Thiago Cardoso de Souza

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)

Abstract

We discuss methods of multiscale forcing to enhance the mixing efficiency of an incompressible flow. To introduce a variety of length- and time-scales into a flow, we focus on two methods. First, we concentrate on effects due to guiding a fluid over a complex-shaped object placed in the flow domain. Specifically, we apply direct numerical simulation to predict flow through a cylindrical pipe in which a periodic array of orifice plates with a fractal perimeter is mounted. To represent the complex orifice, a volume penalisation immersed boundary method is used. Adding a periodic array of fractal orifice plates, derived from the Koch snowflake, to a cylindrical pipe is shown to increase the average laminar stretching rate by a factor of up to five, compared to pipe flow without orifice plates. Second, we consider the inclusion of multiple length- and time scales at inflow boundaries to enhance mixing efficiency for combustion in Bunsen-type flames. By using a combination of large- and small-scale flow perturbations at an inflow, a two-fold increase of flame wrinkling and flame intensity could be realised. The scale-dependency of the intensification of the combustion is investigated, showing a narrow range of length-scales with strongest response, reminiscent of ‘resonant turbulence’ conditions.

Original languageEnglish
Pages (from-to)353-365
Number of pages13
JournalComputers and fluids
Volume176
DOIs
Publication statusPublished - 15 Nov 2018

Keywords

  • Bunsen flame
  • Enhanced mixing
  • Multiscale forcing
  • Pipe flow
  • Turbulence modulation

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