Inproceedings,

A Resolved Simulation Study on the Interactions Between Droplets and Turbulent Flames Using OpenFOAM

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High Performance Computing in Science and Engineering '17, page 205-220. Springer, (2018)

Abstract

This study presents direct numerical simulations (DNS) of turbulent reacting flows around evaporating single fuel droplets and droplet arrays. Statistical analysis of interactions between the droplets and the turbulent flames are used to develop sub-grid scale models for mixture fraction based approaches such as flamelet or conditional moment closure (CMC) methods. The specific challenges are posed by the effects of the evaporating spray on the composition field in inter-droplet space and by the presence of combustion. Here, we analyse the best possible setup for such a fully resolved DNS. The numerical constraints are given by (1) the need to resolve all small scale effects, i.e. the smallest turbulent eddies and the boundary layer thickness around the droplets, and (2) the desire to include scales covering the entire turbulence spectrum to ensure a realistic interaction between the large and small scales. The largest scales are typically limited by the size of the computational domain, and these two demands (high resolution and large domain size) can easily lead to extensive computational requirements. We suggest an optimal setup for fully resolved DNS that ensures a good balance between computational cost and solution accuracy. The optimal mesh resolution and domain size do not introduce any bias for the analysis of characteristic quantities such as mixture fraction, its PDF and conditional scalar dissipation. Further, adequate scalability of OpenFOAM for the different setups is reported.

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