A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

Zhi X. Chen*, N. Anh Khoa Doan, Shaohong Ruan, Ivan Langella, N. Swaminathan

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

13 Citations (Scopus)

Abstract

Subgrid correlation of mixture fraction, Z, and progress variable, c, is investigated using direct numerical dimulation (DNS) data of a hydrogen lifted jet flame. Joint subgrid behaviour of these two scalars are obtained using a Gaussian-type filter for a broad range of filter sizes. A joint probability density function (JPDF) constructed using single-snapshot DNS data is compared qualitatively with that computed using two independent β-PDFs and a copula method. Strong negative correlation observed at different streamwise locations in the flame is captured well by the copula method. The subgrid contribution to the Z–c correlation becomes important if the filter is of the size of the laminar flame thickness or larger. A priori assessment for the filtered reaction rate using the flamelet approach with independent β-PDFs and correlated JPDF is then performed. Comparison with the DNS data shows that both models provide reasonably good results for a range of filter sizes. However, the reaction rate computed using copula JPDF is found to have a better agreement with the DNS data for large filter sizes because the subgrid Z–c correlation effect is included.

Original languageEnglish
Pages (from-to)862-882
Number of pages21
JournalCombustion Theory and Modelling
Volume22
Issue number5
DOIs
Publication statusPublished - 3 Sept 2018
Externally publishedYes

Keywords

  • copula
  • DNS
  • LES
  • partially premixed flame
  • subgrid correlation

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