Modeling differential diffusion of strain-sensitive gas-phase species in turbulent nonpremixed sooting flames

Jeffry K. Lew, Michael E. Mueller

Research output: Contribution to conferencePaperpeer-review


Recent three-dimensional direct numerical simulations (DNS) of soot evolution in turbulent nonpremixed jet flames have shown that polycyclic aromatic hydrocarbons (PAH) are constrained to spatially intermittent regions of low scalar dissipation rate due to their slow chemistry. These regions are on the order of the Kolmogorov scale or smaller, where molecular transport prevails over turbulent transport regardless of the Reynolds number. Therefore, accurately modeling the evolution of these soot precursors requires incorporation of gas-phase differential diffusion effects. Previous works using the nonpremixed flamelet model to account for differential diffusion have applied detailed transport to all species in regions where the Kolmogorov scale is larger than the length scales of fuel-oxidizer mixing. However, such an approach implicitly assumes that the length scales of all species are comparable to those of fuel-oxidizer mixing, which is not the case for spatially intermittent PAH. A new model is proposed that applies differential diffusion locally only to species whose chemistry is slow relative to local mixing. A strain-sensitivity parameter is used to identify these species and will be evaluated against DNS data. Implementation in large eddy simulation (LES) will be discussed.

Original languageEnglish (US)
StatePublished - 2017
Externally publishedYes
Event10th U.S. National Combustion Meeting - College Park, United States
Duration: Apr 23 2017Apr 26 2017


Other10th U.S. National Combustion Meeting
Country/TerritoryUnited States
CityCollege Park

All Science Journal Classification (ASJC) codes

  • General Chemical Engineering
  • Physical and Theoretical Chemistry
  • Mechanical Engineering


  • Differential diffusion
  • LES
  • Soot
  • Turbulent nonpremixed combustion


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