The influence of scalar dissipation rate fluctuations on turbulent premixed flames at varying Karlovitz number

Manifold-based combustion models can be utilized to described turbulent premixed combustion using one-dimensional equations in terms of a progress variable. The progress variable dissipation rate appears as a key parameter in the manifold equations dictating the characteristics of premixed combustion from "flamelet" combustion at lower dissipation rates to "distributed" combustion at higher dissipation rates. However, this dissipation rate is constant in neither time nor space, and these fluctuations have a significant effect on the behavior of the flame structure, specifically that of the reaction zone. To better understand the influence of dissipation rate fluctuations, detailed simulations have been conducted for hydrogen premixed flames at a variety of turbulent conditions and Karlovitz numbers, and the variation of progress variable dissipation rate is assessed at a number of locations within the flame. The influence of the dissipation rate fluctuations on the flame behavior is evaluated through an analysis of the subsequent influence on the thermochemical state.