Abstract
The near-wall behaviour of the generalised flame surface density (FSD) transport in the context of Reynolds Averaged Navier–Stokes (RANS) simulations has been analysed for different values of global Lewis number using three-dimensional Direct Numerical Simulation (DNS) data of head-on quenching of statistically planar turbulent premixed flames by an isothermal inert wall. It has been found that the statistical behaviour of the FSD based reaction rate closure and the terms of the FSD transport equation are significantly affected by the presence of the wall and by the global Lewis number. The near-wall predictions of the standard FSD based mean reaction rate closure and existing sub-models for the unclosed terms of the FSD transport equation have been found to be inadequate based on a-priori DNS assessment, and modifications to these models have been suggested so that the predictions of modified models for reaction rate closure and FSD transport remain satisfactory, both close to the wall and away from it over a wide range of global Lewis number.
Highlights
Direct Numerical Simulation (DNS) contributed significantly to the fundamental under-Please cite this article as: J
The data obtained from the simulations by Bruneaux et al [4] was used to analyse a flame surface density (FSD) based reaction rate closure [5]
Alshalaan and Rutland [6] analysed the near-wall statistics of FSD as well as turbulent scalar transport and wall heat flux
Summary
Direct Numerical Simulation (DNS) contributed significantly to the fundamental under-. The current analysis will focus on the RANS modelling of FSD based mean reaction rate closure in the near-wall region alongside the modelling of the unclosed terms in the transport equation for the generalised FSD (i.e. gen = |∇c| [15], where c is the reaction progress variable and the over-bar denotes Reynolds averaging operation). The near-wall behaviour of FSD based closures has been addressed in the past [5,6], the effects of turbulence intensity and Le on near-wall FSD modelling of FSD have not yet been considered This paper addresses this gap by analysing three-dimensional DNS data of HOQ of statistically planar turbulent premixed flames by an inert isothermal wall. The transport equation for gen takes the following form [10,11,12,13,14,16,18,19,22]:
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