A priori and a posteriori analysis of flamelet modeling for large-eddy simulations of a non-adiabatic backward-facing step

Journal Article (2023)
Author(s)

B. Kruljević (TU Delft - Flight Performance and Propulsion)

N. A.K. Khoa Doan (TU Delft - Aerodynamics)

Paola Breda (University of the Federal Armed Forces Munich)

Michael Pfitzner (University of the Federal Armed Forces Munich)

Ivan Langella (TU Delft - Flight Performance and Propulsion)

Research Group
Flight Performance and Propulsion
Copyright
© 2023 B. Kruljević, Nguyen Anh Khoa Doan, Paola Breda, Michael Pfitzner, I. Langella
DOI related publication
https://doi.org/10.1063/5.0141108
More Info
expand_more
Publication Year
2023
Language
English
Copyright
© 2023 B. Kruljević, Nguyen Anh Khoa Doan, Paola Breda, Michael Pfitzner, I. Langella
Research Group
Flight Performance and Propulsion
Issue number
5
Volume number
35
Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Abstract

A lean premixed ethylene-air flame in a backstep configuration is simulated on multiple grids using both direct numerical simulations (DNS) with reduced order kinetic mechanism and large eddy simulations (LES) with flamelet-based thermochemistry. The configuration includes preheated reactants and a recirculation zone that provides radicals and high temperature gases to stabilize the flame. Heat losses are present due to the proximity of cooled walls. The reacting flow obtained from DNS at different resolutions is first analyzed to investigate the property of heat transfer within the recirculation region. LES based on adiabatic flamelets with a correction of the heat capacity is then tested, and its ability to account for heat losses is compared to results obtained using a three-dimensional non-adiabatic flamelet approach. Mean fields and subgrid properties are compared to those obtained from DNS to assess the capability of the LES models. The results show that the non-adiabatic flamelet approach can predict recirculation region and temperature fields with good accuracy. The model with heat capacity correction is able to effectively correct the heat capacity behavior as observed by a priori comparisons. However, in the a posteriori context, it is observed to overestimate the temperature field, although the correct size of the recirculation region is predicted. The combined a priori and a posteriori analyses on the same configuration and at different mesh resolutions allow for a precise separation of modeling effects due to heat transfer at the wall and combustion closure, thus providing indications on the LES performance in the context of flamelets.