A priori and a posteriori analysis of flamelet modeling for large-eddy simulations of a non-adiabatic backward-facing step
A priori and a posteriori analysis of flamelet modeling for large-eddy simulations of a non-adiabatic backward-facing step
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DOI：
10.1063/5.0141108
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发表时间：
2023-05
影响因子：
4.6
通讯作者：
B. Kruljević;N. Doan;P. Breda;M. Pfitzner;I. Langella
中科院分区：
文献类型：
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作者：
B. Kruljević;N. Doan;P. Breda;M. Pfitzner;I. Langella
采用降阶动力学机制的直接数值模拟（DNS）和基于火焰热化学的大涡模拟（LES），在多网格上模拟了后台阶结构的乙烯-空气稀薄预混火焰。该配置包括预热的反应物和提供自由基和高温气体以稳定火焰的再循环区。由于靠近冷却壁，存在热损失。本文首先对不同分辨率下的DNS反应流场进行了分析，研究了回流区的换热特性。LES的基础上绝热flamelet与校正的热容量进行测试，并将其能力占热损失相比，使用三维非绝热小火焰的方法得到的结果。平均场和次网格属性进行比较，从DNS获得的LES模型的能力进行评估。结果表明，非绝热火焰面方法能较好地预测回流区和温度场。热容修正的模型能够有效地修正先验比较所观察到的热容行为。然而，在后验的情况下，它被观察到高估的温度场，虽然正确的大小的再循环区的预测。在相同的配置和不同的网格分辨率的先验和后验分析相结合，允许精确分离的建模效果，由于在壁和燃烧关闭的热传递，从而提供指示的LES性能的背景下，火焰。
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.