AI 中文总结
本研究以桑迪亚1米甲烷火羽流为基准，采用FPV方法结合LES探究火焰底部燃烧不稳定性，量化了有限速率化学与微分扩散的影响，为大规模湍流浮力火焰高保真模拟提供了指导。
AI 中文摘要
桑迪亚1米甲烷火羽流是用于大规模火焰湍流燃烧建模的成熟基准。本研究探究桑迪亚火羽流底部附近形成的燃烧不稳定性，采用火焰面/进度变量（FPV）方法考虑有限速率化学与微分扩散效应。通过大涡模拟（LES）将FPV方法的性能与涡耗散模型（EDM）及大规模火羽流的实验数据进行对比评估，还通过在不同位置将轴向与径向速度与实验数据对比，系统探究辐射建模与网格分辨率对模型预测能力的影响。尽管所有模型均成功捕捉火羽流的主要流动特征，但考虑微分扩散的FPV模型在近火焰底部区域的预测结果更优。通过涡量方程的收支分析探究火焰底部附近胞状流动结构的形成机制，明确了控制该胞状结构形成的不稳定性类型，还量化了有限速率化学与微分扩散对热化学量预测的单独影响。总体而言，本研究阐释了湍流火羽流底部燃烧不稳定性的 underlying physics，为气态池火LES的火焰面模型性能提供了新见解，为大规模湍流浮力驱动火焰的高保真数值模拟提供了可靠指导。
英文摘要
The Sandia one-meter methane fire plume is an established benchmark for turbulent combustion modeling of large-scale flames. This study investigates the combustion instabilities formed close to the base of the Sandia fire plume. Finite rate chemistry and differential diffusion are considered using a flamelet/progress variable (FPV) approach. The performance of the FPV approach is assessed by comparing with the eddy dissipation model (EDM) and the experimental data for the large-scale fire plume via large eddy simulations (LES). The effects of radiation modeling and mesh resolution on the predictive capability of the model are systematically investigated by comparing the axial and radical velocities against the experimental data at various locations. Although all models successfully capture the primary flow characteristics of fire plumes, the FPV model with differential diffusion yields improved predictions in the near-flame-base region. The formation mechanism of cellular flow structures near the flame base is investigated via a budget analysis of the vorticity equation, and the type of instability governing the formation of the cellular structure is clarified. Finally, the individual effects of finite rate chemistry and differential diffusion on the prediction of the thermo-chemical quantities are quantified. Overall, this study explains the underlying physics governing combustion instabilities at the base of turbulent fire plumes, provides novel insights into the performance of flamelet models for LES of gaseous pool fires, and offers reliable guidance for the high-fidelity numerical simulation of large-scale turbulent buoyancy driven flames.
Comments15pages, 11figures
