Detailed SGS atomization model and its implementation to two-phase flow LES
Detailed SGS atomization model and its implementation to two-phase flow LES
复制标题
详细的SGS雾化模型及其在两相流LES中的实现
DOI：
10.1016/j.combustflame.2018.01.026
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发表时间：
2018
影响因子：
4.4
通讯作者：
Shinjo Junji
中科院分区：
文献类型：
--
作者：
Umemura Akira;Shinjo Junji
在湍流喷雾燃烧大涡模拟（LES）的框架下，建立了一种新的湍流雾化模型，该模型本身是物理封闭的，不需要根据实验数据对参数进行逐例调整。基于我们积累的研究成果，即基本液滴/韧带的产生是一种确定性现象，而不是传统理解中的随机现象，该模型以物理上直接的方式描述了湍流原子化的两种主要模式，即湍流共振模式和瑞利-泰勒（Rayleigh-Taylor）模式。将Umemura（2016）提出的基线理论扩展到包括欧拉液体射流核心和拉格朗日液滴的混合湍流喷雾LES公式，在本研究中完整详细地描述了亚网格尺度（SGS）的雾化特性。利用液相岩心表面的LES分辨湍流韦伯数和Bond数，局部识别液滴大小、数量、喷射速度和岩心回归速度等SGS雾化方式和特征，并将这些信息作为输入信息传回LES代码。柴油机喷流试验表明，该公式能较好地再现湍流喷流特性。通过获得的详细数据，可以从时间和空间上跟踪喷雾形成过程，从最初的头部形成边缘雾化到后期的核心雾化和喷雾扩散。与传统的喷雾模拟方法相反，该湍流雾化模型的本质特点是在没有模糊用户输入的情况下工作良好。这是推动喷雾模拟从非封闭/不可预测到封闭/可预测的范式转变的重大突破，使喷雾模拟的准确性得到了极大的提高，可能对研究和工业应用产生重大影响。
A novel turbulent atomization model, which is physically closed itself and free of case-by-case parameter tuning using experimental data, has been formulated and demonstrated in the framework of turbulent spray combustion large-eddy simulation (LES). Based on our accumulated research findings that elementary droplet/ligament generation is a deterministic phenomenon, not something random as considered in the conventional understanding, the model describes two dominant modes of turbulent atomization, i.e. the turbulent resonant mode and the Rayleigh–Taylor (RT) mode, in a physically straightforward manner. Extending the baseline theory proposed in Umemura (2016), to a hybrid turbulent spray LES formulation which includes both an Eulerian liquid jet core and Lagrangian droplets, the subgrid-scale (SGS) atomization characteristics are completely detailed in this study. Using the LES-resolved turbulent Weber and Bond numbers on the liquid core surface, the atomization mode and the SGS atomization characteristics such as droplet size, number, ejection velocity and core regression velocity are all identified locally, and the information is transferred back to the LES code as input information. Test cases of Diesel fuel jets demonstrate that the present formulation well reproduces the turbulent spray behavior. Thanks to the obtained detailed data, the spray formation process can be tracked both temporally and spatially, from the initial head formation with edge atomization to the later core atomization and spray spreading. It is essentially featured that the present turbulent atomization model works well without ambiguous user input, contrary to the conventional way of spray simulation. This is a significant breakthrough to urge paradigm shift in spray simulation, from unclosed/unpredictable to closed/predictable, which enables drastic improvement in the accuracy of spray simulation and may exert a large impact on both research studies and industrial applications.