A fast, low-memory, and stable algorithm for implementing multicomponent transport in direct numerical simulations
A fast, low-memory, and stable algorithm for implementing multicomponent transport in direct numerical simulations
复制标题
DOI：
10.1016/j.jcp.2019.109185
复制
发表时间：
2018-07
期刊：
影响因子：
--
通讯作者：
Aaron J. Fillo;Jason Schlup;Guillaume Beardsell;G. Blanquart;Kyle E. Niemeyer
中科院分区：
文献类型：
--
作者：
Aaron J. Fillo;Jason Schlup;Guillaume Beardsell;G. Blanquart;Kyle E. Niemeyer
由于计算扩散系数的困难，在反应流模拟中实现多组分扩散模型的计算代价很高。取而代之的是，通常使用混合平均扩散处理来避免这些成本。然而，据我们所知，对于三维湍流预混火焰，混合平均扩散模型的准确性和适用性还没有得到验证。在这项研究中，我们提出了一种快速、高效、低内存的算法，并用它来评估多组分质量扩散在反应流模拟中的作用。通过在NGA中实现Stefan-Maxwell方程，对这些火焰进行了直接的数值模拟。一种半隐式算法在保持精度和保真度的同时，降低了全多分量普通扩散阵求逆的计算量。我们首先通过对预混氢火焰进行一维模拟来验证该方法，并与Cantera中的匹配情况进行了比较。我们证明了该算法是稳定的，并且其性能近似地随物种数的平方而变化。然后，作为多组分扩散的初步研究，我们忽略了二次Soret和Dufour效应，模拟了预混的三维湍流氢火焰。仔细选择模拟条件，以匹配先前发布的结果，并确保有效的比较。结果表明，采用混合平均扩散假设，对预混氢-空气火焰的归一化湍流火焰速度预测偏低15%。湍流火焰速度的这种差异促使人们进一步研究将混合平均扩散假设用于中到高Karlovitz数火焰的数值模拟。
Implementing multicomponent diffusion models in reacting-flow simulations is computationally expensive due to the challenges involved in calculating diffusion coefficients. Instead, mixture-averaged diffusion treatments are typically used to avoid these costs. However, to our knowledge, the accuracy and appropriateness of the mixture-averaged diffusion models has not been verified for three-dimensional turbulent premixed flames. In this study we propose a fast, efficient, low-memory algorithm and use that to evaluate the role of multicomponent mass diffusion in reacting-flow simulations. Direct numerical simulation of these flames is performed by implementing the Stefan–Maxwell equations in NGA. A semi-implicit algorithm decreases the computational expense of inverting the full multicomponent ordinary diffusion array while maintaining accuracy and fidelity. We first verify the method by performing one-dimensional simulations of premixed hydrogen flames and compare with matching cases in Cantera. We demonstrate the algorithm to be stable, and its performance scales approximately with the number of species squared. Then, as an initial study of multicomponent diffusion, we simulate premixed, three-dimensional turbulent hydrogen flames, neglecting secondary Soret and Dufour effects. Simulation conditions are carefully selected to match previously published results and ensure valid comparison. Our results show that using the mixture-averaged diffusion assumption leads to a 15% under-prediction of the normalized turbulent flame speed for a premixed hydrogen-air flame. This difference in the turbulent flame speed motivates further study into using the mixture-averaged diffusion assumption for DNS of moderate-to-high Karlovitz number flames.