A Thickened Stochastic Fields Approach for Turbulent Combustion Simulation.
A Thickened Stochastic Fields Approach for Turbulent Combustion Simulation.
复制标题
湍流燃烧模拟的加厚随机场方法。
DOI：
10.1007/s10494-018-9954-y
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Picciani MA
中科院分区：
文献类型：
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作者：
Picciani MA
随机场方法是将输运概率密度函数模型应用于湍流燃烧大涡模拟的有效途径。然而，在预混湍流燃烧中，薄的火焰状结构出现在随机场方程的解中，所述随机场方程需要比用于大涡模拟的过滤尺度精细得多的网格间距。使用等于过滤器尺度的网格间距的常规方法产生相当大的数值误差，而使用比过滤器长度尺度精细得多的网格间距对于大多数工业相关的燃烧系统来说在计算上是负担不起的。在这项研究中，为了提供物理上准确和数值收敛的随机场方程的解决方案，减少计算时间的加厚随机场方法。加厚随机场制定桥梁之间的传统随机场和传统的加厚火焰的方法，这取决于所使用的数值网格间距。自由传播的湍流预混火焰的一维随机场模拟，以获得所需的增厚因子的标准，作为相关的物理和数值参数的函数，并获得一个模型的效率函数，该函数占的损失解决火焰表面积所造成的应用增厚变换的随机场方程。加厚随机场公式进行测试，通过实验室预混本生火焰的LES。结果表明，加厚随机场方法产生准确的预测，即使使用的网格间距等于过滤器的规模。因此，目前的发展有利于准确应用的随机场的方法，工业相关的燃烧系统。
The Stochastic Fields approach is an effective way to implement transported Probability Density Function modelling into Large Eddy Simulation of turbulent combustion. In premixed turbulent combustion however, thin flame-like structures arise in the solution of the Stochastic Fields equations that require grid spacing much finer than the filter scale used for the Large Eddy Simulation. The conventional approach of using grid spacing equal to the filter scale yields substantial numerical error, whereas using grid spacing much finer than the filter length scale is computationally-unaffordable for most industrially-relevant combustion systems. A Thickened Stochastic Fields approach is developed in this study in order to provide physically-accurate and numerically-converged solutions of the Stochastic Fields equations with reduced compute time. The Thickened Stochastic Fields formulation bridges between the conventional Stochastic Fields and conventional Thickened-Flame approaches depending on the numerical grid spacing utilised. One-dimensional Stochastic Fields simulations of freely-propagating turbulent premixed flames are used in order to obtain criteria for the thickening factor required, as a function of relevant physical and numerical parameters, and to obtain a model for an efficiency function that accounts for the loss of resolved flame surface area caused by applying the thickening transformation to the Stochastic Fields equations. The Thickened Stochastic Fields formulation is tested by performing LES of a laboratory premixed Bunsen flame. The results demonstrate that the Thickened Stochastic Fields method produces accurate predictions even when using a grid spacing equal to the filter scale. The present development therefore facilitates the accurate application of the Stochastic Fields approach to industrially-relevant combustion systems.