Direct Numerical Simulations and Large Eddy Simulations of Unpremixed Turbulent Flames

湍流、非预混燃烧将采用 直接数值模拟（DNS）和大型 涡模拟（LES）方法。 数字将使用 谱配置（傅里叶变换）和谱元素 （切比雪夫变换和P型有限元）技术。 以下物理问题将通过 DNS：接近熄灭时的火焰尖端动力学，提升火焰 结构和验证渗流理论适用于 火焰板“孔”，以及 一个守恒标量的瞬时值及其速率 空间发展湍流火焰中的耗散。 本港就业辅导组 工作的目标是开发一种亚网格湍流闭合 使用标量单点概率密度函数， 应用于均匀湍流， 有限速率二元反应 本研究的主要对象是 湍流上的放热反应，应用 可压缩反应湍流谱元方法 流，以及大涡模拟在有限速率反应中的应用 湍流 结果应查明不足之处 与目前使用的某些湍流模型有关 并指导改进关闭技术的方法， 提高我们的能力， 真实的燃烧室流动。

Turbulent, nonpremixed combustion is to be modeled using a combination of direct numerical simulation (DNS) and large eddy simulation (LES) approaches. The numerics will employ spectral collocation (Fourier transforms) and spectral element (Chebyshev transforms and P-type finite elements) techniques. The following physical issues will be investigated through DNS: flame tip dynamics near extinguishment, lifted flame structure and the validation of percolation theory applied to flame sheet "holes", and the coupling between the instantaneous values of a conserved scalar and its rate of dissipation in spatially developing turbulent flames. The LES work will be aimed at developing a subgrid turbulence closure using a scalar single-point probability density function, with application to a homogeneous turbulent flow undergoing a finite rate binary reaction. The main objects of this research are the effects of exothermic reactions on turbulence, application of the spectral-element method to compressible reacting turbulent flows, and application of LES to finite rate reacting turbulent flows. The results should identify shortcomings associated with some of the turbulence models presently in use and guide the way to improved techniques for closure, thus advancing our ability to reliably model more physically realistic combustion chamber flows.