Interaction of compressible turbulence and radiation of heat using large-eddy simulation

受热辐射影响的湍流的直接数值模拟目前是不可能的(除非在高度简化的环境中)，因为需要巨大的计算工作量。然而，目前可用的高性能计算机足够强大，可以对湍流-辐射相互作用(TRI)进行大涡模拟(LES)。除了极少数例外，到目前为止，TRI一直是在统计水平上处理的，即光谱吸收系数和光谱辐射强度(这只是辐射传递方程中出现的一个特定项)的平均乘积是使用统计平均量来建模的。当辐射传递方程(RTE)进行低通滤波以进行大涡模拟时，会出现未知项，需要建模才能关闭方程。然而，文献中在这个方向上的第一次尝试是不完整的。这个项目的目的是为非散射介质的低通滤波RTE中的所有未闭合项开发一个模拟策略，即亚网格尺度对光谱发射和吸收的贡献。为此，对包含温度和物种质量分数(或混合分数)的过滤密度函数(PDF)的输运方程进行了建模和求解。PDF允许对所有未知的过滤术语进行评估。在温度为1200K的最小通道中，用水蒸气对超音速湍流流动(无辐射)进行了先验测试。当壁面温度为1000K数量级时，由于动能耗散，核心流动至少将达到1200K。这种流场包含温度和组分质量分数的涨落，允许计算辐射性质和辐射强度，而不需要计算辐射和湍流之间的完全耦合。过滤后的DNS数据与辐射传输方程中的模型项(先验检验)的比较将表明该方法的有效性，并允许TRI的大涡模拟。

Direct numerical simulations of turbulent flows that are affected by radiation of heat are not possible at the present time (except in strongly simplified settings) due to the enormous computational effort needed. Presently available high-performance computers are, however, powerful enough to allow for large-eddy simulations (LES) of turbulence-radiation interaction (TRI). With very few exceptions TRI has, up to now, been treated on a statistical level, i.e. the mean product of spectral absorption coefficient and spectral radiation intensity (which is just one specific term appearing in the radiative transfer equation) was modelled using statistically averaged quantities. When the radiative transfer equation (RTE) is low-pass filtered to perform an LES, unknown terms appear that need modelling to close the equation. First attempts in this direction, found in the literature, are however incomplete.It is the aim of this project to develop a modelling strategy for all unclosed terms in the lowpass filtered RTE for a non-scattering medium, i.e. for the subgrid-scale contributions to spectral emission and absorption. To this end a transport equation for the filtered density function (PDF) involving temperature and species mass fractions (or the mixture fraction) is modelled and solved. The PDF allows the evaluation of all unknown filtered terms. A priori tests of this ansatz will be made by performing a DNS of supersonic turbulent flow (without radiation) In a minimal channel using water vapour at a temperature level of 1200 K. When the wall temperatures are of the order of 1000 K the core flow will at least reach 1200 K as a result of kinetic energy dissipation. This flow field contains fluctuations of temperature and species mass fraction and allows the computation of radiation properties and radiation intensities without computing the full coupling between radiation and turbulence. A comparison of filtered DNS data and modelled terms in the radiative transfer equation (a priori test) will show the validity of the approach and allow for LES of TRI.