This paper presents an analysis of numerical and modelling issues based on a simulation of nitrogen-diluted hydrogen lifted flame evolving in a hot co-flow. We apply the large-eddy simulations (LES) method with the so-called ‘no combustion model’ and concentrate on the impact of chemical mechanisms and various discretisation schemes on the obtained results. The main attention is put to the latter issue in which we analyse to what extent a discretisation method of the convective terms of the scalar equations for the species and enthalpy affects the solutions. We consider eight commonly known total variation diminishing (TVD) schemes and three upwind schemes of the second order. The remaining terms in the scalar equations and all the terms in the Navier–Stokes equations are discretised applying the sixth-order compact difference method. Such an approach makes the discretisation errors of the convective terms the main factor affecting the solutions from the numerical point of view. Prior to the main analysis, the differences caused by the use of various TVD or upwind schemes are highlighted based on a single scalar transport equation with a known analytical solution. The results obtained for the flame are compared to experimental data taken from the literature. It is shown that the differences due to the application of a particular discretisation method are of similar magnitude as the differences between the simulation results and experimental data. Moreover, analysis of the impact of the chemical mechanism showed that observed differences are comparable to these originating from the use of different discretisation methods.

本文基于对热协流中氮稀释氢气升起火焰的模拟，对数值和建模问题进行了分析。我们将大涡模拟 (LES) 方法与所谓的“无燃烧模型”一起应用，并专注于化学机制和各种离散化方案对获得结果的影响。主要关注后一个问题，我们分析了物质和焓的标量方程的对流项的离散化方法在多大程度上影响解。我们考虑了八个众所周知的总变差递减 (TVD) 方案和三个二阶逆风方案。标量方程中的其余项和 Navier-Stokes 方程中的所有项均采用六阶紧致差分法进行离散化。从数值的角度来看，这种方法使对流项的离散化误差成​​为影响解的主要因素。在主要分析之前，根据具有已知解析解的单个标量传输方程突出显示了使用各种 TVD 或逆风方案引起的差异。将火焰获得的结果与文献中的实验数据进行比较。结果表明，由于应用特定离散化方法而导致的差异与模拟结果和实验数据之间的差异具有相似的幅度。此外，对化学机制影响的分析表明，观察到的差异与使用不同离散化方法产生的差异相当。