多相反应的统计粒子方法建模与模拟
Modelling and Simulation of Heterogeneous Reactions with Statistical Particle Methods
摘要：
估计再入飞行器的热负荷是准备重返大气层机动的一个关键部分。高空再入流处于稀薄状态，并受高湍流度和热力学非平衡控制。此外，催化气体表面反应改变了气体流的组成，并可能对传热产生重大影响。我们的目标是估计热负荷没有先验拟合的模拟参数的实验。我们使用的工具PICLas模拟这样的稀薄气体流动。它结合了不同的粒子方法，包括直接模拟蒙特卡罗方法，用于气体建模。最近，它已扩展到包括不同的催化模型来处理表面上的反应。我们评估的动力学蒙特卡罗方法来模拟催化气体表面相互作用结合使用粒子方法的流动模拟。在这里，吸附质分布是通过使用动力学蒙特卡罗方法再现表面系统和使用模型假设估计必要的参数来建模的。这种催化模型相比，一个简单的重组模型。我们提出了模拟，显示的能力的实施模型的$\mathrm{SiO_2}$表面的氧气流。此外，模拟结果进行了比较，从各自的实验获得的热通量和复合系数。结果表明，使用动力学蒙特卡罗方法的模拟匹配的实验获得的值。因此，该方法可用于估计氧气流过$\mathrm{SiO_2}$表面的反应性。
英文摘要：
Estimating the heat loads on re-entry vehicles is a crucial part of preparing for atmospheric re-entry manoeuvres. Re-entry flows at high altitudes are in the rarefied regime and are governed by high enthalpies and thermodynamic non-equilibrium. Additionally, catalytic gas-surface reactions change the gas flow composition and can have a major influence on the heat transfer. Our goal is to estimate the heat loads without a priori fitting of simulation parameters to experiments. We use the tool PICLas for simulations of such rarefied gas flows. It combines different particle methods, including the Direct Simulation Monte Carlo method, for modelling of gases. Recently it has been extended to include different catalysis models to treat reactions on surfaces. We evaluate a kinetic Monte Carlo approach to model catalytic gas-surface interactions in combination with flow simulations using particle methods. Here, the adsorbate distribution is modelled by reproducing a surface system using a kinetic Monte Carlo approach and estimating the necessary parameters using model assumptions. This catalytic model is compared to a simple recombination model. We present simulations that show the capability of the implemented models for a $\mathrm{SiO_2}$ surface in an Oxygen flow. Furthermore, simulation results are compared to heat fluxes and recombination coefficient obtained from the respective experiment. The results show that simulations using the kinetic Monte Carlo approach match the experimentally obtained values. Thus, the approach can be used to estimate the reactivity of oxygen flows over $\mathrm{SiO_2}$ surfaces.
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