基于自适应网格的钝头体激波诱导燃烧现象数值模拟研究

Numerical Study on Shock-Induced Combustion of a Blunt Projectile via an Adaptive Mesh Program

关键词:  自适应网格加密  激波诱导燃烧  爆震  限制器  化学反应机理

Key words:  Adaptive mesh refinement  Shock-induced combustion  Detonation  Slope limiter  Chemical reaction mechanisms

摘要:

钝头体激波诱导燃烧是爆震研究的一个基本问题。针对化学恰当量比的H₂/Air预混气体在Ma=4.79和Ma=6.46时的激波诱导燃烧现象开展数值研究，采用基于有限体积法的块结构自适应网格加密程序AMROC，对带化学反应源项的轴对称Euler方程解耦求解，考察了数值模拟中不同形式的MUSCL重构格式、限制器类型以及化学反应机理等重要因素对模拟结果的影响。结果表明，程序能够根据设定的加密判据较好地实现网格自适应加密，减小总网格量，实现高效数值模拟。与实验数据的对比表明，非定常激波诱导燃烧算例的准确程度不仅取决于化学反应机理，也取决于限制器类型，而采用两种不同形式的MUSCL重构格式获得的振荡频率则几乎一致，与试验结果的误差分别为1.17%和0.97%。模拟对比经典的Jachimowski机理和近年来新发展的几种包含压力相关反应步的氢/氧反应机理，模拟结果表明：对于Ma=4.79时的非定常激波诱导燃烧模拟，经典的Jachimowski机理仍然是能够给出与实验结果最接近的反应机理；而对于Ma=6.46时的定常激波诱导燃烧模拟，几种反应机理均能给出与实验吻合较好的结果。

Abstract:

Shock-induced combustion of a blunt projectile is a basic problem in detonation research. Numerical simulations were conducted to study the shock-induced combustion phenomenon of a stoichiometric H₂/Air mixture at the flow Mach numbers of 4.79 and 6.46. The block-structured adaptive mesh refinement program AMROC based on the finite volume method was adopted to solve the axisymmetric Euler equations with chemical reaction source terms， and the influence of some important factors such as the form of the MUSCL reconstruction， the slope limiter types， and the chemical reaction mechanisms were investigated. The results show that， based on the mesh adaption flag parameters， the program can realize adaptive mesh refinement efficiently. The comparisons with experimental results show that the accuracy of the unsteady shock-induced combustion simulation depends not only on the chemical reaction mechanism， but also on the form of the limiter. Adopting two different forms of the MUSCL reconstruction format acquires almost the same oscillating frequencies， which is 1.17% and 0.97% different from the result obtained in the experiment， respectively. Numerical study is conducted for comparing the classic Jachimowski mechanism with several newly developed pressure-dependent hydrogen/oxygen reaction mechanisms. It is shown that， in the unsteady shock-induced combustion case at Ma=4.79， the classic Jachimowski mechanism is still the most suitable mechanism to obtain the closest oscillating frequency to the experimental result. While in the steady shock-induced combustion case at Ma=6.46， all of the given mechanisms can give results that are in good agreements with the experiment.