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通常的CFD计算都是确定性的,然而复杂工程数值模拟中必然存在误差与不确定度,分析与辨识其不确定度来源,对不确定度进行量化分析,对数值模拟可信度评估有重要意义。在高超声速飞行器气动热计算中,为获得更加可靠的气动热数据和鉴定影响气动热预测的关键因素,对返回舱开展了气动热不确定性量化分析和敏感性分析。首先选取来流速度、来流温度、壁面温度和来流密度4个不确定性输入变量。并且假定来流速度变化范围为±120m/s(±2%),来流温度、壁面温度和来流密度变化范围为±10%。然后采用拉丁超立方抽样法生成样本,再通过热化学非平衡数值模拟方法进行气动热计算,最后分别运用基于非嵌入式多项式混沌(NIPC)的方法和基于Sobol指数的方法开展不确定度量化和敏感性分析。结果表明,在给定的输入变量不确定度的条件下,壁面热流不确定度不小于15.9%,在驻点和肩部存在峰值分别约为19.8%(0.087 MW/m2)和17.3%(0.076 MW/m2);相比而言,在给定变化范围内壁面热流对来流密度和来流速度更为敏感,来流温度和壁面温度对热流变化不产生明显影响。
Common CFD calculations are deterministic, however, errors and uncertainties in the numerical simulation of complex projects inevitably exist. Analysis and identification of the source of the uncertainties, quantification of uncertainty, and importance in the reliability assessment of numerical simulation significance. In the aerodynamic calculation of hypersonic vehicle, quantitative and aerodynamic thermal uncertainty quantitative analysis and sensitivity analysis are carried out for the return capsule in order to obtain more reliable aerodynamic heat data and to identify the key factors affecting aerodynamic heat prediction. First, four uncertainties, ie, flow rate, flow temperature, wall temperature and flow density, are input. And assuming that the incoming velocity varies in a range of ± 120 m / s (± 2%), the incoming flow temperature, wall temperature and incoming flow density range from ± 10%. Then, the samples are generated by using the Latin hypercube sampling method, and the aerodynamic heat is calculated by thermochemical non-equilibrium numerical simulation. Finally, the methods of non-embedded polynomial chaos (NIPC) and Sobol index Sensitivity analysis. The results show that the uncertainty of wall heat flow is not less than 15.9% for a given input variable uncertainty and about 19.8% (0.087 MW / m2) and 17.3% (0.076 MW / m2). In contrast, the wall heat flux is more sensitive to the incoming flow rate and the incoming velocity within a given range of variation. The temperature of the flow and wall temperature have no significant effect on the heat flow.