Uncertainty quantification (UQ) in the hypersonic flow regime offers valuable information to determine physical models in need of improvement and to assist in design of vehicles and flight experiments. Here we present results of UQ analysis based on polynomial chaos method to determine flowfield and surface heat flux uncertainty under typical blunt-body re-entry conditions. The NASA Langley code, LAURA, was used for axisymmetric CFD calculations of chemically reacting hypersonic flow over FIRE-II configuration. A third order polynomial chaos (PC) method using the Gauss-Hermite quadrature was applied for determining probability density functions and moments of output quantities. Input parameters such as freestream density, velocity, and temperature were varied and the propagation of their corresponding uncertainties on output properties of interest through the flowfield were studied. An order of magnitude increase in surface heat flux uncertainties was observed for an input freestream velocity uncertainty of ±100 ft/s, or 0.29%. This parameter thus has the greatest sensitivity to variations, and conversely the freestream temperature has the least sensitivity.
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机译：高超声速流动状态下的不确定度量化（UQ）提供了有价值的信息，可用于确定需要改进的物理模型，并有助于车辆设计和飞行实验。在这里，我们介绍基于多项式混沌方法的UQ分析结果，以确定典型钝体再入条件下的流场和表面热通量不确定性。 NASA Langley代码LAURA用于在FIRE-II配置上对高超声速化学反应流进行轴对称CFD计算。应用了使用高斯-赫姆特正交的三阶多项式混沌（PC）方法来确定概率密度函数和输出量矩。输入参数（如自由流密度，速度和温度）发生变化，并且研究了它们相应的不确定性在流场中对目标输出特性的影响。对于输入自由流速度不确定度为±100 ft / s或0.29％，观察到表面热通量不确定度增加了一个数量级。因此，该参数对变化的灵敏度最高，相反，自由流温度的灵敏度最低。
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