Abstract In this study, an uncertainty analysis for the infrared radiation characteristics of rocket exhaust plumes at representative trajectory points is performed. Owing to the instability of the rocket motor’s working characteristics, numerical rocket plume infrared radiation predictions possess significant uncertainties. In this study, four epistemic uncertain variables (freestream velocity, nozzle exit pressure, temperature, and velocity) are considered for uncertainty and sensitivity analyses. Based on the infrared signature analysis tool, the response surface of statistical samples is established through the point collocation nonintrusive polynomial chaos expansion method. Polynomial chaos expansion coefficients are solved using the quadrature method to calculate the statistical characteristics and uncertainty of random input variables. The tensor-product quadrature sparse grid method is utilized to reduce the number of samples for multiple input variables. Based on these models, the uncertainty quantification of infrared radiation for Atlas-IIA rocket plumes is analyzed, including the flows, radiation images, spectra, and radiance. The results show that the uncertainty mainly results from afterburning at low altitude, and the nozzle exit velocity has a significant influence on the radiation intensity of the plume. With an increase in altitude, the uncertainty of infrared radiation owing to the afterburning effect decreases, and the influence of the freestream velocity increases. In addition, the proportion of radiation intensity in the 4.3-μm band is higher than that in the 2.7-μm band, and the corresponding uncertainty band is gradually widened. The nozzle exit temperature is the dominant factor that affects the radiation characteristics of the plume at high altitudes. These results of uncertainty and sensitivity analyses are helpful for improving numerical models of the plume infrared signature.

中文翻译：

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基于 NIPC 的喷嘴出口条件引起的火箭尾气红外辐射的不确定性分析

摘要 在本研究中，对代表性轨迹点的火箭排气羽流的红外辐射特性进行了不确定性分析。由于火箭发动机工作特性的不稳定性，数值火箭羽流红外辐射预测具有很大的不确定性。在这项研究中，四个认知不确定变量（自由流速度、喷嘴出口压力、温度和速度）被考虑用于不确定性和敏感性分析。基于红外特征分析工具，通过点搭配非侵入式多项式混沌展开法建立统计样本的响应面。多项式混沌展开系数采用求积法求解，计算随机输入变量的统计特征和不确定性。张量积正交稀疏网格方法用于减少多个输入变量的样本数量。基于这些模型，分析了 Atlas-IIA 火箭羽流红外辐射的不确定性量化，包括流量、辐射图像、光谱和辐射。结果表明，不确定性主要来自低空加力，喷嘴出口速度对羽流辐射强度有显着影响。随着高度的增加，后燃效应对红外辐射的不确定性降低，自由流速度的影响增加。此外，4.3-μm波段的辐射强度比例高于2.7-μm波段，相应的不确定度带逐渐变宽。喷嘴出口温度是影响高海拔羽流辐射特性的主要因素。这些不确定性和敏感性分析的结果有助于改进羽状红外特征的数值模型。