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Modeling and simulation of high-speed wake flows.

机译：高速尾流的建模和仿真。

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High-speed, unsteady flows represent a unique challenge in computational hypersonics research. They are found in nearly all applications of interest, including the wakes of reentry vehicles, RCS jet interactions, and scramjet combustors. In each of these examples, accurate modeling of the flow dynamics plays a critical role in design performance. Nevertheless, literature surveys reveal that very little modern research effort has been made toward understanding these problems. The objective of this work is to synthesize current computational methods for high-speed flows with ideas commonly used to model low-speed, turbulent flows in order to create a framework by which we may reliably predict unsteady, hypersonic flows.;In particular, we wish to validate the new methodology for the case of a turbulent wake flow at reentry conditions. Currently, heat shield designs incur significant mass penalties due to the large margins applied to vehicle afterbodies in lieu of a thorough understanding of the wake aerothermodynamics. Comprehensive validation studies are required to accurately quantify these modeling uncertainties. To this end, we select three candidate experiments against which we evaluate the accuracy of our methodology. The first set of experiments concern the Mars Science Laboratory (MSL) parachute system and serve to demonstrate that our implementation produces results consistent with prior studies at supersonic conditions. Second, we use the Reentry-F flight test to expand the application envelope to realistic flight conditions. Finally, in the last set of experiments, we examine a spherical capsule wind tunnel configuration in order to perform a more detailed analysis of a realistic flight geometry.;In each case, we find that current 1st order in time, 2nd order in space upwind numerical methods are sufficiently accurate to predict statistical measurements: mean, RMS, standard deviation, and so forth. Further potential gains in numerical accuracy are demonstrated using a new class of flux evaluation schemes in combination with 2nd order dual-time stepping. For cases with transitional or turbulent Reynolds numbers, we show that the detached eddy simulation (DES) method holds clear advantage over heritage RANS methods. From this, we conclude that the current methodology is sufficient to predict heating of external, reentry-type applications within experimental uncertainty.
机译：高速，不稳定的流动是计算超音速研究中的独特挑战。在几乎所有感兴趣的应用中都可以找到它们，包括折返飞行器的尾流，RCS喷射相互作用和超燃燃烧器。在每个这些示例中，对流动力学的精确建模在设计性能中都起着至关重要的作用。然而，文献调查表明，为了解这些问题很少进行现代研究。这项工作的目的是将目前用于高速流动的计算方法与通常用于对低速湍流进行建模的思想综合起来，以创建一个可以可靠地预测不稳定的高超声速流动的框架。希望针对折返条件下尾流湍流的情况验证新方法。当前，由于对尾流空气热力学的透彻理解，隔热罩设计由于施加于车辆后车身的较大余量而招致重大的质量损失。需要进行全面的验证研究才能准确地量化这些建模不确定性。为此，我们选择了三个候选实验，以此来评估方法论的准确性。第一组实验涉及火星科学实验室（MSL）的降落伞系统，用于证明我们的实施产生的结果与先前在超音速条件下的研究一致。其次，我们使用Reentry-F飞行测试将应用范围扩展到现实的飞行条件。最后，在最后一组实验中，我们检查了球形胶囊风洞的构型，以便对实际的飞行几何形状进行更详细的分析。在每种情况下，我们发现当前的第一阶时间，第二阶空间逆风数值方法足够准确，可以预测统计量：均值，RMS，标准差等。使用一类新型的磁通评估方案与二阶双时间步进相结合，进一步证明了数值精度的潜在优势。对于具有过渡雷诺数或湍流雷诺数的情况，我们证明了分离涡模拟（DES）方法比传统RANS方法具有明显的优势。据此，我们得出结论，当前的方法足以预测在实验不确定性范围内外部折返型应用的升温。

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