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Enhancements of the parallelized DSMC-MLG method for applications to complex hypersonic transitional-regime flows.

机译：DSMC-MLG并行化方法的增强，适用于复杂的高超声速过渡体制流程。

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Previous applications of the combined Direct Simulation Monte Carlo (DSMC) and Monotonic Lagrangian Grid (MLG) methodology have been limited to simple rectangular geometries. Real flow problems in many areas of physics and engineering often involve complex geometries. This dissertation describes the application of the combined DSMC-MLG method to a more complex flowfield. The flow conditions being studied belong to the transitional flow regime of fluid dynamics.; Direct Simulation Monte Carlo is a molecular approach that has been used widely and with great success in predicting transitional regime flows. The MLG technique combined with DSMC allows automatic grid adaptation based on the local number densities. The DSMC-MLG code, recently optimized on the CM-5E parallel supercomputer, has proven to be fast and efficient. The improvement in the computing speed has made it possible to apply the DSMC-MLG technique to more complex flowfields.; The present work is the first to successfully simulate a high-speed, high Kn flow through a channel with a wedge using DSMC-MLG. The channel-wedge geometry creates a complex flowfield with a wide range of fundamental aerodynamic phenomena, such as oblique shocks, rarefraction waves, boundary layers, boundary layer separation, recirculating region, and their mutual interactions. The calculations also show low-density effects such as the slip in velocity and temperature of the gas adjacent to the solid surfaces.; A method was developed to obtain a geometry-conforming MLG and was successfully demonstrated for the channel-wedge system. Furthermore, the method of Stochastic Grid Restructuring (SGR) is included in the current code to find a high-quality MLG for the channel-wedge calculations. The results obtained with a high-quality MLG indicates sharper and more resolved flowfield features than those obtained with a poor-quality MLG. The implementation of a new inflow-outflow boundary condition to the code resulted in accurate control of the geometric length of the channel. Pressure calculations using molecular momentum transfer show that the perfect gas equation of state is applicable at low-density conditions.
机译：组合的直接模拟蒙特卡洛（DSMC）和单调拉格朗日网格（MLG）方法的先前应用仅限于简单的矩形几何。在物理学和工程学的许多领域中，实际的流动问题通常涉及复杂的几何形状。本文介绍了DSMC-MLG组合方法在更复杂的流场中的应用。研究的流动条件属于流体动力学的过渡流动状态。直接模拟蒙特卡洛（Monte Carlo）是一种已广泛使用的分子方法，在预测过渡态流动方面取得了巨大成功。 MLG技术与DSMC相结合，可以根据本地数字密度自动进行网格调整。最近在CM-5E并行超级计算机上优化的DSMC-MLG代码已被证明是快速，高效的。计算速度的提高使得将DSMC-MLG技术应用于更复杂的流场成为可能。本工作是首次使用DSMC-MLG成功模拟通过楔形通道的高速，高Kn流量。通道楔形的几何形状创建了一个复杂的流场，该流场具有多种基本的空气动力学现象，例如斜向冲击，稀有波，边界层，边界层分离，再循环区域及其相互影响。计算还显示出低密度效应，例如邻近固体表面的气体的速度和温度的滑移。开发了一种获得符合几何形状的MLG的方法，并成功地为通道楔系统进行了演示。此外，当前代码中包含了随机网格重构（SGR）方法，以找到用于信道楔计算的高质量MLG。与低质量的MLG相比，高质量的MLG所获得的结果表明流场特征更清晰，解析度更高。对代码的新的流入-流出边界条件的实现导致对通道几何长度的精确控制。使用分子动量传递的压力计算表明，理想的气体状态方程适用于低密度条件。

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