Abstract Immersed boundary conditions (IBC) have become a practical tool to simplify the meshing process for the simulation of complex geometries in CFD. This approach has reached a sufficient level of maturity to allow the simulation of compressible high Reynolds number flows. However, the access of physical quantities at the immersed wall is far from being straightforward. This paper provides two methods for the reconstruction of fluctuating wall quantities relying on the creation of explicit watertight surface meshes of the immersed boundary. These surface meshes are used for the investigation of highly unsteady compressible flows of two generic space launcher afterbody configurations using Zonal Detached Eddy Simulation (ZDES). Since the flows are massively separated, the side load arising from the pressure is mainly responsible for the global load unsteadiness. Therefore, in the present study the focus is put on the accuracy of the wall pressure reconstructed on immersed boundaries and compared to validated numerical simulations using a classical body-fitted approach and experimental data. The numerical results demonstrate the ability of the present approaches to accurately capture the global load fluctuation around both afterbody configurations. Moreover, the IBC surface meshes simplify the overall post-processing operations and allow the extraction of wall quantities for unsteady simulation at low computational cost. This last feature has been used for the spectral analysis on IBC surfaces which reproduced successfully the location and the intensity of the pressure fluctuation.

中文翻译：

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基于浸入边界条件的非定常气动力和壁面谱含量的估计

摘要 浸入边界条件 (IBC) 已成为简化 CFD 中复杂几何体模拟的网格划分过程的实用工具。这种方法已经达到足够的成熟度，可以模拟可压缩的高雷诺数流。然而，在浸入墙处获取物理量远非直接的。本文提供了两种方法，用于依赖于浸没边界的显式水密表面网格的创建来重建波动壁量。这些表面网格用于使用区域分离涡流模拟 (ZDES) 研究两种通用空间发射器后体配置的高度不稳定的可压缩流。由于流量被大量分离，压力产生的侧向载荷是全局载荷不稳定的主要原因。因此，在本研究中，重点放在浸入边界上重建的壁压力的准确性上，并与使用经典贴体方法和实验数据的经过验证的数值模拟进行比较。数值结果证明了本方法能够准确捕获两种后体配置周围的全局载荷波动。此外，IBC 表面网格简化了整体后处理操作，并允许以低计算成本提取壁面数量以进行非稳态模拟。最后一个特征已用于 IBC 表面的光谱分析，成功再现了压力波动的位置和强度。在本研究中，重点放在浸入边界上重建的壁压力的准确性上，并与使用经典贴体方法和实验数据的经过验证的数值模拟进行比较。数值结果证明了本方法能够准确捕获两种后体配置周围的全局载荷波动。此外，IBC 表面网格简化了整体后处理操作，并允许以低计算成本提取壁面数量以进行非稳态模拟。最后一个特征已用于 IBC 表面的光谱分析，成功再现了压力波动的位置和强度。在本研究中，重点放在浸入边界上重建的壁压力的准确性上，并与使用经典贴体方法和实验数据的经过验证的数值模拟进行比较。数值结果证明了本方法能够准确捕获两种后体配置周围的全局载荷波动。此外，IBC 表面网格简化了整体后处理操作，并允许以低计算成本提取壁面数量以进行非稳态模拟。最后一个特征已用于 IBC 表面的光谱分析，成功再现了压力波动的位置和强度。