The turbulent wake of a planar generic space launcher equipped with a dual-bell nozzle is numerically investigated to examine the interaction of the dual-bell nozzle jet and the wake flow. The simulation is performed at transonic freestream condition, i.e., freestream Mach number M a ∞ = 0.8 $Ma_{\infty }= 0.8$ and freestream Reynolds number based on the launcher thickness R e D = 4.3 ⋅ 10 5 , with the dual-bell nozzle operating at sea-level mode. A zonal RANS/LES approach is used and the time-resolved flow field data is analyzed by classical spectral analysis and modal decomposition techniques, i.e., proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). The overall flow topology of the recirculation region downstream of the base and the pressure loads on the outer nozzle fairing are only slightly affected by the modified nozzle shape. However, the changed nozzle flow topology characterized by the flow separation at the nozzle contour inflection leads to a backflow region and an entrainment of the outer flow into the nozzle extension which results in increased pressure loads on the inner nozzle wall. Using spectral, POD, and DMD analyses, the outer wake flow is investigated, revealing a growing and contracting of the separation bubble and an undulating motion of the shear layer similar to the “cross-pumping” and “cross-flapping” motion detected in previous investigations of a configuration with a classical nozzle and a jetless backward facing step setup. The spectral and modal analysis of the nozzle flow shows that the increased pressure loads detected at the inner wall of the nozzle extension are caused by an interaction of the separated shear layer inside the nozzle extension with the shock pattern that leads to a streamwise oscillation of the shock and a pumping or wave-like motion of the shear layer.

中文翻译：

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双钟形喷嘴射流尾流相互作用的数值研究

对配备双钟罩喷嘴的平面通用太空发射器的湍流尾流进行了数值研究，以检查双钟罩喷嘴射流与尾流的相互作用。模拟在跨音速自由流条件下进行，即自由流马赫数 M a ∞ = 0.8 $Ma_{\infty }= 0.8$ 和基于发射器厚度的自由流雷诺数 R e D = 4.3 ⋅ 10 5 ，具有双重钟形喷嘴在海平面模式下运行。使用区域 RANS/LES 方法，并通过经典频谱分析和模态分解技术，即适当的正交分解 (POD) 和动态模式分解 (DMD)，分析时间分辨流场数据。底座下游再循环区域的整体流动拓扑结构和外部喷嘴整流罩上的压力负载仅受修改后的喷嘴形状的轻微影响。然而，以喷嘴轮廓拐点处的流动分离为特征的改变的喷嘴流动拓扑结构导致回流区域和外流夹带进入喷嘴延伸部，这导致内喷嘴壁上的压力负载增加。使用光谱、POD 和 DMD 分析，研究了外部尾流，揭示了分离气泡的生长和收缩以及剪切层的起伏运动，类似于在先前对具有经典喷嘴和无喷射后向阶梯设置的配置的研究。