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Modeling capabilities of unsteady RANS for the simulation of turbulent swirling flow in an annular bluff-body combustor geometry
Applied Mathematical Modelling ( IF 5 ) Pub Date : 2021-01-01 , DOI: 10.1016/j.apm.2020.07.037
Yang Zhang , Maarten Vanierschot

Abstract In this paper, we investigate the capabilities of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations for capturing the helical structures found in a three-dimensional, incompressible and isothermal annular swirling jet undergoing vortex breakdown. The flow topology is representative of a bluff-body combustor operating at a Reynolds number Re = 8500 and swirl number S = 0.39. As a turbulence model, the SSG Reynolds stress model (RSM) was chosen. The numerical simulation is validated by means of tomographic particle image velocimetry measurements of the same flow configuration. To detect the coherent structures in the flow field, the recently introduced spectral proper orthogonal decomposition technique is adopted, which gives both temporal and spatial information on the large scale coherent structures. The spectral analysis of the sampled velocity signals identified a precessing vortex core with a frequency of 24.3 Hz. In particular, two different large-scale helical flow structures are identified: a single and a double helix. Both of them are wound in the counter-swirl direction and wrapped around the central breakdown bubble. Those findings are quite similar to recent experimental tomographic particle image velocimetry results (Vanierschot et al., Phys. Rev. Fluids (2018) & J. Fluid Mech. (2020)). This study demonstrates that the unsteady RANS approach with RSM is able to predict the coherent structures found in an annular swirling jet undergoing vortex breakdown both temporally and spatially with reasonable accuracy and this approach can hence be used in the design of bluff-body combustors, where a multi-dimensional parameter space may require many simulations to find the optimal design.

中文翻译:

非定常 RANS 模拟环形钝体燃烧器几何中湍流涡流的建模能力

摘要 在本文中,我们研究了非定常雷诺平均纳维 - 斯托克斯 (URANS) 方程用于捕获在经历涡流击穿的三维、不可压缩和等温环形旋流射流中发现的螺旋结构的能力。流动拓扑代表在雷诺数 Re = 8500 和涡流数 S = 0.39 下运行的钝体燃烧器。作为湍流模型,选择了 SSG 雷诺应力模型 (RSM)。数值模拟通过相同流动配置的断层扫描粒子图像测速测量得到验证。为了检测流场中的相干结构,采用了最近引入的光谱适当正交分解技术,该技术提供了大尺度相干结构的时间和空间信息。采样速度信号的频谱分析确定了一个频率为 24.3 Hz 的进动涡核。特别是,确定了两种不同的大规模螺旋流结构:单螺旋和双螺旋。它们都以反旋流方向缠绕并缠绕在中心击穿气泡上。这些发现与最近的实验断层扫描粒子图像测速结果非常相似(Vanierschot 等人,Phys. Rev. Fluids (2018) & J. Fluid Mech. (2020))。这项研究表明,使用 RSM 的非定常 RANS 方法能够以合理的精度预测在时间和空间上发生涡流击穿的环形旋流射流中发现的相干结构,因此该方法可用于钝体燃烧器的设计,
更新日期:2021-01-01
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