POD and DMD analysis of dynamic flow structures in the recirculation region of an unconfined swirl cup

IF 2.8 2区工程技术 Q2 ENGINEERING, MECHANICAL Experimental Thermal and Fluid Science Pub Date : 2024-09-04 DOI:10.1016/j.expthermflusci.2024.111306

Tianxiong Li , Yingchun Wu , Yu Wang , Ge Song , Jiahuan Cui , Qi Gao , Gaofeng Wang , Xuecheng Wu

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Abstract

The flow field of the swirl-stabilized combustor plays a significant role in fuel atomization and flame stability. The experimental investigation of the non-reacting flow field downstream of a swirl cup with no confinement is carried out by means of particle image velocimetry measurements. The statistical uncertainty is calculated to evaluate the turbulence convergence and projection errors. The flow fields provide a compelling picture of the basic characteristics of the swirl flow, while the root mean square velocity analysis illustrates the upward and downward fluctuations of the emanating jet. The proper orthogonal decomposition (POD) modes reveal the most pronounced features of the flow, namely the central recirculation zone and the precessing vortex core (PVC) at its boundaries, as well as a significant feature that occurs several times in the modes, i.e., the entrainment of the surrounding atmosphere as an alternative to the corner recirculation zone. Furthermore, the dynamic mode decomposition (DMD) modes in the low-frequency region characterize the slow change ( $S_{t} = 0.0026$ ) that occurs when the emanating jet is shifted upward as well as the PVC oscillations ( $S_{t} = 0.113$ ) in the flow. The DMD modes in the high-frequency then characterize the high-frequency oscillations induced by vortex shedding in the swirl flow. The research is helping to provide a clear picture of the flow downstream of the swirl cup without any confinement.

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无约束漩涡杯再循环区域动态流动结构的 POD 和 DMD 分析

漩涡稳定燃烧器的流场对燃料雾化和火焰稳定性起着重要作用。通过粒子图像测速仪测量，对无限制漩涡杯下游的非反应流场进行了实验研究。通过计算统计不确定性来评估湍流收敛和投影误差。流场为漩涡流的基本特征提供了令人信服的图像，而均方根速度分析则说明了喷出射流的上下波动。正交分解（POD）模式揭示了漩涡流最明显的特征，即中心再循环区和其边界的前冲漩涡核心（PVC），以及在模式中多次出现的一个重要特征，即作为角再循环区替代物的周围大气的夹带。此外，低频区的动态模态分解（DMD）模态描述了射流向上移动时发生的缓慢变化（St=0.0026），以及流动中的聚氯乙烯振荡（St=0.113）。然后，高频区的 DMD 模式描述了漩涡流中涡流脱落引起的高频振荡。这项研究有助于提供漩涡杯下游无任何限制流动的清晰图像。

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来源期刊

Experimental Thermal and Fluid Science 工程技术-工程：机械

CiteScore

6.70

自引率

3.10%

发文量

159

审稿时长

34 days

期刊介绍： Experimental Thermal and Fluid Science provides a forum for research emphasizing experimental work that enhances fundamental understanding of heat transfer, thermodynamics, and fluid mechanics. In addition to the principal areas of research, the journal covers research results in related fields, including combined heat and mass transfer, flows with phase transition, micro- and nano-scale systems, multiphase flow, combustion, radiative transfer, porous media, cryogenics, turbulence, and novel experimental techniques.