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镜像对称顶盖驱动方腔内流过渡流临界特性研究

ON THE TRANSITIONAL CHARACTERISTICS OF MIRROR SYMMETRIC LID-DRIVEN CAVITY FLOW

  • 摘要: 流场过渡流临界特性是指流场因流动状态改变而引起的流场物理特性变化. 如流动从定常演化为非定常周期性时, 流动处于过渡状态的物理性质. 它从根本上决定了流动演化模式和流场特性等物理规律, 对认清流动现象的形成机理有重要意义. 本文在之前腔体内流流场过渡流临界特性研究的基础上, 针对镜像对称顶盖驱动方腔内流开展数值模拟和流场稳定性分析研究, 捕捉各流动分岔点, 如Hopf流动分岔点和Neimark-Sacker流动分岔点等, 并揭示其对流场特性的影响; 分析流场演化模式, 随着雷诺数增大从定常状态依次演化为非定常周期性流动、准周期性流动和湍流; 揭示各种流动现象的形成机理, 如流动滞后、对称性破坏、能量级串等; 分析流场拓扑结构, 阐明流场镜像对称性和流场稳定性的关系. 本文研究成果有助于揭示该流场的物理特性, 进一步完善了内流流场特性的研究. 研究发现, 针对本文镜像对称方腔顶盖驱动内流, 流场稳定性的破坏总是以Hopf流动分岔点的出现而发生并且伴随着流场对称性的破坏; 流场演化模式符合经典的Ruelle-Takens模式; 流动从定常状态演化至非定常周期性流动时存在流动滞后现象.

     

    Abstract: The transitional critical characteristics refer to the change of physical properties of flow field caused by the change of different flow states, which is amid the transitional stages. For instance, when flow evolves from steady to unsteady periodic. It fundamentally determines physical laws, like evolution mode and flow characteristics, deep inside the corresponding flow field, which is of great importance and necessity to understand the formation mechanism of flow phenomena. In this paper, the numerical simulations and flow stability analysis are carried out for the mirror symmetric lid driven cavity flow. The flow bifurcations, such as Hopf bifurcation and Neimark-Sacker bifurcation, are captured and their influence on the flow characteristics is discussed. The flow evolution mode is analyzed as well, it is found that with the increase of Reynolds numbers, the flow evolves from a steady state to a unsteady periodic state, then to a quasi-periodic state and finally into chaos. It is explained that the formation mechanism of various flow phenomena, for example, flow hysteresis, symmetry loss, energy cascade, etc. The flow topology is analyzed and the relation between mirror symmetry and stability is clarified. The conclusions of the present study is helpful to better understand the physics of this internal flow field, further completing the corresponding research of on this research direction, such as the classic lid driven cavity flow. Based on the findings of present study, we have found that the unsteadiness of flow field always starts as the Hopf bifurcation appears, the flow symmetry breaks as soon as the flow unsteadiness shows up. It is found that the flow evolves as the classic Ruelle-Takens mode and the flow hysteresis is observed when flow evolves from a steady state to an unsteady periodic state.

     

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