Abstract The study numerically investigated the instability characteristics of a 3D highly separated natural convection flow developing within a cold cubic enclosure in the presence of a tandem of hot and cold horizontally aligned cylinders. The immersed boundary (IB) method was utilized to enforce kinematic no-slip and thermal boundary conditions on the surfaces of the two cylinders. The obtained results were based on the analysis of slightly supercritical flows simulated for three different distances between the cylinders and for Rayleigh numbers R a ∝ O ( 10 6 ) . It was found that the transition to unsteadiness of the flow sets in via the first Hopf bifurcation, which preserves two types of reflectional symmetry with respect to the central cross-section of the cubic enclosure. The impact of the closeness of the cavity boundaries to the cylinder surfaces on the quantitative and qualitative characteristics of the observed instabilities was extensively investigated. The study elucidated the fundamental instability characteristics typical of highly separated thermally driven flows in confined containers in terms of the bifurcation characteristics and the impact of the object orientation and closeness to the container boundaries on preserving the spatio-temporal symmetries of the slightly supercritical flow.

中文翻译：

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高度分离的自然对流流动的不稳定性特征：放置在冷立方体外壳内的冷热水平定向圆柱体的串联配置

摘要 该研究以数值方式研究了在冷热立方体外壳内在存在串联的冷热水平排列圆柱体的情况下产生的 3D 高度分离的自然对流流动的不稳定性特征。浸入边界 (IB) 方法用于在两个圆柱体的表面上强制执行运动学无滑移和热边界条件。获得的结果基于对三种不同圆柱之间距离和瑞利数 R a ∝ O (10 6) 模拟的轻微超临界流动的分析。发现流向不稳定的过渡是通过第一个 Hopf 分岔开始的，这保留了两种类型的关于立方体外壳中心横截面的反射对称性。腔边界与圆柱表面的接近程度对观察到的不稳定性的定量和定性特征的影响进行了广泛的研究。该研究阐明了密闭容器中高度分离的热驱动流典型的基本不稳定性特征，包括分叉特征以及物体方向和容器边界的接近度对保持微超临界流的时空对称性的影响。