Abstract Direct numerical simulations of the passive heat transfer in pressure-driven flows through concentric annuli were performed in the subcritical Reynolds-number regime. In this regime, the intermittent-turbulent velocity field would exhibit large-scale patterns of the laminar-turbulent coexistence. The main emphasis was placed on the influence of transition structures on the heat transfer at two radius ratios, r in / r out = 0.5 and 0.8, at which point a helically-shaped, turbulent transition structure was present. An incompressible Newtonian fluid was considered with fixed fluid properties and a Prandtl number of 0.71. We investigated the dependence of this heat-transfer on the Reynolds number, radius ratio, and thermal bounding condition. The state of helical turbulence was found to provide high heat-transfer rates close to those estimated by the turbulence empirical function even in the transitional regime. The present results showed that the wall-normal turbulent heat flux occurred in both longitudinal-vortex clusters around the turbulent bands as well as inside of the localized turbulent region. The non-turbulent vortex cluster provided a promotion of heat transfer that occurs in intermittent turbulent states.

中文翻译：

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环流中螺旋湍流过渡区的传热

摘要 在亚临界雷诺数状态下，对通过同心环面的压力驱动流中的被动传热进行了直接数值模拟。在这种情况下，间歇湍流速度场将表现出层流湍流共存的大规模模式。主要强调过渡结构在两个半径比下对传热的影响，r in / r out = 0.5 和 0.8，此时存在螺旋形湍流过渡结构。不可压缩的牛顿流体被认为具有固定的流体特性和 0.71 的普朗特数。我们研究了这种传热对雷诺数、半径比和热边界条件的依赖性。发现螺旋湍流状态提供接近于湍流经验函数估计的高传热率，即使在过渡状态下也是如此。目前的结果表明，壁面法向湍流热通量发生在湍流带周围的纵向涡团以及局部湍流区域内部。非湍流涡团促进了间歇湍流状态下发生的热传递。