Aspect-ratio dependence of heat and angular momentum transport in turbulent Taylor-Couette flows with axial thermal forcing
Aspect-ratio dependence of heat and angular momentum transport in turbulent Taylor-Couette flows with axial thermal forcing
复制标题
具有轴向热强迫的泰勒-库埃特湍流中热量和角动量传输的纵横比依赖性
DOI：
10.1016/j.ijheatmasstransfer.2022.123194
复制
发表时间：
2022
影响因子：
5.2
通讯作者：
Jin-Qiang Zhong
中科院分区：
文献类型：
--
作者：
X.-Y. Leng;Jin-Qiang Zhong
·有限系统中确定的输运的标度律可以外推到大尺度流动。·泰勒涡形式的相干湍流结构促进热量和角传输。·热量和角动量输运的幅度取决于畴纵横比。数值研究了在垂直不稳定温度梯度作用下的Taylor-Couette湍流中，几何因子（即纵横比Γ和半径比η）对轴向热输运Nu和径向角动量输运N ω的影响.对于给定的雷诺数Re，Nu和N ω的大小都表现出明显的展弦比依赖性。在长圆柱中，角动量输运减少，因为端壁效应随着Γ的增加而减弱。对于大- Γ柱的换热，在低Re区，Nu显著降低，而在湍流泰勒涡区，Nu显著提高。前者的Nu-减少与热羽流被边界附近的Ekman涡扫走的过程有关，并且在块体区域中相邻涡之间的流体交换受到严重限制。后一种Nu-增强归因于大- Γ柱中产生的增强的剪切，导致更湍流的边界层。此外，湍流TV的显著相互混合不断地将热（冷）流体泵入本体，从而强化了传输过程。结果表明，在低Re区，端壁的约束对热输运和角动量输运有影响，但在高Re区，端壁的约束对热输运和角动量输运的标度性质影响不大.因此，我们期望用有限的Γ确定的Nu（Re）和N ω（Re）的标度关系可以外推到大尺度，甚至垂直无界的工业和地球物理流。
• Scaling law of transports determined in finite systems can be extrapolated to large-scale flows. • Coherent turbulent structures in form of Taylor vortices promote heat and angular transports. • Magnitudes of both heat and angular momentum transport depend on domain aspect-ratio. We report numerical studies of the effects of geometry factors, i.e. the aspect ratio Γ and radius ratio η , on the axial heat transport N u and the radial angular momentum transport N ω by turbulent Taylor-Couette flows that are subjected to a vertically destabilizing temperature gradient. For a given Reynolds number R e the magnitudes of both N u and N ω exhibit a pronounced aspect-ratio dependence. The angular momentum transport is reduced in long cylinders, since endwall effects are weakened as Γ increases. For the heat transfer in large- Γ cylinders, a significant N u -reduction appears for low- R e regime, whereas N u can be greatly enhanced in the regime of turbulent Taylor vortex (TV). The former N u -reduction is associated with the process that the thermal plumes are swept away by the Ekman vortices near the boundaries, and the fluid exchange is severely restricted between adjacent vortices in the bulk region. The latter N u -enhancement is attributed to the strengthened shears arising in large- Γ cylinders, resulting in a more turbulent boundary layer. Moreover, the pronounced inter-mixing of turbulent TVs continuously pumps the hot (cold) fluids into the bulk, intensifying the transport processes. It is found that although the constraints from the endwalls impact the global heat and angular momentum transport in the low- R e regime, they hardly affect their scaling properties in the high- R e regime with large Γ . We thus expect that the scaling relationship of N u ( R e ) and N ω ( R e ) determined with finite Γ can be extrapolated to large-scale, and even vertically unbounded industrial and geophysical flows.