Rotation of spheroidal particles in Couette flows
Rotation of spheroidal particles in Couette flows
复制标题
库埃特流中球形颗粒的旋转
DOI：
10.1017/jfm.2011.519
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发表时间：
2012-02-10
影响因子：
3.7
通讯作者：
Lu, Xi-Yun
中科院分区：
文献类型：
--
作者：
Huang, Haibo;Yang, Xin;Lu, Xi-Yun
摘要采用多松弛时间（MRT）晶格玻尔兹曼方法研究了中性浮力球形粒子在Couette流中的旋转。对于雷诺数（$\mathit{Re}$）超过305的长球面，我们发现了几个新的周期和稳定的旋转模式。模拟覆盖了直到$\mathit{Re}\leq 700$的区域。球体的旋转行为不仅对雷诺数敏感，而且对其初始取向敏感。我们详细讨论了初始取向的影响。对于$305\lt \mathit{Re}\lt 345$，我们发现长球体达到了一个周期模式，其特征是围绕一个靠近中间平面的倾斜轴的进动和章动，其中速度为零。对于$345\lt \mathit{Re}\lt 385$，长球体以章动形式绕涡度方向进动。对于$\mathit{Re}$接近临界${\mathit{Re}}_{c} \approx 345$，可以观察到周期加倍现象。我们还确定了一个静止模式，在较高的雷诺数（$\mathit{Re}\gt 445$）为长球体。对于椭球体，在$\mathit{Re}$从0到520的范围内，得到了原木滚动、倾斜滚动和不同稳态的动态平衡模式。通过模拟每个$\mathit{Re}$所研究的57个均匀分布的初始定向来研究初始定向效应。对于$\mathit{Re}\lt 120$和$385\lt \mathit{Re}\lt 445$只有一种模态。在其他$\mathit{Re}$体制中，可能有一种以上的模式，最终模式对初始方向敏感。然而，扁球动力学对其初始方向不敏感。
Abstract The rotation of a neutrally buoyant spheroidal particle in a Couette flow is studied by a multi-relaxation-time (MRT) lattice Boltzmann method. We find several new periodic and steady rotation modes for a prolate spheroid for Reynolds numbers ($\mathit{Re}$) exceeding 305. The simulations cover the regime up to $\mathit{Re}\leq 700$. The rotational behaviour of the spheroid appears to be not only sensitive to the Reynolds number but also to its initial orientation. We discuss the effects of initial orientation in detail. For $305\lt \mathit{Re}\lt 345$ we find that the prolate spheroid reaches a periodic mode characterized by precession and nutation around an inclined axis which is located close to the middle plane where the velocity is zero. For $345\lt \mathit{Re}\lt 385$, the prolate spheroid precesses around the vorticity direction with a nutation. For $\mathit{Re}$ close to the critical ${\mathit{Re}}_{c} \approx 345$, a period-doubling phenomenon is observed. We also identify a motionless mode at higher Reynolds numbers ($\mathit{Re}\gt 445$) for the prolate spheroid. For the oblate spheroid the dynamic equilibrium modes found are log rolling, inclined rolling and different steady states for $\mathit{Re}$ increasing from 0 to 520. The initial-orientation effects are studied by simulations of 57 evenly distributed initial orientations for each $\mathit{Re}$ investigated. Only one mode is found for the prolate spheroid for $\mathit{Re}\lt 120$ and $385\lt \mathit{Re}\lt 445$. In other $\mathit{Re}$ regimes, more than one mode is possible and the final mode is sensitive to the initial orientation. However, the oblate spheroid dynamics are insensitive to its initial orientation.