ABSTRACT Ellipsoidal particles are anisotropic in shape. Production practice often involves the distribution and convection of ellipsoidal particles under external excitation. However, few studies have focused on convection in ellipsoidal particles. Herein, we experimentally investigated the convection behavior of ellipsoidal particles in a two-dimensional bed under vertical vibration. Several patterns were observed at the dimensionless vibration acceleration (Г) values of 1–6 within the frequency (ƒ) range of 12–70 Hz. The displacement vectors of single roll, asymmetrical double rolls and symmetrical double rolls were drawn. At fixed Г, the system changed from global convection to local convection with increased ƒ. To describe convection intensity, the expansion of bed and the volume fraction of convection region were proposed. Results showed that higher Г or lower ƒ led to stronger convection intensity. The relationship between the pattern and input energy distribution was further discussed. The arrangement of the ellipsoidal-particle long axis along the streamline or at an angle was observed under weak vibration. Two necessary conditions for this phenomenon were observed, namely, nonspherical particles and low input energy.

中文翻译：

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垂直振动下准二维床层中椭球粒子的对流行为

摘要 椭球粒子在形状上是各向异性的。生产实践中常涉及椭球体粒子在外部激发下的分布和对流。然而，很少有研究关注椭球粒子中的对流。在这里，我们通过实验研究了椭圆体粒子在垂直振动下二维床中的对流行为。在 12-70 Hz 的频率 (ƒ) 范围内，在 1-6 的无量纲振动加速度 (Г) 值下观察到了几种模式。绘制了单辊、非对称双辊和对称双辊的位移矢量。在固定 Г 时，系统随着 ƒ 的增加从全局对流变为局部对流。为了描述对流强度，提出了床的膨胀和对流区域的体积分数。结果表明，较高的 Г 或较低的 ƒ 导致更强的对流强度。进一步讨论了模式和输入能量分布之间的关系。在弱振动下观察到椭球粒子长轴沿流线或成一定角度的排列。观察到这种现象的两个必要条件，即非球形粒子和低输入能量。