The motion of a small sphere in a rotating velocity field: A possible mechanism for suspending particles in turbulence
The motion of a small sphere in a rotating velocity field: A possible mechanism for suspending particles in turbulence
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小球体在旋转速度场中的运动：湍流中悬浮颗粒的可能机制
DOI：
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
J. Isaacs
中科院分区：
文献类型：
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作者：
Paul Tooby;G. Wick;J. Isaacs
湍流中悬浮颗粒的扩散和输运取决于颗粒与湍流之间的相互作用。为了研究可能的颗粒湍流相互作用，我们观察到粒子的轨迹在旋转流体中的固体速度分布，可能会发生在一个漩涡或涡流的核心。实验是用一系列单个小球（颗粒雷诺数低）在绕其中心轴以恒定速度旋转的水平圆柱体中下沉或上升进行的。每个球被发现遵循一个接近圆形的轨道在垂直于圆柱轴的垂直平面。轨道中心非常靠近通过圆柱体轴线的水平面，并且位于流体中流体速度与粒子的终端速度相等且相反的点处。粒子的轨迹也在缓慢地演化，要么向内，要么向外。颗粒运动的理论描述表明，颗粒上的两个主要力，流体阻力和重力-浮力，占圆周运动。由于粒子惯性产生的力（来自其轨道中心的离心力），对阻力的小的位置依赖性壁效应，非常小的力（也受壁的影响）和非常小的离心浮力解释了长期向内或向外的螺旋。这种系统的相互作用，其中颗粒寻求并保持在流体中，与它们自己的运动紧密相反，可能在某些湍流中的小颗粒悬浮中起作用。
The diffusion and transport of particles suspended in turbulent flows depend on the interaction between the particles and the turbulence. To investigate a possible particle-turbulence interaction, we observed particle trajectories in a rotating fluid with a solid body velocity profile, as might occur in the core of a vortex or an eddy. The experiments were conducted with a series of single small spheres (with low particle Reynolds numbers) sinking or rising in a horizontal cylinder rotating about its central axis at a constant speed. Each sphere was found to follow a nearly circular orbit in a vertical plane perpendicular to the cylinder axis. The orbit center lay very near the horizontal plane through the axis of the cylinder and was at the point in the fluid where the velocity of the fluid was equal and opposite to the terminal velocity of the particle. The particle trajectories also evolved slowly, spiraling either inward or outward. A theoretical description of the particle motion shows that the two principal forces on the particle, fluid drag and gravity-buoyancy, account for the circular motion. A force due to particle inertia (a centrifugal force from the center of its orbit), a small position-dependent wall effect on drag, a very small force (also affected by the walls), and a very small centrifugal buoyancy force account for the long-term inward or outward spirals. This kind of systematic interaction in which particles seek and remain in fluid closely opposing their own motion could have a role in the suspension of small particles in some turbulent flows.