Boundary effect on the drag force on a nonhomogeneous floc.
Boundary effect on the drag force on a nonhomogeneous floc.
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DOI：
10.1016/s0021-9797(03)00506-x
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发表时间：
2003-08
影响因子：
9.9
通讯作者：
J. Hsu;Yu-Heng Hsieh
中科院分区：
文献类型：
--
作者：
J. Hsu;Yu-Heng Hsieh
通过考虑圆柱管中心线处的球形絮体，研究了作用在非均匀结构球形絮体上的阻力的边界效应。用具有两层结构的实体来模拟絮凝体，通过改变其内层和外层渗透率的相对大小来模拟其多孔性。数值模拟结果表明，管壁具有压缩流线和涡量线的作用。同样，在刚性实体的情况下，由于流体的对流运动而产生的絮体后部区域的尾迹被抑制。在体积平均渗透率固定的情况下，管壁对非均质絮体行为的影响大于对均质絮体行为的影响，且影响随管壁结构的不同而不同。由于絮体的非均质结构导致修正后的阻力系数-雷诺数关系偏离了stokes - laws -类相关。絮凝体的平均渗透率越小，偏差越大，但管壁的存在有减小偏差的作用。
The boundary effect on the drag force acting on a spherical floc having a nonhomogeneous structure is examined by considering a spherical floc at the centerline of a cylindrical tube. The floc is simulated by an entity having a two-layer structure, and its porous nature mimicked by varying the relative magnitude of the permeability of its inner and outer layers. The results of numerical simulation reveal that the tube wall has the effect of compressing the streamlines and vorticity contours. Also, as in the case of a rigid entity, the wake in the rear region of a floc, which arises from the convective motion of the fluid, is depressed. For fixed volume-averaged permeability, the influence of the tube wall on the behavior of a heterogeneous floc is more significant than that on the behavior of a homogeneous floc, and the influence varies with the structure of the former. The heterogeneous structure of a floc leads to a deviation in the modified drag coefficient–Reynolds number relation from a Stokes-law-like correlation. The smaller the average permeability of a floc the greater the deviation, but the presence of the tube wall has the effect of reducing the deviation.