SELF-DIFFUSION OF PARTICLES IN SHEAR-FLOW OF A SUSPENSION
SELF-DIFFUSION OF PARTICLES IN SHEAR-FLOW OF A SUSPENSION
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DOI：
10.1017/s0022112077000111
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发表时间：
1977-01-01
影响因子：
3.7
通讯作者：
SHAPIRO, AH
中科院分区：
文献类型：
--
作者：
ECKSTEIN, EC;BAILEY, DG;SHAPIRO, AH
通过实验确定球形和盘状颗粒在雷诺数非常低的浆料线性剪切流中的横向分散的自扩散系数。使用同心圆柱库埃特装置，对特定放射性标记粒子的横向位置进行反复观察。使用遍历假设，通过随机游走理论计算自扩散系数 D。由于实验难度较大，D的计算值精度不高，但误差在2倍以内。在 0 < phi < 0·2 范围内，D/a2ω 从 0 开始随 phi 线性增加，直至 D/a2ω ≅ 0·02（其中 phi = 颗粒体积浓度，a = 颗粒半径，ω = 悬浮流体的平均剪切速率）。在0·2 < 0·5范围内，由于实验分散，D/a2ω的趋势并不明显，但在该范围内D/a2ω≅0·025在2倍以内。在实验精度范围内，球体和圆盘具有相同的D/a2ω值。
Self-diffusion coefficients were determined experimentally for lateral dispersion of spherical and disk-like particles in linear shear flow of a slurry at very low Reynolds number. Using a concentric-cylinder Couette apparatus, recurrent observations were made of the lateral position of a particular radioactively labelled particle. The self-diffusion coefficient D was calculated by means of random-walk theory, using the ergodic hypothesis. Owing to great experimental difficulties, the calculated values of D are not of high accuracy, but are correct to within a factor of two. In the range 0 < ϕ < 0·2, D/a2ω increases from zero linearly with ϕ up to D/a2ω ≅ 0·02 (where ϕ = volumetric concentration of particles, a = particle radius, ω = mean shear rate of suspending fluid). In the range 0·2 < 0·5, the trend of D/a2ω is not clear because of experimental scatter, but in this range D/a2ω ≅ 0·025 to within a factor of two. Within the experimental accuracy, spheres and disks have the same value of D/a2ω.