Terminal falling velocities
In many process design calculations, it is necessary to know the terminal
velocity of a sphere settling in a fluid under the influence of the gravitational
field. When a spherical particle at rest is introduced into a liquid, it acceler-ates
until the buoyant weight is exactly balanced by the fluid dynamic drag.
Although the so-called terminal velocity is approached asymptotically, the
effective transition period is generally of short duration for Newtonian and
power-law fluids [Chhabra et al., 1998]. For instance, in the creeping flow
regime, the terminal velocity is attained after the particle has traversed a path
.of length equal to only a few diameters
Example 5.3
For spheres of equal terminal falling velocities, obtain the relationship between diameter
and density difference between particle and fluid for creeping flow in power law
fluids.
Solution
From equation (5.11), the terminal settling velocity of a sphere increases with both its
density and size. For two spheres of different diameters dA, dB and densities, SA and
SB, settling in the same fluid, the factor X is a function of n only (see Table 5.1) and
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
|