3.6.2 Bingham plastic fluids
The laminar axial flow of Bingham plastic fluids through a concentric annulus
has generated even more interest than that for the power-law fluids, e.g. see
refs. [Laird, 1957; Fredrickson and Bird, 1958; Bird et al., 1983; Fordham
et al., 1991]. The main feature which distinguishes the flow of a Bingham
plastic fluid from that of a power-law fluid is the existence of a plug region
in which the shear stress is less than the yield stress. Figure 3.18 shows qualitatively
the salient features of the velocity distribution in an annulus; the
corresponding profile for a fluid without the yield stress (e.g. power-law fluid)
is also shown for the sake of comparison
In principle, the velocity distribution and the mean velocity of a Bingham
plastic fluid flowing through an annulus can be deduced by substituting for
the shear stress in equation (3.76) in terms of the Bingham plastic model,
equation (3.10). However, the signs of the shear stress (considered positive in
the same sense as the flow) and the velocity gradients in the two flow regions
need to be treated with special care. With reference to the sketch shown in
Figure 3.18, the shearing force on the fluid is positive (R r ??R) where
the velocity gradient is also positive. Thus, in this region
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 .
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