Rotational viscometers
Due to their relative importance as tools for the rheological characterisation of
non-Newtonian fluid behaviour, we concentrate on this class of rheometers by
considering the two main types, namely; the controlled shear rate instruments
(also known as controlled rate devices) and controlled stress instruments. Both
types are usually supplied with the same range of measuring geometries,
principally the concentric cylinder, cone-and-plate and parallel plate systems.
The relative merits, potential drawbacks, working equations and other formulae
associated with these designs have been described in great detail elsewhere
(e.g., see Walters, 1975; Whorlow, 1992; Macosko, 1994) and so only their
. most basic aspects are covered here
The concentric cylinder geometry
It is appropriate to begin by considering this geometry as it was the basis of the
first practical rotational rheometer. Ideally the sample is contained in a narrow
gap between two concentric cylinders (as shown in Figure 2.3). Typically the
outer ‘cup’ rotates and the torque T on the inner cylinder, which is usually
. suspended from a torsion wire or bar, is measured
Working equations relating the measured torque to the requisite shear stress,
and angular velocity (of the cup) to the requisite shear rate, are widely
available
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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