Off-line measurement of viscosity

The Ostwald U-tube instrument is the most common type of viscometer based upon this principle (Fig. 6.37a and Table 6.7). The viscometer is filled with liquid until the liquid level is such that the bottom of the meniscus in the right-hand limb coincides with the mark C. The fluid is drawn up the left-hand limb to a level about 5 mm above A and then released. The time t taken for the bottom of the meniscus to fall from A to B is recorded. The dynamic viscosity p is determined from Poiseuille s law (Volume 1, equation 3.30 and Section 9.4.3) which under the 

Many modifications of the basic Ostwald geometry are employed in different situations. One example is the Cannon-Fenske routine viscometer (Fig. 6.37b) which is used in the oil industry for measuring kinematic viscosities of 0.02 m2/s and less(4 ). As viscosity is sensitive to variations in temperature, these types of viscometer are always immersed in a constant temperature bath. They are not normally suitable for non-Newtonian fluids although FAROOQI and Richardson(47) have employed a capillary viscometer to characterise a power-law fluid. 

Measurement of the Time Taken for a Body to Fall Freely Through a Fluid 

The falling sphere instrument is representative of this class of viscometer and is employed with higher viscosity liquids. A stainless steel ball is allowed to sink through a column of the liquid under test, and the time taken to fall from one designated level to another at its terminal falling velocity is recorded. In order that the terminal 

Measurement of the Torque Exerted on a Stationary Surface by an Adjacent Moving Surface 

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