Unformatted text preview: ust | e-Text Main Menu | Textbook Table of Contents | Study Guide 388 Chapter 6 Viscous Flow in Ducts be aligned with the flow parallel to their axis of rotation. They can sense reverse flow
because they will then rotate in the opposite direction. All these rotating sensors can
be attached to counters or sensed by electromagnetic or slip-ring devices for either a
continuous or a digital reading of flow velocity. All have the disadvantage of being relatively large and thus not representing a “point.” Pitot-static tube. A slender tube aligned with the flow (Figs. 6.29g and 6.30) can measure local velocity by means of a pressure difference. It has sidewall holes to measure
the static pressure ps in the moving stream and a hole in the front to measure the stagnation pressure p0, where the stream is decelerated to zero velocity. Instead of measuring p0 or ps separately, it is customary to measure their difference with, say, a transducer, as in Fig. 6.30.
If ReD 1000, where D is the probe diameter,...
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