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Unformatted text preview: r is called transition to turbulence. In Fig. 5.3a we saw
that transition on the cylinder and sphere occurred at about Re 3 105, where the
sharp drop in the drag coefficient appeared. Transition depends upon many effects, e.g.,
wall roughness (Fig. 5.3b) or fluctuations in the inlet stream, but the primary parameter is the Reynolds number. There are a great many data on transition but only a small
amount of theory [1 to 3].
Turbulence can be detected from a measurement by a small, sensitive instrument
such as a hot-wire anemometer (Fig. 6.29e) or a piezoelectric pressure transducer. The | v v 325 | e-Text Main Menu | Textbook Table of Contents | Study Guide 326 Chapter 6 Viscous Flow in Ducts u u Small natural
damp quickly Fig. 6.1 The three regimes of viscous flow: (a) laminar flow at low
Re; (b) transition at intermediate
Re; (c) turbulent flow at high Re. u Continuous
(a) t t (b) (c) flow will appear steady on average but will reveal rapid, random fluctuations if turbulence is present, as sketched in Fig. 6.1. If the flow is laminar, there...
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- Spring '08