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2300. With d known, we introduce
the appropriate fluid properties at 20°C from Tables A.3 and A.4:
(b) Water: Vd (1.205 kg/m3)V(0.05 m)
1.80 E-5 kg/(m s) Vd (998 kg/m3)V(0.05 m)
0.001 kg/(m s) 2300
2300 or V or V 0.7 m
s 0.046 m
s These are very low velocities, so most engineering air and water pipe flows are turbulent, not
laminar. We might expect laminar duct flow with more viscous fluids such as lubricating oils or
glycerin. | v v In free surface flows, turbulence can be observed directly. Figure 6.2 shows liquid
flow issuing from the open end of a tube. The low-Reynolds-number jet (Fig. 6.2a) is
smooth and laminar, with the fast center motion and slower wall flow forming different
trajectories joined by a liquid sheet. The higher-Reynolds-number turbulent flow (Fig.
6.2b) is unsteady and irregular but, when averaged over time, is steady and predictable. | e-Text Main Menu | Textbook Table of Contents | Study Guide 6.1 Reynolds-Number Regimes 327 Fig. 6.2 Flow issuing at constant
speed from a pipe...
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- Spring '08