Steady Nonuniform Flow http://edugen.wiley.com/edugen/courses/crs2436/crowe9771/crowe9771...
15.4 Steady onuniform Flow
As stated in the beginning of this chapter, and shown in Fig. 15.1, all open-channel flows are classified as either
uniform or nonuniform. Recall that uniform flow has constant velocity along a streamline, and thus has constant
depth for a constant cross section. In steady nonuniform flow, the depth and velocity change over distance (but
not with time). For all such cases, the energy equation as generally introduced in Section 15.2 is invoked to
compare two cross sections. However, for analysis of nonuniform flow, it is useful to distinguish whether the
depth and velocity change occurs over a short distance, referred to as rapidly varied flow, or over a long reach
of the channel, referred to as gradually varied flow (Fig. 15.6). The head loss term is different for these two
cases. For rapidly varied flow, one can neglect the resistance of the channel walls and bottom because it occurs
over a short distance. For gradually varied flow, because of the long distances involved, the surface resistance is
a signficant variable in the energy balance.
Figure 15.6 Classifying nonuniform flow.
Copyright � 2009 John Wiley & Sons, Inc. All rights reserved.
1 of 1 1/15/2009 1:31 AM