fluid_mechanics

10
Open-Channel
Flow
CHAPTER OPENING PHOTO: Hydraulic jump: Under certain conditions, when water flows in an open channel,
even if it has constant geometry, the depth of the water may increase considerably over a short distance
along the channel. This phenomenon is termed a hydraulic jump (water flow from left to right).
Learning Objectives
After completing this chapter, you should be able to:
■ discuss the general characteristics of open-channel flow.
■ use a specific energy diagram.
■ apply appropriate equations to analyze open-channel flow with uniform
depth.
■ calculate key properties of a hydraulic jump.
■ determine flowrates based on open-channel flow-measuring devices.
V10.1 Off-shore oil
drilling platform.
Open-channel flow involves the flow of a liquid in a channel or conduit that is not completely
filled. A free surface exists between the flowing fluid (usually water) and fluid above it (usually
the atmosphere). The main driving force for such flows is the fluid weight—gravity forces the fluid
to flow downhill. Most open-channel flow results are based on correlations obtained from model
and full-scale experiments. Additional information can be gained from various analytical and numerical
efforts.
Open-channel flows are essential to the world as we know it. The natural drainage of water
through the numerous creek and river systems is a complex example of open-channel flow. Although
the flow geometry for these systems is extremely complex, the resulting flow properties are of
considerable economic, ecological, and recreational importance. Other examples of open-channel flows
include the flow of rainwater in the gutters of our houses; the flow in canals, drainage ditches, sewers,
and gutters along roads; the flow of small rivulets and sheets of water across fields or parking lots;
and the flow in the chutes of water rides in amusement parks.
Open-channel flow involves the existence of a free surface which can distort into various shapes.
Thus, a brief introduction into the properties and characteristics of surface waves is included.
The purpose of this chapter is to investigate the concepts of open-channel flow. Because of
the amount and variety of material available, only a brief introduction to the topic can be presented.
Further information can be obtained from the references indicated.
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