tailieunhanh - Open channel hydraulics for engineers. Chapter 4 non uniform flow
Linking up with Chapter 2, dealing with uniform flow in open channels, it may be noted that any change in the flow phenomenon (. flow rate, velocity, flow depth, flow area, bed slope do not remain constant) causes the flow to be non-uniform. This chapter will discuss the effect of change in any one of the above quantities, including specific energy, critical depth and slope, and flow types. How to draw water surface profiles will also be introduced. | OPEN CHANNEL HYDRAULICS FOR ENGINEERS ----------------------------------------------------------------------------------------------------------------------------------- Chapter NON-UNIFORM FLOW _ . Introduction . Gradually-varied steady flow . Types of water surface profiles . Drawing water surface profiles _ Summary Linking up with Chapter 2, dealing with uniform flow in open channels, it may be noted that any change in the flow phenomenon (. flow rate, velocity, flow depth, flow area, bed slope do not remain constant) causes the flow to be non-uniform. This chapter will discuss the effect of change in any one of the above quantities, including specific energy, critical depth and slope, and flow types. How to draw water surface profiles will also be introduced. Key words Non-uniform; specific energy; critical; gradually-varied steady flow; water surface profiles _ . INTRODUCTION . General In the previous Chapter 2, the flow was uniform under all circumstances under consideration. In many situations the flow in an open channel is not of uniform depth along the channel. In this chapter the flow conditions studied relate to steady, but non-uniform, flow. This type of flow is created by, among other things, the following major causes: Changes in the channel cross-section. Changes in the channel slope. Certain obstructions, such as dams or gates, in the stream’s path. Changes in the discharge – such as in a river, where tributaries enter the main stream. A non-uniform flow is characterized by a varied depth and a varied mean flow velocity: V h 0 or 0 (4-1) s s If the bottom slope and the energy line slope are not equal, the flow depth will vary along the channel, either increasing or decreasing in the flow .
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