Before You Watch

In this lecture, we will continue our discussions on critical flow and depth. We will discuss how to determine depth changes when channels go through contractions or expansions and what happens if the contraction point causes the water to reach critical flow. In our lectures last week, we covered the specific energy diagram and how it can be used to evaluate a transition in the channel bottom while this week we will discuss how they can be used to evaluate contraction and expansions in channels. Additionally, we will look at another diagram, called the discharge diagram, that can also be employed to evaluate the contractions and expansions in channels. We will also examine obtaining critical depth values in non-rectangular channels. Lastly, we will discuss one of nature's energy dissipation devices that occur in channels, called hydraulic jumps.

How can the specific energy diagram be used to analyze contractions and expansions that occur in channels?
What is the procedure for developing a discharge diagram?
How can the discharge diagrams be used to also evaluate contractions and expansions in channels?
How to determine the critical depth in non-rectangular channels?
How to determine the sequent depths associated with a hydraulic jumps in a channel?

Video

Download/print PDF lecture slides: Critical Flow - Additional Evaluations

Key Takeaways

Now, revisit the above questions with the lecture material and your assigned reading. In this week, you should know how to employ a specific energy and discharge diagrams to determine changes in channel depths and water surface elevations due to contractions or expansions in a channel. Also, you should know how to determine critical depth in non-rectangular channels.