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53:071 Principles of Hydraulics Laboratory Experiment #3 Analysis of Open-Channel Flow Transitions Using Specific Energy Diagram. Li-Chuan Chen, Marian Muste, and Larry Weber. Objective. To observe the changes in the behavior of the free surface when subjected to changes in the channel bed.

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Li-Chuan Chen, Marian Muste, and Larry Weber

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## 53:071 Principles of HydraulicsLaboratory Experiment #3Analysis of Open-Channel Flow Transitions Using Specific Energy Diagram

Li-Chuan Chen, Marian Muste, and Larry Weber

### Objective

• To observe the changes in the behavior of the free surface when subjected to changes in the channel bed.

ybump (ft)

0.24

x (ft)

5

5.87

6.96

7.78

### Apparatus — Obstruction

For x  5ybump = 0

For 5 < x  5.87ybump = 0.276x – 1.38

For 5.87 < x  6.96ybump = 0.24

For 6.96 < x  7.78ybump = 2.28 - 0.293x

For x > 7.78ybump = 0

### What are we going to do?

• We are going to measure the water surface elevation along a open channel.

### Procedures

• Establish a stabilized discharge in the system.

• Measure the water level difference on the differential manometer for computing discharge.

• Measure the water surface elevation upstream, above, and downstream of the obstruction.

• Change the flow rate and repeat Step 2 and 3 for another flow condition.

• Observe the ripples formed at the tip of the point gage.

Flow Situation I

Flow Situation II

h= (ft); Q = (cfs); yc1= (ft)

h= (ft); Q = (cfs); yc1= (ft)

Track

(ft)

Water Surface Elevation (ft)

Bump

Geometry (ft)

Actual depth

(ft)

Track (ft)

Water Surface Elevation (ft)

Bump

Geometry (ft)

Actual depth

(ft)

### Analysis

• Plot the water surface elevation in the vicinity of the channel transition.

• Construct the specific energy diagram using the measured data.

• Compare theoretical specific energy diagrams with the experimental curves.

• Comment on the flow behavior in the two flow situation.

### Further Considerations

• What are the main assumptions associated with the use of the specific energy diagram?

• Comment on the differences noticed on the ripples produced by the point gage upstream and downstream the obstruction.

• Analyze the water surface behavior for the same unit discharges used in your experiment hypothesizing the flow enters in the obstruction as supercritical flow.