5. Hydraulics and Hydrology

Question 1

What is the height of 1 psi of water?

Answer 1

2.32 ft

Question 2

How must psi does 1 ft of water create?

Answer 2

0.433 psi

Question 3

For friction loss in pipes, friction loss increases as?

Answer 3

• pipe wall roughness increases
• pipe diameter decreases (pipe is constricted)
• flow rate increases
• length increases
• fluid viscosity increases
• density decreases

Question 4

What channel cross-section is the most efficient?

Answer 4

The one with the minimum wetted perimeter, thus semi-circle.

Question 5

What is the minimum velocity in storm sewers?

Answer 5

At least 2 fps, but preferably 2.5 fps to prevent settlement of solids.

Question 6

What is the maximum velocity in storm sewers?

Answer 6

10 fps (also for sanitary sewers).

Question 7

What are the factors affecting the flow through a culvert?

Answer 7

1. Size of the opening (x-section area)
2. Entrance geometry
3. Length of the Barrel
4. Roughness of the barrel
5. Slope
   6 Downstream depth of flow (tailwater)

Question 8

What is intel control?

Answer 8

• Culvert barrel is capable of conveying more flow than the inlet will accept.
• Control section is just inside the entrance
• Flow regime immediately downstream is supercritical (high velocity shallow flow)

Question 9

What is outel control?

Answer 9

• Culvert barrel is NOT capable of conveying as much flow as the inlet will accept.
• Control section is at the exit or further downstream
• Flow in the barrel is either subcritical (low velocity deeper flow) or pressure flow.

Question 10

How does a culver under inlet control conditions perform?

Answer 10

as an orifice when the inlet is submerged and as a weir when it is unsubmerged.

Question 11

What is a detention basin?

Answer 11

a storage facility that impounds the storm water runoff temporarily and releases in slowly through an outlet structure.

Question 12

What is a retention basin?

Answer 12

Wet basin, larger storage that collects water as a final storage destination (i.e. water is help until it evaporates or infiltrates into the soil)

Question 13

In open channel flow, what is uniform flow?

Answer 13

When depth does not change at every section, aka normal depth

Question 14

In open channel flow, what is non-uniform flow?

Answer 14

depth changes at every section, either gradually varied or rapidly varied.

Question 15

What is unsteady flow?

Answer 15

depth of flow changes with a time interval.