Hydraulic Engineering
First Test, Spring 2012 (100/106)
Full Name: ____KEY______
Rules: one page cheat sheet one sided allowed; Walton text notes and textbook. No: cell phones, non-ABET calculators, or other materials. Fill in the answers in the space provided with units; use the white space to show your work. You MUST show work to receive credit & all answers MUST have appropriate units. Extra credit problems are more difficult.
- Casio: All fx-115 models. Any Casio calculator must contain fx-115 in its model name.
- Hewlett-Packard: The HP33s and HP 35s models, but no others
- Texas Instruments: All TI-30X and TI-36X models. Any Texas Instruments calculator must contain either TI-30X or TI-36X in its model name.
I promise that I did not use any unauthorized material or was helped by anyone or helped anyone in this exam.
SIGNATURE:______
Presentations and Reading Section (warning! Do not spend too much time looking things up or you will run out of time in the problems).
- (4) A simple stream channel is straightened within the floodplain shown. 10 years later it looks like (draw it)?
Answer: Show meanders along stream
2. (4) A fault disrupts a stream causing the profile shown below, (you were shown the Deresuyu River, Turkey in class). What happened less than a year later? Draw the new profile. (note, we are looking from the side, not from above)
Answer:
3.(4) Hunter Rouse a) wrote the textbook for this class, b) had more hair than Walton, c) was a professor at Stanford University when he made the videos.
Answer: b, he had a full head of hair, which you would know if you watched the videos
4. (4) In a straight channel the maximum shear stress is: a) at maximum channel depth, b) center of the channel, c) side of the channel, d) wetted area/(hydraulic radius) depth, e) 1/3 of the distance from the sides
Answer: a, maximum depth
5. (4) For erodible channels there are two methods used to make sure the channels don’t erode away. These are: Permissible ______and Permissible ______.
Answer: permissible velocity and permissible shear stress, allowable shear stress or similar is OK
6. (4) Caballo dam was built for: a) flood control, b) long term water storage, c) electricity production, d) as a diversion dam
Answer: c, to store water for electricity production
7. (4) American dam was built for: a) flood control, b) long term water storage, c) electricity production, d) as a diversion dam
Answer: d) diversion dam
8. The water is coming in at the normal depth shown. The rectangular channel is 3 m wide and has water flowing at 5 m3/s. The Manning n is 0.018. Water backs up from the horizontal section a little ways onto the incoming sloped section.
a) (4) The velocity of the incoming water is:
ans: 5.56 m/s
b) (6) A hydraulic jump will occur ( Yes No) Why?/ prove it with numbers
yes, because flow is supercritical because Fr = 3.2 and/or y<ycrit = 0.656
c) (6) The flow profile designations for the two transitions are (label on the figure), why?
Answer: S1 because flow is supercritical going to horizontal (jump)
c) (4) The critical depth is:
ans: 0.657 m
Answer:
9.
a) (4) What is the hydraulic radius?
b) (4) What is the flow velocity?
c) (4) What is the discharge?
d) (6) If the slope is doubled, how much will the discharge increase?
Answer for d, Increases by the square root of 2 = 1.414
10. A leaky 12 inch concrete pipe is to be fixed by inserting a plastic liner pipe with an internal diameter of 10 inches. The roughness height for the concrete pipe is 0.048 inches, the plastic liner is smooth. The temperature of the water is 60 degrees F. The Reynolds number for the concrete pipe is 106. Discharge is constant when the pumps are operating to move the water between tanks.
a) (6) What is the friction factor for the concrete pipe (show on Moody diagram)?
b) (6) What is the friction factor for the plastic pipe (show on Moody diagram)?
c) (6 Extra Credit) What is the friction slope in the plastic pipe in comparison to the concrete pipe? (FSplastic/FSconcrete)
Answer:
Assume fully turbulent flow in each case, use energy equation to PROVE your answers for 9 and 10 by solving for the velocity using the symbols K1 for entry minor loss and K2 for exit minor loss (minor losses assumed same for all cases shown).
11. (6) Pipes a and b are identical, rank the discharge as: a) a > b, b) a = b, c) a < b
Answer: all the same, solve energy equation for V = Sqrt[2 g (z1-z2)/(f L/D + K1+K2)]
12. (6) Pipes a and b are identical except a plastic and b is concrete, rank the velocity as: a) a > b, b) a = b, c) a < b
a> b, energy equation is the same
13. (10) Label where the flow is sub and supercritical. What is meant by the term “Normal Depth”? Label the flow profiles in this horizontal channel.
Normal depth is the uniform flow depth that forms in long straight channels; it is the depth given by the Manning Equation.
Profiles are H2 and H3
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