Hydraulic Engineering Third Exam Fall 2012
(105/100) Full Name: _unchecked key___
Rules: two 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.
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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 TI36X 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:____________________________________
1. (12) The small stream below produced the following hydrograph from a 1.5 cm rain storm that lasted an hour.
The drainage area is 58,000 square meters. Make a (1 cm) unit hydrograph. Plot the unit hydrograph on the
figure. (note: units error in setting this one up, be generous in grading to compensate as poor numbers made
this one confusing)
8
7
6
Q, m3/s
5
4
3
2
1
0
0
2
4
6
8
10
12
14
t, hr
½ base*height = 8 m^3/s*hr = 28800 m^3
scale factor = 0.02 = 1/50 (nonsensical given 1.5 cm rain was specified)
unit hydrograph is a) take off base flow then put back 1/50 th of the triangle
Grading: area (4 pts), scale factor (4 pts), subtract base flow (4 pts) don’t expect correct answer
consider putting a correct version of this on the final
2.
(18) The EGL and HGL for a horizontal pipe are shown in feet. Datum is at the same level as the pipe and the
values for the EGL and HGL are shown on the figure. Note that the pipe is located just above the letters A-F
(someone erased it).
Label the EGL and HGL. (upper is EGL, 1 pts)
The pipe section CD is 6 inches in diameter. Find the velocity and discharge in CD.
V2/2g = (191.1-175.1) and also = (143.1-127.1) = 16 ft
V=sqrt(2*32.2*16) = 32.1 ft/s
(3 pts)
Q = V*A = 32.1*0.25^2*Pi = 6.3 cfs (3 pts)
Find the pressure in lbf/ft2 at point B.
P/rho g = 196 or P = rho g *196 = 62.4*196 = 12230 lbf/ft^2 (3 pts)
Find the discharge in pipe section AB.
same as in CD (3 pts) credit as long as same as prior answer
What is the friction head loss in each section of pipe listed below? (1 pt each)
A-B: 201-197 = 4 ft
B-C: 197-191.1 = 5.9 ft
C-D: 191.1-143.1= 48 ft
Is pipe E-F larger, the same size, or smaller than the pipe from C-D? (2 pts)
Fatter because velocity head is lower
3. (18) The velocity in the pipe is 7.7 ft/s. Assuming the pump is located 500 feet from tank A (4000 ft from tank B)
at an elevation of 250 feet. Find the pressure head in ft and pressure in lbf/ft2 just prior to the pump. Assume
the loss coefficient leaving tank A is 0.5 and the loss coefficient entering tank B is 1.0. Begin with full energy
equation and simplify it as appropriate.
Note: if you can’t solve the problem earn a few points by calculating the head loss leaving tank A and the head
loss traveling along the pipe from tank A to the pump.
Point 1 is at top of tank A, point 2 is just before pump, start with full energy equation with head loss, solve for
P2/rho g = z1-z2-V^2/2g(fL/D + 1.5) = 300-250-7.7^2/(2*32.2)*(0.02*500/(10/12) +1.5) = 37.6 ft
6 pts begin with full energy equation with proper two points (could also go from second tank but its more work)
6 pts properly simplify and solve equation for pressure head
6 pts correct numbers and final answer
4. (9) Label the confined and unconfined aquifers. Upper unconfined, lower confined
Is the lower, right side stream gaining or losing? _____gaining___
What is the pressure of the water at the water table? __zero___
5. (12) The markings are every 10 cm, the tube is 2 m long, the piezometers show the water level. The hydraulic
conductivity is 10-4 cm/s. Datum is at the top of the bar at A. Find the rate and direction of flow in the tube.
Show the direction of flow with an arrow. Show the pressure head, elevation head, and total head at each end
of the flow tube.
Point 1: z~40 cm, p/rg~110 cm total ~ 150 cm Point 2: z~80 cm, p/rg~50 cm total 130 cm
V=-K(H2-H1)/(X2-X1) = + 10^-4 cm/s*20 cm/200 cm = 1E-5 cm/s from left to right (positive direction)
6. (3) The Theis Curve is used to: a) evaluate pump tests, b) show the profile of head loss in passing through a pipe
expansion, c) estimate the probability of the 100 year storm (as well as other lengths), d) none of the above.
7. (6) Estimate the discharge, horsepower, and pump efficiency of the system below using the given pump. Show
your work by drawing on the figure. (3 points each)
System curve
8. (3) The pump from Dr. Turner’s well was a multistage _centrifugal_ pump.
9. (12) Label the location(s) where the pressure is lowest, the location(s) where the pressure is greatest, where the
total hydraulic head is greatest, where the total hydraulic head is lowest.
pressure lowest near S, highest in pipe just outside Tank A, head is greatest in Tank A and close to that just
outside tank A in the pipe, head lowest in Tank B or if only pipe is considered just before Tank B (3 pts each)
10. (3) It’s just banging around in my head, but I can’t remember what this graph from your textbook refers to.
What is it? Water hammer, this is just a check if students read material, otherwise one could not tell, question
too picky
11. (9) The water pressure is a) greater at 3 than 4, b) the same at 3 and 4, c) less at 3 than at 4.
The velocity head is: a) greater at 3 than 4, b) the same at 3 and 4, c) less at 3 than at 4.
The total head is a) greater at 3 than 4, b) the same at 3 and 4, c) less at 3 than at 4.
really like this question, much subtle thinking, no calculations, because of friction head will decline from 3 to 4;
by continuity the flow is the same at 3 and 4 and the diameter is the same so velocity head is the same (energy
is lost, elevation is gained, velocity and discharge are constant); going from 3 to 4 the pipe moves up, converting
pressure energy to elevation and some pressure is lost to friction, both of these make pressure greater at 3
expect this same figure and questions on the final with different points chosen