Full worked out solutions are required for these questions. The answers are provided in the square brackets. Hand written solutions and are fine.
Question 1. A town of population 41,000 people is growing at the rate of 3% a year. Industry currently uses 40% of the water consumption and is predicted to rise to 55% of the town's water consumption in 15 years time. The current average domestic consumption is 240 litres per persoNday. Calculate the average daily water demand for the town in 15 years time, assuming that the average domestic consumption will increase to 260 litres per person/day.
Question 2. Flow records from a water supply catchment have been kept over 40 years. Monthly runoff volumes for the three driest consecutive years are tabulated below in Mega-litres (ML).
Draw a mass diagram, and determine the storage required to supply a community of 6000 persons, if the water demand is 450 UpersoNday. The data below must be used to construct a mass diagram for the total period of three years in the order in which they are give. (The sequence of the flows are an important factor in the assessment of the water deficit and hence the dam storage required.)
|
|
1982
|
1983
|
1984
|
|
J
|
250
|
170
|
170
|
|
F
|
220
|
160
|
130
|
|
M
|
170
|
120
|
90
|
|
A
|
195
|
80
|
40
|
|
M
|
60
|
30
|
20
|
|
J
|
45
|
10
|
20
|
|
J
|
40
|
20
|
40
|
|
A
|
20
|
20
|
60
|
|
S
|
0
|
10
|
100
|
|
0
|
40
|
30
|
160
|
|
N
|
120
|
70
|
190
|
|
D
|
160
|
90
|
150
|
(Demand: 82.125 MUday; Volume required: 450 ML approximate
Question 3. The following results were obtained during a labora ory test on a centrifugal pump.
|
Discharge (Us)
|
0
|
38
|
61
|
76
|
98
|
121
|
|
Head (m)
|
37.8
|
36.3
|
34.5
|
31.7
|
27.4
|
20.1
|
|
Efficiency (%)
|
0
|
54
|
64
|
68
|
70
|
67
|
This pump is now used to pump water to a static height of a 20 m through a 150 mm diameter pipe of effective length 83 m. The friction factor a= 0.0224
(i) Derive the equation for the system head curve.
Then plot the head and efficiency characteristic curves for the pump and determine:
(i) The discharge
(ii) The operating head
(iii) The power required to drive the pump
The Head - Discharge (H-Q) data for a centrifugal pump is given below:
|
H(m)
|
22.5
|
22.0
|
20.9
|
19.0
|
16.3
|
12.7
|
7.7
|
0
|
|
Q(m3/s)
|
0
|
0.05
|
0.10
|
0.15
|
0.20
|
0.25
|
0.30
|
0.35
|
The pump is to be connected to a rising main which has a diameter of 400mm and a length of 137 m. The entry, exit and minor head losses in the pipeline can be taken collectively as 80'D using the equivalent pipe length concept. The friction loss can be computed using the Darcy-Weisbach equation, with A= 0.04. The static lift is 10 m. Neatly graph the pump curve and the system curve. By considering a single pump, two pumps in series, and two pumps in parallel determine which combination will be capable of discharging at least 0.3 m3/s, with the ability to pump up to 0.35 m3/s if the need arises.
Question 4.
a. Calculate the discharge through a v-shaped earth channel having side slopes of 1:4 on one side and 1:2 on the other side if the longitudinal slope is 2%, Manning's n = 0.025 and the flow depth = 322mm at the deepest point.
b. A concrete pipe of diameter 375mm is laid on a slope of 1 in 200. Assuming Manning's n=0.012, determine the flow velocity and the discharge when the pipe is flowing half full.
c. What is the pipe diameter required for a full pipe flow of 0.25 m3/s where the Manning's n for the pipe is 0.02 and the pipe grade is 1:150?
Question 5.
(a) Calculate, using the Manning formula, the full flow velocity and discharge, through a 600mm diameter sewer, at a slope of 1:200. Assume Manning's n = 0.012.
(b) Obtain the corresponding values with the aid of the design chart in Appendix A7. What are the possible reasons for discrepancies in the answers?
(c) Based on the full flow values obtained in (a) above, what would be the theoretical velocity and discharge, (i.e. based on Manning formula) if the sewer flows half full?
(d) With the aid of the partial flow curves in Appendix A6, determine the velocity and discharge if:
(i) the pipe flows half full, and
(ii) if d/D = 0.8
(e) Give an explanation for the difference in answers between (c) and (dXi) above. 3.2 For the pipe parameters given in 4(a), determine the velocity and discharge using the chart in Appendix A5. What is the reason for the difference between these and the answers in 4(b)?
Attachment:- Appendix.pdf