SOLUTION TO THE PROBLEMS:
1. A trapezoidal canal has one side vertical & the other sloping @ 450. Its discharge is 25.5 m3/s and its mean velocity is 1 m/s. Its hydraulic slope is at its barest minimum. Calculate the base & depth of the section.
2. A trapezoidal earth canal (n = 0.032) with its side sloped at 2 horizontal to 1 vertical, carries water at the rate of 6.25 m3/sec. It has a grade of 27 cm per km. For a most efficient section, the hydraulic radius is twice the depth of the canal. Determine the bottom width of the canal. (Hint: For a most efficient section, width @ the top = sum of sides)
3. Find the required diameter for circular pipes such that two of them will be just sufficient to carry the water delivered by an open channel of half square section 1.8 m wide & 900 mm deep. Given for the channel & pipe S = 0.0009 & C = 66.
4. Determine the depth of flow and the base of an efficient trapezoidal canal to carry a discharge of 10,000 li/s. of water at a velocity of 1 m/s. The canal side has an inclination of 2 horizontal to 1 vertical. Find the necessary bed slope for the canal if the roughness coefficient has a value of 0.025.
5. What size of a sewer pipe should be laid @ a slope of 0.0001 to carry a discharge of 650 lps when flowing half full? The pipe is circular & the roughness of coef “n” has a value of 0.015.
6. An earth canal containing weeds and grass has bottom width of 6.6m & side slope of 2 horizontal to 1 vertical. The depth of water is 2 m and the slope is 0.07%. It is desired to change the section to a semi-circular concrete lined canal having a slope of 1.5m in 1 km. Determine the radius of the channel if it flows full. Use n = 0.035 for earth canal and n = 0.012 for concrete lined canal.
7. Design a trapezoidal earth canal to irrigate a 300 ha rice farm. The maximum water requirement occurs during the land preparation period @ an average 12 mm/day. Base your design on the following conditions:
Irrigation period - 24 hr/day
Overall system efficiency - 40%
Manning’s “n” - 0.025
Max permissible velocity - 0.8 m/s
Channel bottom slope - 0.15%
Side slope V:H - 1:1.5
a) Determine the design discharge in liters per second,
b) Determine the typical cross-section of the canal at the headgate.
8. An irrigation system at the College of Agriculture used an old 20 cm G.I. pipe with friction factor, f = 0.033. The pipe is 750 m long and conveys water from the pump (elevation 65m) to a tank whose surface area has an elevation of 170m. The pump discharges 70 liters/sec. How many Hp would be saved if the pipe will be replaced with a new 25 cm G.I. pipe with friction factor , f = 0.022?
9. Design a concrete-lined trapezoidal irrigation canal to carry a maximum discharge of 2,500 liters per second laid on a slope of 0.04%. The bed material is sandy loam.
10. Design a trapezoidal irrigation canal to carry a maximum discharge of 1500 li/s & to be laid on a slope of 0.0015. The bed material is cohesive compact clay, n = 0.025 & a maximum permissible velocity of 3 ft/s.
11. Using TF method max permissible TF = 8.1 N/m3, design a trapezoidal irrigation canal to carry a maximum discharge of 1500 li/s & to be laid on a slope of 0.0015. The bed material is cohesive compact clay, n = 0.025 & a maximum permissible velocity of 3 ft/s..
12. The discharge pressure gage of a pump reads 1020.42 Kpa. The suction pressure gage is attached 1.22m below the centerline of the discharge gage and reads 50.8mm Hg vacuum. The pump is delivering 2.273 m3/min of water. The diameters of suction and discharge pipes are 127mm and 102mm, respectively. The power input to the pump is 61KW and electrical input to the driving motor is 74KW.
Determine:
(a) WP
(b) Np
(c) Nc
13. A single suction pump has a capacity of 19 liters/second with maximum developed head of 61m. Equivalent rotative speed is 1200rpm. It is proposed that same type of pump is to be installed but with double suction & to operate at a head of 30m & a discharge of 25 liter per second. Determine the speed of the proposed pump at which it will operate.
14. A centrifugal pump design for a 1800 rpm operation and head of 60m has a capacity of 11.36 m3/min with a power input of 132KW.
a. What effect will a speed reduction to 1200 rpm have on the head, capacity and power input of the pump?
b. What will be the change in these variables if the impeller diameter is reduced from 304mm to 254mm while the speed is held constant at 1800 rpm?
15. A centrifugal pump discharges 25 liters/s against a total head of 15 m at 1400 rpm and the diameter of the impeller is 0.45 m. A geometrically similar pump of 0.30 m diameter is to run at 2800 rpm. Calculate the head, the discharge, and the brake power ratio required.
16. From a reservoir whose surface elevation is at 30 m, water is pumped at an elevation of 95 m. The total length of a 0.60m diameter suction pipe is 1500m and that of 0.50m diameter discharge pipe is 1000m. Find the required Hp of the pump if the discharge is to be maintained at 0.48 m3/s. Assume a pipe friction factor of f = 0.02 for both pipes and let minor losses be equal to 10% of the major losses.
Note: Minor head loss formula is 
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