Question 1

(a) Compute the depth ‘h’ on the composite channel section (symmetrical) shown in Figure Q2 to maintain a velocity of 2m/s. the bed slope of channel is 1 in 1500, and channel boundary is made of brick in cement mortar

(b) After flowing over the concrete spillway of a dam, 250 m3 /s then passes over a level concrete (trowel finish) apron. The velocity of water at the bottom of the spillway is 12 m/s. The width of the apron is 55 m. if the depth of water in the channel below the apron is 3m:

i) Determine whether a hydraulic jump will occur downstream of spillway

ii) What is the pre-jump depth?

iii) Determine the energy dissipated in the jump

Question 2

(a) Explain with the help of specific energy diagram about two types of flows that are possible in a given channel at constant discharge. Also, comment on the flow condition when the specific energy is minimum.

(b) An analysis has revealed that a circular pipe discharging fluid at a depth of 92.5% of it’s total diameter will flow at maximum capacity (best hydraulic section). For a flow rate of 750 litters per second, calculate the optimum diameter of a circular pipe with a gradient of 0.222% and a Chezy coefficient of 50.

Question 3

(a) How is wave front celerity, within a closed pipeline, affected by variations in fluid compressibility, pipe material elasticity, pipe material rigidity, and pipeline restraint?

(b) A utility company wishes to procure a pressurized pipeline to convey drinking water to a new residential development at a rate of 300 liters per second. Prior to preparing detailed tender documents, the company requires two outline designs to be carried out to compare the individual benefits of the use of differing pipe materials.

The finished pipeline is to be constructed within an excavated trench and surrounded in concrete. The two options to be considered are a steel pipe of internal diameter 300 mm and pipe wall thickness of 6 mm, and a plastic pipe of internal diameter 350 mm and pipe wall thickness of 8 mm. take young’s modulus to be 211×109N/m2 and 4.0×109N/m2 for the steel and plastic respectively

Stating your assumptions and taking the bulk modulus of water to be 2.10×109N/m2. Compare the theoretical surge pressure induced within the pipeline, if it were to be constructed in steel or plastic, by the instantaneous closure of an on-line valve.

Question 4

A hydroelectric scheme comprises an upper storage lake and a lower impounding reservoir connected by a tunnel of 1.3 km total length, internal finished diameter of 0.9 m and Darcy friction factor of 0.01. The tunnel delivers water to an on-line turbine hall at a normal operating rate of 850 liters per second. A surge tank constructed within a circular shaft is positioned 100 m upstream of the lower impounding reservoir and has an internal finished diameter of 2300 mm. In the event that the turbines experience shutdown, derive the maximum likely instantaneous water level within the surge tank. Take a time interval of 20 sec.

Table:

t v -dy V2 Hf y Hf-y -dv

t = time interval

v = velocity

Hf = loss of energy

dv = change in velocity

y = water level in surge tank (above/below reservoir level)

dy = change in water level