Section A
Q1.
(a) A pipeline carrying water has surface roughness of average height 1.165 mm. If the shear stress developed is 3.6 N/m^2, what is the nature of the pipe surface? The velocity of flow in a badly corroded 8.0 cm pipe is found to increase 30% as a pitot tube is moved from a point 1.0 cm from the wall to 2.0 cm from the wall. Assuming pipe to be a rough pipe, estimate the height of roughness elements.
(b) A trapezoidal channel with side slopes of 1:2 has to be designed to convey 8.0 \text m3/s at a velocity of 1.0 m/s, so that the amount of concrete lining for the bed and sides is the minimum. Calculate the area of lining required for one metre length of the channel. If the roughness coefficient is n = 0.015, calculate the bed slope of the channel for uniform flow.
(c) During a major flood event, water overflows a roadway during which the roadway acts as a broad-crested weir. A vehicle stalled on the roadway will be washed off the roadway into the downstream channel when water depth exceeds 0.6 m. Determine the head (H) on the broad-crested weir for a discharge rate of 400 \text m3/s if the overflow section of the roadway is horizontal and 200 m long. Assume a weir coefficient of 0.33. Also, compute the water depth and velocity on the roadway. Will a stalled vehicle on the roadway remain on the road during the flood or get washed off? Take g = 9.81 m/s2. Give reasons for your answer.
(d) A wastewater sample was diluted 10% with tap water for conducting BOD Test. The DO content in wastewater sample was 1.2 mg/l and water was 6 mg/l. After 5 days incubation at 20\circC, the DO of the sample was 0.5 mg/l. Calculate 5 day BOD of wastewater and ultimate BOD. Assume K20 = 0.12/day.
(e) With the help of data given below, estimate the per capita solid waste generated per day in a colony with 20,000 houses. Volume of waste/truck load = 20 \text m3 Volume of waste/tractor load = 2 \text m3 Volume of waste/small truck = 8 \text m3 No. of truck loads = 2/day No. of tractor loads = 1/day No. of small truck loads = 3/day Avg. no. of people/house = 4 Specific weight of waste in (kg/m3) = 500 for truck; 225 for small truck; 50 for tractor.
