# Water flowing in a pipe, is taking water from a reservoir some 100m above a city what is the pressure in the pipe as its enters the city?

**Unit Number and Title: Unit 43 Hydraulics**

**Assignment Title: Hydraulics for Civil Engineering**

**Unit Learning Outcomes**

LO1 Apply concepts of physics to develop solutions for hydrostatic and hydrodynamic problems.

LO2 Calculate forces related to fluids at rest and in motion.

LO3 Develop practical solutions for the distribution of fluids within correctly sized pipes.

LO4. Calculate the hydrostatic pressure exerted on substructures for a given context.

**Assignment Brief and Guidance**

**Scenario:**

The company you work for has recently taken on work involved with hydraulic structures as someone who has recently graduated from a programme which includes significant civil engineering hydraulics you are asked to join the management team with respect to these projects.

**Task 1.**

a) Water flowing in a pipe, is taking water from a reservoir some 100m above a city what is the pressure in the pipe as its enters the city? If a open channel was to bring the water into the city from the same reservoir, what would the pressure be in the opne channel. Explain briefly why.

b) What are the two main forces of resistance to water flow in pipes?

c) How does water temperature affect these forces?

d) Explain the difference between laminar and turbulent flow.

e) What is Reynolds Number and how is it related to turbulent flow?

f) What is the boundary layer and how is it affected by the roughness of the surface over which water is flowing?

g) How is the resistance to water flow reduced either in a pipe or in an open channel?

h) The water supply to a rapidly expanding town was laid out many years ago when the town was small and appeared to have a stable population. Outline how additional supplies can be piped in without disrupting the current supplies

**Task 2**

a) Water is needed to supply a canal system, which may require up to 30m3 s -1 the channel is 2 metres wide calculate the depth of flow at maximum given that the Manning n value of this stretch of the channel is 0.02.

b) A proposal has been suggested that the excess water above a flow rate of 25m3 s -1 could be diverted through a pipe to a reservoir some 2km distant . An automatic system would be installed which opened a valve into this pipeline as soon as the flow exceeded this level. The pipe would need to be able to take water at the rate of 10m3 s -1 . Using the Darcey Weisbach equation for laminar flow calculate the head loss through a pipe with a friction factor of 0.006 and a pipe diameter of 1.5m.

c) The reservoir (in part b) is 50m below the surface of the river. Comment on whether it will be possible to achieve the 10m3 s -1 flow and what steps could be taken.

d) Comment on the differences between pipe flow and open channel flow and estimate the dimensions of an open channel 2m deep that would be needed to conduct 10m3 s -1 to reservoir.

**Task 3**

a) Estimate the head loss in a pipe line of 10km length and 1.4 m in diameter carrying water at the rate of 30m3 s -1 to supply a town. The Darcey Weisbach friction factor is 0.004 and the minor losses are 10 times the velocity head.

b) The difference in height between the start and end of the pipe line is 20m. What additional pressure would need to be supplied by a pump to achieve the required delivery?

c) As an alternative design the feasibility of using a bigger diameter of pipe needs to be considered. Find the smalledst diameter of pipe that would achieve this.

d) Discuss the real life factors that would go into deciding whether to use a pump based system or one based on gravity alone.

**Task 4**

a) Ground water is found at a depth of 1.5m and a below ground car park is being built in this area. The depth of the car park is 9m to allow for two levels of parking. Calculate the force on the boundary walls and the upwelling force on the floor. The dsimensions of the car park are 20m x 60m. Assume that this is fresh water with a density of 1000kgm-3

b) What materials and structures would be needed for the outer walls of the car park bearing in mind that they also act as the main structural support for the building.

c) What structure and materials would be suitable for the flooring?

**Unit Number and Title: Unit 43 Hydraulics**

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