A hydroelectricity plant is supplied from a reservoir via a pipeline 2 km long and 2.5 m in diameter. The pipeline terminates at its downstream end in a control valve.

Under normal operating conditions the hydro plant runs with a steady discharge of 30 cumecsand the water level in the surge tank is 19.0m below the level in the supply reservoir.

You have been given the task of determining the size of the surge tank which is to be installed at the downstream end of this pipeline and immediately upstream of the valve. This tank must be designed in order to deal with the surge that would occur when the valve downstream of the tank is closed completely and instantaneously

Surge Tank Design Criteria:

Unrestricted on inlet (FS = 0)

Maximum allowable water height 8.5m above the level in reservoir.

Task:

a)      Determine the minimum surge tank size (nearest ½ m) to satisfy the max. allowableheight

For the case of complete closure (Q changes from 30 m3/s to Q = 0)

b)      Plot the water level in the surge tank (relative to reservoir) over time for at least 2upsurges

c)      Plot the velocity in the pipeline over the same period.

d)

HINT: The surge tank in the tutorial problem reaches a maximum height of 11.8m