Discharge under Falling Head.

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When the inflow is less than the outflow then that condition is called the falling head condition.The time required for a certain quantity of water to flow from a reservoir can be calculated by equating the volume of water that flows through the orifice or pipe in time dt to the volume decrease in the reservoir. If the area of the reservoir is constant,

t=2A (?h₁ -?h₂)/ (Ca ?2g)

where h₁= head at the start, ft (m)

h₂ =head at the end, ft (m)

t =time interval for head to fall from h₁ to h₂,(s )

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