Orifice Discharge Under a Given Head

Equation: flow through an orifice, Q = Cd·A·√(2gh). Values: Cd = 0.62 is the discharge coefficient given. A is the orifice area, π(0.100)²/4 = 0.00785 m², from d = 100 mm. g = 9.81 m/s². h = 3.0 m is the head, measured from the free water surface down to the centre of the orifice. Step 1: ideal jet velocity, √(2gh) = √(2 × 9.81 × 3.0) = √58.9 = 7.67 m/s. Step 2: Q = 0.62 × 0.00785 × 7.67 = 0.0374 m³/s. Leaving out Cd gives 0.0602 m³/s, the ideal flow that ignores contraction and friction at the orifice.