(See [p. 168].)
[66] See Punjab Irrigation Branch Paper No. 12, “Results of Tests of Kennedy’s Gauge Outlet.”
[Fig. 31] shows a bell-mouthed orifice discharging into an air-space. The jet springs across the air-space and traverses a gradually diverging tube. Let a, A be the sectional areas of the stream at the air-space and the downstream end of the tube respectively, and let V, v, and Pₐ, P₁ be the corresponding velocities and pressures. Let resistances be neglected. Since the pressure in the air-space is Pₐ,
V = √2gh₀
or the discharge through the tube depends only on h₀ and not on h₁.
Fig. 31.
By Bernouilli’s theorem,
V²2g + PₐW = v²2g + P₁W
or