16.5 : 自由噴流

Free jets demonstrate fluid behavior described by Bernoulli's equation, as the fluid exits a nozzle and flows freely into the air.

The flow velocity at the nozzle is determined by the height of the fluid column above it, which converts potential energy into kinetic energy.

The jet's exit pressure matches the atmospheric pressure, and the velocity increases as the fluid flows from a large reservoir.

Due to fluid inertia, the jet narrows just outside the nozzle, forming the smallest cross-sectional area. This phenomenon is known as the vena contracta.

The ratio of the area of the jet at the vena contracta and the area of the nozzle gives the contraction coefficient.

Various nozzle shapes, such as knife-edge, well-rounded, sharp-edge, and re-entrant designs, impact the flow pattern and the contraction coefficient.

In designing systems such as spillways and weirs, the vena contracta effect is considered for accurate flow measurement.

Free jets are crucial in civil engineering applications for controlling fluid flow and minimizing structural impact.