Why velocity head increases and pressure head decreases when the sectional area reduces?
Answers
Due to the Bernoulli theory, the pressure falls into a convergence nozzle.
At the end of the nozzle hose or pipe is used to control the movement of liquids such as water or air. A convergent nozzle is a nozzle which grows and becomes smaller - a reduction in cross-sectional area. Since a fluid enters a small cross section, it has to grow faster due to the preservation of the mass. To maintain the continuous amount of fluid running through the restricted portion of the nozzle, the fluid should move rapidly.
The energy to increase this fluid speed is to come from anywhere. Some energy is in random speed of molecules, which we see as pressure. In this random motion the energy is swiftly converted to the speed forward, which is known as stream flow. This change creates pressure drop.
The opposite is contrary to the pressure area, if everything else remains the same. In this case, the energy causing the pressure is converted into any other kind of energy, hence both the pressure and the area decreases.