Convergent-Divergent Nozzle

A convergent-divergent nozzle is a type of nozzle used in rocket engines to accelerate the exhaust gases to supersonic speeds. It consists of a converging section, followed by a throat, and then a diverging section.

Choked Flow

Choked flow is a condition where the flow velocity of a fluid is at its maximum possible velocity, and any further increase in flow rate will not result in an increase in velocity but will instead cause a decrease in pressure. When the flow is choked, the nozzle is said to be at its critical flow rate.

Choked Nozzle

When the flow rate through a convergent-divergent nozzle is such that the flow velocity at the throat is equal to the speed of sound, the flow becomes choked, and the nozzle is said to be choked. In a choked nozzle, the pressure at the throat is at a minimum, and any further decrease in pressure will result in a decrease in the flow rate.

Isentropic Flow

Isentropic flow is a type of flow where the entropy of the fluid remains constant. In an isentropic flow, there is no loss of energy due to friction or heat transfer. In a convergent-divergent nozzle, the flow is isentropic only if the nozzle is designed to operate at a specific load.

Correctly Designed Convergent-Divergent Nozzle

A correctly designed convergent-divergent nozzle working at a designed load is always choked because the flow rate through the nozzle is designed to be such that the flow velocity at the throat is equal to the speed of sound. However, the flow through the nozzle is not isentropic because there is a loss of energy due to friction and heat transfer.