A convergent-divergent nozzle, also known as a de Laval nozzle, is a nozzle design commonly used in rocket engines and supersonic aircraft to accelerate high-speed gases.
The mass flow rate through a convergent-divergent nozzle is the quantity of fluid passing through the nozzle per unit time. This nozzle design is particularly important for achieving supersonic flow, where the nozzle consists of a converging section followed by a diverging section. The converging part accelerates the flow to sonic speed, and the diverging section continues the acceleration to supersonic speeds.
The velocity () in terms of the local speed of sound () is given by:
which gives,
where,
- ṁ is the mass flow rate of the nozzle
- is the density of the exhaust gases at the throat
- A is the throat nozzle area
- M is the Mach Number
- a is the speed of sound in the medium