# NOZZLE CHOKING:
Table of Contents:
- What Is Nozzle Choking?
- Various Phenomenon Of Nozzle Choking
- Nozzle Choking – Through Varying Area Duct
- Nozzle Choking – With Friction
- Nozzle Choking – With Heat Addition
What Is Nozzle Choking?
Nozzle choking is a compressible flow effect that obstructs the flow, setting a limit to fluid velocity because the flow becomes supersonic and perturbations cannot move upstream; in gas flow, choking takes place when a subsonic flow reaches M=1.
Nozzle choking is a fluid dynamic condition associated with the venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe) into a lower pressure environment the fluid velocity increases. At initially subsonic upstream conditions, the conservation of mass principle requires the fluid velocity to increase as it flows through the smaller cross-sectional area of the constriction. At the same time, the venturi effect causes the static pressure, and therefore the density, to decrease at the constriction.
Choked flow is a limiting condition where the mass flow will not increase with a further decrease in the downstream pressure environment for a fixed upstream pressure and temperature. For homogeneous fluids, the physical point at which the choking occurs for adiabatic conditions, is when the exit plane velocity is at sonic conditions; i.e., at a Mach number of 1. At choked flow, the mass flow rate can be increased only by increasing density upstream and at the choke point.
Various Phenomenon Of Nozzle Choking:
The phenomenon of nozzle choking exists only in compressible flow and can occur in several flow situations.
- Through Varying Area Duct
- With Friction
- With Heat Addition