A converging-diverging nozzle is a type of nozzle used to accelerate fluid flow, particularly in applications involving gases. It has a narrow throat section where the cross-sectional area decreases (converging) and then expands again (diverging). This design allows the fluid to reach supersonic speeds as it exits the nozzle, making it essential in various engineering applications, including rocket propulsion and jet engines. The principle behind the converging-diverging nozzle is based on the Bernoulli's principle and the continuity equation. As the fluid passes through the converging section, its velocity increases while pressure decreases. Upon entering the diverging section, the fluid continues to accelerate, achieving high velocities necessary for efficient propulsion systems.