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# What is under expanded nozzle flow?

## What is under expanded nozzle flow?

Ideally, the nozzle should have been shorter to eliminate this unnecessary wall. The opposite situation, in which the atmospheric pressure is lower than the exit pressure, is called underexpanded. In this case, the flow continues to expand outward after it has exited the nozzle.

What happens if over expansion happens in nozzles?

Over Expanded Nozzle: When an overexpanded flow passes through a nozzle, the higher atmospheric pressure causes it to squeeze back inward and separate from the walls of the nozzle. This “pinching” of the flow reduces efficiency because that extra nozzle wall is wasted and does nothing to generate any additional thrust.

What is over expanded flow?

Over-expanded flow continues as the back pressure ratio is decreased until a critical back pressure ratio is reached where the exit pressure is exactly equal to the back pressure. This type of flow is called perfectly-expanded flow or flow at design conditions.

### What is Underexpanded Overexpanded nozzle?

If the pressure of the exhaust leaving the nozzle exit is still above ambient pressure, then a nozzle is said to be underexpanded; if the exhaust is below ambient pressure, then it is overexpanded. Slight overexpansion causes a slight reduction in efficiency, but otherwise does little harm.

What is supersonic nozzle?

A convergent-divergent nozzle with a variable area and profile through which the relative airflow is supersonic. An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc.

What is over expansion and under expansion inside a supersonic nozzle?

## What is meant by expansion ratio?

Expansion ratio is defined by the rate of change of circumference relative to the initial of one section.

What is relation between expansion ratio?

The relation between the coefficients of linear expansion, α and volume expansion, γ is. A. γ = 3α B.

What is optimum expansion?

It is under this condition, Pe=Pa where Pe is the pressure at the nozzle exit and Pa is the outside ambient pressure, that thrust is maximum and the nozzle is said to be adapted, also called optimum or correct expansion. When Pe is greater than Pa, the nozzle is under-extended.