Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Nozzle Operation: Subsonic and Supersonic Flow

In course

ME-343: Compressible-fluid dynamics

Fluides compressibles, vitesse sonique, ondes de choc, détente. ...

Description

This lecture covers the operation of nozzles in subsonic and supersonic flow conditions, discussing the pressure at the outlet and back of the nozzle, the definitions of free surface and shear surface, and the differences between subsonic and supersonic flows. The instructor explains the relationship between the outlet pressure and the back pressure, as well as the concepts of over-relaxed and under-relaxed points in nozzle operation.

This video is available exclusively on Mediaspace for a restricted audience. Please log in to MediaSpace to access it if you have the necessary permissions.

Watch on Mediaspace

Instructor

Flavio Noca

Official source

Related concepts (16)

De Laval nozzle

A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a compressible fluid to supersonic speeds in the axial (thrust) direction, by converting the thermal energy of the flow into kinetic energy. De Laval nozzles are widely used in some types of steam turbines and rocket engine nozzles. It also sees use in supersonic jet engines.

Compressible flow

Compressible flow (or gas dynamics) is the branch of fluid mechanics that deals with flows having significant changes in fluid density. While all flows are compressible, flows are usually treated as being incompressible when the Mach number (the ratio of the speed of the flow to the speed of sound) is smaller than 0.3 (since the density change due to velocity is about 5% in that case). The study of compressible flow is relevant to high-speed aircraft, jet engines, rocket motors, high-speed entry into a planetary atmosphere, gas pipelines, commercial applications such as abrasive blasting, and many other fields.

Nozzle

A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, and it can be used to direct or modify the flow of a fluid (liquid or gas). Nozzles are frequently used to control the rate of flow, speed, direction, mass, shape, and/or the pressure of the stream that emerges from them. In a nozzle, the velocity of fluid increases at the expense of its pressure energy.

Transonic

Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic flow is seen at flight speeds close to the speed of sound (343 m/s at sea level), typically between Mach 0.8 and 1.2. The issue of transonic speed (or transonic region) first appeared during World War II. Pilots found as they approached the sound barrier the airflow caused aircraft to become unsteady.

Supersonic aircraft

A supersonic aircraft is an aircraft capable of supersonic flight, that is, flying faster than the speed of sound (Mach 1). Supersonic aircraft were developed in the second half of the twentieth century. Supersonic aircraft have been used for research and military purposes, but only two supersonic aircraft, the Tupolev Tu-144 (first flown on December 31, 1968) and the Concorde (first flown on March 2, 1969), ever entered service for civil use as airliners. Fighter jets are the most common example of supersonic aircraft.

Related lectures (30)

Supersonic Wind Tunnel - EPFL Rocket Team

Presents a project to visualize supersonic flows for rocket design.

Momentum Equation

Explores the application of the momentum equation in fluid flow analysis, emphasizing force calculations on structures and practical examples.

Newton's Laws of Fluid Motion

Covers the fundamental principles of fluid dynamics and Newton's laws applied to fluid motion.

Hydrostatics: Understanding Fluid Behavior at Rest

Covers hydrostatics, focusing on fluids at rest and the behavior of pressure within them.

Straight Shocks: Entropy Log in to Mediaspace to watch this video