Eulerian Description

• A control volume is a general region.
• Examples: a jet engine, balloon, the vicinity of a car or a plane, ...
• At different times, a control volume will usually not contain the same fluid.
• While a Lagrangian description follows the fluid, a typical Eulerian decription keeps the spatial location constant.

Warning:

The laws of physics and thermodynamics do not apply directly to control volumes. Corrections are needed:

• for regions: integrals over the surface
• for pointwise quantities: conversion of Lagrangian time derivatives

Exercise:

Give some simple examples of control volumes where the basic laws of physics or thermodynamics are not satisfied.