02 1.1 What is a fluid?
A fluid is any material that has the ability to flow and has no shape of its own. Fluids include liquids and gases.
1Compressibility
Liquids
- resist compression almost completely (incompressible)
Gases
- easily compressed
2Volume
Liquids
- definite volume
Gases
- occupy any space available to them
3Shape
Liquids
- take the shape of the container
Gases
- take the shape and volume of the container
Because liquids are practically incompressible, we treat liquid flow as incompressible laminar flow: the density of the moving liquid does not change.