2. Hydraulics

2.1 Some physical quantities useful in hydraulics

• Density: the ratio between a mass m (in kg) of homogeneous matter and the volume V (in m ³ ) occupied by this mass in kg · m ^–3 : ρ = m/V. Its inverse, called mass volume, is sometimes used. It can be seen that the densities of liquids are around 1,000 times higher than those of gases (liquids are in a more condensed form than gases). When a fluid maintains a constant density, it is said to be in incompressible flow. Otherwise, the flow is said to be compressible. Liquids can largely be considered to be incompressible.

• Density: this is the ratio between the mass of a certain volume of a...