Compressibility of Fluids Review and Equation

Fluid Flow Table of Contents
Hydraulic and Pneumatic Knowledge

Compressibility of Fluids Review and Equation

Compressibility is the measure of the change in volume a substance undergoes when a pressure is exerted on the substance. Liquids are generally considered to be incompressible. For instance, a pressure of 16,400 psig will cause a given volume of water to decrease by only 5% from its volume at atmospheric pressure. Gases on the other hand, are very compressible. The volume of a gas can be readily changed by exerting an external pressure on the gas

Equation:

where V is volume and p is pressure

Earth Vertical, drained compressibilities

Vertical, drained compressibilities Material β (m²/N or Pa^-1)

Vertical, drained compressibilities Material β (m²/N or Pa −1 )

Material	β (m2/N or Pa -1 )
Plastic clay	2 × 10-6 – 2.6 × 10 -7
Stiff clay	2.6 × 10 -7 – 1.3 × 10-7
Medium-hard clay	1.3 × 10 -7 – 6.9 × 10 -8
Loose sand	1 × 10 -7 – 5.2 × 10 -8
Dense sand	2 × 10 -8 – 1.3 × 10 -8
Dense, sandy gravel	1 × 10 -8 – 5.2 × 10 -9
Rock, fissured	6.9 × 10 -10 – 3.3 × 10 –10
Rock, sound	<3.3 × 10 –10
Water at 25 °C (undrained)	4.6 × 10 –10
Ethyl alcohol	110 × 10 –11
Carbon disulfide	93 × 10 –11
Glycerine	21 × 10 –11
Mercury	3.7 × 10–11