BULK MODULUS
BULK MODULUS
The Bulk Modulus Elasticity is a material property characterizing the compressibility of a fluid - how easy a unit of the fluid volume can be changed when changing the pressure working upon it.
The Bulk Modulus Elasticity can be expressed as
E = - dp / (dV / V) (1)
where
E = bulk modulus elasticity
dp = differential change in pressure on the object
dV = differential change in volume of the object
V = initial volume of the object
The Bulk Modulus Elasticity can be alternatively expressed as
E = dp / (dρ / ρ) (2)
where
dρ = differential change in density of the object
ρ = initial density of the object
An increase in the pressure will decrease the volume (1). A decrease in the volume will increase the density (2).
• The SI unit of the bulk modulus elasticity is N/m2 (Pa)
• The imperial (BG) unit is lbf/in2 (psi)
• 1 lbf/in2 (psi) = 6.894 103 N/m2 (Pa)
A large Bulk Modulus indicate a relative incompressible fluid.
Bulk Modulus for some common fluids can be found in the table below:
|
Bulk Modulus - E |
Imperial Units - BG |
SI Units |
|
Acetone |
1.34 |
0.92 |
|
Carbon Tetrachloride |
1.91 |
1.32 |
|
Ethyl Alcohol |
1.54 |
1.06 |
|
Gasoline |
1.9 |
1.3 |
|
Glycerin |
6.31 |
4.35 |
|
Mercury |
41.4 |
28.5 |
|
Paraffin Oil |
2.41 |
1.66 |
|
Petrol |
1.55 - 2.16 |
1.07 - 1.49 |
|
SAE 30 Oil |
2.2 |
1.5 |
|
Seawater |
3.39 |
2.34 |
|
Water |
3.12 |
2.15 |
