Page 28 - ebook fluid mechanics_finalize

FLUID MECHANICS

2.2.6 Fluid Compressibility

All fluids are compressible under the application of external forces. The
compressibility of a fluid is expressed by its bulk modulus of elasticity, E which is the ratio

of the change in unit pressure to the corresponding volume change per unit volume. For

most practical purposes liquids may be regarded as incompressible.

Example 1 :

3
Calculate the mass density, ρ of fluid, if mass is 450 g and the volume is 9 cm .

m
 = 450  10 − 3 = 50 10 kg / m 3
3
Solution : =
V 9 10 − 6

Example 2 :

3
Calculate the specific weight,  of fluid (in kN/m ) if the weight of fluid is 10 N and the
2
volume is 500 cm .

W 10
3
Solution :  = = = 20 000 N/m = 20 kN / m 3
V 500 10 − 6

Example 3 :

Calculate the specific gravity of fluid in Example 2


s = subs tan ce 20 10 3
Solution :  water = 1000 ( 81.9 ) 2= . 039

Example 4 :

Calculate the specific volume, v of fluid in Example 1.

V 9 10 − 6 − 5 3
Solution : v = = 2= 10 m / kg
m 450 10 − 3

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