Chapter1 : Introduction and Fundamental Concepts
Lecture 1 :


Fluid Properties :

Characteristics of a continuous fluid which are independent of the motion of the fluid are called basic properties of the fluid. Some of the basic properties are as discussed below.

Property
Symbol
Definition
Unit
Density
ρ

The density p of a fluid is its mass per unit volume . If a fluid element enclosing a point P has a volume Δ and mass Δm (Fig. 1.4), then density (ρ)at point P is written as

 

However, in a medium where continuum model is valid one can write -

(1.3)

 

   

Fig 1.4 A fluid element enclosing point P

 
kg/m3
Specific Weight
γ

The specific weight is the weight of fluid per unit volume. The specific weight is given

by     γ= ρg     (1.4)

Where g is the gravitational acceleration. Just as weight must be clearly distinguished from mass, so must the specific weight be distinguished from density.
N/m3
Specific Volume
v

The specific volume of a fluid is the volume occupied by unit mass of fluid.

Thus

(1.5)

m3 /kg
Specific Gravity
s

For liquids, it is the ratio of density of a liquid at actual conditions to the density of pure water at 101 kN/m2 , and at 4°C.

The specific gravity of a gas is the ratio of its density to that of either hydrogen or air at some specified temperature or pressure.

However, there is no general standard; so the conditions must be stated while referring to the specific gravity of a gas.
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