Definition, Characteristics, Types of Fluids

DEFINITION OF FLUIDS

Fluid is a substance which is capable of flowing. It may be in the form of liquid or vapour or gas. It has no definite shape, but it takes the shape of the container (or) vessel. 

1. Characteristics of the fluids

✓ It is capable of flowing

✓ It flows under its own weight

✓ It has no definite shape but conforms to the shape of the containing vessel

✓ A fluid in equilibrium cannot sustain any shear

✓ Shear stresses occurs in fluids only when they are in motion

2. Types of fluids

A fluid may be divided into three types, they are as follows:

a) Liquids:

Liquids have definite volume and high specific mass. Ex: Water, Oil, Petrol etc 

b) Gases:

Gases have no definite volume and low specific mass. It is compressible. It occupies the entire volume of the container. Ex: air, oxygen, nitrogen etc

c) Vapour:

Vapour is a form of gas whose temperature and pressure are very near to the liquid state. 

Ex: Steam, ammonia

The following figure 1.1 shows the volume & shape of the solid, liquid and gas containing vessel.