FLUID AND TYPES OF FLUIDS CLASSIFICATION OF FLUIDS

 FLUID AND TYPES OF FLUIDS

FLUID- 

• substance in liquid or Gaseous phase is called fluid. 
• They are capable of deforming continuously under the action of shear stress

                 

                                        

  Types Of Fluids 

1. Ideal Fluid -   

•  A fluid is said to be ideal fluid ,which is incompressible and is having no viscosity, is known as an ideal fluid . 
• Ideal fluid is only an imaginary fluid as all the fluids, which exist, have some viscosity.

Surface tension =0 

Bulk modulus = infinity

 

 2.  Real fluid -

• A fluid is said to be real fluid ,which possesses viscosity, is known as real fluid . All the fluid in actual practice are real fluids . 

 (a)  Highly viscous fluid = bitumen ,honey etc.

(b) Least viscous fluid = Water, blood etc.

         

   Honey      bitumen      Blood         water

                                                               

3. NEWTONIAN AND NON-NEWTONIAN FLUIDS

i) Newtonian fluid -: 

Real fluid in which Shear stress is directly proportional to the rate of shear strain or velocity gradient, is known as Newtonian Fluid.

                               τ =μ(du/dy)

   Example - water, Glycerine, Alcohol.

   

       Water        Glycerine       Alcohol

ii) Non-NewtonianFluid -:

Real fluid, in which shear stress is not directly proportional to the rate of shear strain or velocity gradient, is known as Non-Newtonian Fluid.

                               τ = A(du/dy)^n+B

         Where  A  = Apparent viscosity

                       B= initial yield stress

Note - Ideal plastic fluid, Dilatant fluid, Pseudoplastic fluid, Thixotropic fluid & Rheopactic fluid are the types of Non-Newtonian fluid.

a) Ideal plastic fluid -:

A fluid is to be ideal plastic fluid, in which the shear stress is more than yield and shear stress is proportional to the rate of shear strain or velocity gradient is known as ideal plastic fluid.

Example -: clay suspension , chocolate, toothpaste.

 

Chocolate.         Thoothpaste

b) Dilatant fluid -:

In Dilatant fluid Apparent viscosity increased with Shear rate ( du/dy).

                     τ =  A(du/dy)^n +B

When apparent viscosity increase n>1

When apparent viscosity decrease n<1

In this fluid yield stress is not required B=0

Example -: Sugar in water, butter, sand, starch.

  

Butter             Sand

c) Pseudoplastic fluid -:

Fluid In which apparent viscosity is decreased with shear rate.This fluid is also known as shear thinning fluids .

           τ = u (du/dy ) ^n<1

Example- Milk, Paint, Gelatin, Blood.

   

 Paint              Milk               Blood

d) Thixotropic fluid -:

A fluid is said to be an thixotropic fluid ,in which the microstructure break and viscosity increase with time is known as  thixotropic fluid .

This fluid is also known as time dependent fluid . 

Example- Printer ink , Enamels.

 

Enamels

e) Rheopactic fluid -:

 A fluid in which the viscosity decrease with time dependent is known as rheopectic fluid .

 Example- Gypsum paste, Lubricants.

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Read also :

          Surface tension and Capillarity effects

          

           Properties of fluids

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