This document provides an overview of fluid mechanics, focusing on viscosity and its role in shear stress and shear strain. It distinguishes between Newtonian and non-Newtonian fluids, highlighting examples such as water and blood. The document also includes details on the units and dimensions of viscosity.

1. Basics of Fluid
Mechanics
Let the fun begin…

2. VISCOSITY
.


VISCOSITY
dy
du



dy
du

 Constant of proportionality = dynamic viscosity


•VISCOSITRate of shear strain=Rate of shear deformation = Velocity gradient

dy
du

3. Viscosity
Rate of shear strain
= Rate of shear deformation
= Velocity gradient
Constant of proportionality
= dynamic viscosity
 dy
du

 Newton’s law of viscosity
Water, air, mercury etc. is called Newtonian fluid.
The fluid which does not obey Newton’s law of viscosity, is called Non-
Newtonian fluid, i.e., blood, paint slurry etc.
Note: Frictional force comes due to shear stress which comes from viscosity or viscous
force.
Note: Shear stress is zero does not mean that there is no velocity. If both the fluid
layers are moving same speed then shear stress between the two layers will be zero.
Units of viscosity
M, L, T are basic dimensions.
Or,
SI unit, or Kg/ms.
CGS unit, or Poise.
1 centipoise (CP) =1 Poise/100
10 Poise =1 NS/m2.
 
1
1
1
2
2
1
2
/






















 T
ML
T
L
MLT
T
FL
dy
du


2
2



 FTL
length
time
Force

2
/ m
NS

2
/ cm
dyneS
