### Viscosity : Flow Measurement - The Incredible Truth

#
VISCOSITY : Flow Measurement

All we know
about the friction force. When the term friction comes in a fluid, then it is
called viscosity. Viscosity of a fluid is basically friction between the fluid
and a surface. The viscosity of a fluid is the measure of its resistance to gradual
deformation by shear stress and tensile stress. For liquids, the viscosity
depends mainly on the thickness: for example butter has more viscosity than
water.

Viscosity
is a physical property of a fluid which resists the fluid to flow upon a
surface that is moving at different velocities. In simple words, the viscosity
means friction between the molecules of fluid and the particles of the surface.

We will
discuss here the viscosity based upon the flow rate measurement.

**there are two types of viscosity. Such as Absolute viscosity and Kinetic viscosity.**

*Types :*#
Absolute Viscosity (µ):

Absolute
viscosity or the Dynamic viscosity of a fluid is the measurement of the fluid’s
internal resistance to flow.

Mathematically,

F ∝ V

F ∝ A

F ∝ 1/d

So,

F ∝ VA/d

F = µ VA/d

µ = Property of the liquid and known as
absolute viscosity of the liquid.

Mathematically,

**µ = (Fd)/(VA)**

*Unit,*
µ = Newton . Meter / Meter / Sec . Meter

^{2}
= N.
Sec

^{2}/ m^{2}= Pascal. Sec
1 CST (centistoke) = 10

^{-3 }Pascal. Sec

*NOTE,*
Absolute viscosity is highly temperature
dependent and is different for liquid and gas.

µ

_{Liquid }∝ 1/T
And, µ

_{Gas }∝ T
Where, T is the temperature

µ

_{Liquid }> µ_{Gas }_{}

*Some Cases,*
I)
Absolute viscosity of Water, µ

_{Water }= 1 CST
II)
Absolute viscosity of Water, µ

_{Honey }= 300 CST
III)
Absolute viscosity of Water, µ

_{Butter }= 10,000 CST

*Also,*
F = (µVA)/d

µ = Fd/VA = (F/A)/(V/d)

__µ = Shear stress / Shear rate__

#
Kinematic
Viscosity (v):

The
resistance experienced by the liquid measure when the fluid falls down by the virtue
of gravity.

Liquid with
more density will experience more force and will go down fast.

F = ma = v ρ g

The time taken (t) by the fluid to fall down is inversely proportional
to the density (ρ).

t ∝ 1/ ρ

t ∝ µ

v ∝ µ / ρ

v = c µ / ρ , c is
the proportional constant

When, c = 1

v = µ / ρ

It means,

__Kinematic Viscosity = Absolute Viscosity / density of the fluid__

__Read Also,__**Reynolds number -**http://www.theincredibletruths.com/2018/10/reynolds-number-reynolds-number-is.html

**Specific Gravity - http://www.theincredibletruths.com/2018/09/specific-gravity-industrial.html**

## Comments

## Post a Comment