a complete description of types of fluids and its flow pattern

1. Fluids, Types of Fluids, and its
Flow Pattern
Presenters
•Ameer Muawiya (011)
•Ch Waqar Ahmed (013)
•M Saud Khalid (036)
•Faizan Ahmad (029)
•Bilal Azam (038)
•Saqib Suleman (041)

2. What are Fluids?
• Any thing that can be flow is known as
Fluids. It has no definite shape of its own. It
assumes the shape of its container.
• Actually there are two types of Fluids.
1. Liquid Fluids
2. Gasses Fluids

3. Definition of Flow
• Flow is defined as the quantity of fluid (gas,
liquid, vapour or sublimate) that passes a
point per unit time.
• A simple equation to represent this is:
Flow (F) = Quantity (Q)
Time (t)
• Flow is sometimes written as ∆Q (rate of
change of a quantity).

4. Viscosity
• Viscosity of a fluid is the measure of its
resistance to flow.
• It is the frictional effect between different
layers of a flowing fluid.
• It measures that how much force is required
to slide one layer of the liquid over another
layer.

5. Examples
• Substances like honey and thick tar have
large coefficient of viscosity. So they cannot
flow easily.
• Substance like water and milk has small
coefficient of viscosity . So they can flow
easily.

6. Units of Viscosity
• The SI unit of coefficient of viscosity is
kgm-1s-1 or Nm-2s
• Its dimension is [ML-1T-1].

7. Viscosity of Liquids and Gasses
• Liquids and gases have non -zero, viscosity.
• Viscosity of gases increases with increase in
temperature while that of solids and liquids
decreases.

8. Types of Fluids
Fluids can be classified into four basic types,
they are:
1. Ideal Fluid
2. Real Fluid
3. Newtonian Fluid
4. Non-Newtonian Fluid

9. 1. Ideal Fluid:
An Ideal Fluid is a fluid that has no viscosity.
It is incompressible in nature. Practically,
no ideal fluid exists.
2. Real Fluid:
Real fluids are compressible in nature. They
have some viscosity.
Examples: Kerosene, Petrol, Castor oil

10. 3. Newtonian Fluid:
Fluids that obey Newton’s law of viscosity are
known as Newtonian Fluids. For a
Newtonian fluid, viscosity is entirely
dependent upon
the temperature and pressure of the fluid.
Examples: water, air, emulsions

11. 4. Non-Newtonian Fluid:
Fluids that do not obey Newton’s law of
viscosity are non-Newtonian fluids.
Examples: Flubbed, Oobleck (suspension of
starch in water)

12. Flow pattern of Fluids

14. Types of Flow Pattern of Fluids
 Fluids can move or flow in many ways.
• Water may flow smoothly and slowly in a
quiet stream or violently over a waterfall.
• The air may form a gentle breeze or a
raging tornado.
• To deal with such diversity, it helps to
identify some of the basic types of fluid
flow.

15. Steady or Unsteady Fluid Flow
•In steady flow the velocity of the fluid particles at
any point is constant as time passes.
•Unsteady flow exists whenever the velocity at a
point in the fluid changes as time passes.

16. Turbulent Flow
•Turbulent flow is an extreme kind of
unsteady flow and occurs when there
are sharp obstacles or bends in the path
of a fast-moving fluid.
•In turbulent flow, the velocity at a
point changes erratically from moment
to moment, both in magnitude and
direction.

17. Compressible or
Incompressible Fluid Flow
Most liquids are nearly incompressible; that is, the density of a
liquid remains almost constant as the pressure changes.
To a good approximation, then, liquids flow in an
incompressible manner.
In contrast, gases are highly compressible. However, there are
situations in which the density of a flowing gas remains
constant enough that the flow can be considered
incompressible.

18. Viscous or Non-viscous Fluid Flow
•A viscous fluid, such as honey, does not flow readily and is
said to have a large viscosity.
•In contrast, water is less viscous and flows more readily;
water has a smaller viscosity than honey.
•The flow of a viscous fluid is an energy-dissipating process.
•A fluid with zero viscosity flows in an unhindered manner
with no dissipation of energy.
•Although no real fluid has zero viscosity at normal
temperatures, some fluids have negligibly small viscosities.
•An incompressible, nonviscous fluid is called an ideal fluid.

19. Streamline Flow
•When the flow is steady, streamlines are often used to represent
the trajectories of the fluid particles.
•A streamline is a line drawn in the fluid such that a tangent to the
streamline at any point is parallel to the fluid velocity at that point.
•Steady flow is often called streamline flow.

20. (a) In the steady flow of a liquid, a colored dye reveals the
streamlines. (b) A smoke streamer reveals a streamline
pattern for the air flowing around this pursuit cyclist, as he
tests his bike for wind resistance in a wind tunnel.

21. Flow Pattern with Baffles

22. Agitated Vessels with baffle
Round bottom to eliminate corners where fluid
cannot penetrate
Impeller is mounted on a shaft
Shaft driven by a motor
Baffles to reduce tangential motion of fluid

23. Design of an Agitated Vessel

24. Impellers
• 2 types
1. Generate currents parallel with the
axis of impeller shaft  Axial-flow
impeller
2. Generate currents in a radial or
tangential direction Radial flow
impellers
• Axial flow impellers impose basically
bulk motion, and are used in
homogenization processes
• Radial flow impellers impose shear
stress to the fluid, and are used to mix
immiscible liquids
• Axial is in left and Radial is in right
side.

25. High Efficiency Impellers
• High efficiency impellers are
designed to produce more uniform
axial flow and better mixing
• It Reduces power requirements
• In high efficiency impellers, blades
are sometimes folded to decrease the
blade angle near tip
• It is used to mix low to moderate
viscosity liquids but not for very
viscous liquids or dispersing gases.

26. Propeller
• Axial flow, high speed impeller is used for liquids of
low viscosity
• Its rotation forces liquid downward until deflected
by the floor vessel
• Propeller blades cut or shear the liquid
• Produces a helix in the fluid

27. Flow patterns in Baffled (Agitated) Vessels
Depends upon
• Type of impeller
• Characteristics of the liquid (esp viscosity)
• Size and proportions of the tank, baffles and the
impeller

28. Flow patterns in agitated vessels– Axial
flow impellers
• When swirling or spinning is stopped; flow patterns
depends on the type of impeller
• Propeller agitators drive the liquid down to the bottom
of the tank, where stream spreads radially in all
directions toward the wall and flows upward along the
wall and returns to the suction of the propeller from top.
– For keeping solid particles in suspensions
• Axial flow impellers change their flow pattern from
axial flow at low liq viscosity to radial at high viscosity.

29. Flow patterns in agitated vessels– flat blade
turbines
• Flat blade turbines give good radial flow
• Stream moves at the wall and divides
• One portion flows downward along the wall and
back to the center of the impeller from below
• Another portion flows upward toward the surface
and back to impeller from above