Fluid dynamics or HYDRODYNAMICS for class 11th

This ppt has been made by yuvraj

1. ❖HYDRODYNAMICS
▪Branch of physics which deals with the study of fluid
in motion called fluid dynamics or hydrodynamics
Yuvi

2. ➢Idal liquid
•A liquid is said to be ideal, if
I.It is incompressible (density remain constant
irrespective of pressure
II. It is NON viscous
III. Its flow is steady, cannot withstand any shearing
stress

3. Streamline flow
Definition of Streamline Flow:
Streamline flow (also calledlaminar flow) is the type of fluid flow in which
the fluid particles move in smooth, regular paths or layers, without crossing
each other
1.Examples:
1.Flow of oil in a thin tube
2.Flow of blood in capillaries
3.Motion of honey or glycerin

4. ❑Properties of streamlines
(i)In streamline flow, no two streamlines can cross each
other. If they do so, the particles of the liquid at the
point of intersection will have two different directions
for their
(ii)flow, which will destroy the steady nature of the liquid
flow. (ii) The greater is the crowding of streamline at a
place greater is the velocity of the liquid particles at
that place and vice-versa.

5. Turbulent flow
Turbulent flow is the type of fluid motion in which the particles of
the fluid move inirregular, random, and chaotic paths, mixing
with each other. Unlike streamline (laminar) flow, it does not have
smooth layers.
Examples of Turbulent Flow:
•Flow of river water during floods
•Smoke rising from a chimney
•Flow of air around fast-moving
vehicles or airplanes
•Ocean currents

7. ➢Viscosity
Viscosity (η):
Viscosity is the property of a fluid (liquid or gas) that opposes the relative
motion between its layers.
It is basically the internal friction of the fluid
Everyday Examples of Viscosity:
•Honey flows more slowly than water because
honey has higher viscosity.
•Engine oils are designed with proper viscosity for
smooth lubrication.
•Air resistance is also due to viscosity of air

8. ❑ Viscosity

9. ✓Cause of viscosity
2. Molecular Motion / Momentum Transfer
•Ingases, viscosity is mainly due torandom molecular motion.
•Gas molecules moving between layers carry momentum from one layer
to another, creating resistance to flow.
•So, unlike liquids, viscosity in gases increases with temperature (more
collisions).
1. Intermolecular Forces
• Inliquids, strongcohesive forces(attractive forces between
molecules] resist the relative motion of layers.
• The stronger the intermolecular forces → thehigher the viscosity.
•Example: Honey > Water because honey molecules attract each
other more strongly.

10. •η is coefficient of viscosity of
liquid

11. ➢Viscosity

13. ❖Viscosity and non-viscosity
❑viscosity ❑non-viscosity

14. Stoke`s law
Its states that the backward dragging force acting on a spherical
body of radius `r` moving with velocity `v` through a fluid of viscosity
`n` is

15. ❑Stoke`s law
Figure

16. Figure

17. ❖Application of stokes` law
1. Determination of viscosity of liquids
•Using Stokes’ method: A small spherical ball is dropped in a
viscous liquid. By measuring its terminal velocity, we can
calculate the viscosity of the liquid.
2. Raindrops falling through air
•Stokes’ law explains why raindrops do not keep accelerating
indefinitely.
•Due to viscous drag, they quickly attainterminal velocity, so they
fall at a steady speed (instead of hitting us at very high speeds)

18. ❖Application of stokes` law
3. Settling of particles in liquids
•Used insedimentation process(e.g., separating cream from
milk, or in wastewater treatment).
•Heavier particles settle faster than lighter ones because terminal
velocity depends on particle size and density
4.Blood flow in capillaries
•Motion of red blood cells in plasma (a viscous medium)
follows Stokes’ law at low Reynolds number

19. ❑Terminal velocity
The maximum constant velocity acquired by a body while
falling through a viscous fluid is called its terminal velocity

20. ➢Equation of continuity
Equation of Continuity
The equation of continuity is a fundamental principle of
fluid dynamics. It expresses the conservation of mass for
an incompressible fluid in steady flow
Where:
•A1,A2A1​,A2​= cross-sectional areas of the pipe at two points
•v1,v2v1​,v2​= fluid velocities at those points

21. Meaning
•If the pipe becomesnarrow, velocity increases.
•If the pipe becomeswider, velocity decreases
➢Equation of continuity

22. ❑Step by step prove of equation of continuity

24. ❑example

25. ❖Different energy of flowing liquid
•There are three type of energies in a flowing
liquid
1.Kinetic Energy (KE)
2. Potential Energy (PE)
3.Pressure Energy

26. 1.Kinetic Energy (KE)
•Due to the motion of the liquid.
•Per unit volume:

27. 2.Potential Energy (PE)
•Due to the height of liquid (position in a
gravitational field).
•Per unit volume:

28. 3.Pressure Energy
•Due to the pressure exerted by surrounding fluid.
•Per unit volume:

29. Bernoulli’s Theorem
•Bernoulli’s theorem is based onlaw of conservation of
energyapplied to a flowing incompressible, non-
viscous fluid in streamline flow.
Statement
For a liquid in streamline flow, thesum of Pressure energy,
Kinetic energy, and Potential energy per unit volume
remains constantat every point along a streamline.

30. ❑Mathematical Form

31. Limitations of Bernoulli’s Theorem
1.Ideal Fluid Assumption
1.It is valid only forideal fluids(incompressible, non-viscous, no
internal friction).
2.Real fluids (like water, oil, air) have viscosity, so energy is lost as
heat.
2.Steady / Streamline Flow Only
1.It applies only tosteady or streamline flow, not to turbulent
flow.
3.No Viscous Losses
1.It ignores the loss of energy due to viscosity (internal friction) of
liquid.