materi fisika aplikasi

1. Fisika Aplikasi
Konsep Dasar Pergerakan Fluida

2. Konsep Dasar Pergerakan Fluida
• Various types of fluid motion
• Stream lines
• Persamaan Kontinuitas (Continuity Equation)
• Persamaan Bernoulli (Bernoulli Equation)

3. Various types of fluid motion
• Laminar
• Transition
• Turbulent
• steady (constant velocity at any point) and unsteady
• uniform (flow parameter remains constant) and non-uniform

4. Laminar
A type of flow in which fluid particles move along a well-defined path
or flow, and all streamlines are straight and parallel.

5. Transition
• the process of a laminar flow becoming turbulent .
• 𝑅𝑒𝑦𝑛𝑜𝑙𝑑 𝑛𝑢𝑚𝑏𝑒𝑟 =
𝑑𝑒𝑛𝑠𝑖𝑡𝑎𝑠 .𝑣𝑜𝑙𝑢𝑚𝑒 .𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟
𝑣𝑖𝑠𝑘𝑜𝑠𝑖𝑡𝑎𝑠
• <2000: laminar
• 2000-2300: transition
• >2300: turbulent

6. Turbulent
The type of flow in which fluid particles move in a zigzag manner.

9. Stream lines
• In fluid mechanics, the path of imaginary particles suspended in the
fluid and carried along with it.
• In steady flow, the fluid is in motion but the streamlines are fixed.

10. • A line in the fluid whose tangent is parallel to at a given instant t.
• The family of streamlines at time t are solutions of
• Where are velocity components in the respective
direction
u

)
,
(
)
,
(
)
,
( t
r
u
dz
t
r
u
dy
t
r
u
dx
z
y
x


 

z
y
x u
and
u
u



,
,

11. Pathline
• A line traced by an individual fluid particle :
• For a steady flow the pathlines are identical with the streamlines.
)
(t
r


13. Equation of Continuity
We will deal with laminar flow.
The mass flow rate is the mass that passes a given point per unit time.
The flow rates at any two points must be equal, as long as no fluid is
being added or taken away.
This gives us the equation of continuity:
© 2014 Pearson Education, Inc.
(10-4a)

14. Equation of Continuity
If the density doesn’t change—typical for liquids—this simplifies to A1v1 =
A2v2. Where the pipe is wider, the flow is slower.
© 2014 Pearson Education, Inc.

15. Flow Rate
• Volume of fluid/unit time
• Rate = Area x speed of fluid
• R = Av
• A fluid is pumped into a pipe at a flow rate of 80cm3/s. If the
diameter of the pipe is 1.4cm, what is the average speed of the fluid
at this point?

16. Making Fluids Flow Faster
• Pump it faster
• Pinch the hose or make the pipe smaller

17. Example
• The radius of a fluid-carrying pipe at a certain point is 2.0cm and the
average speed of the fluid is 14cm/s. What is the average speed of
the fluid at a point where the radius is only 1.3cm?

18. Bernoulli’s Equation
A fluid can also change its height. By
looking at the work done as it moves, we
find:
This is Bernoulli’s equation. One thing it
tells us is that as the speed goes up, the
pressure goes down.
© 2014 Pearson Education, Inc.
(10-5)

19. Applications of Bernoulli’s Principle:
Airplanes
Lift on an airplane wing is due to the different air speeds and pressures
on the two surfaces of the wing.
© 2014 Pearson Education, Inc.

20. Applications of Bernoulli’s Principle:
Blood Flow
A person with constricted
arteries will find that they may
experience a temporary lack of
blood to the brain as blood
speeds up to get past the
constriction, thereby reducing
the pressure.
© 2014 Pearson Education, Inc.

21. Applications of Bernoulli’s Principle
A venturi meter can be used to measure fluid flow by measuring pressure
differences.
© 2014 Pearson Education, Inc.

22. Applications of Bernoulli’s Principle
Air flow across the top helps smoke go up a chimney, and air flow over
multiple openings can provide the needed circulation in underground
burrows.
© 2014 Pearson Education, Inc.

23. Example
• Water whose density is 1000kg/m3flows through a pipe with a flow
rate of 0.80m3/s. The cross sectional area of the pipe is initially
0.25m2 and the pressure is 5.2Pa. The cross sectional area of the pipe
becomes 0.40m2, what is the new pressure of the fluid.

24. Example
• Ethyl alcohol (ρ = 810kg/m3) has a flow rate of 0.24m3/s through a
pipe whose cross sectional area is 0.060m2 and in which the pressure
is 9.5x104Pa. The centerline of the pipes rises 4.0m and the area is
reduced to 0.020m2. What is the fluid pressure in the elevated pipe?