1. Fluid Dynamics Grow More Faculty of Engineering , Himatnagar
GUJARAT TECHNOLOGICAL UNIVERSITY
Chandkheda, Ahmedabad
Grow More Faculty of Engineering , Himatnagar
A PPT On
Sub : FLUID MECHANICS( )
Fluid Dynamics
(Branch : Civil Engineering)
Submitted By:
Gadhavi Bhagyashree S ( )
Patel Dhara H ( )
Patel Jinal R ( )

2. Objectives
II. FLUID MECHANICS AND THERMAL PHYSICS
A. Fluid Mechanics
1. Hydrostatic pressure
Students should understand the concept of pressure as it applies to fluids, so they can:
a) Apply the relationship between pressure, force, and area.
b) Apply the principle that a fluid exerts pressure in all directions.
c) Apply the principle that a fluid at rest exerts pressure perpendicular to any surface that it contacts.

3. Fluid mechanics, cont.
d) Determine locations of equal pressure in a fluid.
e) Determine the values of absolute and gauge pressure for a particular situation.
f) Apply the relationship between pressure and depth in a liquid, DP = r g Dh

4. Fluid Mechanics, cont. 2. Buoyancy
Students should understand the concept of buoyancy, so they can:
a) Determine the forces on an object immersed partly or completely in a liquid.
b) Apply Archimedes’ principle to determine buoyant forces and densities of solids and liquids.

5. Fluid Mechanics, cont. 3. Fluid flow continuity
Students should understand the equation of continuity so that they can apply it to
fluids in motion.
4. Bernoulli’s equation
Students should understand Bernoulli’s equation so that they can apply it to fluids in motion.

6. Unit Plan Read Chapter 10.1-10 re Fluid Mechanics in Giancoli
Assignment:
Q/4,7,11
P/5,6,11,12,14,16,25,33,35,
and 44,46,48

7. 10.1&2 Density & Specific Gravity
The mass density  of a substance is the mass of the substance divided by the volume it occupies:
unit: kg/m3
r for aluminum 2700 kg/m3 or 2.70 g/cm3
mass can be written as m = rV and
weight as mg = rVg
Specific Gravity: r substance / r water

8. Problem 10.5
5. (II) A bottle has a mass of g when empty and g when filled with water. When filled with another fluid, the mass is g. What is the specific gravity of this other fluid?
Take the ratio of the density of the fluid to that of water, noting that the same volume is used for both liquids.
SGfluid

9. A fluid - a substance that flows and conforms to the boundaries of its container.
A fluid could be a gas or a liquid; however on the AP Physics B exam fluids are typically liquids which are constant in density.

10. An ideal fluid is assumed
to be incompressible (so that its density does not change),
to flow at a steady rate,
to be nonviscous (no friction between the fluid and the container through which it is flowing), and
flows irrotationally (no swirls or eddies).

11. 10.3 Pressure
Any fluid can exert a force perpendicular to its surface on the walls of its container. The force is described in terms of the pressure it exerts, or force per unit area:
Units: N/m2 or Pa (1 Pascal*)
dynes/cm2 or PSI (lb/in2)
1 atm = x 105 Pa or 15 lbs/in2
*One atmosphere is the pressure exerted on us every day by the earth’s atmosphere.

12. The pressure is the same in every direction in a fluid at a given depth.
Pressure varies with depth. 
P = F = rAhg so P = rgh
A A

13. A FLUID AT REST EXERTS PRESSURE PERPENDICULAR TO ANY SURFACE THAT IT CONTACTS. THERE IS NO PARALLEL COMPONENT THAT WOULD CAUSE A FLUID AT REST TO FLOW.

14. PROBLEM 10-9
(I) (a) Calculate the total force of the atmosphere acting on the top of a table that measures
(b) What is the total force acting upward on the underside of the table?
9. (a) The total force of the atmosphere on the table will be the air pressure times the area of the table.
(b) Since the atmospheric pressure is the same on the underside of the table (the height difference is minimal), the upward force of air pressure is the same as the downward force of air on the top of the table,

15. 10.4 Atmospheric Pressure and Gauge Pressure
The pressure p1 on the surface of the water is 1 atm, or x 105 Pa. If we go down to a depth h below the surface, the pressure becomes greater by the product of the density of the water , the acceleration due to gravity g, and the depth h. Thus the pressure p2 at this depth is h p2 p1

16. In this case, p2 is called the absolute pressure -- the total static pressure at a certain depth in a fluid, including the pressure at the surface of the fluid
The difference in pressure between the surface and the depth h is gauge pressure
Note that the pressure at any depth does not depend of the shape of the container, only the pressure at some reference level (like the surface) and the vertical distance below that level. h p2 p1

17. 14.(II) (a) What are the total force and the absolute pressure on the bottom of a swimming pool 22.0 m by 8.5 m whose uniform depth is 2.0 m? (b) What will be the pressure against the side of the pool near the bottom?
(a)The absolute pressure is given by Eq. 10-3c, and the total force is the absolute pressure times the area of the bottom of the pool.

18. (b) The pressure against the side of the pool, near the bottom, will be the same as the pressure at the
bottom,

19. 10.5 Pascal’s Principle
Pascal’s Principle - if an external pressure is applied to a confined fluid, the pressure at every point within the fluid increases by that amount. Applications: hydraulic lift and brakes
Pout = Pin
And since P = F/a
Fout = Fin
Aout Ain
Mechanical Advantage:
Fout = Aout
Fin Ain

20. Problem 10-10
10.(II) In a movie, Tarzan evades his captors by hiding underwater for many minutes while breathing through a long, thin reed. Assuming the maximum pressure difference his lungs can manage and still breathe is calculate the deepest he could have been. (See page 261.)
10.The pressure difference on the lungs is the pressure change from the depth of water

21. 10-7 Buoyancy and Archimedes’ Principle
This is an object submerged in a fluid. There is a net force on the object because the pressures at the top and bottom of it are different.
The buoyant force is found to be the upward force on the same volume of water:

22. 10-7 Buoyancy and Archimedes’ Principle
The net force on the object is then the difference between the buoyant force and the gravitational force.

23. 10-7 Buoyancy and Archimedes’ Principle
If the object’s density is less than that of water, there will be an upward net force on it, and it will rise until it is partially out of the water.

24. 10-7 Buoyancy and Archimedes’ Principle
For a floating object, the fraction that is submerged is given by the ratio of the object’s density to that of the fluid.

25. 10-7 Buoyancy and Archimedes’ Principle
This principle also works in the air; this is why hot-air and helium balloons rise.

26. 10-8 Fluids in Motion; Flow Rate and the Equation of Continuity
If the flow of a fluid is smooth, it is called streamline or laminar flow (a).
Above a certain speed, the flow becomes turbulent (b). Turbulent flow has eddies; the viscosity of the fluid is much greater when eddies are present.

27. 10-8 Fluids in Motion; Flow Rate and the 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:
(10-4a)

28. 10-8 Fluids in Motion; Flow Rate and the Equation of Continuity
If the density doesn’t change – typical for liquids – this simplifies to Where the pipe is wider, the flow is slower.

29. 10-9 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.

30. Visit the follow website from Boston University
For more information about (choose from left panel)
Pressure; Fluid Statics
Fluid Dynamics
Viscosity