pressure & head (part-1)

ACTIVE LEARNING ASSIGNMENT PRESENTATIONFLUID MECHANICS (2141906)

TOPIC

PRESSURE & HEAD (PART-1)

PREPARED BYMECHANICAL – 4B2

DEVANSU KHORASIYA (150120119066)

GUIDED BYPROF. SHAIVAL PARIKH

PREPARED BY : DEVANSU KHORASIYA(GIT-150120119066)

INTRODUCTIONSo, Before Starting The Chapter Clear Some Doubts….

This Chapter Deals With Forces Applied By Fluid at Rest. When A Certain Mass of Fluid is held in static Equilibrium by confining Within Solid Boundaries, it exerts forces Against Boundary surfaces.

The Forces Exerted always in The Direction normal to The Surface in The Contact. This is So because a fluid at Rest Cannot Sustain Shear Stress. No Shear Force is Present as Fluid Particles do not Move With Respect To One Another.

Let’s Start The Journey…


First Of All…

What is Pressure ?? Pressure is defined as a normal force exerted by a fluid per

unit area. Pressure is the force per unit area, where the force is

perpendicular to the area. Units of pressure are N/m2, which is called a Pascal (Pa). Since the unit of Pa is too small..! For pressures Encountered

in practice kilopascal (1 KPa = 103 Pa) and megapascal (1 MPa = 106 Pa) are commonly used.

p=A m

2

Nm-2

(Pa)

NF pa= 105 Nm-2

1psi =6895Pa

1 psi = 1 lbf ( 1 in ) 2 ≈ 4.4482 N ( 0.0254 m ) 2 ≈ 6894.757 Nm-2PREPARED BY : DEVANSU KHORASIYA(GIT-

150120119066)

Pressure in a fluid acts equally in all directions.Pressure in a static liquid increases linearly with depth

P= Increase In Depth (M)

Pressure Increase

GH

The pressure at a given depth in a continuous, static body of liquid is constant.

p1 p2

p3 p1 = p2 = p3

A = 2 cm2

1.5 kg2

-4 2

(1.5 kg)(9.8 m/s )2 x 10 m

FPA

P = 73,500 N/m2


Fluid exerts forces in many directions. Try to submerse a rubber ball in water to see that an upward force acts on the ball.

Fluids exert pressure in all directions.

F

Fluid Pressure


Properties of Fluid PressureWater seeks its own level,

indicating that fluid pressure is independent of area and shape of its container.At any depth h below the surface of the water in any column, the pressure P is the same. The shape and area are not factors.The forces exerted by a fluid on the walls of its container

are always perpendicular.The fluid pressure is directly proportional to the depth of

the fluid and to its density.At any particular depth, the fluid pressure is the same in

all directions.Fluid pressure is independent of the shape or area of its

container.PREPARED BY : DEVANSU KHORASIYA(GIT-150120119066)

What is Pressure Head ???In a Static Liquid, Vertical Distance From Datum Line to the Free Surface of Liquid is Known as Pressure Head.

In fluid mechanics, pressure head is the internal energy of a fluid due to the pressure exerted on its container. It may also be called static pressure head or simply static head (but not static head pressure).


What is Pressure at a Point ?Pressure at any point in a fluid is the same in all directions.Pressure has a magnitude, but not a specific direction, and thus it is a scalar quantity.

Scuba Diving and Hydrostatic PressurePREPARED BY : DEVANSU KHORASIYA(GIT-150120119066)

Pressure Variation In A Fluid At Rest; ; mgP m V V Ah

A

Vg AhgPA A

h

mgArea

P = gh

• Pressure at any point in a fluid is directly proportional to the density of the fluid and to the depth in the fluid.


Pascal’s Law

FoutFin AoutAin

Pressure in = Pressure out

in out

in out

F FA A

Pascal’s Law: “An external pressure applied to an enclosed fluid is transmitted uniformly throughout the volume of the liquid.” Or“The Intensity of Pressure at any Point in a Fluid at Rest, is Same in All Directions”


1. Absolute Pressure2. Gage Pressure3. Vacuum Pressure

Types Of Pressure

Absolute PressureAbsolute Pressure: The sum of

the pressure due to a fluid and the pressure due to atmosphere.Gauge Pressure: The difference between the absolute pressure and the pressure due to the atmosphere:

Absolute Pressure = Gauge Pressure + 1 atm

h P = 196 kPa

1 atm = 101.3 kPa


Vacuum Pressure

atm atm h

Mercury

P = 0One way to measure atmospheric pressure is to fill a test tube with mercury, then invert it into a bowl of mercury.Pressure below atmospheric pressure are called vacuum pressure, Pvac=Patm - Pabs.Density of Hg = 13,600 kg/m3

Patm = ghh = 0.760 mPatm = (13,600 kg/m3)(9.8 m/s2)(0.760 m)

Patm = 101,300 Pa

Gage PressureMost pressure-measuring devices are calibrated to

read zero in the atmosphere, and therefore indicate gage pressure, Pgage=Pabs - Patm.


Absolute, Gage, And Vacuum Pressures


Pressure Measurement Pressure is an important variable in fluid

mechanics and many instruments have been devised for its measurement.

Many devices are based on hydrostatics such as barometers and manometers, i.e., determine pressure through measurement of a column (or columns) of a liquid using the pressure variation with elevation equation for an incompressible fluid

Enlarged LegTwo Fluid

Inclined Tube

Inverted U-Tube

U-Tube Manometer


Manometers are used for measuring pressures by balancing the fluid column of fluid against another column of fluid of known specific gravity. Manometers can be classified as:Simple manometers :It consists of a glass tube with one end open to the atmosphere and other end connected to a point at which pressure is to be measured.a. PiezometerIt consists of glass tube connected to a vessel or pipe at which static pressure is to be measured. It is the simplest of all the manometers (Fig. 5.1). It is used to measure very low pressures.The pressure in piezometer is given by the following equation.

Where, = density of liquidh = height of liquid in the piezometer from the centre of the pipe.g = acceleration due to gravity

Fig. Piezometer

b.U-tube manometerThe manometer is named so because it consists of a glass tube having the shape of alphabet ‘U’. One end is open to the atmosphere and other end connected to a point at which pressure is to be measured.


Column ManometerOne of the limbs in double column manometer is converted into a reservoir having large cross sectional area (about 100 times) with respect to the other limb. Fig. shows a vertical single column manometer. Initially, the both limbs of the manometer are exposed to atmospheric pressure. When the left limb with reservoir is connected to container, the liquid pressure of it pushes down the level A1 B1 to A2 B2causing !l h downward movement of liquid in the reservoir.For any variation in pressure, the change in the liquid level in the reservoir will be very small, which may be neglected and hence pressure is given by the height of liquid in the other limb.


http://www.mechanical-engineering-assignment.com/wp-content/uploads/2013/01/1104.png

AT THE LAST…….One Humble Request to all of YOU….

Make sure Your House, School, College, Society, Road, State, Nation, World is Neat and Clean……PREPARED BY : DEVANSU KHORASIYA(GIT-150120119066)

THANK YOU GUYS FOR LISTINING ME……

PRESENTATION & DESIGNED BYDEVANSU KHORASIYA

(150120119066)MY AIM IS….

CLEAN INDIAGREEN INDIA &MAKE IN INDIA.


pressure & head (part-1)

Engineering