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Ch_2_(34-68).pdf

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2

CHAPTER

2.1

PRESSURE AND ITS

MEASUREMENT

FLUID PRESSURE AT A POINT

Consider a small area dA in large mass of fluid. If the fluid is stationary, then the force exerted by the surrounding fluid on the area dA will always be perpendicular to the surface dA. Let dF is the force dF is known as the intensity of acting on the area dA in the normal direction. Then the ratio of dA pressure or simply pressure and this ratio is represented by p. Hence mathematically the pressure at a point in a fluid at rest is dF

. dA

If the force (F) is uniformly distributed over the area (A), then pressure at any point is given by

p =

F

Force

=

.

A

Area

\ Force or pressure force, F = p ¥ A.

The units of pressure are : (i) kgf/m2 and kgf/cm 2 in MKS units, (ii) Newton/m 2 or N/m 2 and

N/mm2 in SI units. N/m2 is known as Pascal and is represented by Pa. Other commonly used units of pressure are : kPa = kilo pascal = 1000 N/m2 bar = 100 kPa = 105 N/m2.

p =

2.2 PASCAL'S LAW

It states that the pressure or intensity of pressure at a point in a static fluid is equal in all directions. This is proved as :

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Ch_17_(803-852).pdf

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17

CHAPTER

17.1

IMPACT OF JETS AND

JET PROPULSION

INTRODUCTION

The liquid comes out in the form of a jet from the outlet of a nozzle, which is fitted to a pipe through which the liquid is flowing under pressure. If some plate, which may be fixed or moving, is placed in the path of the jet, a force is exerted by the jet on the plate. This force is obtained from

Newton’s second law of motion or from impulse-momentum equation. Thus impact of jet means the force exerted by the jet on a plate which may be stationary or moving. In this chapter, the following cases of the impact of jet i.e., the force exerted by the jet on a plate, will be considered :

1. Force exerted by the jet on a stationary plate when

(a) Plate is vertical to the jet, (b) Plate is inclined to the jet, and (c) Plate is curved.

2. Force exerted by the jet on a moving plate, when

(a) Plate is vertical to the jet, (b) Plate is inclined to the jet, and (c) Plate is curved.

17.2

FORCE EXERTED BY THE JET ON A STATIONARY VERTICAL PLATE

Consider a jet of water coming out from the nozzle, strikes a flat vertical plate as shown in Fig. 17.1

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Ch_21_(1041_1061).pdf

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21

FLUID SYSTEM

CHAPTER

21.1

INTRODUCTION

Fluid system is defined as the device in which power is transmitted with the help of a fluid which may be liquid (water or oil) or a gas (air) under pressure. Most of these devices are based on the principles of fluid statics and fluid kinematics. In this chapter, the following devices will be discussed:

1. The hydraulic press,

2. The hydraulic accumulator,

3. The hydraulic intensifier,

4. The hydraulic ram,

5. The hydraulic lift,

6. The hydraulic crane,

7. The fluid or hydraulic coupling,

8. The fluid or hydraulic torque converter,

9. The air lift pump, and

10. The gear-wheel pump.

21.2

THE HYDRAULIC PRESS

The hydraulic press is a device used for lifting heavy weights by the application of a much smaller force. It is based on Pascal’s law, which states that the intensity of pressure in a static fluid is transmitted equally in all directions.

The hydraulic press consists of two cylinders of different diameters. One of the cylinder is of large diameter and contains a ram, while the other cylinder is of smaller diameter and contains a plunger as shown in Fig. 21.1. The two cylinders are connected by a pipe. The cylinders and pipe contain a liquid through which pressure is transmitted.

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Ch_4_(131-162).pdf

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4

CHAPTER

4.1

BUOYANCY AND

FLOATATION

INTRODUCTION

In this chapter, the equilibrium of the floating and sub-merged bodies will be considered. Thus the chapter will include : 1. Buoyancy, 2. Centre of buoyancy, 3. Metacentre, 4. Metacentric height,

5. Analytical method for determining metacentric height, 6. Conditions of equilibrium of a floating and sub-merged body, and 7. Experimental method for metacentric height.

4.2 BUOYANCY

When a body is immersed in a fluid, an upward force is exerted by the fluid on the body. This upward force is equal to the weight of the fluid displaced by the body and is called the force of buoyancy or simply buoyancy.

4.3

CENTRE OF BUOYANCY

It is defined as the point, through which the force of buoyancy is supposed to act. As the force of buoyancy is a vertical force and is equal to the weight of the fluid displaced by the body, the centre of buoyancy will be the centre of gravity of the fluid displaced.

Problem 4.1 Find the volume of the water displaced and position of centre of buoyancy for a wooden block of width 2.5 m and of depth 1.5 m, when it floats horizontally in water. The density of wooden block is 650 kg/m3 and its length 6.0 m.

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Ch_5_(163-258).pdf

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5

CHAPTER

KINEMATICS OF FLOW

AND IDEAL FLOW

A. KINEMATICS OF FLOW

5.1

INTRODUCTION

Kinematics is defined as that branch of science which deals with motion of particles without considering the forces causing the motion. The velocity at any point in a flow field at any time is studied in this branch of fluid mechanics. Once the velocity is known, then the pressure distribution and hence forces acting on the fluid can be determined. In this chapter, the methods of determining velocity and acceleration are discussed.

5.2 METHODS OF DESCRIBING FLUID MOTION

The fluid motion is described by two methods. They are —(i) Lagrangian Method, and (ii) Eulerian

Method. In the Lagrangian method, a single fluid particle is followed during its motion and its velocity, acceleration, density, etc., are described. In case of Eulerian method, the velocity, acceleration, pressure, density etc., are described at a point in flow field. The Eulerian method is commonly used in fluid mechanics.

5.3

TYPES OF FLUID FLOW

The fluid flow is classified as :

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