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ME 101202 - Fluid Mechanics and Machinery

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Question Bank (Two Marks Questions and Answers)

Year / Sem: II / III

UNIT- I BASIC CONCEPTS AND PROPERTIES

1. Define fluids.Fluid may be defined as a substance which is capable of flowing. It has no definite shape of itsown, but confirms to the shape of the containing vessel.

2. Classify the different types of fluids.i) Ideal and real fluids ii) Newtonian and Non-Newtonian fluids

3. What are the properties of ideal fluid?Ideal fluids have following properties

i) It is incompressible ii) It has zero viscosityiii) Shear force is zero

4. What are the properties of real fluid? (or) What is a real fluid?The fluid which is having the following properties is known as real fluids.

i) It is compressible ii) They are viscous in natureiii) Some resistance is always offered by the fluid when it is in motion

iv) Shear force exists always in such fluids.

5. Why are some fluids classified as Newtonian fluids? Give examples.In Newtonian fluids, a linear relationship exists between the magnitude of shear stress and

resulting rate of deformation.

Example: Water, Kerosene

6. What are Non-Newtonian fluids?In Non-Newtonian fluids, there is a non-linear between the magnitude of shear stress and

resulting rate of deformation.

7. Define density and specific weight.Density is defined as mass per unit volume i.e., mass of the fluid contained in unit volume. It is

also called mass density.

Density,V

m

volume

mass kg/m

3

Specific weight is defined as weight possessed per unit volume. It is varies from place to place

because of change in acceleration due to gravity.

Specific weight,V

W

volume

weightw N/m

3

8. Define Specific volume and Specific Gravity.Specific volume is defined as volume of fluid occupied by unit mass (m3/kg)

Specific volume,m

V

mass

Volumev m

3/kg

Specific gravity is defined as the ratio of specific weight of fluid to the specific weight of

standard fluid.

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Specific gravity,liquidstandardofweightSpecific

liquidofweightSpecificS

9. Define Surface tension and Capillarity.Surface tension is due to the force of cohesion between the liquid particles at the free surface.

Capillary is a phenomenon of rise or fall of liquid surface relative to the adjacent general level

of liquid.

10.Define Viscosity.It is defined as the property of a liquid due to which it offers resistance to the movement of one

layer of liquid over another adjacent layer. (N-s/m2 or kg/m-s)

11.Define kinematic viscosity.It is defined as the ratio of dynamic viscosity to mass density.

i.e.,

m/sec

12.Define dynamic viscosity.The dynamic viscosity is defined as the shear stress required to produce unit rate of shear

deformation.

13.Define Relative or Specific viscosity.It is the ratio of dynamic viscosity of fluid to dynamic viscosity of water at 20C.

Relative of Specific viscosity,C20atwaterofviscosityDynamic

fluidgivenofviscosityDynamic

0

14.What is the effect of temperature on viscosity of water and that of air?When the temperature of water increases, the viscosity will decrease but it will increase with

increase in temperature of air.

15.Define the term absolute temperature.The temperature measured from the absolute zero temperature is called as absolute

temperature.

16.Define Compressibility.It is the property by virtue of which fluids undergoes a change in volume under the action of

external pressure.

17.Define Newtons law of Viscosity.According to Newtons law of viscosity the shear force F acting between two layers of fluid is

proportional to the difference in their velocities du and area A of the plate and inversely

proportional to the distance between them.

18.What is cohesion and adhesion in fluids?Cohesion is due to the force of attraction between the molecules of the same liquid. The inner

molecular attraction holds the liquid molecules together are known as cohesion.

Adhesion is due to the force of attraction between the molecules of two different liquids or

between the molecules of the liquid and molecules of the solid boundary surface. This property

enables a liquid to stick over another body.

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19.What is surface tension?Surface tension is due to the force of cohesion between the liquid particles at the free surface.

20.Write the equation of surface tension of liquid jet, liquid droplet and soap bubble.Surface tension in liquid droplet,

4pd

d4p

Surface tension in Soap Bubble,8

pd

d

8p

Surface tension in liquid jet,2

pd

d

2p

21.Define capillarity.Capillarity is a phenomenon of rise or fall of liquid surface relative to the adjacent general

level of liquid. This phenomenon is due to the combined effect of cohesion and adhesion of

liquid particles. The rise of liquid level is known as capillary rise where as the fall of liquid isknown as capillary depression.

22.What are the parameters depends on magnitude of capillary?The magnitude of capillary is depends upon

i) Diameter of the tubeii) Specific weight of liquidiii) Surface tension of liquid

23.Explain the effect of property of capillarity.This phenomenon is due to the combined effect of cohesion and adhesion of liquid particle. So,

the surface will act around the circumference of the tube.

24.Define the term fluid statics.Fluid statics is the study of a fluid at rest; the concept includes the situation where the fluids

are either actually at rest or undergo uniform acceleration in a container or rotate as a solid

mass.

25.How can we define vacuum pressure?The pressure below the atmospheric pressure is called as vacuum pressure.

26.State Pascal law?The intensity of pressure at any point in a static fluid is equal in all directionsPx= Py=Pz

27.State momentum of momentum equation?It states that the resulting torque acting on a rotating fluid is equal to the rate of change of

moment of momentum

28.What is momentum equation

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It is based on the law of conservation of momentum or on the momentum principle It states

that, the net force acting on a fluid mass is equal to the change in momentum of flow per unittime in that direction.

29 Give the Eulers equation of motion?0dvvdzg

p

dp

30What are the assumptions made in deriving Bernouillies equation?a. The fluid is ideal

b. The flow is steady.c. The flow is incompressible.d. The flow is irrotational.

31State Bernouillies Theorem as applicable to fluid flow.It states that an ideal incompressible fluid when the flow is steady and continuous, the sum of

pressure energy, kinetic energy and potential energy is constant along the streamline

Constantzg2

v

w

p 2

32 What is Bernouillies equation for real fluid?12

2

221

2

11 hzg2

v

gp

pz

g2

v

gp

p

Where, hl - loss of energy, (p/pg) - Pressure energy, (v2/2g) - Kinetic energy and

z - Datum energy

33 State the application of Bernouillies equation? Or Name the three flow measuringinstruments.

It has the application on the following measuring devices.

a. Orifice meter. b.Venturimeter. c.Pitot tube34 What are the assumptions made on Bernoullis equation?

a. The liquid is ideal and incompressibleb. The flow is steady and continuousc. The velocity is uniform over the cross section and is equal to mean velocityd. The only forces acting on the fluids are the gravity force and the pressure forcee.

All the frictional forces are negligible

35 Write down the limitations of Bernoullis equation.a. Velocity of flow across the cross section is assumed to be constant whereas it is not so

in actual practice. The velocity of liquid particle is maximum at the center of the pipe

and gradually decreases towards the wall of the pipe due to pipe friction

b. The equation has been derived under the assumption that no external force, except thegravity force, is acting on the liquid. But in actual practice the force such as pipe

friction is acting on the liquid

c. No loss of energy is assumed. But during turbulent flow, kinetic energy is convertedinto heat energy. Some energy is lost due to shear force in viscous flow. All these

losses are considered.

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36 Why large reduction of diameters from inlet throat is not allowed in venturimeter?Due to large reduction in diameters, the cavitation will occur. It will amaze and corrode the

pipe. So, large reduction of diameters is not allowed.

37 Co-efficient of discharge of venturimeter is always greater than orifice meter, why?Loss of energy due to sudden enlargement is higher than loss of energy due to gradualcontraction. So the coefficient of discharge is greater than orifice meter.

38 Write down the expression for discharge through a venturimeter explaining each term in it.hg2x

aa

axaxCQ

2

2

2

1

21d

a1 - Area of inlet section pipe, a2 - Area of outlet section pipe, h - Manometric head difference,

and g - Acceleration due to gravity

39 Why pressure difference is not measured between throat and exit?In exit portion of the venturimeter the flow separation takes place. So the pressure difference ismeasured between inlet and throat

40 What is venturimeter and explain its basic principles?A venturimeter is a device, which is used for measuring the rate of flow of fluid through pipes.

The basic principle of venturimeter is that by reducing the cross sectional area along the pipe, apressure difference is created from the pressure we can calculate the discharge through the

pipe.

41 What are the various parts in venturimeter?a. Inlet section followed by convergent portion b. Throat partc.Divergent cone followed by outlet section

42 Why convergent portion is smaller than divergent portion?This is because of avoiding flow separation and consequent energy loss in that portion. But

flow separation is occurring in divergent portion and therefore it is not used for flow

measurement

43 What is cavitation in venturimeter and give its effects?Due to reduction in area the velocity of fluids increased and pressure decreased. When pressure

comes below that of vapour pressure of the flowing fluid then the liquid will be vapourized.

This phenomenon is called cavitation.

Effects: Cavitation will very damage the pipe walls and also corrodes the pipes

44 What are the advantages of venturimeter?a. Loss of head is small and hence high Cd value and it may approach unity under

favorable condition

b. No wear and tear c. Less likelihood of becoming clogged with sedimentd. Well-established characteristics

e. Suitable for large flow of water, process fluids, wastes gases and suspended solids

45 What are the disadvantages of venturimeter?a. Long laying length b. More space requirementc. Quit expense in installation and replacement

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d. Possibility of cavitation46 What is orifice meter and explain its basic principles?The orifice meter also a device used for measuring the discharge through pipes. The basic

principle of orifice meter is that by reducing the cross sectional area of the pipe, a pressure

difference is created from the pressure difference. We can calculate the discharge through the

pipes.

47 What are the advantages of orifice meter?a. Low initial cost

b. Ease of installation and replacementc. Requires less space as compared with venturimeterd. Can be used in wide range of pipe sizes (0.01 m to 1.5 m)

48 What are the disadvantages of orifice meter?a. High loss of head

b. Co-efficient of discharge has a low valuec. Susceptible to in accuracies resulting from erosion, corrosion and scaling

UNIT-II FLOW THROUGH CIRCULAR CONDUITS

49 Define fluid kinematics.Fluid kinematics is a science which deals with the geometry of motion in terms of

displacement, velocity and acceleration and their distribution in space without considering any

force or energy involved. Thus kinematics involves only the description of the motion of fluids

in terms of space-time relationship.

50 What stream lines?A streamline is an imaginary line drawn through a flowing fluid in such a way that the tangent

at any point on it indicates the velocity at the point

51Name the different forces present in fluid flow.a. Inertia force b.Viscous force c.Surface tension force d.Gravity force

52 Classify the different types of fluid flow.The fluid flow can be classified in several ways:

a. Steat flow and unsteady flowb.

Uniform and non-uniform flowc. One-dimensional, two-dimensional and three-dimensional flows

d. Rotational and irrational flowe. Laminar and turbulent flowf. Compressible and incompressible flow

53 When in a fluid considered steady? Give an example for steady flowIn steady flow, various characteristics of following fluids such as velocity, pressure, density,

temperature etc at a point do not change with time. So it is called steady flow

Example

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a. Flow of water in a pipeline due to a centrifugal pump run at uniform speedb. Liquid efflux from a vessel in which constant level is maintained

54 When is the flow regarded as unsteady? Give an example for unsteady flow.The various characteristics of following fluids such as velocity, pressure, density, and

temperature etc of a point change with respect to time.

0t

p;0tv

Example

a. Liquid falling under gravity out of an opening in the bottom of a vesselb. Liquid flow in the suction and pressure pipes of a reciprocating pumpc. Wave movements in a sea

55 Define uniform and non-uniform flow.Uniform flow: It is a flow in which the velocity at any given instant does not change both in

magnitude and direction with respect to space. Mathematically 0v

s

Non-uniform flow: The velocity of flow of fluid changes from one point to another point at any

instant. Mathematically 0v

s

56 What are one, two and three-dimensional flows?One-dimensional flow: In this type, various characteristics are function of time and one space

co-ordinate only

Two-dimensional flow: In this type of flow, various characteristics are function of time and

two space (rectangular) co-ordinates only

Three-dimensional flow: In this type of flow, various characteristics are function of time and

three space co-ordinates system

57 Distinguish between rotation and circularity in fluid flow.A rotational flow exists when the fluid particles rotate about their mass centers while moving

along a streamline

Circulation is defined as the flow along a closed curve. Mathematically, the circulation is

defined as the line integral of the tangential velocity about a closed curve.

58 Explain the terms rotational and irrotaional flow. Give examples.A rotational flow exists when the fluid particles rotate about their mass centres, while moving

along a streamline.

Example:i. Liquid in a rotating tank where the velocity varies directly with a distance from centre.ii. Flow near the solid boundaries

An irrotaional flow exists when the fluid particles do not rotate about their mass centres while

moving along a streamline

Example:

i. A vortex or whirlpool, which develops above a drain in the bottom of a stationary tankii. Flow above a drain hole of a washbasin.

59 What is laminar and turbulent flow?

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A laminar flow is one in which the fluid particles move in layer with one layer of fluid sliding

smoothly over an adjacent layerA turbulent flow is one in which the fluid particles move in an entirely haphazard or erratic

manner

60 Mention the general characteristics of laminar flow.a. There is a shear stress between fluid layersb. No slip at the boundaryc. The flow is rotationald. There is a continuous dissipation of energy due to viscous shear

61 What is compressible and incompressible flow?A flow is said to be compressible if the density changes from point to point due to pressure and

temperature. Mathematically constant

A flow is said to be incompressible if the density is constant in flow field

62 What are streamline and path lines?A streamline is an imaginary line drawn through a flowing fluid in such a way that the tangentat any point on it indicates the velocity at that point

A path line is a line that is traced by a single fluid particle as it moves over a period of time.

Path line shows the direction of velocity of the same fluid particles at successive instants of

time

63 Explain the various characteristics of streamline.a. Streamlines do not cross to each other

b. There cannot be any movement of fluid mass across the streamlinesc. For steady flow the streamline pattern remains the same at different timesd. Streamline spacing varies inversely as the velocitye. The series of streamlines represent the flow pattern at an instant

64 What is stream tube?A stream tube is tube imagined to be formed by a group of neighboring streamlines passing

through a small closed curve, which may or may not be circulate

65 What is streak line? Give examples.The streak line is a line that is traced by fluid particles passing through a fixed point in a flow

field. It gives an instantaneous picture of the position of the fluid particles that have passed

through a fixed point. Example:

a.

The path traced by a smoke coming out of a man when smokingb. The path of the smoke coming out of the chimney66 State and explain the basic principles of continuity equation.It states that the mass of fluid flowing through the pipe at all cross section remains constant

67 Define stream function.The stream function is defined as a scalar function of space and time, such that its partial

derivative with respect to any direction gives the velocity component at right angles to this

direction

68 Write the condition to satisfy the irrotational flow

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0y

x

2

2

2

2

69 Mention the few properties of stream function.a. If stream function exists, it is possible case of fluid flow

b. If stream function satisfies Laplace equation it is possible case of an irrotational flow70 Define potential functionThe potential function or velocity potential function is defined as a scalar function of space and

time such that its negative direction with respect to any direction gives the velocity of fluid in

that direction

71 Mention the few properties of potential function.a. If velocity potential exists, the slow should be irrotational

b. The velocity potential satisfies, the Laplace equation, it represents the possible steadyincompressible irrotational flow

72

Define fluid dynamics.The study of fluid motion considering the forces which cause acceleration and forces which

resist acceleration is known as fluid dynamics

73 What is meant by equation of motion?The dynamic behavior of fluid motion is governed by a cup of equations, known as equations

of motion

74 What is Hagen poiseuilles formula?2f

21

dg

L U32h

g

PP Hagen poiseuille formula

Where

P1-P2/g Loss of pressure head

U Average velocity

Coefficient of viscosity

D Diameter of pipe

L Length of pipe

75 What are the factors influencing the frictional loss in pipe flow?Frictional resistance for the turbulent flow is

i) Proportional to vn where v varies from 1.5 to 2.0.ii)

Proportional to the density of fluid.iii) Proportional to the area of surface in contact.

iv) Independent of pressure.v) Depend on the nature of the surface in contact.

76 What is the expression for head loss due to friction in Darcy formula?dg2

VLf4h

2

f

Where f - Coefficient of friction in pipe

L - Length of the pipe

D - Diameter of pipe, and V - Velocity of the fluid

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77 Where the Darcy weishbach and Chezys formulas are used?Darcy weishbach equation is generally used for the flow through pipesChezys formula is generally used for the flow through open channels

78 What do you understand by the terms a) major energy losses, b) minor energy lossesMajor energy losses - This loss due to friction and it is calculated by Darcy weishbach formula

and chezys formula.Minor energy losses - This is due to

i. Sudden expansion in pipe.ii. Sudden contraction in pipe.iii. Bend in pipe.iv. Due to obstruction in pipe.

79 What are the losses experienced by a fluid when it is passing through a pipe?a. Loss of energy due to sudden enlargement

b. Loss of head due to sudden contractionc. Loss of energy at the exit from the piped. Loss of energy due to gradual contraction or enlargemente. Loss of energy due to an obstruction in pipef. Loss of energy at the entrance to a pipeg. Loss of energy in bendsh. Loss of energy in various pipe fittings

80 Give an expression for loss of head due to sudden enlargement of the pipe.g2

)V(Vh

2

21e

Where

he - Loss of head due to sudden enlargement of pipe.V1 - Velocity of flow at section 1-1

V2 - Velocity of flow at section 2-2

81 What are eddies and vena contracta in pipe minor losses?Due to sudden contraction, the streamline coverage to a minimum cross section is called vena

contracta

In between vena-contracta and wall of the pipe a lot of eddies are formed. These eddies cause a

considerable dissipation of energy.

82 Give an expression for loss of head due to sudden contraction.g2

V0.5h

2

c

Where, hc - Loss of head due to sudden contraction & V - Velocity at outlet of pipe

83 Give an expression for loss of head at the entrance of the pipe.g2

V0.5h

2

i

Where, hi - Loss of head at entrance of pipe & V - Velocity of liquid at inlet and outlet of the

pipe

84 Write the formula for loss of energy due to gradual enlargement and also bend in pipe.

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Loss of energy due to gradual enlargement

g2

VVkh

2

2

2

1L

kCo-efficient which depends on angle of convergence

Loss of head due to bend in pipe

g2VKh

2

b

85 Define the terms a) Hydraulic gradient line [HGL] and b) Total Energy line [TEL]Hydraulic gradient line: Defined as the line which gives the sum of pressure head and datum

head of a flowing fluid in apipe with respect the reference line.

Total energy line: Defined as the line which gives the sum of pressure head, datum head and

kinetic head of a flowing fluid in a pipe with respect to some reference line.

86 What is syphon? Where it is used?Syphon is along bend pipe which is used to transfer liquid from a reservoir at a higher

elevation to another reservoir at a lower level.Uses of syphon:

i. To carry water from one reservoir to another reservoir separated by a hill ridge.ii. To empty a channel not provided with any outlet sluice.

87 What are the basic educations to solve the problems in flow through branched pipes?i. Continuity equation.ii. Bernoullis formula.iii. Darcy weisbach equation.

88

What is Dupuits equation ?

55

3

3

5

2

2

5

1

1

d

L

d

L

d

L

d

L

Where

L1, d1 - Length and diameter of the pipe 1



89 What are the types of fluid flow?i) Steady & unsteady fluid flowii) Uniform & Non-uniform flowiii) One dimensional, two-dimensional & three-dimensional flowsiv) Rotational & Irrotational flow

90 When in a fluid considered steady?In steady flow, various characteristics of following fluids such as velocity, pressure, density,

temperature etc at a point do not change with time. So it is called steady flow.

91 Define co-efficient of friction.It is the ratio of actual discharge to theoretical discharge of the pipe

92

What is co-efficient of velocity?

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It is the ratio of actual velocity of fluid to theoretical velocity.th e

actv

V

VC

93 Define co-efficient of contractionIt is the ratio of area at vena contraction area to orifice area of the pipe

OrificeatArea

ncontractioat venaAreancontractiooftCoefficein

94 How pressure can be measured in pitot tube?The velocity of flow can be determined by measuring the increase in pressure energy at this

point

95 How the term dimensional analysis can be defined?Dimensional analysis is a mathematical tool or technique to study dimensions of several

problems

96 Write down the Navier-Stokes equation.The equation of motion without considering force due to turbulence and considering thegravity, pressure and viscosity forces are known as Navier-Stokes equation.

zvzpzgz

yvypygy

xvxpxgx

FFFF

FFFF

FFFF

Where Fg - Gravity force, Fp - Pressure force & Fv - Viscous force

97 What are energy lines and hydraulic gradient lines?Energy line: If different sections of the pipe total energy is plotted to scale and joined by a line,

the line is called energy grade line

Hydraulic gradient line: The pressure head in a pipe decreased gradually from section to

section of the pipe in the direction of the fluid flow due to loss of energy. If pressure heads at

the different sections of the pipe are joined by a straight line. This line is called hydraulic

gradient line or pressure line

98 What is hydraulic mean depth or hydraulic radius?Hydraulic radius is the ratio of cross sectional area to perimeter of that section.

P

Am

99 What is pipe?Pipe is a closed conduit, which is used for carrying fluids under pressure

100What are pipes in series?

It is defined as the pipes of different diameters and lengths are connected with one another toform a single pipeline

101What is equivalent pipe?

A compound pipe consisting of several pipes of varying diameters and length may be replaced

by a pipe of uniform diameter, which is known as equivalent pipe

102What do you mean by flow through parallel pipes?

When a main pipeline divides into two or more parallel pipes, which again join together to

form a single pipe and continue as a main line. These pipes are said to be pipes in parllel

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103Define displacement thickness.It is defined as the distance measured perpendicular to the boundary by which the mainstream

is displaced to on account of formation of boundary layer

104Define momentum thickness.It is defined as the distance, measured perpendicular to the boundary, by which the boundaryshould be displaced to compensate for reduction in momentum of the flowing fluid on account

of boundary layer formation

105 Define energy thickness.

It is defined as the distance measured perpendicular to the boundary, by which the boundary

should be displaced to compensate for reduction of kinetic energy of the flowing fluid on

account of boundary layer formation

106Define drag and lift.

The component of the total force in the direction of flow of fluid is known as drag

The component of the total force in the direction perpendicular to the direction of flow isknown as lift

UNIT III DIMENSIONAL ANALYSIS

1. State the methods of dimensional analysis.a. Rayleighs method

b. Buckinghams theorem2. State Buckinghams theorem

It states that if there are n variables in a dimensionally homogeneous equation and if these

variables contain m fundamental dimensions (M, L, T), then they are grouped into (n-m),

dimensionless independent-terms.

3. State the limitations of dimensional analysis.a. Dimensional analysis does not give any due regarding the selection of variables.

b. The complete information is not provided by dimensional analysis.c. The values of coefficient and the nature of function can be obtained only by

experiments or from mathematical analysis.

4. Define SimilitudeSimilitude is defined as the complete similarity between the model and prototype.

5. State Froudes model lawOnly Gravitational force is more predominant force. The law states The Froudes number is

same for both model and prototype.

6. Give the dimensions of the following physical quantities.(a) Pressure (b) Surface Tension (c) Dynamic viscosity

(d) Kinematic viscosity

(a) PressureML-1T2 (b) Surface TensionML

-1T2

(c) Dynamic viscosityML-1

T-1

(d) Kinematic viscosity L2

T-1

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7. State the Fourier law of dimensional homogeneityThe law of Fourier principle of dimensional homogeneity states an equation which expresses

a physical phenomenon of fluid flow should be algebraically correct and dimensionally

homogenous

8. What is dimensionally homogenous equation? Give examples.Dimensionally homogenous equations means, the dimensions of the terms of left hand sideshould be same as the dimensions of the terms on right hand side

9. What are the uses of dimensional homogeneity?a. To check the dimensional homogeneity of the given equation

b. To determine the dimension of a physical variablec. To convert units from one system to another through dimensional homogeneityd. It is a step towards dimensional analysis

10.What are the points to be remembered while deriving expressions using dimensional analysis?a. First the variables controlling the phenomenon should be identified and expressed in

terms of primary dimensions

b. Any mathematical equation should be dimensionally homogenousc. In typical cases, a suitable mathematical model is constructed to simplify the problem

with suitable assumptions

11.How equations are derived in Raleighs method?The expression is determined for a variable depending upon maximum three or four variables

only. If the number of independent variables becomes more than four, it is very difficult to find

the expression for the dependent variables. So, a functional relationship between variables is

expressed in exponential form of equations.

12.Describe briefly the selection of repeating variables in Buckingham Theorem.There is no separate rule for selecting repeating variables. But the number of repeating

variables is equal to the fundamental dimensions of the problem. Generally, , v, l or , v, D

are chosen as repeating variables. It means, one refers to fluid property () one refers to flow

property (v) and the other one refers to geometric property (l or D). In addition to this, the

following points should be kept in mind while selecting repeating variables.

1. No one variable should be dimensionless.2. The selected two repeating variables should not have the same dimensions.3. The selected repeating variables should be independent as far as possible.

13.Define weber number.It is the ratio of the square root of the inertia force to the surface tension force.

VL

L

VL

forceTensionSurface

forceInertiaW

222

e

14.Define Reynolds number.It is defined as the ratio of the inertia force to the viscous force of a flowing fluid. Denoted by

Re.

VL(or)

VL

forceViscous

forceInertiaRe ; ( / = = Kinematic viscosity)

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15.Define Mach numberIt is defined as the square root of the inertia force of a flowing fluid to the elastic force

k

V

Lk

VL

forceElastic

forceInertia

2

2

22

16.Mention the applications of model testing?a. Civil engineering structures such as dams, weirs, canals etc

b. Design of harbour, ships and submarinesc. Aero planes, rockets and machines, missiles

17.What are the advantages of model testing?a. The model tests are quite economical and convenient and operation of a model may be

changed several times if necessary, without of increasing much expenditure

b. With the use of models the performance of hydraulic structure/hydraulic machines canbe predicted in advance

c. Model testing can be used to detect and rectify the defects of an existing structure,which is not functioning properly

18.What are the similarities between model and prototype?a. Geometric similarity b. Kinematic similarityc. Dynamic similarity

19.What is meant by Kinematic similarity?Kinematic similarity is the similarity of motion. It corresponds to the points in the mode and in

the prototype.

20.In fluid flow, what does dynamic similarity mean? What are the non-dimensional numbersassociated with dynamic similarity?

It is the similarity of forces. The flows in the model and prototype are of dynamic similar.

Dimensional numbers are weight, force, dynamic viscosity, surface tension, capillarity etc

21.Mention the significance of Reynolds model lawa. Motion of air planes.

b. Flow of incompressible fluid in closed pipes.c. Motion of submarines, andd. Flow around structures and other bodies immersed fully in moving fluids.

22.Write down the scale ratio for discharge, energy and momentumDischarge, Qr - Lr

5/2

Energy, Er - Lr4

Momentum, Mr - Lr7/2

23.State the Euler model law and give its significanceOnly pressure for is more predominant force in addition to the inertia force. According to this

law, the Euler number is same for both prototype and model.

The Euler number itself is sufficient centerion in the following phenomena:

1. Where the gravity and surface tension forces are fully absent and the turbulence is fullydeveloped with negligible viscous force.

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2. It is applied in cavitation phenomena24.Mention the types of models

i) Undistorted models. ii) Distorted models25.What is meant by undistorted models?

The model which is geometrically similar to its prototype is known as undistorted models. Insuch models the conditions of similitude are fully satisfied.

26.Define the term scale effectIt is impossible to product the exact behaviour of the prototype by model testing alone. The

two models of same prototype behaviour with different. Solve ratios will not be same. So

discrepancy between models and prototype will always occur. It is known as scale effect.

27.Obtain scale ratio of discharge for distorted models.2

3

VrHrrLxLQratio,scaleDischarge

UNIT-IV ROTODYNAMIC MACHINES

1. Define fluid machines.The device in which the fluid is in continuous motion and imparts energy conversion is known

as fluid machines.

2. Define hydraulic machines / turbine.Hydraulic machines which convert the energy of flowing water into mechanical energy

3. What is hydroelectric power?The turbine converts hydraulic energy into mechanical energy. This mechanical energy is

converted into electrical energy. So conversion of energy from hydraulic to electric is called

hydroelectric power.

4. What is the basis of classification of turbines?a) According to the action of the water flowing

b) According to the main direction of flow of waterc) According to head and quantity of water requiredd) According to the specific speed

5. Classify the different types of turbinea) Action of the water flowing

i. Impulse turbine ii. Reaction turbineb) Main direction of water flow

i. Tangential flow turbine ii. Radial flow turbineiii. Axial flow turbine iv. Mixed flow turbine

c) Head and quantity basisi. High head turbine ii.Medium head turbine

iii.Low head turbine

d)

Specific speed basis

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i. Low specific speed ii.Medium specific speediii. High specific speed

6. Give example for a low head, medium head and high head turbine.Low head turbineKaplan turbine

Medium head turbineModern Francis turbine

High head turbinePelton wheel

7. Write the Eulers equation for turbo machines.The force exerted by the water in the direction of motion is given by

)V(VVaF w2w11

Hence the momentum of the water or impulse = F x u = u)V(VVa w2w11

8. What are the components of energy transfer in turbo machines?a) Whirl velocity b) Flow velocity c) Relative velocity

9. Define degree of reaction.The ratio between the kinetic energy change in the moving blade to the kinetic energy in thestage. Or it is the ratio between increase in relative kinetic energy in moving blade to the stage

work output.

Degree of reaction,outpuworkStage

blademovinginenergykineticrelativeinIncreaseR

10.What is impulse turbine? Give example.In impulse turbine all potential energy converted into kinetic energy. From these the turbine

will develop high kinetic energy power. This turbine is called impulse turbine. Example: Pelton

turbine

11.What is reaction turbine? Give example.In a reaction turbine, the runner utilizes both potential and kinetic energies. Here portion of

potential energy is converted into kinetic energy before entering into the turbine. Example:

Francis and Kaplan turbine.

12.Differentiate the impulse and reaction turbine.S.No. Impulse turbine Reaction turbine

1

All the potential energy is converted into

kinetic energy by nozzle before enteringto turbine runner

Only a portion of the fluid energy is

transferred into kinetic energy beforethe fluid enters the turbine

2 Flow regulation is possible without loss Flow regulation is possible with loss

3Blades are only in action when they are

i.e. infront of nozzleBlades are in action at all the time

4Water may be allowed to enter a part or

whole of the wheel circumference

Water is admitted over the wheel

circumference

5Wheel does not run full and air has free

access to the bucket

Water completely fills the vane

passages throughout the operation of

the turbine

6 Unit is installed above the tailrace Unit is kept entirely submerged in

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water below tailrace

7Flow is regulated by means of a needle

valve fitted into the nozzle

Flow is regulated by means of a

guide-vane assembly

13.What is tangential flow turbine?The water flows along the tangent to the path of rotation of the runner.

Example: Pelton wheel

14.What is radial flow turbine?In the turbine, water flows along the radial direction and mainly in the plane normal to the axis

of the rotation as is passes through the runner. It may be either inward radial flow type or

outward radial type.

15.What is axial flow turbine?In axial flow turbine water flows parallel to the axis of the turbine shaft.

Example: Kaplan turbine, propeller turbine

16.What is mixed flow turbine?In mixed flow water enters the blades radially and comes out axially, parallel to the turbineshaft. Example: Modern Francis turbine.

17.Differentiate the inward flow reaction turbine and outward flow reaction turbine.S.No. Inward flow reaction turbine Outward flow reaction turbine

1

Water enters at the outer periphery,

flows inward and towards the centre of

the turbine and discharges at the outer

periphery

Water enters at the outer periphery

flows outward and discharges at the

outer periphery

2 The discharge does not increase The discharge increases

3 Easy and effective speed control Very difficult to speed control

4Good for medium and high heads and

suitable for large outputs and unitsGood for medium or low heads

5 Commonly used for power projects Practically obsolete

18.Differentiate the Francis and Kaplan turbine.S.No. Francis turbine Kaplan turbine

1

Correct disposition of the guide and

moving vanes is obtained at full load

only

Correct disposition of the guide and

moving vanes is obtained at any load

2

System may have one or two

servomotors depending on the size of the

unit

Two servomotors respective of the

size of the unit always do governing

3Since only the guide vanes are controlled

high efficiency is obtained

Both guide and runner vanes high

efficiency is obtained even at partial

loads

4Servomotors are kept outside the turbine

shaft

Both servomotors are kept inside the

hollow shaft of the turbine runner

19.What are the main parts of pelton wheel?

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a) Penstock b) Spear and nozzlec) Runner and buckets d) Break nozzle

e) Outer casing f) Governing mechanism

20.What is penstock in pelton wheel?Penstock is a large sized pipe, which conveys water from the high level reservoir to the turbine.

Depending upon low head or high head installations, a penstock is made of wood, concrete orsteel. In order to control the water flow penstocks have different control valves at different

sections.

21.What is the function of spear and nozzle?The nozzle is used to convert whole hydraulic energy into kinetic energy. Thus the nozzle

delivers high speed jet. To regulate the water flow through the nozzle and to obtain a good jet

of water spear or nozzle is arranged.

22.What is function of outer casing?A casing is made of cast iron or fabricated steel plate. It is used to prevent the splacing of water

and discharge of water to tailstock. It is also act as a safeguard against accidents.

23.What is break nozzle and mention its function?If the spear nozzle set was closed the runner will revolve long time due to inertia. To stop the

runner in a short time a small nozzle provided which directs a jet of water on the backside of

the buckets.

24.What is the function of governing mechanism in pelton wheel?Governing mechanism is used to regulate the water flow to the turbine at constant level so that

the speed of the turbine kept constant. This automatically regulates the quantity of water

flowing through the runner in accordance with any variation of load.

25.Define gross head and net or effective head.Gross Head: The gross head is the difference between the water level at the reservoir and the

level at the tailstock.

Effective Head: The head available at the inlet of the turbine.

26.Define water and bucket power.Water power: The power supplied by water jet

Bucket power: The power developed by the bucket wheel

27.Define hydraulic efficiency.It is defined as the ratio of power developed by the runner to the power supplied by the water

jet.jetwaterby thesuppliedPower

runnerby thedevelopedPowerh

28.Define mechanical efficiency.It is defined as the ratio of power available at the turbine shaft to the power developed by the

turbine runner.

powerWater

powerShaft

runnerturbineby thedevelopedPower

shaftturbinetheavailablePowerm

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29.Define volumetric efficiency.It is defined as the volume of water actually striking the buckets to the total water supplied bythe jet.

Q

q-Q

Q

Q av ; v lies between 0.97 to 0.99

30.Define overall efficiency.It is defined as the ratio of power available at the turbine shaft to the power available from the

water jet.

HQw

P

powerWater

powerShafto

31.What is scroll or spiral casing?The water from the penstock enters the scroll casing which completely surrounds by the

runner. The cross sectional area of the scroll casing decreases along the flow of direction, area

is maximum at inlet and nearly zero at exit.

32.What is speed rings or stay ring?The speed rings consists of an upper and lower ring held together by series of fixed vanes

called stay vanes. The number of stay vanes is usually taken as half to direct the water from the

scroll casing to the guide vanes and also it resists the load imposed upon it.

33.What is the function of guide vanes or wicket gates in Francis turbine?The guide vanes direct the water on to the runner at appropriate angles as per design. Also it is

used to regulate the quantity of water supplied to the runner the guide vanes are airfoil shaped

and they may be made of cast steel, stainless steel or plate steel.

34.What are draft tube and its function?After passing through the runner, the water is discharged to the tailrace through a gradually

expanding tube called draft tube.

The pressure at the exit of the runner of a reaction turbine is generally less than atmospheric

pressure. By passing reduced through draft tube, the outer velocity of water is reduced and gain

in useful pressure head is activated to increase the output of turbine.

35.What are the main components in Kaplan turbine?The Kaplan turbine consists of the following main components

a) Scroll casing b) Stay ringc) Guide vanes d)Draft tube e) Runner

36.What are the significant of unit quantities and specific quantities?a) To predict the behavior of a turbine working under different conditions

b) Make comparison between the performances of turbine of same types of different sizesc) Compare the performance

37.Define unit speed (Nu) of turbine.Unit speed is defines as the speed of turbine when working under a unit head.

H

NNu

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38.Define unit discharge.It is the theoretical discharge of a turbine when working under unit head

H

QQdischarge,Unit u

39.Define unit power.It is the theoretical power of a turbine when working under unit head

2

3u

H

PPpower,Unit

40.Define the specific speed of a turbine.Specific speed is the speed of a geometrically similar turbine, which will develop unit power

when working under unit head.

41.Give the range of specific speed values for Kaplan turbine and pelton wheel.a) Range of speed for Kaplan turbine = 257 to 858

b)Range of specific speed for pelton wheel = 10 to 30-single jet= 17 to 50-two jets

= 24 to 70-with four jets

42.What is meant by surge tank?A surge tank is small reservoir or tank in which the water level rises or falls to reduce

43.What are the purposes of providing surge tank?a) When sudden closure of valve, sudden reduction of flow in the penstock will occur. To

avoid this reduction of rate of flow, surge tanks are provided in the upstream of the

pipelineb)To reduce the rapid velocity fluctuation in pipeline during starts and shut down of aturbine

44.What are the different types of surge tanks?a) Simple surge tank b) Incline surge tankc) Differential surge tank

45.A turbine develops 5 MW under a head of 20 m at 125 rpm. What is the specific speed?

Given: P = 5 MW, H = 20 m; N = 125 rpm Solution: 45s H

PN

N = 208.98 (Ans)

46.What is draft tube? In which type of turbine it is mostly used?The tube which increases the outlet velocity of turbines is known as draft tube. So, head is

saved by fitting draft tube.

47.Write the function of draft tube in turbine outlet.a) It allows the turbine to set above tail-water level without loss of head for doing

inspection and maintenance.

b) It regains the major portion of the kinetic energy delivered from the runner by diffuseaction.

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UNIT-V POSITIVE DISPLACEMENT PUMPS

1. What is meant by Pump?A pump is device which converts mechanical energy into hydraulic energy.

2. State the important classification of centrifugal pump.According to number of stagesi) Single stage pump ii. Multi-stage pump

3. Mention main components of Centrifugal pump.i. Impeller ii. Casing

iii.Suction pipe, strainer & Foot valve iv. Delivery pipe & Delivery valve

4. What are the purposes of providing casing on the centrifugal pump?i) To guide water to and from the impeller, andii) To partially convert the kinetic energy into pressure energy

5. What are the various types of casing?i. Volute casing ii. Vortex casing

iii.Volute casing with guide blades

6. Where the suction pipe is placed? For what?It is provided with a strainer at its lower en so as to prevent the entry of solid particles, debris

etc into the pump.

7. What is meant by Priming?The delivery valve is closed and the suction pipe, casing and portion of the delivery pipe upto

delivery valve are completely filled with the liquid so that no air pocket is left. This is called as

priming.

8. Define Manometric head.It is the head against which a centrifugal pump works.

9. Write down the formula for manometric efficiency.impellerby theimpartedPower

pumptheofOutput

liquidoimpeller tbyimpartesHead

headManometricmano

10.Define volumetric efficiency.It is defines as the ratio of quantity of liquid discharged per second from the pump to the

quantity passing per second through the impeller.

11.Write down the relationship between overall efficiency, manometric efficiency, volumetricefficiency and mechanical efficiency.

mechvmanoo xx

12.Define Mechanical efficiency.

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It is defined as the ratio of the power actually delivered by the impeller to the power supplied

to the shaft.

shaftat thePower

impellerat thePowermech

13.Define overall efficiency.It is the ratio of power output of the pump to the power input to the pump.

pumptheofinputPower

pumptheofoutputPowero

14.What are backward curved vanes?When the outlet tip of blade curves in a direction opposite to that of motion, then it is called

backward curved vanes

15.Define radial vane.The liquid leaves the vane with relative velocity in a radial direction.

16.What are forward curved vanes?When the outlet tip of blade curves in the direction of motion, then it is called forward curved

vanes

17.Write down the formula for specific speed of a pump.5/4

m

3/4

m

sH

PN

H

QNN

18.Define speed ratio, flow ratio.Speed ratio: It is the ratio of peripheral speed at outlet (u2) to the theoretical velocity of jetcorresponding to manometric head (Hm).

m

2u

2gH

uK Ku varies from 0.95 to 1.25

Flow ratio: It is the ratio of the velocity of flow at exit (V f2) to the theoretical velocity of jet

corresponding to manometric head (Hm).

m

f2f

2gH

VK Kfvaries from 0.1 to 0.25

19.How can we obtain a high head in a pump network?A number of impellers are mounted on the same shaft in series to obtain a high head.

Hn xH total

20.What will be the effect of arranging the pumps in parallel?A number of pumps are arranged in parallel for obtaining high discharge.

Qn xQ total

21.What are the characteristics curves?i) Main characteristics curves

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ii) Operating characteristics curvesiii) Constant efficiency or Muschel curvesiv) Constant head and constant discharge curves.

22.What is the principle of reciprocating pumps? And state its displacement type.It operates on a principle of actual displacement of liquid by a piston or plunger, which

reciprocates in a closely fitting cylinder.

23.State the main classification of reciprocating pump. According to the liquid being in contact with piston or plunger. According to the number of cylinders provided.

24.Mention main components of Reciprocating pump.i) Piton or Plunger ii) Suction and delivery pipe

iii) Crank and Connecting rod

25.What is the main difference between single acting and double acting reciprocating pump?In single acting reciprocating pump, the liquids acts on one side of the piston only whereas indouble acting reciprocating pump, the liquid acts on both sides of the piston.

26.Write down the formula for discharge, work done and power required for double acting pump.60

NLA2QDischarge,

)h(h60

NLAw2WWorkdone, dsD

)h(h60

NLAw2Ppump,thedrivetorequiredPower ds

27.Define Slip of reciprocating pump. When does the negative slip does occur?The difference between the theoretical discharge and actual discharge is called slip of the

pump.

actth Q-QSlip

100x)C-(1100xQ

Q-1100x

Q

Q-QSlipPercentage d

th

act

th

actth

But in sometimes actual discharge may be higher than theoretical discharge, in such a case

coefficient of discharge is greater than unity and the slip will be negative called as negative

slip.

It is possible when the delivery pipe is shorter than the suction pipe with higher running speed.

28.What is indicator diagram?Indicator diagram is nothing but a graph plotted between the pressure head in the cylinder and

the distance traveled by the piston from inner dead center for one complete revolution of the

crank.

29.Write down the formula for work done by the pump in an indicator diagram.

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Work done = K x Area of indicator diagram

pumpactingsinglefordiagramindicatorofAreax60

NAw

pumpactingdoublefordiagramindicatorofAreax60

NAw2

30.Define suction head.It is the vertical height of the centre line of the pump shaft above the liquid surface in the sump

from which the liquid is being raised.

31.Write down the formula for saving in work by fitting air vessels.100x

W

W-WsavedWork

1

21

32.What is meant by Cavitations?It is defined phenomenon of formation of vapor bubbles of a flowing liquid in a region where

the pressure of the liquid falls below its vapor pressure and the sudden collapsing of theses

vapor bubbles in a region of high pressure.

33.What is the effect of cavitations in pumps?Breakdown of the machine itself due to severe pitting and erosion of blade surface

34.How can we identify the cavitation in pumps?i) Sudden drop in efficiency ii) Head falls suddenly

iii) More power requirement iv) Noise and vibration

v) Pitting and erosion of surface

35.State any precautions against cavitations.i) The pressure should not be allowed to fall below its vapour pressureii) Special material coatings can be given to the surfaces where the cavitation occurs

36.What are rotary pumps? Give various types.Rotary pumps resemble like a centrifugal pumps in appearance. But the working method

differs. Uniform discharge and positive displacement can be obtained by using these rotary

pumps; it has the combined advantages of both centrifugal and reciprocating pumps.

The various types are: External and Internal gear pump, Lobe pump and Vane pump.

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