11two Marks With Answer (1)

8/13/2019 11two Marks With Answer (1)

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MECHANICS OF FLUIDS CE2202

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TWO M RKS WITHNSWER


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UNIT-I

DEFINITION AND FLUID PROPERTIES

DefinitionsFluid and fluid mechanicsDimensions and unitsFluid properties

Continuum Concept of system and control volume.

1. Define the following fluid properties. State their dimensions and units: specificweight and specific gravity. (Nov/Dec 2008)

Specific weight: (w)

Specific weight or weight density of a fluid is the ration between the weight ofa fluid to its volume.

The value of specific weight for water is 9.81X 1000 N/m3

Specific gravity :(S)

It is defined as the ratio of the weight density of a fluid to the weight density of

a standard fluid. It is dimensionless quantity and is denoted by the symbol S.

2. State and explain Newtons law of viscosity. (Nov/Dec 2008, Nov/Dec 2008 )The shear force acting between two layers of the fluid is propotional to the

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

distance between them.

3. What is dynamic viscosity? What are its units? (May/June 2009, May/June 2007)It is defined as the shear stress required to produce unit rate of shear

deformation.

=

4. Define viscosity. (Nov/Dec 2010, Nov/Dec 2011)Viscosity is the property of a liquid which determines the amount of resistance

to a shearing stress. It can also be defined as the property of a fluid due to which it

offers resistance to the movement of one layer of the fluid over another adjacent layer.

5. Define cohesion and adhesion. (Nov/Dec 2010)Cohesion means intermolecular attraction between the molecules of the some

liquid. It enables a liquid to resist small amount of tensile stresses.Adhesion means attraction between the molecules of a liquid and the

molecules of a solid boundary surface in contact with the liquid. This property enablesa liquid to stick to another body.

6. What is meant by control volume of liquid?(Nov/Dec 2010)A specified large number of fluid and thermal devices have mass flow in and

out of a system is called as control volume.

7. What is compressibility of fluid.(Nov/Dec 2010)Compressibility is the measure of relative change of volume when the fluid is

subjected to a pressure change. It is the reciprocal of bulk modulus of elasticity.


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8. Calculate the capillary rise in a glass tube of 1.8mm diameter when immersedvertically in water. Take surface tension of water as 0.073 N/m. (May/June 2007)

h=

=

= 0.028 m

= 2.8 cm

9. Differentiate between specific volume and specific weight. (Nov/Dec 2007)Specific volume Specific weight

(i) Specific volume is defined asvolume per unit mass of fluid(ii)w=(iii) expressed in kg/m3

(i) specific weight is defined as theweight per unit volume.(ii)V=(iii) Expressed in m3/kg

10.Distinguish between real and ideal fluid. (Nov/Dec 2007)A fluid, which is compressible and is having no viscosity and surface tension is

known as an ideal fluid. Ideal fluids is only an imaginary fluid. But real fluid possesses

viscosity, surface tension and compressibility. All the fluids, in actual practice are realfluids.

11.Define fluid mechanics and fluid.Fluid mechanics is that branch of science which deals with the behavior of the

fluids and liquids.

12.What are the types of fluids?Ideal fluidReal fluid

Newtonian fluidNon Newtonian fluid

Ideal plastic fluid

13.Define fluid statics.The study of fluid at rest is called fluid statics.

14.Define fluid dynamics.The study of fluids in motion, where pressure, force are consider for the fluid in

motion.


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15.Define fluid kinematics.The study of fluid in motion, where pressure, force are not consider is called

fluid kinematics.

16.Define kinematic viscosity.It is defined as the ratio between the dynamic viscosity and density of fluid. It

is denotedby .

= dynamic viscosity / density

17.Define bulk modulus.It is defined as the ratio between the compressive stress to volumetric strain.

18.Define continuum.A continuum is the homogeneous medium , in which the overall properties and

behavior of fluid can be studied without its atomic and molecular structure.

19.Define control volume.Control volume is defined as the volume of fixed space. The boundaries around

the control volume are referred to as control surface.

20.Define cavitation.If the low pressure are equal or less than the vapour pressure. Vapour bubbles

are formed in the flow and this condition is known as cavitation.


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8.What is stream line. (Nov/Dec 2010)

A streamline is an imaginary line drawn through a flowing fluid in such a waythat the tangent at any point on it indicates the velocity at that point.

9. What are the commonly used mechanical gauges? (Nov/Dec 2010)

(i) Bourdon tube pressure gauge(ii) Diaphragm gauge(iii) Vaccum gauge

10. What is flow net.(Nov/Dec 2010)A grid obtained by draing a series streamlines and equipotential lines is known

as flow net.

11.Explain the term metacentre. (Nov/Dec 2011)It is defined as the point about which a body starts oscillating when the body is

tilted by a small angle.

12.Define a rotational flow and irrotational flow.(Nov/Dec 2011)A rotational flow exists when the fluid particles rotate about their mass centre,

while moving along a streamline. An irrotational flow exists when the fluid particles do

not rotate about their mass centre while moving along a streamline.

13.Write the formula used to determine the Meta Centric Height. (May/June 2007)The distance between the metacentre of a floating body(M) and the centre of

gravity of the body (G) is called metacentric height.

Meta-centric height (GM) = - BG

14.Differentiate stream line and path line. (May/June 2007)Path line Stream line

i) It is the path followed by the fluidparticles in motion

ii) It gives the path of one particle atsuccessive instants of time

i) It is defined as an imaginary linewithin the flow so that the

tangent at any point on it

indicates the velocity at thatpoint

ii) Indicates the direction of a numberof particles at the same instant

15.Define centre of pressure. (Nov/Dec 2007)Centre of pressure is defined as the point of application of the total pressure on

the surface.


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16.What are the types pressure? Atmospheric pressure Absolute pressure Gauge pressure Vaccumm pressure

17.What are the instruments used to measure the pressure of a fluid. Peizometer Manometer Mechanical gauges.

18.What are the types of manometers? U-tube manometer Inverted U-tube manometer Simple manometer single column manometer

19.What is meant 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.

20.Define total pressure .It is defined as the force extended by a static fluid on a surface either plain or

curve, When the fluid come in a contact with the surface.


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UNIT-III

FLUID DYNAMICSEuler and Bernoullis equations Application of Bernoullis equation Discharge

measurementLaminar flows through pipes and between platesHagen Poiseuille equation

Turbulent flowDarcy-Weisbach formulaMoody diagramMomentum Principle.

1. State the assumptions used in deriving Bernoullis equation. (May/June 2007,Nov/Dec 2010)

(i) The fluid is ideal(ii) The flow is steady and continuous(iii) The flow is compressible(iv) The flow is irrotational(v) The flow is along the streamline

2. State Bernoullis equation. (Nov/Dec 2007, Nov/Dec 2008)It states that in a steady flow of an incompressible fluid, the total energy at any

point of the fluid is constant. The total energy consists of pressure energy, kinetic

energy and potential energy.

+ + z = constant

3. What is Moodys diagram? (Nov/Dec 2007, Nov/Dec 2007)Moodys diagram is plot between various values of friction factor(f), Reynolds

number (Re) and relative roughness . For any turbulent flow problem, the values

of friction factor can therefore be determined form moodys diagram, if the numerical

values of (R/K) for the pipe and Reof flow are known.

4. Write the energy equation for a real fluid flow. (May/June 2009)Bernoulli equation is also known as energy equation. It is given by,

+ + z = constant

5. What is a laminar flow? Give examples. (May/June 2009)Laminar flow is defined as that type of flow in which the fluid particles move

along well-defined paths or stream line and all the stream line are straight and parallel.

Examples: flow through capillary pipe, flow of blood in veins and arteries

6. State the types of equilibrium. (Nov/Dec 2010)a) Stable equilibrium

b) Unstable equilibriumc) Neutral equilibrium

7. State the characteristics of laminar flow. (Nov/Dec 2010)(i) There is a shear stress between fluid layers(ii) No slip at the boundary(iii) The flow is rotational


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(iv) There is continuous dissipation of energy due to viscous shear. So, theenergy must be supplied to maintain the flow.

(v) Loss of energy is propotional to the first to the first power of velocityand first power of viscosity

8. Define co-efficient of friction.

It is defined as the ration of actual discharge to theoretical discharge of the

pipe.

9. What is cavitation in venturimeter?

Due to reduction in area the velocity of fluids is increased and pressure isdecreased. When the pressure comes below that of vapour pressure of the flowing

fluid, then the liquid will be vapourized. This phenomenon is called cavitation.

10. Define weir.

A weir is defined as a concrete or masonry structure built across a river or

stream in order to raise the level of water on the upstream side and allow excess water

flow to the downstream side.

11. Classify weirs based on the width of the crest.

a) Narrow crested weirb) Broad-crested weir

12. Where are the Darcy weishbach and Chezys forumalae used?

Darcy weishbach equation is generally used for the flow through pipes. Chezys

formula is generally used for the flow through open through open channels.

13. State the principle of momentum.

It states that the time rate of change of momentum is propotional to the

impressed force and takes place in the direction in which force acts

14.What is meant by fluid dynamics?The study of fluids in motion, where pressure, force are consider for the fluid in

motion.

15.What are the applications of Bernoullis equation? Venturimeter Orificemeter Pitot tube

16.What is meant by venturimeter?A venturimeter is a device used for measuring the rate of flow of a fluid

flowing through pipe.

17.What is meant by orificemeter?It is a device used for measuring the rate of flow of a fluid through a pipe. It is

cheaper device as compare to venturimeter.


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UNIT-IV

BOUNDARY LAYER AND FLOW THROUGH PIPESDefinition of boundary layerThickness and classificationDisplacement and momentum

thicknessDevelopment of laminar and turbulent flows in circular pipesMajor and minor

losses of flow in pipesPipes in series and in parallelPipe network

1. What is meant by laminar sub layer? (May/June 2007)In turbulent boundary layer region, adjacent to the solid boundary velocity for a

small thickness variation is influenced by viscous effect. This layer is called as laminar

sub layer.

2. Define energy thickness. (Nov/Dec 2007)It is defined as the distance, measured perpendicular to the boundary of the

solid body, by which the boundary should be displaced to compensate for the reduction

in kinetic energy of the flowing fluid on accound of boundary layer formation.**=

3. What is meant by hydraulic gradient line. (Nov/Dec 2007)It is defined as the line which gives the sum of pressure head, datum head of a

flowing fluid in a pipe with respect to some reference line. Sometimes the hydraulic

grade line is also known as piezometric head. (p/w + z)

4. Define displacement thickness. (Nov/Dec 2008)It is defined as the distance measured perpendicular to the boundary of thesolid body, by which the boundary should be displaced to compensate for the reduction

in flow rate on account of boundary layer formation.

**=

uvelocity of fluid at the elemental strip

5. Define momentum thickness of boundary layer. (May/June 2009)It is defined as the distance measured perpendicular to the boundary of the solid

body, by which the boundary should be displaced to compensate for the reduction

in momentum of the flowing fluid of boundary layer for motion.

=

6. What is hydraulic mean depth or hydraulic radius? (Nov/Dec 2010)The ratio of area of flow and perimeter(wetted) is called hydraulic mean depth

or hydraulic radius and it is denoted by m. the value of m for pipe is always equal to

d/4.

7. What are eddies and vena contracta in pipe minor losses? (Nov/Dec 2010)Due to sudden contraction, the streamline coverage to a minimum cross section

is called vena contracta. Inbetween vena-contracta and wall of the pipe, a lot of eddiesare formed. These eddies cause a considerable dissipation of energy.


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8. What is equivalent pipe? (Nov/Dec 2010, May/June 2009)An equivalent pipe is defined as the pipe of uniform diameter having loss of

head and discharge equal t the loss of head and discharge of a compound pipe

consisting of several pipes of different lengths and diameters.

9. What is boundary layer. (Nov/Dec 2010)When a solid body is immersed in a flowing fluid, there is a narrow region of

the fluid in the neighbourhood of the solid body, where the velocity of fluid varies

from zero to free stream velocity. This narrow region of fluid is called boundary layer.

10.What are the methods adopted for controlling the boundary layer? (Nov/Dec2010)(i) Suction of the slow moving fluid by a suction flot or through a porous surface(ii) Injecting fluid into the region of boundary layer from the interior of the body

with the help of blower

(iii) Providing slots near the leading edge(iv) Placing some disturbance near the boundary in the approach section

11.Why are the pipes connected in parallel? (Nov/Dec 2011)Pipes are said to be parallel, when a main pipe divides into two or more parallel

pipes which again join together downstream and continues as a mainline. The pipes are

connected in parallel in order to increase the discharge passing through the main.

12.What are the classifications of boundary layer?

Laminar boundary layer Turbulent boundary layer Laminar sub layer.

13.What are the losses in pipes and explain it? Major losses: this is due to friction and it is calculated by Darcy

weisbach formula and chezys formula.

Minor losses: this is due to the sudden expansion, contraction, bendingin pipes and also due to pipe fittings and obstruction in pipe fittings.

14.What are the minor losses in pipes? Losses of head due to sudden enlargement. Losses of head due to sudden contraction Losses of head at entrance Losses of head at exit Losses of head due to obstruction in pipe. Losses of head due to bending in pipes

15.What is meant by pipe network?A pipe network is an inter connection system of pipe forming several loops or

circuits.


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UNIT-V

SIMILITUDE AND MODEL STUDYDimensional AnalysisRayleighs method, Buckinghams Pi-theoremSimilitude and

modelsScale effect and distorted models.

1. Define Reynolds model law. (May/June 2007)Reynolds model law is the law in which models are based on reynolds

number. Models based on reynolds number include:

(i) Pipe flow(ii) Resistance experienced by sub-marines, airplanes, etc

2. What is meant by the term distorted model? (May/June 2007, May/June 2009)A model which is not geometrically similar to its prototype but it may be

similar in appearance with its prototype. The following distortions may occur in

distorted model:

(i) Geometrical distortion(ii) Material distortion(iii) Distortion of hydraulic quantities

3. What is meant by dimensional homogeneity? (Nov/Dec 2007, May/Jne 2009)Dimensional homogeneity means the dimensions of each terms in an equation

on both sides equal. For example V=

Dimensions on L.H.S = V=L/T = LT-1

Dimensionson R.H.S = = L/T = LT

-1

4. State Buckinghams pie theorem. (Nov/Dec 2007, Nov/Dec 2008, Nov/Dec 2010,Nov/Dec 2011)

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 pie terms.

5. What is meant by similitude? (Nov/Dec 2008)Similitude is defined as the complete similarity between the model and the

prototype.

6. What is meant by repeating variables? (May/June 2009)Each of pie terms is dimensionless and independent of the system. Division of

multiplication by a constant does not change the character of the pie term. Each of pie

term contains variables, where m is the number of fundamental dimensions and is alsocalled repeating variables.

The number of repeating variables are equal to the number of fundamental

dimensions of the problem.

7. What is HGL and TEL? (May/June 2009)Hydraulic Gradient Line is defined as the line which gives the sum of pressure

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


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Gravity force Pressure force Surface tension force Elastic force.

15. What are the dimensionless numbers? Reynoldss number Froudes number Eulers number Webers number Machs number

16. What are the model laws in similitude? Reynoldss model law Froudes model law Eulers model law Webers model law Machs model law

17. What is meant by undistorted model?This models are those models which are geometrically similar to their

prototype or in other words, if the scale ratio for the linear dimensions of the model

and its prototype is same, the model is called undistorted model.

18. What are the advantages of distorted models? The vertical dimensions of the model can be measured accurately. The cost of the model can be reduced. Turbulent flow in the model can be maintained.

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