ME2204 / FLUID MECHANICS AND MACHINERY 2014 Questions Bank

Anna University, Chennai

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SRINIVASAN ENGINEERING COLLEGE

DEPART MENT OF MECHANICAL ENGINEERING

ACADEMIC YEAR 2013- 2014 / ODD SEMESTER

QUESTION BANK

SUBJECT CODE & NAME : ME2204 / FLUID MECHANICS AND MACHINERY

YEAR/SEM : II/III

UNIT- I INTRODUCTION

PART-B (16 Marks)

1. a) What are the different types fluids? Explain each type.

b) Discuss the thermodynamic properties of fluids (8)

2. a) One litre of crude oil weighs 9.6 N. Calculate its Specific weight, density and specific weight. (8) b) The Velocity Distribution for flow over a flat plate is given by

u=(2/3)y-y2, Where u is the point velocity in meters per second at a distance y metre above the plate. Determine the shear stress at y=0 and y=15 cm.

Assume dynamic viscosity as 8.63 poises (8)

3. a) A plate, 0.025 mm distant from a fixed plate, moves at 50 cm/s and requires a force of 1.471 N/ m2 to maintain this speed. Determine the fluid viscosity between plates in the poise. (8)

b) Determine the intensity of shear of an oil having viscosity =1.2 poise and is used for lubrication in the clearance between a 10 cm diameter shaft and its journal bearing. The clearance is 1.0 mm and Shaft rotates at 200 r.p.m (8)

4. a) Two plates are placed at a distance of 0.15mm apart. The lower plate is fixed while the upper plate having surface area 1.0 m2 is pulled at

0.3 Nm/s. Find the force and power required to maintain this speed, if the fluid separating them is having viscosity 1.5 poise. (8)

b) An oil film of thickness 1.5 mm is used for lubrication between a square plate of size 0.9m *0.9m and an inclined plane having an angle of inclination 200 . . The weight of square plate is 392.4 N and its slides down the plane with a uniform velocity of 0.2 m/s. find the dynamic viscosity of the oil. (8)

5. a) Assuming the bulk modulus of elasticity of water is 2.07 x10 6

2

kN/m

at standard atmospheric condition determine the increase of

pressure necessary to produce one percent reduction in volume at the same temperature. (8) b)

Calculate the capillary rise in glass tube pf 3mm diameter when immersed in mercury, take the surface tension and angle of contact of mercury as

0.52 N/m and 1300 respectively. Also determine the minimum size of the

glass tube, if it is immersed in water, given that the surface tension of water is 0.0725 N/m

and Capillary rise in tube is not exceed 0.5mm. (8)

6. a) Explain all three Simple manometers with neat sketch. (8)

b) Explain Differential manometer With Neat sketch. (8)


UNIT II

FLOW THROUGH CIRCULAR CONDUITS

1. a) Derive an expression for the velocity distribution for viscous flow through a circular pipe. (8)

b) A main pipe divides into two parallel pipes, which again forms one pipe. The length and diameter for the first parallel pipe are 2000m and 1m respectively, while the length and diameter of second parallel pipe are 2000 and 0.8 m respectively. Find the rate of flow in each parallel pipe, if total flow in the main is 3 m³/s. The

coefficient of friction for each parallel (8)

pipe is same and equal to 0.005.

2. Two pipes of 15 cm and 30 cm diameters are laid in parallel to pass a total discharge of 100 liters/ second. Each pipe is 250 m long. Determine discharge through each pipe. Now these pipes are connected in series to connect two tanks 500 m apart, to carry same total discharge. Determine water level difference between the tanks. Neglect minor losses in both cases, f=0.02 fn both pipes. (8)

b) A pipe line carrying oil of specific gravity 0.85, changes in diameter from 350 mm at position 1 to 550 mm diameter to a position 2, which is at 6 m at a higher level. If the pressure at position 1 and 2 are taken as 20

N/cm2 and 15 N/ cm2 respectively and discharge through the pipe is 0.2

m³/s. determine the loss of head. (8)

3. Obtain an expression for Hagen- Poisulle flow. Deduce the condition of maximum velocity. (16)

4. A flat plate 1.5 m X 1.5 m moves at 50 km / h in a stationary air density

1.15 kg/ m³. If the coefficient of drag and lift are 0.15 and 0.75 respectively, determine (i) the lift force (ii) the drag force (iii) the resultant force and (iv) the power required to set the plate in motion .(1 6)

5. a). The rate of flow of water through a horizontal pipe is 0.3 m³/s. The diameter of the pipe is suddenly enlarged from 25 cm to 50 cm. The

pressure intensity in the smaller pipe is 14N/m². Determine (i) Loss of head due to sudden enlargement. (ii) Pressure intensity in the large pipe and (iii) Power lost due to enlargement. (8)

b) Water is flowing through a tapering pipe of length 200 m having diameters 500 mm at the upper end and 250 mm at the lower end, the pipe has a slope of 1 in 40. The rate of flow through the pipe is 250 lit/ sec. the

pressure at the lower end and the upper end are 20 N/cm² and 10 N/ ²

respectively. Find the loss of head and direction of flow (8)

6. A horizontal pipe of 400 mm diameter is suddenly contracted to a diameter of 200 mm. The pressure intensities in the large and small pipe is

given as 15 N/ ²

and 10 N/ ²

respectively. Find the loss of head due to

contraction, if Cc=0.62, determine also the rate of flow of water. (8)

7.Determine the length of an equivalent pipe of diameter 20 cm and friction factor 0.02 for a given pipe system discharging 0. 1m³ s. The pipe system

consists of the following: (16)

(i) A 10 m line of 20 cm dia with f=0.03 (ii)Three 90º bend, k=0.5 for each

(iii) Two sudden expansion of diameter 20 to 30 cm

(iv) A 15 m line of 30 cm diameter with f=0.025

and

(v) A global valve, fully open,


UNIT III DIMENSIONAL ANALYSIS

1. The frictional torque T of a disc diameter D rotating at a speed N in a fluid of

Viscosity μ and density ρ in a turbulent flow is given by T=D 5N

2 ρФ(μ/D 2 Nρ). Prove this Buckingham ’s Π theorem. 16)

2. Explain the different types of similarities.

3. Explain the dimensional analysis with suitable example.

2. 4. The frictional torque T of a disc diameter D rotating at a speed N in a fluid of

Viscosity μ and density ρ in a turbulent flow is given by T=D 5N

2 ρФ(μ/D 2 Nρ). Prove this Rayleigh’s Π theorem. 16)


UNIT IV ROTADYNAMIC MACHINES

1. Obtain en expression for the work done per second by water on the runner of a –pelton wheel. Hence derive an expression for maximum efficiency of the pelton wheel giving the relationship between the jet speed and bucket speed. 16)

2. a) A pelton wheel is having a mean bucket diameter of 1 m and is running at 1000 rpm. The net head on the pelton wheel is 700 m. If the side clearance angle is 15º and discharge through nozzle is 0.1 m³ s, find

(1) power available at nozzle and (2) hydraulic efficiency of the turbine. Take Cv=1 (8) b) A turbine is to operate under a head of 25 m at 200 rpm. The discharge is 9 m³ s. If the efficiency is 90% determine, Specific

speed of the machine, Power generated and type of turbine. (8)

3. A pelton turbine is required to develop 9000 KW when working under a head of 300 m the impeller may rotate at 500 rpm. Assuming a jet ratio of 10 And an overall efficiency of 85% calculate (1) Quantity of water required. (2) Diameter of the wheel (3) Number of jets (4) Number and size of the bucket vanes on the runner. (16)

An Outward flow reaction turbine has internal and external diameters of the runner as 0.5 m and 1.0 m respectively. The turbine is running

at 250 rpm and rate of flow of water through the turbine is 8 m³ s. The

width of the runner is constant at inlet and out let and is equal to 30 cm. The head on the turbine is 10 m and discharge at outlet6 is radial, determine (1) Vane angle at inlet and outlet. (2) Velocity of flow at inlet and outlet. 16)

5. The Nozzle of a pelton Wheel gives a jet of 9 cm diameter and velocity

75 m/s. Coefficient of velocity is 0.978. The pitch circle diameter is 1.5 m and the deflection angle of the bucket is 170º. The wheel velocity is 0.46 times the

jet velocity. Estimate the speed of the pelton wheel

turbine in rpm, theoretical power developed and also the efficiency of

the turbine. (16)

6. a) A turbine is to operate a head of a 25 m at 200 rpm; the available discharge is 9 m³/s assuming an efficiency of 90%. Determine (1) Specific speed (2)

Power generated (3) Performance under a head of

20 m (4) The type of turbine (8)

b) A vertical reaction turbine under 6m head at 400 rpm the area and diameter of runner at inlet are 0.7 m² and 1m respective the absolute and relative velocities of fluid entering are 1 5ºand 60º to the tangential

direction. Calculate hydraulic efficiency. (8)

7. A Francis turbine has an inlet diameter of 2.0 m and an outlet diameter

of 1 .2m. The width of the blades is constant at 0.2 m. The runner rotates at a speed of 250 rpm with a discharge of 8 m³ s .The vanes are radial at the inlet and

the discharge is radially outwards at the outlet. Calculate the angle of guide vane at inlet and blade angle at the outlet. (16)

8. A Kaplan turbine develops 20000KW at a head of 35 m and at rotational speed of 420 rpm. The outer diameter of the blades is 2.5 m and the hub diameter is

0.85m. If the overall efficiency is 85% and the hydraulic

efficiency is 88%. Calculate the discharge, the inlet flow angle and the blade angle at the inlet. (16)


UNIT V

POSITIVE DISPLACEMENT MACHINES

1. Write short notes on the following (1) Cavitations in hydraulic machines their causes, effects and remedies. (2) Type of rotary

pumps. (16)

2. Draw a neat sketch of centrifugal pump and explain the working principle of the centrifugal pump. (16)

3. Draw a neat sketch of Reciprocating pump and explain the working

principle of single acing and double acting Reciprocating pump. (16)

4. A radial flow impeller has a diameter 25 cm and width 7.5 cm at exit. It delivers 120 liters of water per second against a head of

24 m at 1440 rpm. Assuming the vanes block the flow area by 5% and hydraulic efficiency of 0.8, estimate the vane angle at exit. Also calculate the torque exerted on the driving shaft if the

mechanical efficiency is 95%. (16)

5. Find the power required to drive a centrifugal pump which to drive a centrifugal pump which delivers 0.04 m3 /s of water to a height of 20 m through a 15 cm diameter pipe and 100 m long. The over all efficiency of the pump is

70% and coefficient of friction is 0.15 in the formula hf=4flv2/2gd. (16)

6. A Centrifugal pump having outer diameter equal to 2 times the inner diameter and running at 1200 rpm works against a total head of 75 m. The Velocity of flow through the impeller is constant and equal to 3 m/s. The vanes are set back at an angle of 30º at out let. If the outer diameter of impeller is 600 mm and