Cec 107 Practical - Introduction to Fluid Mechanics

5/27/2018 Cec 107 Practical - Introduction to Fluid Mechanics

UNESCO-NIGERIA TECHNICAL

& VOCATIONAL EDUCATION

REVITALISATION PROJECT-

PHASE II

YEAR I- SEMESTER 1PRACTICAL

NATIONAL DIPLOMA IN

CIVIL ENGINEERING TECHNOLOGY

INTRODUCTION TO FLUID MECHANICS

COURSE CODE: CEC107


CIVIL ENGINEERING TECHNOLOGY

INTRODUCTORY FLUID MECHANICS (CEC 107)

COURSE CONTENTS

WEEK 1

Application of specific energy momentum function

WEEK 2

Continuation of practical in week one

WEEK 3

Flow over weirs

WEEK 4

Continuation of the practical in week three

WEEK 5

Diffusion of gas

WEEK 6

Applying the momentum flow on a jet of water

striking flat plate

WEEK 7 4.0 FLOW IN PIPES

4.1 Fluid in motion

4.2 Uniform and steady flow4.3 Rate of flow

4.4 Continuity equation

PRACTICAL

Minor losses in pipes

WEEK 8

Site visit to Gurara Dam to see pipe laying

WEEK 9


Site visit to Kangimi Dam to see different types of

weirs

WEEK 10

Site visit to a site where construction of open drain is

In progress

WEEK 11Experiment on Reynolds' dye

WEEK 12

Visit to irrigation sites to see water pumps

WEEK 13

Visit to Malali treatment plant to see more pumps

WEEK 14

Visit to Barnawa water treatment plant to see more

pumps

WEEK 15

Second visit to Gurara Dam to see turbine


PRACTICAL

WEEK ONE

APPLICATION OF SPECIFIC ENERGY AND MOMENTUM

FUNCTIONS

AIM

1) To confirm the theory relating to the flow under a sluice gate with the formation

of a hydraulic jump in a rectangular channel;

2) To estimate the force exerted by the sluice gate on the flow from the momentum

function consideration;

3) To estimate the energy head loss and the power loss due to the hydraulic jump by

specific energy consideration.

APPARATUS

a) A rectangular open channel model with down stream control weir;b)

Constant and steady supply of water into the channel with a means of

varying the flow;

c) Sluice gate;d) Depth measuring device;e) Flow rate measuring facility;f) Stop watch andg) Measuring scale.


Adjustable

Sluice gateHydraulic jump

channel

Downstream controlweir

pump

Fig.1

y3 y1

y2

Fig. 2


From fig. 2 above, at any point the specific energy E and momentum function M

is given by:

E = y + q2

2gy

2

and

M = q2

+ y2 per unit width

gy 2

where y = depth of flowq = flow rate per unit width = Q/b

Q = total discharge

b = channel width

Applying the E and M concepts to the flow under sluice gate with the formation

of a hydraulic jump, gives:

a) For flow under sluice gate;

E1 = E2

And P = P/g = M2 M1

Where P = force per unit width exerted by the sluice gate on the fluid.

b) For hydraulic jumps:

M2= M3

i.e. q2 + y22 = q2 + y3

2

gy2 2 gy3 2

y3 = y2 [1 + 8F22] - 1

2

Where F = Froude number = q

gy23

Due to lack of time, we stopped the practical here. We will continue and finish the

remaining next week


PRACTICAL

WEEK TWO

The practical started in the first week continued in this week because we are not

able to finish it last week.

Procedure

Adjust the channel bed model to a horizontal position and place sluice gate at a

fixed height above bed, sealing the openings between the gate and channel well to

prevent leakage.

Record the height of the gate above the channel bed and the width of the channel

(b).

Admit water into the channel and adjust the flow control and downstream control

weir to give the required flow profile.

Allow the system to steady and take the discharge Q, and the flow depths y1, y2

and y3.

Vary the flow rates and repeat the readings. Take at least 4 readings and record

them as shown on the observation table below:

Readings:

Channel width (b) = .

Height of gate above channel bed =

Vol. of

water

collected

Time

(s)

Discharge

Q (m3/s)

y1

(m)

y2 (m) y3 (m) q(m2/s) E2

(m)

E3

(m)

E2-E3

(m)


(m3)

Choose any experimental value of q and with varying depth of flow, using the

equation E = y + q2 Plot the depths against specific energy E.

2gy2


PRACTICAL

WEEK THREE

FLOW OVER WEIRS

Objectives

1. To determine the relationship between head H and flow rate Q over rectangular

and Vee notches (weirs).

2. To determine the discharge coefficient C for each notch by comparing the

measured flow with the ideal flow.

Method

1. Stand the apparatus on the hydraulic bench and connect the bench supply hoseto the inlet pipe. Fix the flexible outlet hose into the pipe leading to the bench

weighing tank.

2. Carefully slide the rectangular notch plate into the groove on the apparatus and

check that the rubber seal makes contact with the plate along all three edges.

3. Switch on the bench pump and open the bench supply valve. Fill the apparatus

with water until the level reaches the bottom crest of the notch. Close the supply

valve.

4. Using a beaker, add or remove water until the water surface is just level with the

notch crest. Use a steel rule to check that the level is correct.

5. Set the hook gauge dial to zero and slide the hook up and down until the point of

the hook just coincide with the water surface. Subsequent readings of the water

level will then be relative to the true datum at crest level.


6. Set the hook gauge to a reading of 60 mm. Then adjust the bench supply valve

until the water level corresponds roughly to the hook gauge setting.

7. Wait until the water level had settled to a constant value, then adjust the hook to

this level and read the value of the head.

8. Measure the flow rate by timing the collection of water in the bench weighing

tank. Again use the hook gauge to measure the water level and record a mean value

of head.

9. Now decrease the head by about 5 mm and take another set of head and flow rate

readings. Repeat this procedure until you have about 8 sets of readings over a range

of heads down to about 15 mm.

10. Close the bench supply valve and fix the Vee notch to the apparatus. Set the

water level to the base of the Vee notch by adding or removing water. Check that

the level is correct by observing the notch from close to the water surface. The point

of the Vee and its reflection should coincide.

11. Repeat the procedures given in steps (5) to (9), but this time obtain readings

over a range of heads between 80 to 30 mm.

12. Switch off the bench pump. Record the width of the rectangular notch and the

semi-angle of the Vee notch

We will stop here and the practical will be concluded next week.


PRACTICAL

WEEK FOUR

This week we will conclude the practical we started last week.

Results

The Volume flow rates for the two notches are given by the following equations:

Rectangular:

Q = C 2 [2gb H3/2]

3

Vee Notch:

Q = C 8 [ 2g tan] H5/215

The expressions in square brackets represent the ideal fix rates. The discharge

coefficient C is thus the ratio of the actual flow to the ideal flow for each notch.

Both equations can be expressed in logarithmic form as:

Log Q = log K + n log H

1. Convert your values of Q and H to units of m3/ sec and m of water. Plot

curves of Q against H.

2. Plot graphs of log Q against H. The points should lay on straight lines of

slope n = 3/2 and 5/2.

1. Now obtain values of k and hence calculate the discharge coefficient C foreach notch using the following expressions:


For rectangular:

C = k

2/3 2gb

For Vee Notch

C = k

8/152g tan

Conclusion

In his laboratory report, the student is expected to write a summary of what he has

learnt, which will answer the following questions:

1. To what extent has the results obtained confirmed the theory learnt in thelectures.

2. Is the value of C constant over the flow range for each notch?3. If the drawing of the graphs were to be drawn on the logarithmic sheets, at

slightly different slopes, how would this affect the values of C?


PRACTICAL

WEEK FIVE

DIFFUSION OF GAS

EXPERIMENT

To determine the diffusion coefficient of a gas by evaporation from a liquid

surface.

Theory

Consider a liquid evaporating by the diffusion of its vapour up a tube with zero

concentration at the top.

Let x be the length of the diffusion path.

i.e. x = xoat time = 0

and x = xtat time = t

From the diffusion equation, the following c an be derived for pseudo-state

conditions:

CLdx = c D (M1 M2)dt x ML

where

CL= Molar density of A in liquid phase

c = Total molar concentration in gas phase

D = Diffusion constant

M1= Molar fraction of A in gas phase at liquid surface

M2= Molar fraction of A in gas phase at top of tube (zero in this


Experiment

dx = Rate of change of diffusion path with time.

dt

ML= Vapour of liquid

ln (mole fraction of air at the top of tube/ mole fraction of air atbottom of tube)

Readings to be taken

o Switch on the temperature controlled water bath and obtain asteady temperature of say, 40

0C.

oPartially fill the vertical tube of the diffusion apparatus with

acetone and immerse in the water bath.

o With a flow of air across the top, take readings with the measuringmicroscope, of the acetone level at intervals of time and take a

reading of the top of the vertical line.

Results

Reading of top of tube:

Time (t) Liquid level

reading

X02

Xt2

Xt2- X0

2

Plot Xt2- X0

2as a function of time. A straight line should result.


Repeat the experiment at different temperatures and comment on the effect of

temperature on the diffusion.


PRACTICAL

WEEK SIX

APPLYING THE MOMENTUM EQUATION ON A JET OT WATER

STRIKING FLAT PLATE

y

V1Q1 x

V2Q2

Nozzle

Consider a jet of ideal flow (fluid without viscosity) striking a flat smooth plane.

Hence there is no shear force parallel to the plate working on the body of fluid.

Velocity on the jet to the plane is the same on that leaving the plane, i.e. V1= V2.

As there are no forces working on the fluid in x-direction and applying the

momentum equation in x-direction it is possible to determine the quantities Q1and

Q2 as follows:

Q1- Q2= Q Cos

The only force working on the plate is (in opposite direction on the fluid) is in Y

direction. Applying again the momentum equation it is clear that no fluid after

striking the plane is flowing in Y direction.

Conclusion: Force on the plate is working normal to the plate in magnitude eQv

Sin


Students are expected to determine Q1and Q2according to how they taught in the

class.


PRACTICAL

WEEK SEVEN

EXPERIMENT: MINOR LOSSES IN PIPES

AIM

1) To examine the minor energy head loss at:a) sudden contraction;b) a gate valvec) a 900flow elbowd) a 900 long radius bend2) to determine the loss coefficient K for each fittings.

PROCEDURE

Record the diameters of the pipe upstream and downstream of the fittings and the

length between pressure taping for each fitting.

Connect the sudden contraction apparatus to the experimental system and fit the

pressure tapings upstream and downstream of the contraction. Purge the system of

air and check the manometer.

Adjust the flow control valve to give maximum flow. Allow the flow conditions to

steady and record the flow rate C, and water levels h1 and h2 in the manometer

limbs.

Reduce the flow rate in steps and take a series of readings of Q, h1and h2.

Repeat the procedure for each fitting.


THEORY

Minor energy head loss hein pipe is given as:

he= Kv2

2g

Where:

K = loss coefficient

For sudden contractions he= Kv2

2g

Where:

K = (1/C-1)

2

v = velocity of flow downstream of contraction.

For elbows, bends, valves etc,

hL= Kv2

2g

Where v = velocity of flow downstream of fitting.

If velocity loss is taken into account, the total energy head loss (h 1- h2) is equal to

the sum of hfand hLwhich is given by:

Total energy head loss H = hf+ hL

h1 h2= FLV2

+ Kv2

2gd 2g

Where L = Length of pipes between pressure tappings.

d = Pipe diameter


Readings

h1(m) h2

(m)

h1

h2

(m)

hf(m) hL

(m)

H20

volume

(m3)

Time

(sec)

Q

(m3/sec)

Velocity

(m/sec)

V2/2g

(m)


PRACTICAL

WEEK EIGHT

The students were taken to a site visit where a contractor is excavating and laying

new pipes to connect the Gurara water in Kaduna state with Abuja, the Federal

Capital of Nigeria. During the visit, the students were conducted around the area

and they asked the site engineer of the project various questions.

After our return, the students were asked to write on the following:

1) The diameter of the pipes laid;2) The distance between the project site to Usma Dam in Abuja where the water

will be transferred to;

3) The expected velocity of the water;4) Then calculate the expected amount of water (Discharge) that will be

delivered to Abuja


PRACTICAL

WEEK NINE

This week the students were taken for a visit to Kangimi village along Jos road. The

dam is used for water supply and irrigation. The purpose of the visit is for the

students to see various types of weirs and spillway.

The students were given assignment on the visit as follows:

1) Draw the types of weirs that you saw at Kangimi dam;2) All the parameters needed to calculate the discharge in trapezoidal and

rectangular weirs were given to the students at the dam site. Therefore the

students are expected to calculate the discharges at theses weirs.


PRACTICAL

WEEK TEN

This week the students were taken to a construction site in Kaduna town where

constructions of open drains are in progress. The students were conducted round to

different parts of the project. After the visits, the students were asked the following

questions:

1) What are the dimensions of the rectangular drain? Draw a section.2) What are the sides' slopes of the trapezoidal drain? Also draw the section?3) Calculate the areas of these drains and the expected run off water that they will

carry.


PRACTICAL

WEEK ELEVEN

The students were taken to the laboratory where they were shown a model of

Reynolds' dye experiment. Starting with a low velocity, the students were

shown the behaviour of the applied dye. After the increase in velocity, they

saw how the dye filament scattered.

At the end of many demonstrations, the students were given assignment as

follows:

1) Draw and explain how Reynolds' apparatus is working.2) Using the following data determine the types of flow in the following

cases:

i) if the density of water is 1000 kg/m3, pipe diameter of 250 mm and the

coefficient viscosity of 100 x 10-3 Ns / m2. Take the velocity to be 2.5 m

/sec.

ii) if the density of the fluid is 800 kg / m3 and a pipe diameter of

300mm. The velocity of flow is 3 m and the coefficient of dynamic

viscosity is 110 x 10-3

Ns


PRACTICALWEEK TWELVE

The students were taken on a visit to two irrigation sites in Igabi local Government

of Kaduna State. In both sites, the students saw how water pumps are used to raise

water from one position to other. They saw different types of water pumps and they

asked the farmers how they are using the pumps and how efficient are the pumps in

lifting water for the irrigation work they are doing.

The students were asked to answer the following questions:

1) Explain the working principles of the different types of pumps you saw at thetwo sites.

2) From your observations which of the pumps is more efficient in lifting the waterand at what head?

3) What are the problems that the farmers are facing in operating and maintenanceof the pumps?


PRACTICAL

WEEK THIRTEEN

This week the students were taken for a visit to Malali water works in Kaduna

North Local Government area of Kaduna state. The students were conducted round

the treatment plants where they were shown different types of pumps that are used

in lifting water right from the intake up to distribution stage.

The students were given these questions related to their visits:

1) Which type of pump is use in lifting water from the intake to the treatmentplant?

2) Have you noticed that without the pumps the treatment of water would havebeen very difficult?


PRACTICAL

WEEK FOURTEEN

This week the students paid similar visit as that of last week to Barnawa treatment

plant in Kaduna South area of Kaduna State. The students were conducted round

the plant by the Water Engineer in charge of the plant. The engineer explained

that the major difference between the Barnawa treatment plant and the Malali

plant that the students visited last week is that most of the industries are located in

Kaduna South; therefore this plant is dealing with raw water that includes

industries industrial wastes.

The students were therefore asked:

1) What extra effort has the Barnawa treatment plant to do apart from the normal

treatment in order to take care of the pollution from the industries?


PRACTICAL

WEEK FIFTEEN

This week the students for the second time re-visited the Gurara dam where they

expected to see some turbines brought by the contractors for installation at the site

of the dam for the purpose of generating electricity in some parts of Kaduna State.

The turbines have not been installed but the students were taken round and they

were shown the turbines.

At the end of the visit, the students were asked:

1) Explain the type of turbine you were shown at the site

Cec 107 Practical - Introduction to Fluid Mechanics

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