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No. DokumenTB/ MMB/ BMCF2223/ 2

No. Isu./ Tarikh2/ 24-11-2007

FLUID MECHANICS 1Fluid Friction No. Semakan/ Tarikh1/ 12-12-2007 Jum Mukasurat6

OBJECTIVES

1.  To determine the relation between friction head loss and velocity for flow of waterthrough smooth bore pipes.

2. 

To compare the head loss predicted by a pipe friction equation with direct measurehead loss.

LEARNING OUTCOME

At the end of this lab session, students should be able to

1.  Investigate and draw the relationship between head loss and velocity at differenttype of flow

THEORY 

Professor Osborne Reynolds demonstrated that two types of flow may exist in a pipe: -

1 L i fl t l l iti h h∝

UNIVERSITI TEKNIKALMALAYSIA MELAKA 

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1 Laminar flow at low velocities where uh∝

For a circular pipe flowing full, the head loss due to friction may be calculated from theformula:

h =gd 

 fLu

2

2

(1)

where  L = length of the pipe between tappings

d  = internal diameter of the pipe

u = mean velocity of water in m/ s

g = acceleration due to gravity in m/ s2 

 f  = friction coefficient.

The Reynolds’ number, Re, can be found using the following equation:

Re =μ 

 ρ ud (2)

where μ = dynamic viscosity

 ρ = mass density

Having established the value of Reynolds’ number for flow in the pipe, the value of  f may

be determined using a Moody diagram.

APPARATUS

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PROCEDURES

1.  Switch on the pump and open the supply valve fully. Set the pressure digital meter byplugging into pipe tapping. Make sure there were no air bubbles present in the rubber

hose.

2.  Switch on the equipment to allow water f lowing in the pipe assembly. The flowingwater will push the air bubbles out of the rubber hose. Make sure no air bubblespresent in the rubber hose.

3.  If the air bubbles were not present in the rubber hose, quickly connect the rubber hoseto the pressure digital meter.

4.  Before making any measurement, make sure the condition of the C6-MKII-10 FluidFriction Apparatus is as follow: -

a.  Gate valve and Globe valve are fully open.b.  Ball valve 2 is fully open, while ball valves 1, 3, 4 and 5 are fully close.c.  The supply valve is fully close now.

5.  Open the supply valve by ¼ turn (quarter turn).

6. 

Record (into Table 1) the time taken for 5 liters of water to f ill in the volumetric tank. Todo this, stop the water from flowing into the sump with the ball in the armfield, so thatwater is retaining in the volumetric tank. Its level will start to rise as may be seen at thesight gauge. Remember to lif t the ball to allow water flowing back into the sump af terthe time is recorded.

7.  Record the pressure difference reading from the hand held pressure digital meter intoTable 1.

8 Take press re different reading at se eral different flo rates b altering the flo

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FLUIDFRICTION

Name: _________________________________ MetricNumber: _________________Section/ Group: _________________________ Dateof experiment: ______________

EXPERIMENTALDATA

Density of water,   (fromtable) = kg/ 3

Dynamic viscosity of water,  (fromtable)= kg/ m

Lengthof pipes, =

Internal diameter of pipe,d  =

Table1 Fluid FrictionExperimental Data

Volume

V  (litres)

 Time

T  

(s)

Flowrate

Q 

(m3/s)

Diameter

d 

(m)

Velocity

u 

(m/s)

R

FromMoody

Diagram

Calculate

HeadLoss

(mH2O)

Measure

Head Loss(mH2O)

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Plota graphof logh versus logu . Confirmthat the graphisa straight line for the zone of 

turbulent flow

n

uh  . Determine the slope of the straight line to find n.

DISCUSSION

1. Discussthe relationship of head lossand velocity based onGraphh versusu: 

 ___________________________________________________________________  ___________________________________________________________________  ___________________________________________________________________  ___________________________________________________________________  ___________________________________________________________________  ___________________________________________________________________  ___________________________________________________________________ 

2. Fromthe graph, analyse the transition phase value and explain how it could behappen.__________________________________________________________________ 

 __________________________________________________________________  __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 

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1

APPENDIX A - Moodydiagram

 To find f  , first locate

the respective D 

curve at the rightvertical axis; In yourcase of smooth pipes,use the curve labeledsmooth. After that,locate the respectiveReat the bottomhorizontal axis. At theintersection point, movehorizontally to the left isthe correspondingfrictionfactor.