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Civil 151 Fluid Mechanic Laboratory Experiment Manual 2

Fluid Flow measurement

1. Obective!

"o observe characteristics o# #low over a rectan$ular notch %part &' and a (ee notch

%part )'

2. Experimental setup!

& *ydraulic )ench+ *oo, and point -ua$e+ top watch+ /ectan$ular notch and (ee

notch

1

0. art &! /ectan$ular notch weir

0.1 ummary o# "heory

)y applyin$ the )ernoulli Euation %conservation o# ener$y euation' to a

simpli#ied #low model o# a rectan$ular notch weir+ we can develop the #ollowin$

relationship!

20

20

2HgLCQ d=

1Robert L. Street, Gary Z. Watters, John K. Vennard, Elementary Fluid Mechanics !""#, $ thedition%, &.##'

Robert L. Street, Gary Z. Watters, John K. Vennard, Elementary Fluid Mechanics !""#, $ thedition%, &.##$

Robert L. Street, Gary Z. Watters, John K. Vennard, Elementary Fluid Mechanics !""#, $ thedition%, &.##$

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3here 4 6ischar$e

Cd Coe##icient o# dischar$e

L )reath o# notch

* *ead above bottom o# notch

7ote! "he coe##icient o# dischar$e allows #or the di##erences between the simpli#ied

#low model used to derive the above #ormula and the real #low situation.

rocedure!

1' 8nsert the rectan$ular weir into the hydraulic bench and #it the weir ti$htly by usin$

screws in order to prevent lea,a$e to occur.

2' Open the water supply and allow water #low over the weir. %i.e. * is not eual to

9ero'.

0' &dust the water supply so as to ma,e the water level become steady. Let the water

#low over the weir and wait until steady state o# #low is reached.

:' &dust the (ernier *ei$ht -au$e and its pointer ust touch the water sur#ace. et

the readin$ to be 9ero so that the bottom o# the notch is ta,en as the datum. Ma,e

sure the vernier does not slide alon$ the mast durin$ the experiment until all data

have been recorded.

5' Open the water supplies a$ain slowly+ adust the #low rate and measure the head

%*' by the vernier. )e#ore measurin$+ wait at least one minute #or lettin$ the #low

to stabili9e. "hen measure the * #or twice #or better accuracy.

;' witch on the stopwatch and record the time #or admittin$ 1< litres o# water

#lowin$ over the weir. &lso+ measure the time #or 1< litres o# water #low. Find the

di##erence between the times. 8t is a $ood way to maintain the consistency o# the

experiment. 8# the di##erence between the two =times> is $reater than one minute+

measure the time a$ain as the error is too lar$e.

?' /epeat step : to step ; by usin$ di##erent #low rate o# water+ which can be done by

adustin$ the water supply. Measure and record the * and the time #or 1< litres to

#low until 1< sets o# data have been ta,en.

@' /ecord breadth o# notch #or calculation o# dischar$e coe##icient.

/esult and calculation

1. lease derive theory #rom 1stprinciple i.e. conservation o# mass and ener$y.

2. lease calculate and plot relevant $raphs to show your results.

0. Aou may su$$est a #unctional relationship between dischar$e coe##icient

and other parameters.

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:. 6iscuss assumptions o# the theory and possible experimental errors.

:. art )! (eeBnotch 3eir

:.1 ummary o# theory

imilarly+ by applyin$ )ernoulli euation %conservation o# ener$y euation' to a

simpli#ied #low model o# a (eeBnotch+ we can develop the #ollowin$ relationship!

2

5

22

tan15

@HgCQ d

=

3here 4 6ischar$e

Cd Coe##icient o# dischar$e

2 *al# the enclosed an$le o# the (ee

* *ead above bottom o# notch

:.2 rocedure

lease #ollow same procedures described in part 0.2 except that a vee notch+

instead o# a rectan$ular notch+ should be installed to the hydraulic bench.

:.0 /esult and calculation

1. lease derive theory #rom 1stprinciple i.e. conservation o# mass and ener$y.

2. lease calculate and plot relevant $raphs to show your results.

0. Aou may su$$est a #unctional relationship between dischar$e coe##icient

and other parameters.:. 6iscuss assumptions o# the theory and possible experimental errors.

5 6eadline #or report submission

1. Each $roup o# students MD" submit one report to pi$eon hole outside "&

o##ice %rm212;' 2 wee,s a#ter the date o# experiment.

2. "he report should be typed and wellBwritten. oor report will not be accepted.

0. Copyin$ is not allowed and re#erence must be clearly stated at the end o# report.

E/O mar,s mi$ht be $iven i# cases o# pla$iarism are #ound.

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6ata Lo$$in$ sheet -roup no.

/ectan$ularBnotch 3eir

* %mm' (olume %L' "ime %s'

"rial 1

"rial 2

"rial 0

"rial :

"rial 5

"rial ;

"rial ?

"rial @

"rial G

"rial 1