Fluid Mechanic-Fundamentals of Fluid Flow

8/17/2019 Fluid Mechanic-Fundamentals of Fluid Flow

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ME411Y-Fluid

MechanicsFundamentals of Fluid Flow


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Denition of Terms

Osborne Reynolds


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Discharge or Flow Rate,

QAmount of uid passing through a section per unit of time. This is expressed as a mass ow rate ( ex. g!sec ", weightow rate ( ex. #$!sec ", and %olume ow rate or ow rate( ex. & lit!s ".

Volume Flow Rate, Q = AV where'

Mass Flow Rate = pQ Q Discharge in cu. meter per sec orft)!s

Weight Flow Rate = wQ A *ross +ectional area of owm or ft

- ean -elocit/ of ow in m!s or ft!s

p ass Densit/ in #!m) or slugs!ft)

w 0eight Densit/ in $!m) or l1!ft)


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*ontinuous Flow2ccurs when at an/ time, the discharge Q at

e%er/ section of the stream is the same.(principle of conser%ation of mass"


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3aminar Flow The ow is said to 1e laminar when the path

of indi%idual uid particles do not cross orintersect. For 3aminar ow, the Re/nold4snum1er, Re5666


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Tur1ulent Flow The ow is said to 1e tur1ulent when the path

of indi%idual particles are irregular andcontinuousl/ crossing each other. For

Tur1ulent Flow, Re78666


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2ne Dimensional Flow2ccurs when in an incompressi1le uid, the

direction and magnitude of the %elocit/ at allpoints are identical


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Two9Dimensional Flow2ccurs when the uid particles mo%e in

planes or parallel planes and the streamlinepatterns are identical in each plane


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+treamlines These are imaginar/ cur%es drwn through a

uid to indicate the direction of motion in%arious sections of the uid s/stem


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+treamtu1esRepresents elementar/ portions of a owing

uid 1ounded 1/ a group of streamtu1eswhich conne the ow.


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Flow $ets These are drawn to indicate ow patterns of

two9demensional ow, or e%en threedimensional ow


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:nerg/ and ;ead

James Watt


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:nerg/ and ;ead The energ/ possessed 1/ a owing uid

consists of the #inetic and the potentialenerg/.


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inetic :nerg/ The a1ilit/ of the uid mass to do wor# 1/

%irtue of its %elocit/

KE = ½ MV 2

= ½ (W/g)V 2

where'

mass of uid- -elocit/ Flow0 0eight of Fluid


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:le%ation :nerg/ The energ/ possessed 1/ the uid 1/ %irtue of

its position or ele%ation with respect to adatum plane.

*onsider a tan# which is full of water. =f a holeat the 1ottom is opened, the uid will ow 1/%irtue of the height of the water a1o%e thehole.


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ut

if the top will 1e su1?ect to a pressure of p, uidwould ow. =n *hapter , the e@ui%alent head(pressure head" for a pressure of p is p!w. ;encethe pressure energ/ is e@ui%alent to'


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Total :nerg/ Flow, : The total energ/ or head in a uid ow is the

sum of the #inetic energ/ and potentialenergies. =t can 1e summaried as'


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>ernoulli4s :nerg/

Theorem

Daniel >ernoulli


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>ernoulli4s :nerg/

TheoremResults from the applications of the principles

of the conser%ation of energ/. This e@uationma/ 1e summaried as follows'


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>ernoulli4s :nerg/ Theorem (without

head lost"=f the uid experiences no head lost in mo%ing

from section B to section then the totalenerg/ at section B must 1e e@ual to the totalenerg/ at section . neglecting head lost inthe uid ow, the %alues that we can get arecalled theoretical values


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>ernoulli4s :nerg/ Theorem

(with head lost"*onsidering head lost, the %alues that we can

attain are called actual values.


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(with head lost"


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(with head lost"


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(with pump"


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(with pump"


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(with tur1ine or motor" Tur1ines or motors extracts ow energ/ to do

mechanical wor# which is con%erted intoelecrical energ/ for tur1ines


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(with tur1ine or motor"

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Fluid Mechanic-Fundamentals of Fluid Flow