car aerodynamics (lecture) - new (2)

7/25/2019 Car Aerodynamics (Lecture) - New (2)

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VEHICLE AERODYNAMICS

ANDBODY CONSTRUCTIONS

Presenter: Mahona: John. P

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Mahona: John. P

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MODULE DESCRIPTION &CONTENTS

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Unit I: Introduction Den!t!on"

so#r$es o% ra' Me$han!$s o% a!r (o) aro#n a

*eh!$+e

Aero,na-!$ %or$es an Dra'$o-onents

Aero,na-!$ a!s / B#-er so!+ers"

A!r a-s" De$0 +! so!+ers" )!no)

i


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Unit II: Drag

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A!r ens!t," an Dra' $oe2$!ent

E3er!-enta+ te$hn!4#es to

eter-!ne ra' an ra'$oe2$!ents.

Dra' $oe2$!ents %or *ar!o#s

shaes S!e %or$e" +!%t %or$e" P!t$h!n'

-o-ent" Ya)!n' -o-ent" Ro++!n'

-o-ent an $ross )!nU III


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Un t III:

Signifcance oaerodynamic drag on

vehicle body shapes

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5a$tors !n(#en$!n' aero,na-!$ ra'

Re#$t!on o% ra' $oe2$!ent an %#e+

e$ono-,Tr#$0 & B#s aero,na-!$s /

6Co--er$!a+ *eh!$+es7 S!'n!$an$e o%

aero,na-!$ ra'


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:Vehicle body constructionCars7

Methos o% !-ro*!n'

*!s!9!+!t, an sa$e !n $ars Sa%et,:

Des!'n sa%et, e4#!-ent %or$ars.

Car 9o, $onstr#$t!on


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Unit V:Commercial vehicles

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Tr#$0s Bo, t,es D!-ens!ons o%r!*er;s seat re+at!on to $ontro+s Dr!*ers$a9 es!'n" 5ra-e $onstr#$t!on.

B#ses 5ra-e $onstr#$t!on" Do#9+e s0!n$onstr#$t!on T,es o% -eta+ se$t!on #seRe'#+at!ons Con*ent!ona+ an !nte'ra+

t,e $onstr#$t!on. Passen'er anL#''a'e re4#!re-ents" 9o, !-ens!onsan stanars a#to-ot!*e Bo, rea!ran ren!sh!n'.


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Assess-ent $r!ter!a9

Cont!n#o#s Assess-ent:

Co-r!ses o% :

Ho-e)or0 ?

Pro@e$tro# H

C+assroo- Test ?

Se-ester E3a-!nat!on: =>


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INTRODUCTION


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1!!"1#!Aatat!ono% shaes %ro- other

e+s


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Experimental

cars

1#!"1$! Aatat!on o% res#+ts o%a!r+ane an a!rsh! e*e+o-ent:strea-+!n!n'


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1$!"1!: Deta!+ot!-!1at!ons


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INTRODUCTION%erodynamics" !s a 9ran$h o% ,na-!$s

$on$erne )!th st#,!n' the -o*e-ent o% a!ran other 'ases )hen !ntera$t!n' )!th -o*!n'so+! o9@e$ts an stat!onar, ones. Th!s!ntera$t!ons ta0es +a$e 9et)een the 9o,

s#r%a$es an s#rro#n!n' a!r )!th *ar,!n' re+at!*esees an )!n !re$t!ons. In short it is a studyof airow & the forces involved when an objectmoves through the air or when air moves past an

object.Aero,na-!$s !n$+#es the st#, o% the!ntera$t!ons o% a!r )!th -o*!n' o9@e$ts" s#$h asa!r+anes" $ars" 9!$,$+e an o% the eFe$ts o%

-o*!n' a!r on stat!onar, o9@e$ts" s#$h as 9#!+!n's.
http://en.wikipedia.org/wiki/Dynamics_(physics)http://en.wikipedia.org/wiki/Dynamics_(physics)


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""

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%utomotive*Vehicle aerodynamics.

S!n$e o#r tar'et so+! o9@e$t !s the *eh!$+e or$ar

Is the st#, o% the aero,na-!$s o% roa*eh!$+es.

Roa *eh!$+es !n$+#e a++ -oes o% s#r%a$etransort +,!n' on the roa aro#n the)or+.

A vehicle !s a -o9!+e -a$h!ne that !ses!'ne or #se to transort assen'ers or$ar'o. Most o%ten *eh!$+es are -an#%a$t#re"s#$h as 9!$,$+es" $ars" -otor$,$+es" tra!ns"

sh!s" 9oats an a!r$ra%t.


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INTRODUCTION / $ontVehicle construction re%ers to ho) a*eh!$+e

!s -ae or %a9r!$ateVeh!$+es are a -ae # o% !ntera$t!n'

-e$han!$a+e+e$tr!$a+ s,ste-s an o*erG"=== arts are #se !n a t,!$a+ *eh!$+eDa-a'e to one art $an aFe$t theoerat!on o% another see-!n'+, #nre+ate

art an D!Ferent t,es o% *eh!$+e$onstr#$t!on re4#!re !Ferent -ethos o%rea!r %ra-e#n!9o, a-a'e


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INTRODUCTION / $ont%gain + Vehicle construction re%ers to ho)

a *eh!$+e !s -ae or %a9r!$ate !s !nterre+ate)!th *ar!o#s En'!neer!n' an non En'!neer!n'areas !n*o+*e !n the *eh!$+es es!'nsto'ether )!th the!r oerat!ons

Ma!n+, these are $ate'or!$a++, )or0e asEn'!neer!n' a$t!*!t!es an H#-an 5a$tors an

that the, $annot )or0 as the searate ent!t,9oth !n t!-e an -ater!a++,


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START ??=


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7C0%&ICS )9 %I( 9,). >C)&' "

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hereas the -athe-at!$a+ -oe+ o%+a-!nar a!r(o) !s rather stra!'ht%or)ar"

Con!t!ons are -#$h -ore $o-+e3 !nt#r9#+ent (o)" )h!$h t,!$a++, o$$#rs !nthe resen$e e!ther o% o9sta$+es or o%h!'h sees.

7C0%&ICS )9 %I( 9,). >


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7C0%&ICS )9 %I( 9,). >C)&' "

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In 'enera+ Aero,na-!$s theor!es are

'o*erne 9, *ar!o#s %a$tors $ons!ere !n

the -e$han!$s o% a!r (o) s#$h as

Streamlines

Velocity Distribution,aminar 9lo/

'urbulent 9lo/

7C0%&ICS )9 %I( 9,). >


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7C0%&ICS )9 %I( 9,). >C)&' "

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Viscosity

(eynolds &umber

@oundary ,ayer

S=in 9riction+ @ernoulliAs8rinciple B Dynamic pressure

8itot 'ube

8ressure Coecient


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Br!e% e3+anat!ons on these

'o*ern!n' %a$tors

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StreamlinesC#r*es asso$!ate )!th a !$tor!a+ reresentat!on o% a!r

(o)

S-o0e !s $o--on+, #se !n )!n t#nne+s to reresentthe strea-+!nes

Strea-+!nes are #se to st#, a!r (o)

Ve+o$!t, D!str!9#t!on


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Ve+o$!t, D!str!9#t!on

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The nat#re o% the (#! (o)

A -eas#re o% $han'es !n a!r (o)s*e+o$!t, $+ose to the *eh!$+e


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La-!nar 5+o)

5+#! -ot!on that !s )e++ or'an!1e

5+#! )!th ara++e+ *e+o$!t, *e$tors

enera++," +a-!nar (o) has the !ea+

aero,na-!$ roert!es

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T#r9#+ent 5+o)

5+#! -ot!on that !s not )e++ or'an!1e

5+#! )!th ara++e+ an other *e+o$!t,*e$tors

enera++," t#r9#+ent (o) has #nes!ra9+eroert!es

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! !


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V!s$os!t,64

The %o++o)!n' !s the P!$tor!a+ reresentat!ons o% (#!


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The %o++o)!n' !s the P!$tor!a+ reresentat!ons o% (#!*!s$os!t,

R + N 9


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Re,no+s N#-9er

Q#ant!es the ro#$t o% see t!-ess!1e

Is a !-ens!on+ess n#-9er here"

!s (#! ens!t,"

!s the *!s$os!t,"

V !s the *e+o$!t,"

an L !s the +en'tho% theo9@e$t

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Re,no+s N#-9er

Reresents the rat!o 9et)een !nert!a+ an*!s$o#s %or$es

Co-ensates %or s$a+e !Feren$es

Re $an !n!$ate the nat#re o% the (#! (o)

H!'her *a+#es !n!$ate t#r9#+ent (o)

Lo)er *a+#es !n!$ate +a-!nar (o)

D!Ferent (o)s $an 9e $ons!ere the sa-e !%the, ha*e s!-!+ar Re *a+#es

A++o)s s$a+e -oe+s to 9e a$$#rate+, teste !n

)!n t#nne+s #s!n' !Ferent (#!s an or

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B L


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Bo#nar, La,er

The th!n +a,er o% ra! tan'ent!a+ *e+o$!t, $han'e$+ose to an o9@e$ts s#r%a$e

enera++, !n$reases !n th!$0ness )!th the +en'tho% the o9@e$t

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Berno#++!s E4#at!on69

"P ! ! + & D !


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"Pr!n$!+e & D,na-!$ress#re70


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(A)T(* +,AM-(+)

5UNDAMENTAL PRINCIPLES


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. Mass !s ne!ther $reate nor estro,e 6-ass !s $onser*e7Conservation o 7ass

O%ten a+so $a++e: Cont!n#!t,

?. S#- o% 5or$es T!-e Rate Chan'e o% Mo-ent#- 6Ne)tons ?n

La)7O%ten re#$es to: S#- o% 5or$es Mass 3 A$$e+erat!on 69 -a7

7omentum uation

Berno#++!s E4#at!on" E#+er E4#at!on" Na*!erSto0es E4#at!on

. Ener', ne!ther $reate nor estro,e 6ener', !s $onser*e7

Can on+, $han'e h,s!$a+ %or-

nergy uation6stLa) o% Ther-o,na-!$s7

Ho) o )e e3ress these state-ents -athe-at!$a++,

SUMMARY O5 OVERNIN EQUATIONS


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STEADY AND INVISCID 5LO

.

..

.

//

..//

.

/

.

/VpVp

VAVA

+=+

=

( )

...

///

.

..

.

//

/

.

/

.

/

.

/

...///

.

/

.

/

RTp

RTp

VTcVTc

T

T

p

p

VAVA

pp

=

=

+=+

=

=

=

0 Incompressibleflow of fluid along a

streamline or in a stream tue of

varying area

0 Most important variales1 p and 2

0 T and are constants throughout flow

0 Compressible, isen!ropic

#adiaatic and frictionless%

flow along a streamline or in a

stream tue of varying area

0 T& p& & and 2 are all variales

continuity

3ernoulli

continuity

isentropic

energy

e'uation of state

at any point

CONSERVATION O5 MASS


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Ph,s!$a+ Pr!n$!+e: Mass $an 9e ne!ther $reate nor estro,e

)tream tue

0 As long as flow is s!e"#$& mass that flows through cross section at point

#at entrance% must e same as mass that flows through point #at e4it%

0 $low cannot enter or leave any other way #definition of a stream tue%

0 Also applies to solid surfaces& pipe& funnel& wind tunnels& airplane engine

0 %&'"! goes in one si#e m(s! come o(! !'e o!'er si#e)

A

A

2

2

$unnel wall

CONSERVATION O5 MASS


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)tream tue

0 Consider all fluid elements in plane A

0 During time dt& elements have moved 2dt and swept out volume A2dt

0 Mass of fluid swept through Aduring dt1 dm5#A2dt%

A1 cross6sectional area

of stream tue at

21 flow velocity

7ormal #perpendicular% to A

s

kg$lowMass

mm

VAm

VAmdtdm

=

=

===

+


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E3a-+e

hat !s a *eh!$+es ra' %or$e" )!th a %ronta+

Area o% .G -?" CDo% =.


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%ir 9lo/ around a

VehicleTo #nerstan th!s (o)" ,o# $an *!s#a+!1e a$ar -o*!n' thro#'h the a!r 6%o++o)!n' '#res7.

As )e a++ 0no)" !t ta0es so-e ener', to -o*e

the $ar thro#'h the a!r.A'a!n" %or a *eh!$+e" e3terna+ an !nterna+ (o)

are $+ose+, re+ate.

The e3terna+ (o) has 'reat !n(#en$e on theer%or-an$e $hara$ter!st!$s an the!re$t!ona+ sta9!+!t, o% the *eh!$+e" )hereasthe !nterna+ (o) -a0es re%eren$e to the

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car aerodynamics (lecture) - new (2)

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