Modified Whortman Airfoil Ppt

8/18/2019 Modified Whortman Airfoil Ppt

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Study and Simulation of Flow Over Modified Wortmann high lift Airfoil at00 angle of attack Using cfd tool and Validation with XF!

Neeraj Shukla

M.Tech. Student, Department of Applied Mechanics, MNNIT Allahabad, India

[email protected]

A"S#!A$#

In this study we have obtained the drag and lift coefficients and forces using CFD. hrough analytical !ethodthan it can be validated by "F#$ software% analysis of the two di!ensional subsonic flow over an &odified

'hort!ann high lift air foil (F" )*+C#,+-* / at 0ero angle of attack and o1erating at a $eynolds nu!ber of

- 2 -3) is 1resented. he si!ulation results of F#45N shows close agree!ent with the "F#$ results. In view

of this study we have obtained lift% drag force with 1ressure distribution on airfoil using CFD.

%eywords& Modified Whortmann ' Fluent ' XF! (

)( *ntroduction

It is a fact of co!!on e21erience that a body in !otion through a fluid e21eriences a resultant force which% in

!ost cases is !ainly a resistance to the !otion. 6 class of body e2ists% however for which the co!1onent of theresultant force nor!al to the direction to the !otion is !any ti!e greater than the co!1onent resisting the

!otion and the 1ossibility of the flight of an air1lane de1ends on the use of the body of this class for wing

structure. 6irfoil is such an aerodyna!ic sha1e that when it !oves through air% the air is s1lit and 1asses above

below the wing. he wings u11er surface is sha1ed so the air rushing over the to1 s1eeds u1 and stretches out.

his decreases the air 1ressure above the wing. he air flowing below the wing !oves in a co!1aratively

straighter line% so its s1eed and air 1ressure re!ains the sa!e% since high air 1ressure always !oves towards low

air 1ressure% the air below the 1ushes u1wards toward the air above the wing. he wing is in the !iddle% and the

whole wing is lifted. he faster an air1lane !oves the !ore lift there is. 'hen the force of lift is greater than the

force of gravity the air1lane is able to fly.

+omenclature of an Airfoil

6n airfoil is anybody which% when set at a suitable angle to a given airflow% 1roduces !uch !ore lift than drag.

o fulfill these re7uire!ents% the body should be sha1ed% in section% s!oothing like the section de1icted in fig -.

his sha1e is designed to ensure strea!line flow as far as 1ossible.

he leading edge is rounded to ensure s!ooth flow. he trailing edge is shar1% so that the 8utta conditions !ay

be satisfied% the wake is ke1t thin and any region of se1arated flow is ke1t as s!all as 1ossible. hese features

hel1 to achieve high lift and low drag.

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Fluids Engineering Laboratory (AM2)

M.Tech. (Fluids Engineering) 2nd Semester

mailto:[email protected]





First International Conference on Applied Mechanics and Materials Engineering, Dec. !"#, $%&, Allahabad, India

Fig9 -. No!enclature of an 6irfoil

he attitude of the airfoil is e21ressed by the angle between the chord line and the free strea! velocity vector.his angle denoted by :% is called the incidence or angle of attack.

Fig9 ;. 6erodyna!ic Forces

he aerodyna!ic force act along line whose intersection% C with the chord line is called the center of 1ressure of

the airfoil as shown in fig.;. he aerodyna!ic force !ay be resolved into two co!1onent one nor!al and one

1arallel to the free strea! direction. hese co!1onents are res1ectively called lift and drag and denoted by # and

D.

• Airfoil9 6n airfoil is the sha1e of a wing or blade (of a 1ro1eller% rotor or turbine/ as seen in cross+

section.

• eading edge& It is the 1oint at the front of the airfoil that has !a2i!u! curvature.

• #railing edge& It is defined as the 1oint of !a2i!u! curvature at the rear of the airfoil.

• $hord line9 6 straight line intersecting leading and trailing edges of the airfoil.

• Mean cam,er line9 6 line drawn halfway between the u11er and lower surfaces of the airfoil.

• Angle of attack -AOA.9 he angle of attack is the angle between the chord line and the average relative

wind.

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• ift9 <11oses the downward force of weight% is 1roduced by the dyna!ic effect of the air acting onthe

airfoil% and acts 1er1endicular to the flight 1ath through the center of lift.

• /rag9 6ir resistance of force o11osite to the direction of !otion of the body.

• $oefficient of drag and lift& he drag e7uation is%

= >>>>>>>..(i/

So the coefficient of drag%

= >>>>>>>>(ii/

is essentially a state!ent that the drag force on any object is 1ro1ortional to the density of the fluid and 1ro1ortional to the s7uare of the relative s1eed between the object and the fluid .In fluid dyna!ics the Cd is adi!ensionless 7uantity that is used to 7uantify the drag or resistance of an object in a fluid environ!ent such asair or water. It is used in the drag e7uation where a lower drag coefficient indicates the object will have less

aerodyna!ic or drag. he drag coefficients always associated with a 1articular surface area. he drag coefficientof any object co!1rises the effects of the two basic contributors to fluid dyna!ics drag9 skin friction and fro!drag. he drag coefficient of a lifting airfoil or hydrofoil also includes the effects of lift induced drag. he dragcoefficient of a co!1lete structure such as an aircraft also includes the effects of interference drag. he overalldrag coefficient defined in the usual !anner is the reference area de1ends on what ty1e of drag coefficient is being !easured. For auto!obiles and !any other objects% the reference area is the 1rojected frontal area of the

vehicle. his !ay not necessarily be the cross sectional area of the vehicle% de1ending on where the cross sectionis taken and for an airfoil the surface area is a 1lane for! area.he lift e7uation%

= >>>>>>. .(iii/

he coefficient of lift given by%

= >>>>>>>>> .(iv/

( 1ro,lem /efinition

o analy0e the &odified 'hort!ann high lift airfoil using 6nsys Fluent for calculation of Coefficient

of Drag and Coefficient of #ift and to validate the results obtained with "F#$, analysis.

2( $om3utational /etails

Co!1utational details are described in the following headings. Details are described in the sa!e !anner

in which the 1rocess was carried out.

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2() 4eometry

?eo!etrical 1oints have been i!1orted fro! 4I4C- data base on which line o1eration was 1erfor!ed followed

by surface o1eration. Co!1utational do!ain of di!ension !entioned in figure is drawn to ca1ture the

1heno!enon. 6irfoil surface was oolean fro! the co!1utational do!ain and new lines were 1rojected on the

surface for !esh generation. Arojected lines divided the do!ain into four regions. 6ll the sketch other than the

1rojected one were su11ressed fro! the surface. 6ll di!ensions were taken in !eter.

2( 4rid 4eneration &6fter creating the geo!etry !eshing tool fro! co!1onent tool directory of 6nsys was dragged and clubbed to

geo!etry. In !esh 1hysics 1reference was converted into CFD and Fluent was given as solver 1reference. 4nder

the inflation section the first layer thickness was given as -B- +*. &eshing was a11roached with block structured

!esh for which four blocks (result of 1rojected lines/ were used. o do that &a11ed face !esh with

uadrilateral !ethod was used. 5ach 1rojected line along with co!1utational boundaries was given the si0ing

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Figure -9 Coordinate I!1orted

Figure ;9 Flow do!ain




under which - divisions with bias of * was given. ias was given in such a way that finer division falls near

the airfoil side.

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Figure 9 5dge si0ing and biasing

Figure *9 &esh Details




2(2 Solver Settings&

Finite volu!e based 1ressure solver was used for co!1uting velocity and 1ressures at different 1oints. For

1ressure velocity cou1ling SI&A#5C was used with skewness correction factor as ;. Second+order u1wind

Discreti0ation sche!e was used for !o!entu!% turbulent kinetic energy and s1ecific dissi1ation rate while for

1ressure standard setting was used in the study. $e based on C is calculated as -E-) which corres1onds to an

u1strea! velocity of -,.* !Gs. Standard values for under+rela2ation factors are set for 1ressure% density% body

forces and !o!entu! in the code. H value for all the cases should be in accordance to ca1ture se1aration

1heno!ena accurately% it is done by ada1ting. 6ll the si!ulations are carried out in the steady+state !ode. he

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Figure ,9 Joo!ed view of airfoil.

Figure 9 &esh Details




steady+state si!ulations are 1erfor!ed for a sufficient nu!ber of iterations until the flow data are converged to a

constant solution.

2(5 #ur,ulence Model&

6irfoil is analy0ed using turbulence !odel under which shear Kstress trans1ort (SS/ k+o!ega was used.

2(6 "oundary and *nitial $onditions&

oundary conditions are given as -,.* !Gs velocity at inlet ($e is -B-)/ of the

co!1utational do!ain% whereas at!os1heric 1ressure was s1ecified at the outlet of the

do!ain. 6irfoil surface is s1ecified as a wall surface with no sli1 condition. he

co!1utational do!ain is far fro! the airfoil surface so that boundary layers for!ed at the

surface does not affect the 1heno!enon occurring on the airfoil. Lelocity at inlet surface is

s1ecified with !agnitude and direction in which direction is given along the 2 a2is i.e. value

of al1ha was set e7ual to 0ero. <ne co!!on boundary condition at outlet s that where

instability waves e!itted fro! the body are free to 1ass and are not reflected back. In this

study a non+reflecting boundary conditions was used at the outer boundary as 1ressure outlet.

5( !esults and /iscussion

Cl and Cd values from Ansys :

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Figure 7: Turbulene model

se!!in s




6( Validation

6nalysis using "F#$ analysis

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$om3arison& ,7w Ansys and XF! data

Analysis !ool Cd Cl #rror$

Ansys 1%1""7 0%013 4%"2$

&F'( 1%24) 0%010 30$

4rid *nde3endency&

*o% of nodes Cd Cl

15351 1%17") 0%01402

34276 1%1"13 0%01350

603)" 1%1""7 0%013)7

)3"70 1%1")6 0%012)

8( $onclusionIn this study we ca!e to an inference that analysis result through "F#$ and that of 6nsys F#45N are not!uch deviating.ased on CFD analysis and "F#$ software the values coefficient of lift are having error lessthan ,M but with coefficient of drag the agree!ent is not so well .It also highlight the li!itation of "F#$ in calculating the coefficient of drag with absolute accuracy because it

usually consider !ainly for! drag .6lso running different si!ulations at different no. of nodes suggests that the result is grid inde1endent.

9( Acknowledgement

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Figure 9 "F#$ result




his work is su11orted by De1t. of Fluid 5ngineering of &NNI% 6llahabad. I a! thankful to Arof. Dr. 6. $.

Aaul and Arof. Dr. L. 8. Aatel who have given us o11ortunity to work on the 1latfor!.. I a! also thankful to our

research scholars for e2tending their su11ort in the 1rocess of learning.

:( !eferences• 4I4C airfoil databse m-selig.ae.illinois.edu/ads/coord_database.html

• k+ O turbulence !odel (&enter% -PP*/

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Modified Whortman Airfoil Ppt

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