Available online at ScienceDirect. Procedia Engineering 105 (2015 )

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1 Available olie at SieeDiret Proedia Egieerig 105 (2015 ) th BSME Iteratioal Coferee o Thermal Egieerig (ICTE 2014) Experimetal ivestigatio o the performae of NACA 4412 aerofoil with urved leadig edge plaform M. Nazmul Haque a*, Mohammad Ali a, Ismat Ara a a Departmet of Mehaial Egieerig, Bagladesh Uiversity of Egieerig ad Tehology, Dhaka-1000, Bagladesh. Abstrat Airraft wigs are the liftig surfaes with the hose aerofoil setios. The effiiey as well as the performae of a airraft mostly depeds o the aerodyami harateristis e.g. lift, drag, lift to drag ratio, et of wigs. Besides may fators, the effets of wig shape are also ruial to airraft performae. This paper represets the experimetal ivestigatio to explore better aerodyami performae by iorporatig urvature at the leadig edge of a wig. A woode model with straight leadig ad trailig edge i.e. retagular plaform ad aother model with urved leadig edge ad straight trailig edge are prepared with NACA 4412 aerofoil i equal legth (spa) ad surfae area. Both the models are tested i a losed iruit wid tuel at air speed of kph (0.07 Mah) i.e. at Reyold s umber 1.82 x The stati pressure at differet agles of attak (-4, 0, 4, 8, 12, 16, 20 & 24 ) are measured from both upper ad lower surfaes of the wig models through differet pressure tapigs by usig a multi-tube water maometer. From the stati pressure distributio, lift oeffiiet, drag oeffiiet ad lift to drag ratio of both the models are aalyzed. After aalyzig the data, it is foud that the urved leadig edge wig plaform is havig higher lift oeffiiet ad lower drag oeffiiet tha the retagular wig plaform. Thus, the urved leadig edge plaform is havig higher lift to drag ratio tha the retagular plaform The The Authors. Published Published by Elsevier by Elsevier Ltd. This Ltd. is a ope aess artile uder the CC BY-NC-ND liese ( Peer-review uder resposibility of orgaizig ommittee of the 6th BSMEIteratioal Coferee o Thermal Egieerig Peer-review (ICTE 2014). uder resposibility of orgaizig ommittee of the 6th BSME Iteratioal Coferee o Thermal Egieerig (ICTE 2014) Keywords: Aerofoil; aerodyami performae ; oeffiiet of lift; oeffiiet of drag; lift to drag ratio; Reyold s umber. * Correspodig author. Tel.: address: azmul_me@hotmail.om The Authors. Published by Elsevier Ltd. This is a ope aess artile uder the CC BY-NC-ND liese ( Peer-review uder resposibility of orgaizig ommittee of the 6th BSME Iteratioal Coferee o Thermal Egieerig (ICTE 2014) doi: /j.proeg

2 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) Itrodutio Similar to a bird s wig, a airraft wig is the liftig surfae with the hose aerofoil setio, whose shape/geometry a be varied spa wise to searh better performae. The lift geerated by the wig sustais the weight of the airraft to make flight i the air. Agai, from a aerodyami perspetive, the mai soure of the airplae drag is assoiated with the wig. Aroud two-thirds of the total drag of typial trasport airraft at ruise oditios is produed by the wig [1]. Therefore, the effets of wig shape ad size are ruial to aerodyami harateristis (lift, drag, lift to drag ratio, et) o whih the effiiey as well as the performae of airraft deped. As suh, researhes o differet wig shapes/geometries are still o throughout the world to explore the maximum possible lift ad miimum possible drag. Hossai et al. [2] oduted a experimetal aalysis for the aerodyami harateristis of retagular wig with ad without bird feather like wiglets for differet Reyolds Number. The experimetal result shows 25~30% redutio i drag oeffiiet ad 10~20% irease i lift oeffiiet by usig bird feather like wiglet at 8 degree agle of attak. Dwivedi et al. [3] adopted a simple approah for experimet o aerodyami stati stability aalysis of differet types of wig shapes. They tested the redued sale size wigs of differet shapes like retagular, retagular with urved tip, tapered, tapered with urved tip, et. i low speed subsoi wid tuel at differet air speeds ad differet agles of attak. The authors foud that the tapered wig with urved tip was the most stable at differet speeds ad rages of workig agles of attak. Miek et al. [4] tested three plaar, utwisted wigs with the same elliptial hord but with differet urvatures of the quarter-hord lie. They foud that the elliptial wig with the uswept quarter-hord lie has the lowest liftig effiiey, the elliptial wig with the uswept trailig edge has the highest liftig effiiey ad the reset-shaped wig has effiiey i betwee. Rektewald [5] tested a irular plaform o-spiig body with a airfoil setio ofiguratio developed ad produed by Geobat Flyig Sauer Aviatio I. i the Aubur Uiversity wid tuel faility. For ompariso purpose, a Cessa 172 model was also tested. The author foud that the lift urve slope of the Geobat was less tha that of Cessa 172 but displayed better stall harateristis. Wakayama [6] studied ad preseted basi results from wig plaform optimizatio for miimum drag with ostraits o strutural weight ad maximum lift. Moreover, aerodyami harateristis aalysis for differet airfoils have also bee oduted at differet orers of the world like Mahmud [7] aalyzed the effetiveess of a airfoil with bi-amber surfae, Kadwal et al. [8] studied the fluid flow ad aerodyami fores o a airfoil, Robert [9] studied the variatio of pressure distributio over a airfoil with Reyold s Number, Sharma [10] aalyzed the flow behavior aroud a airfoil body, et. Researhes o differet airfoils ad ovetioal wig geometries like retagular, sweepbak, tapered or, delta shapes have bee arried out i may plaes aroud the world i a extesive way. But aerodyami harateristis of urved-edge wig geometries are yet to be explored. As suh, the proposed experimetal ivestigatio is arried out i the wid tuel to explore aerodyami harateristis of urved leadig edge wig. Similar harateristis of a retagular wig of equal spa ad surfae area are also ivestigated i the same way for referee. At the ed, the harateristis of the urved leadig edge wig are ompared with that of the retagular wig. Nomelature α C S C L C D L/D R N U P Agle of attak (AOA) Chord legth Spa Coeffiiet of lift Coeffiiet of drag Lift to drag ratio Reyold s umber Free stream veloity of air i the wid tuel Free stream pressure

3 234 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) Desig ad ostrutio The aerodyami harateristis (C L, C D ad L/D) a be alulated from the surfae pressure distributio of the wig [11]. To obtai the pressure distributio over the surfaes, woode wig models are prepared with a speifi aerofoil, suitable fixture is prepared to set the models i the wid tuel ad a multi-tube maometer is fabriated to take the pressure readigs from the surfaes of the wig models Wig models Usig NACA 4412 aerofoil, woode models for retagular wig ad urved leadig edge wig are prepared havig the same spa (245 mm) ad equal surfae area (31115 mm 2 ). Eah model is provided with 32 pressure tapigs alog the spa ad hord (16 at upper surfae & 16 at lower surfae). Alog the spa the wigs are divided ito 4 equal segmets (61.25 mm). For retagular wig, the hord legth is same (127 mm) for all the four segmets but for the urved leadig edge wig, the average hord legth is differet for differet segmets alog the spa (for segmet A mm, for segmet B- 140 mm, for segmet C- 110 mm ad for segmet D mm). 4 pressure tappig poits at upper surfae ad 4 pressure tappig poits at lower surfae are made at 20%, 40%, 60% ad 80% of the average hord legth of eah segmet of both the wigs as show i Fig. 1. The multi-tube maometer maily osists of a water tak ad 36 maometer glass tubes oeted to the tappig poits i wig model surfaes. The water tak is used to store the distilled water. Eah limb is fitted with a sale graduated i mm to measure the differee of water height. The stati pressure is alulated from the differee i water height. a. b. Fig.1. (a) Curved Leadig Edge Plaform (b) Retagular Plaform 2.2. Fixture for alterig AOA A fixture is fabriated ad fixed i the test setio of the wid tuel as show i Fig. 2. The fixture failitates the wig models to rotate ad fix at ay agle of attak. The wig models are tested at AOA from -4 to 24 with a step of 4. Eah model is rotated ad fixed at the desired agle by seeig the preset sales (i degrees) pasted o the frame. 3. Experimetal method 3.1. Experimetal setup The experimet is arried out i a 700mm 700mm losed iruit wid tuel as show i Fig. 2 available at turbulee laboratory of Departmet of Mehaial Egieerig, BUET. The wid speed is reated by the two 700mm outer rotatig fas. At the disharge of the fas there is a sileer to redue the soud level. From the sileer air flow passes through the flow otrollig butterfly valve, diffuser ad the pleum hamber to stabilize the

4 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) flow to ertai level. The fa motors are powered by 400V-3Φ-50Hz power supply through motor speed otroller. Thus the wid speed i the tuel a be varied both by otrollig the fa motor speed as well as by otrollig the butterfly valve. To failitate the preset experimet i the ope air oditio the diffuser at the ed of the test setio is take out ad the disharge side of the test setio is fitted with a 700mm 700mm disharge dut ad a 1000mm 1000mm to 762mm 762mm bell mouth etry is added at the retur dut to have smooth etry. Thus the 406 mm ope flow field reated betwee the disharge dut ad bell mouth etry beome the experimetal spae where desire veloity is obtaied. a. b. Wig model Workig spae AOA alterig fixture Pressure tappig tubes oeted to maometer Retur dut Disharge dut Fig. 2. (a) Wid tuel at BUET s Turbulee laboratory (b) Experimetal set-up 3.2. Test oditios ad proedures All the experimetal data were take at room temperature of 35 C ad at air speed of m/s (85.35 kph) ad the air flow was osidered iompressible throughout the experimet. The stati pressure at differet AOA (-4, 0, 4, 8, 12, 16, 20 & 24 ) are measured from both upper ad lower surfaes of the wig models through differet pressure tapigs by usig a multi-tube water maometer. Speifi desity of both air ad water orrespodig to room temperature was assumed to be kg/m 3 ad 994 kg/m 3 respetively. 4. Mathematial modelig Surfae pressure oeffiiet, C p a be alulated from the stati pressure by the followig formula [12]. p, i pi p 1 U 2 2 (1) Where, P i is the surfae stati pressure. Values of C p at ay poit over the aerofoil surfae a be approximated from the orrespodig boudary values by usig the first order Lagrage iterpolatio ad extrapolatio: x x x x0, 1 x x 1 p ( x) p, o p x0 x1 1 0 (2)

5 236 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) A itegratio of a pressure distributio over a airfoil hord for both upper ad lower surfaes is kow to provide ormal ad axial fore atig o a airfoil setio whe shear stress due to visous effet is egleted [11, 13]. Fig. 3. Diagram of resultat aerodyami fore ad its ompoets atig o a wig setio With x as a hordwise diretio ad y as a perpediular oe, both ormal ad axial fore itegral equatios are give respetively as: 1 ( l u) dx p, (3) p, 0 1 dyu dyl ( p u p l ) dx a, (4), dx dx 0 Whe the otatio l is for the lower surfae ad u is for the upper surfae. The kow pressure oeffiiets from the experimet a be alulated for the ormal ad axial fore by usig a umerial itegratio of the above equatios i the Trapezoidal approximatig forms. Both surfaes are divided ito small paels orrespodig to a total of gaps betwee eah pressure tap loatio. Whe is a umber of paels, the equatios a be overted to: a p l, i p, u, i i1 i1 xi (5), p y u, i yl, i xi u i p l i (6),,,, xi xi The iterpolated ad extrapolated pressure oeffiiets would be applied to Equatio (5) ad (6) i order to get the ormal ad axial fore at a setio of iterest. Lift ad drag oeffiiet a be obtaied from: l d Cos Si Si Cos a a (7) (8) The over-all value of the oeffiiets for the whole wig a be foud out by averagig the same values of eah segmets of the wig alog the spa.

6 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) Results ad disussios 5.1. Surfae pressure distributio Pressure oeffiiet for eah tappig poit (at 20%, 40%, 60% & 80% of hord) is determied from the measured surfae stati pressure ad the pressure oeffiiet of the itermediate poits (at 10%, 30%, 50%, 70% & 90% of hord) are approximated through liear iterpolatio/extrapolatio from the measured boudary values. I Fig. 4, distributio of surfae pressure oeffiiet at 0 AOA is show for eah of the four segmets of both the retagular ad the urved leadig edge wig. Similarly, i Fig. 5, distributio of surfae pressure oeffiiet at 12 AOA is show. From both the figures it is observed that the differee betwee the upper ad lower surfae pressure oeffiiets at 12 AOA is higher tha those at 0 AOA. From Fig. 4, it is observed that the differee betwee upper ad lower surfae pressure oeffiiet ear the root of the wig (i.e. at segmet A) is lower for the urved leadig edge wig tha that of the retagular wig. But ear the tip of the wig (i.e. at segmet D), the said differee is almost equal. However, at the middle of the wig (segmet B & C), the differee is higher for the urved leadig edge wig tha the retagular wig. I Fig. 5, at 12 AOA, the differee betwee upper ad lower surfae pressure oeffiiet i the first two segmets from the root (segmet A & B) is lower for the urved leadig edge plaform tha that of the retagular plaform. But for the ext two segmets towards the tip of the wig (segmet C & D), the differee is relatively higher for the urved leadig edge plaform. a. b.. d. Fig. 4. Surfae C p distributio of differet segmets of both the wigs at α=0

7 238 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) a. b.. d Lift harateristis Fig. 5. Surfae C p distributio of differet segmets of both the wigs at α=12 Variatio of lift oeffiiet at differet agle of attak for both the wigs is show i Fig. 6. It is observed that the lift oeffiiet for urved leadig edge wig is higher tha the lift oeffiiet of retagular wig at every agle of attak. However, greater values of lift oeffiiet are observed at -4, 0 ad 8 agle of attak. Critial agle of attak for both the wigs remais withi the same rage of 12 ~16. Fig. 6. Variatio of lift oeffiiet with AOA

8 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) Drag harateristis I Fig. 7, the variatio of drag oeffiiet for both the wigs are plotted agaist differet agles of attak ad it is observed that the values of drag oeffiiet for urved leadig edge wig is lower tha that of the retagular wig. Promiet redutio i drag oeffiiet values for urved leadig edge wig is foud at -4 ad 12 agle of attak Lift to drag ratio Fig. 7. Variatio of drag oeffiiet with AOA The values of lift to drag ratio are plotted for various agles of attak i Fig. 8 ad it shows that the lift to drag ratio of urved leadig edge wig is higher tha that of the retagular wig. It is also observed that urved leadig edge plaform a provide higher lift to drag ratio tha the retagular plaform at agles of attak below 12. Fig. 8. Variatio of lift to drag ratio with AOA

9 240 M. Nazmul Haque et al. / Proedia Egieerig 105 ( 2015 ) Colusio I this experimet, urvature is iorporated at the leadig edge i suh a way that the surfae area from the middle of the wig towards the root ireases ad towards the tip the area dereases i the same rate. The overall surfae area of the wig remais same as of the retagular plaform. As a result, the wig a produe more lift due to ireased surfae area ear the root. At the same time, flow separatio alog the spa of the wig is redued due to gradual redutio of hord legth alog the spa ad so the drag is also redued. From the aalysis of experimetal data it is observed that the lift oeffiiet of the urved leadig edge plaform ireases ad the drag oeffiiet dereases at agles of attak below 12 i ompariso to the retagular plaform; whereas ritial agle of attak does ot vary sigifiatly betwee the two plaforms. Beyod ritial agle of attak, values of lift ad drag oeffiiets are almost equal. As suh, it a be oluded that the urved leadig edge plaform exhibits better aerodyami performae tha the retagular plaform due to higher lift to drag ratio at agles of attak below the ritial agle of attak. Akowledgemets The authors would like to express their siere gratitude to the Departmet of Mehaial Egieerig, BUET for providig wid tuel failities ad other tehial supports to arry out the researh. Referees [1] Lyh, F.T., Commerial Trasports-Aerodyami Desig for Cruise Performae Effiiey, Chapter II i Trasoi Aerodyamis, David Nixo, Ed., Progress i Astroautis ad Aeroautis, Vol. 81, AIAA, New York, 1982, pp [2] Hossai, A., Rahma, A., Iqbal, A.K.M.P., Ariffi, M., ad Mazia, M., Drag Aalysis of a Airraft Wig Model with ad without Bird Feather like Wiglet, Iteratioal Joural of Aerospae ad Mehaial Egieerig, Vol. 6, No.1, 2012, pp [3] Dwivedi, Y.D., Prasad, M.S., ad Dwivedi, S., Experimetal Aerodyami Stati Stability Aalysis of Differet Wig Plaforms, Iteratioal Joural of Advaemets i Researh & Tehology, Vol. 2, No. 6, Jue 2013, pp [4] Miek, R.E., ad Vijge, P.M.H.W., Wid-Tuel Ivestigatio of Aerodyami Effiiey of Three Plaar Elliptial Wigs with Curvature of Quarter-Chord Lie, NASA Tehial Paper 3359, Otober 1993, pp [5] Rektewald, B., Aerodyamis of a Cirular Plaform Airraft, Ameria Istitute of Aeroautis ad Astroautis , 2008, pp.1-7. [6] Wakayama, S., Subsoi Wig Plaform Desig Usig Multidisipliary Optimizatio, Joural of Airraft, Vol. 32, No. 4, July-August 1995, pp [7] Mahmud, M.S., Aalysis of Effetiveess of a Airfoil with Bi-amber Surfae, Iteratioal Joural of Egieerig ad Tehology, Vol. 3, No. 5, May 2013, pp [8] Kadwal, S., ad Sigh, S., Computatioal Fluid Dyamis Study of Fluid Flow ad Aerodyami Fores o a Airfoil, Iteratioal Joural of Egieerig ad Tehology, Vol. 1, No. 7, September 2012, pp.1-8. [9] Robert, M.P., The Variatio with Reyolds Number of Pressure Distributio over a Airfoil Setio, NACA Report No. 613, pp [10] Sharma, A., Evaluatio of Flow Behavior aroud a Airfoil Body, M. Egg thesis, Departmet of Mehaial Egieerig, Thapar Uiversity, Patiala , Idia, July 2012, pp [11] Aderso, J.D., Fudametals of Aerodyamis, MGraw-Hill Series i Aeroautial ad Aerospae Egieerig, 3 rd Editio, pp [12] White, F.M., Fluid Mehais, MGraw-Hill Series i Mehaial Egieerig, 4 th Editio, 1999, pp [13] Deveport, W.J. ad Shetz, J. A., The Ivestigatio of a Iboard-Wiglet Appliatio to a Roadable Airraft, M S i Aerospae Egieerig Thesis, Virgiia Polytehi Istitute ad State Uiversity, May 2002, pp