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1 TO: UNCLASSIFIED AD NUMBER AD LIMITATION CHANGES Apprved fr public release; distributin is unlimited. FROM: Distributin authrized t U.S. Gv't. agencies nly; Test and Evaluatin; DEC Other requests shall be referred t Naval Air Systems Cmmand, Washingtn, DC USNSRDC ltr 24 Apr 1974 AUTHORITY THIS PAGE IS UNCLASSIFIED

2 _- ^*kwi.^..-., vp,, «NVrvJaWW-UarrSKSSS»^.,,..-..lst.(i^.^,. ^.,, >J i Si HI NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER i W Washingtn, D.C * w» 10!l ^1 TWO-DIMENSIONAL TRANSONIC WIND TUNNEL TESTS OF THREE 15-PERCENT THICK CIRCULATION CONTROL AIRFOILS 00 s CL. I CD by Rbert J. Englar M D D C APR *»?! j I cj? a Distributin limited t V.S. Ov't agencies nly; Test and Evaluatin; December 1970, Other requests fr this dcument must be referred t Naval Air Systems Cmmand (AIR32C) 1<J/)sti 3>C c2036 O r- O O *. r-i c:. : < t AViATION DEPARTMENT» -. < : ; ; b ' : i'eehnisal :;te AL-152 t?r: ; 1

3 TWO-DIMENSIONAL TRANSONIC WIND TUNNEL TESTS OF THREE 15-PERCENT THICK CIRCULATION CONTROL AIRFOILS by Rbert J. Englar Distributin United t U.S. Gv't agencies nly; Test and Evaluatin; December 1970» Other requests fr this dcument must be referred t Naval Air Systems Cmmand (AIR 320). December 1970 Technical Rte AL-182

4 SUMMARY Tw-diEensinal transnic wind tunnel tests were cnducted n three fifteen percent circulatin cntrl elliptic airfils ver the range 0.3 * M w 0.9. Mdel cnfiguratins included a pure elliptical shape with bth jet flap and tangential upper surface trailing edge blwing, plus tangential blwing ver an elliptical shape with a runded trailing edge. Perfrmance f the runded trailing edge cnfiguratin was the best f the three at lw speeds, but abve M w 0.55» detachment f the Canda jet caused rapid perfrmance deteriratin Due t its elngated trailing edge and assciated larger effective radius dwnstream f the slt, the tangentially blwn pure ellipse was able t extend the jet detachment Mach number t 0.7, where maximum equivalent lift-t-drag ratis f 22 at C f O.kh were achieved. The jet flap prved t be inferir t the tangentially blwn cnfiguratins in all respects except in its ability as a thrusting, dragreducing bdy» ii

5 TABLE OF CONTENTS Page INTRODUCTION 1 MODELS AND TEST APPARATUS 2 MODELS 2 TEST APPARATUS AND TECHNIQUE 3 DESIGN AND TEST CONSIDERATIONS 6 DISCUSSION 7 ROUNDED TRAILING EDGE ELLIPSE 7 PURE ELLIPTICAL TRAILING EDGE 9 JET FLAP. 10 COMPARISON 11 CONCLUSIONS 12 REFERENCES 15 LIST OF FIGURES Figure 1 - Critical Mach Number f Ellipses at a = Figure 2 - Effect f Runded Trailing Edge Variatin n Maximum Suctin Peaks (incmpressible) 17 Figure 3 - Transnic Mdel Gemetries id Figure k - Transnic Wind Tunnel and Assciated Test Equipment 19 Figure 5 - Cncentric Ring Frce Balance Schematic 20 Figure 6 - Pressure Rati Requirement fr 0,01 Inch Slt Weight 21 Figure 7 - Jet Velcity Rati Resultfcig Frm 0.01 Inch Slt Height and Variatin in Pressure Rati». 22 Figure 8 - Test Reynlds Number Range Based n Mdel Chrd. 23 Figure 9 - Lift Variatin with Mmentum Cefficient fr Runded Ellipse 2k Figure 10 - Lift Variatin with Mach Number fr Runded Ellipse 25 Figure 11 - Lift Variatin with Jet Velcity fr Runded Ellipse 26 Figure 12 - Variatin in Lift Augmentatin with Jet Velcity fr Runded Ellipse. 27 Figure 13 - Drag Variatin with Mmentum Cefficient fr Runded Ellipse 28 iii

6 LIST OF FIGURES (Cntinued) Page Figure 14 - Drag Variatin with Mach Number fr Runded Ellipse.. 29 Figure 15 - Runded Ellipse Drag Reductin 30 Figure 16 - Pressure Distributin fr Runded Ellipse at M., nnlnai 0.9, r Figure 17 - Runded Ellipse Drag Plar 32 Figure 18 - Half Chrd Pitching Mment Variatin fr Runded Ellipse. 33 Figure 19 - Frce-Based Equivalent Lift-t-Drag Rati fr Runded Ellipse 34 Figure 20 - Kinetic Energy-Based Equivalent Lift-t-Drag Rati fr Runded Ellipse 35 Figure 21 - Lift Variatin with Mmentum Cefficient fr Pure Ellipse 36 Figure 22 - Lift Variatin with Mach Number fr Pure Ellipse 37 Figure 23 - Lift Variatin with Jet Velcity fr Pure Ellipse Figure 24 - Variatin in Lift Augmentatin with Jet Velcity Fr Pure Ellipse 39 Figure 25 - Lift Cmparisn f Runded and Pure Ellipses 40 Figure 26 - Drag Variatin with Mmentum Cefficient fr Pure Ellipse 41 Figure 27 - Drag Variatin with Mach Number fr Pure Ellipse 42 Figure 28 - Pressure Distributin fr Pure Ellipse at M., -0.9, cr ?T Figure 29 - Pure Ellipse Drag Reductin 44 Figure 30 - Pure Ellipse Drag Plar 45 Figure 31 - Variatin in Pitching Mment with Mmentum Cefficient fr Pure Ellipse 46 Figure 32 - Frce-Based Equivalent Lift-t-Drag Rati fr Pure Ellipse 47 Figure 33 - Kinetic-Energy-Based Equivalent Lift-t-Drag Rati Figure 34 - Jet Flap Lift Variatin with Mmentum Cefficient Figure 35 - Jet Flap Lift Variatin with Mach Number 50 Figure 36 - Drag Variatin with Mmentum Cefficient fr Jet Flap 51 Figure 37 - Jet Flap Dreg Variatin with Mach Number 52 Figure 38 - Jet Flap Dreg Reductin 53 iv

7 LIST OF FIGURES (Cncluded) Figure 39 - Pressure Distributins Fr Jet Flap at»uu.1 * ' 9» «* - 1 ' 20» Figure 40 - Half Chrd Pitching Mment Variatin with Mmentum Cefficient fr Jet Flap 55 Figure 41 - Jet Flap Drag Plar. 56 Figure 42 - Frce-Based Equivalent Lift-t-Drag Rati fr Jet Flap 57 Figure 43 - Kinetic-Energy-Based Equivalent Lift-t-Drag Rati Fr Jet Flap 58 Figure 44 - Cmparative Lift Characteristics f the Three Mdels. 59 Figure 45 - Cmparisn f MSximum Frce-Based Equivalent Lift-t- Drag Rati fr the Three Cnfiguratins 60 Figure 46 - Cmparisn f Maximum Kinetic-Energy-Based Equivalent Lift-t-Drag Rati fr the Three Cnfiguratins Figure 47 - Lift Crrespnding t Maximum Aerdynamic Efficiency. 62 Figure 48 - Mmentum Cefficients fr Maximum Aerdynamic Efficiencies 63 Page

8 LIST OF SYMBOLS A e slt area» (bh), ft 8 a. lcal speed f sund In the jet, ft /sec A. nzzle thrat area, ft 8 b mdel span» ft c mdel chrd» ft C. tw-dimensinal drag cefficient frm mmentum lss In wake» crrected fr additinal mass efflux f the Jet :. frce-based equivalent drag cefficient, C. + C + C _ \ i V J C. klnetlc-energybesed equivalent drug cefficient, "» Vl V - c d + -^i + <vv7 C, tw-dimensinal lift cefficient Cg pitching mment cefficient abut the half chrd s C pressure cefficient C * critical pressure cefficient (crrespnding t lcal M f 1.0) p C mmentum cefficient, mv./^c) h slt height et nzzle thrat, ft l/d frce-based equivalent lift-t-drag rati l Jt/d^ kinetic-energy based equivalent llft-t-drag rati 8 M erlt N m mass efflux, slug/sec r. free stream static pressure, lb/ft * V \ critical Mach number freestreem Mach number jet Mach number free stream ttal pressure, lb/ft duct (plenum) pressure, lb/ft * 1

9 LIST OF SYMBOL8 (Cntinued) q^ free stream dynamic pressure, lb/ft. r trailing edge radius, ft R Reynld! number, baaed n chrd T ttal temperature, R T. static temperature in the Jet, R L J free stream velcity, ft /sec V. Jet velcity, ft /sec x/c dimenainless chrdviae statin r gemetric angle f attack, degreea Y rati f specific heata 8 lcal angle f Jet at exit relative t free etream 6 chrd line camber, ft # \ vll

10 INTRODUCTION Mdified elliptic circulatin cntrl airfil sectins have been shwn subsnically t be very effective generatrs f high lift cefficients and aerdynamic efficiencies (References 1 and 2). Emplying camber and tangential blwing ver a runded trailing edge, these sectins have generated lift cefficients greater than 6.0 and efficiencies (equivalent liftt-drag ratis) abve 90 (at C, «1.0). These airfils thus appear quite prmising fr applicatin t inbard and mid-span blade sectins f rtary wing e'-rcraft. Hwever, due t their camber and relatively large thidmesst-chrd rati (20 t 30 percent r greater), their effectiveness at the high speed rtr tip wuld tend t be reduced. Examinatin f the rtr tip flw regime indicates that present high speed helicpter cnfiguratins are limited by three main prblem areas: cmpressibility r Mach number effects, retreating blade stall, and blade structural limitatins. These criteria lead t the demand fr a tip sectin designed t (l) increase the drag divergent Mach number, (2) maintain gd transnic lift cefficient and equivalent lift-t-drag rati, and (3) cntrl the shck lcatin and clsely related bundary layer separatin. In additin, the sectin must still maintain relatively gd subsnic characteristics as the retreating blade wuld be required t perate in the lw speed (r even rtnmrmt flw) regin. It is this requirement t cyclically perate in alternately subsnic and transnic regins which leads t the mechanical and structural cmplexities f present day rtr systems. It is felt that these prblems may be cnsiderably reduced r eliminated by prper design f a circulatin cntrl transnic tip sectin where the necessary cyclic variatins are btained by prgrammed air ejectin ver the trailing edge. The present tests were Intended t Investigate the transnic prperties f a series f relatively thin (15 percent) elliptic sectins with several variatins in blwing schemes. In particular, It was desired t determine if the impressive subsnic efficiencies f the tangentiauy blwn ellipse culd be maintained at high subsnic and transnic speeds, while simultaneusly satisfying the requirements mentined abve fr a high speed tip sectin. Previus tests n transnic circulatin cntrl airfils (Reference 3)

11 with Canda effect tangential blwing ver runded trailing edges have shwn lss f lift augmentatin and sectin efficiency abve a Mach number f 0.55 due t detachment f the jet sheet. Therefre, an imprtant aspect f the present tests was t determine if the Mach number fr jet detachment culd be increased by variatin in trailing edge curvature. M0DEI3 AND TEST APPARATUS übe series f three mdels used in the tw-dimensinal transnic test prgram was cnstructed in a manner similar t previus subsnic ellipses tested at NSRDC (see References 1 and 2). Hwever, certain additinal steps were taken t strengthen the mdels t withstand the higher transnic lads and t prvide a fine surface finish t prevent misrepresentatin f bundary layer separatin and shck wave frmatin. MODELS The basic cnfiguratin fr all three mdels was an uncambered ellipse f 15 percent thickness-t-chrd rati chsen frm the critical Mach number (M t ) cnsideratin shwn in Figure 1, which is based n a Karmann-Tsien rule extensin f ptential flw data«it was expected that the required rtr tip lift cefficient wuld lie in the regin 0 * C, < 1.0; thus the best cmprmise fr increased M.. was the 15 percent ellipse«in cntrast, the thicker 20 percent ellipse wuld prbably nt perfrm ei well in the higher Mach number range where viscus and cmpressibility effects are strng, while the 10 percent sectin wuld fare prly in the subsnic retreating blade regime* In additin t the pure 15 percent ellipse, a trailing edge mre favrable t subsnic circulatin cntrl was chsen, i.e., a circular trailing edge with a radius equal t k percent f the chrd. As shwn in Figure 2, at the higher C. generated subsnically by this runded trailing edge, suctin peaks (minimum C ) less than fr the pure ellipse were present, while the reverse was true at C. < 1.0. These higher peaks at the expected transnic lift cefficients euld reduce the critical Mach number f the sectin. This airfil was included primarily t investigate the high speed Jet detachment phenmenn, and as a representative lw speed prfile fr

12 cmparisn. A third mdel emplying a jet flap was included fr cmparisn purpses with the tangentially blwn cnfiguratins. Figure 3 depicts the gemetries f the three tw-dimensinal mdels. The pure ellipse and the jet flap were unmdified 15 percent thick ellipse sectins sharing a cmmn leading edge with interchangeable trailing edge. Bth had an 8 inch chrd. The tangentially blwn pure 15 percent ellipse (hereafter referred t as the "pure ellipse") had an upper surface tangential slt at 92.If percent chrd frm the leading edge, while the jet flap had a lwer surface slt aligned 30^ t the chrd and at the 98.3 percent statin. The third trailing edge (t be referred t as the runded ellipse) had a 0.31 inch radius trailing edge in place f the pure elliptic radius (:? = 0.09 inch), thus prducing a shrter chrd f 7*70 inches, an actual thickness f 15.6 percent and a slt lcatin at the 96 percent statin. All three mdels were f 0.25 inch thick fiberglass with a 600 fineness finish. Structural strength as well as trailing edge attachment were prvided by a rectangular steel spar, which als served as the frward wall f the blwing plenum chamber in the trailing edge. The slt n the tw tangentially blwn sectins was frmed by a steel blade held in place by a series f jack screws which were als used t adjust the slt height. In all three cnfiguratins, the plenum exit was carefully designed s that the slt exit was the minimum area thrat f a smthly cnverging nzzle. TEST APPARATUS AND TECHNIQUE The intended tw-dimensin tests required that a small transnic tunnel be fund with air supply fr blwing and sme means f blckage cntrl fr the relatively thick high speed mdels. A survey f available tunnels (Reference k) yielded the 12 x 16 inch inductin tunnel at the University f Minnesta's Aer Hypersnic Labratry (previusly Rsemunt Aernautical Labratries). This facility had the advantages f suctin n the sltted flr and ceiling t reduce r eliminate blckage, as well as a high pressure air supply (utlet pressures f 1500 psig). In additin, a preceding blwn airfil test cnducted in that tunnel by Hneywell Inc., (Reference 3), made available t N8RDC a cmplete blwing system hkup cmpatible with the present mdels, plus a cncentric ring

13 strain gage wall balance with minimized effect due t pressure line cnnectins» The tunnel and wall balance are presented in Figures h and 5, btained frm Reference 3. This reference als cntains very detailed Infrmatin n the facility, test setup, and a transnic test technique similar t that emplyed in the present test. The difficulty in evaluating several tares (wall bundary layer, wall deflectin, wall-airfil interactin and air supply pressure hse influence) fr crrectin f balance data made balance drag data almst meaningless and had a lesser but still nticeable effect n lift«an alternative means was thus used as the primary data surce fr lift, drag, and mment«all three mdels were pressure tapped at the center span (as I shwn in Figure 3) t btain lift and pitching mment by numerical integratin arund the airfil sectin«spanwise pressure tapi were emplyed t cnfirm tw-dimensinality f the flw«a ttal head $k tube rake was installed apprximately 1.5 chrd lengths dwnstream f the mdel«drag was calculated by integratin f mmentum lss in the wake using a Lck-Gldstein cmpressible technique (References 5 and 6)«crrected fr the additinal mass efflux f the jet as in Reference 2«All pressure data frm the mdel and rake were recrded n a multiple scannivalve readut system with utput n tape fr cmputerized data reductin«it shuld be nted that the integrated drag data already includes the hrizntal thrust cmpnent f the jet as detected by the wake rake«hwever, integratin f the nrmal frce t btain lift des nt include the vertical cmpnent C sin 6. This term is difficult t evaluate since 6 (the jet angle relative t the freestream directin) is unknwn fr the curved jet«the largest cntributin f this thrust term in percentage f ttal lift wuld ccur fr the case f the jet flap mdel«a nminal slt height f inch was emplyed n each f the three trailing edges. The range f duct (plenum) ttal pressures and assciated jet velcities required t prduce desired mmentum blwing cefficients (C ) based n an isentrpic expansin t free stream static pressure is depicted in Figures 6 and 7«These related figures are fr a 0.01 slt height and 12 inch span (the remainder f the 15 inch mdel span extending thrugi the balance side plates and attaching t the external air supply lines).

14 Ideal Jet velcity (V ) and mass flw rate (m) were calculated based n an isentrpic expansin frm duct ttal pressure t free stream static pressure (which varied with Mach number since the tunnel stagnatin pressure remained cnstant at atmspheric): v j" 'J M J m f i *i' i m t (&) 1 - Chked nzzle: m *" A A, sjk (fer) ZY Unchked nzzle: m - A.P j*t d Y Or-l)BT t and mv %»* The actual test values varied frm the abve in that the trailing edge slt deflected under high plenum pressures and nzzle lsses existed. T accunt fr this, static tests f the mdel were cnducted and the rati f measured-t-isentrpic mass flw was determined as a functin f the pressure rati P B /P. These ratis were then used t calculate the tdst values f blwing cefficients. Plenum air supply was btained thrugh the high pressure Hneywell lines which were sealed int adaptra n the mdel, endplates by 0-rings. These prevented leaks while minimizing any resistance the cnnectins wuld ffer t mdel pitching mment. Ttal pressure and temperature in the plenum were measured by internal pressure gage and thermcuple. Tunnel free stream static pressure (^) was measured in the tanks adjacent t the sltted ceiling and flr f the test sectin, with blckage being reduced r eliminated at higher Meet: numbers by prper adjustment f suctin ut f

15 these tanks. Test sectin Mach number and dynamic pressure were determined frm the relatins M -1 i where free stream ttal pressure P. was atmspheric. DESIGN AND TEST CONSIDERATIONS It was surmised that generatin f high equivalent lift-t-drag ratis in the transnic regime culd he accmplished if an effective means f drag reductin culd be fund which did nt demand large additinal blwing pwer penalties«the jet flap has been shwn (Reference 7) t shift the shck wave lcatin rearward and thus favrably effect shck induced separatin and related drag«it als exhibited gd thrust recvery«hwever, the jet angles fr desirable drag characteristics were frequently different frm thse fr gd lift augmentatin. On the ther hand, tangen- tial blwing ver a runded trailing edge was superir subsnically t the jet flap in lift augmentatin and equivalent lift-t-drag rati, but began t lse this superirity transnically due t jet detachment. A cmprmise between these tw cnfiguratin!: was needed and the design criteria became ne fr favrable transnic lift augmentatin and drag reductin (including thrust augmentatin)«it was felt that this culd be accmplished with an elngated trailing edge, i.e., a larger radius after the slt but preceding a relatively small trailing edge radius, übe pure 15 percent ellipse with slt at 92.4 percent chrd met this criteria, even thugh Its shape was prbably nt the ptimum. Size f the mdel was chsen frm cnsideratin f Reynlds number effect n scaling. Reference 8 indicates that (1.5 t 2) z l(f was the

16 minimum Reynlds number t represent transitin and shck-bundary layer interactin phenmenn characteristic f full scale. An 8 inch chrd prvided Reynlds numbers abve this limit thrughut the Mach number range abve 0.35 (see Figure 8). Natural (free) bundary layer transitin was allwed since full scale Reynlds number was expected t be f the same rder f magnitude as the mdel values. The range f mmentum cefficients used (0 C S O.OB) was based n an upper limit f k$ psig plenum pressure, abve which pressure seals in the mdel and supply cnnectin had leaked. The range f indicated gemetric angle f attack was small, cp cr* 2 (which was fund t be in actuality -1.2 a * 0.8 ) with practically all f the runs being made at r = -1.2 (actual), flie discrepancy is indicated and actual gemetric r was due t misalignment f the mdel relative t the angle f attack setting reference. ROUNDED TRAILING EDGE ELLIPSE DISCUSSION r Test were cnducted n the 15.6 percent thick runded trailing edge (r/c * 0.0*0 cnfiguratin at a -1.2 Lift, drag and mment data are presented in Figures 9 thrugh 20. At Mach numbers f 0.5 and lwer, lift variatin with blwing shwed the characteristic subsnic trend, i.e., cntinual increase with n apparent drp ff at higher values-f C (Figures 9 and 10). At higher Mach numbers, (M 0 * 0.6) maximum lift cefficient was reached and sn fllwed by a decrease in c. with added blwing. The critical Mach number at which this "C stall" began was apprximately 0.55$ very clse t the same phenmenn fund in Reference 3. That related study attributes the lift lss t detachment f the Canda Jet frst the runded trailing edge and immediate decrease in circulatin. Figure 11 and 12 depict the variatin f lift cefficient and lift augmentatin ( AC*/AC ) with jet velcity rati (V./v^) and the assciated effect f nzzle chking. Althugh the lift cefficient cntinued t increase beynd the chken (M In the nzzle thrat) value f V./v,, the lift augmentatin began t drp ff rapidly.

17 Drag shwed an even mre prnunced variatin than lift with increase in blwing and Mach number (Figures 13 and Ik). Fr M 0.4, an intial 00 decrease in C. with increased blwing was fllwed by a rapid rise in drag. Analysis f the assciated pressure distributins shwed reductins in the trailing edge suctin peaks with increase in Mach number in the regime where this drag rice ccurred, thus again indicating jet detachment as the cause f deteriratin f mdel perfrmance. At M = 0.9, appearance f upper and 09 lwer surface shcks prduced a large wave drag cntributin t c,. Assciated with the jet detachment phenmenn was the prgressive lss f drag reductin with increased Mach number. Figure 15 depicts this trend, where the drag reductin factr is indicative f an increase (psitive ä c. / A C ) r decrease in drag cefficient relative t the unblwn value. In additin, increased blwing abve the critical Mach number shwed little r n effect n the shck lcatin (Figure 16). Assciated lift and drag data are pre- sented in the drag plar (Figure 17)» while the effect f trailing edge suctin peaks due t higher C n pitching mment at the half chrd is shwn in Figure 18. Mdel perfrmance was best indicated by an equivalent lift-t-drag rati which included in the drag term a penalty fr blwing* This enabled the blwn airfil t be cmpared in efficiency t an unblwn cnfiguratin. A simplified equivalent drag cefficient (essentially a frce-baaed ceffi- cient) culd be defined as d e 1 d I* V Av. v. d I* Mj where the third term n the right is an intake penalty described in mre detail in Reference 2. Using this parameter the runded trailing edge yielded a maximum i/d f 30 at M^ - O.k and C^ (Figure 19). A mre apprpriate equivalent C d was derived fr kinetic energy and pwer required t prduce the necessary blwing: K.E. - iavj* Arm i A»V» 8

18 Then the ttal equivalent drag was r in cefficient frm QA AV. a mv S C A + s j ; + r-z = c, + c -^ where C. was the mmentum drag cefficient as measured by the wake rake* The latter parameter (l/& ) is preferred fr cmparisn t ther airfils, but requires that the jet velcity be knwn. This parameter reduced the maximum i/d A t 25.9 at M - O.k, with efficiencies f 1? r less in the e^ Mach number range M^ a 0.55 (Figure 20). PURE ELLIPTICAL TRAILING EDGE. The 15 percent thick pure elliptic sectin with tangential blwing was tested primarily at r -1.2 (fr cmparisn t the preceding mdel) with several additinal runs at r = 0.8. At lw Mach number, the Canda jet was nt as effective ver this smaller trailing edge radius*(r/c * 0,01125), yielding maximum lift cefficients f 0.91 at a = -1.2 (Figure 21), abut half that f the runded ellipse (Figure 9). Hwever, at M w * 0.7» C, was twice that btained by the runded trailing edge«in additin, the maximum lift peaks ccurred at prgressively greater Mach number with decrease in C (Figure 22); whereas fr the runded ellipse, maximum C, always ccurred at M = 0.3 (Figure 10)«The limited amunt f data at a = 0.8 shwed a C. increase at M 0.7 f as much as 36 percent with the 2 angle f attack change, übe effects f slt chking n lift and lift augmentatin were nt as nticeable as fr the runded ellipse. Figures 23 and 2k indicate that bth Cj and A C 7A C cntinued t rise beynd the chking value f V,/v w. A maximum lift augmentatin f k3 was realised at H m «0.7 fr the pure ellipse, cmparable t a similar maximum fr the runded mdel which was

19 reached at M =0.3. The pure ellipse's lifting characteristics at Oft higher M thus appeared superir, CL. further emphasized by the cmparisns f Figure 25. Drag characteristics als shwed an imprvement with the elngated trailing edge. At Nach numbers less than 0.9, an increase in blwing was accmpanied by a drag reductin (Figures 26, 27) very similar t trends characteristically exhibited by a jet flap. One drag rise with increased C experienced by the runded ellipse was eliminated except at M w = 0.9, where, befre the rise ccurred, C d was favrably reduced with blwing. This latter bservatin was due t the rearward mvement f the upper surface shck with an increase in blwing (Figure 28). A rearward shck mvement f 20 percent f the chrd was pssible with a C increase f ; additinal blwing abve that did nt relcate the shck«drag reductin was cnsider- ably imprved ver the runded ellipse. Figure 29 indicates reductin with increased C at all Mach numbers, althugh at 0.9 an Initial large reductin at very lw C was rapidly fllwed by a reversed trend which pinted twards a net drag increase fr C abve Crrelated drag and lift data are presented in the drag plar f Figure 30 while Figure 31 presents variatin in half chrd mment cefficient with C Sectin perfrmance was again indicated by the tw equivalent lift-t- drag ratis (Figures 32, 33). Cnsidering the efficiency based n kinetic energy, the pure ellipse yielded a maximum (V* e ) f 22,6 at M^ 0.7, almst 3.3 times greater than the runded ellipse at the sane speed, and nly slightly less than the runded edge's maximum at N * 0 9 h. The higher speed superirity f the pure ellipse ver the runded versin in lift, drag, and efficiency was thus well demnstrated. JET FLAP The 30 deflectin Jet flap n the 15 percent thick elliptic sectin was tested at r» Generated lift cefficients (Figures 3h and 35) were cnsiderably smaller than either f the tangentially blwn mdels; maximum C % was rughly half that f the pure ellipse and 30 percent f the runded ellipse maximums. Hwever, the jet flap did nt experience the "C^ stall" phenmenn f the tangential mdels, prbably because the jet was nt detachable frm the trailing edge. The jet als fixed the rear 10

20 Stagnatin pint, and thus reduced the supercirculatin capability f the airfil. It was effectively a thrust prducer, and its effect n drag reductin is shwn in Figures 36 thrugh 38, where the trends are similar t the pure ellipse fr M 0.8 and C < At M = 0.9, 00 U, Ott drag cntinued t be reduced by additinal blwing, a trend nt present fr the tangential mdels. Pressure distributins at this Mach number (Figure 39) indicated that there was sme mvement (abut 5 percent chrd) f the upper surface shck with C variatin and the lwer surface shck mved rearward apprximately 5 percent f the chrd als. The lack f high trailing edge suctin peaks led t a large reductin in the negative pitching mment typically generated by tangential blwing (Figure t). Figure kl depicts the jet-flap lift-drag relatinship. In spite f the large drag reductin frm the unblwn case, the verall efficiencies f the jet flap were lw due t the lack f lift augmentatin (Figures k2 9 1*3). A maximum jft/d f abut 8 was generated at M ä = O.U (and C- 0.26), with lesser values at high Mach numbers, all f which were cnsiderably smaller than fr the preceding mdels. COMPARISON Characteristics f the blwn sectins can best be summarized by direct cmparisn f the three mdels. Maximum lift generated fr C O.08 (due t mdel limitatins) is shwn in Figure kh, where the subsnic lifting capability f the runded ellipse yielded t the better transnic prperties f the pure ellipse abve M «0.55. The jet flap cnfiguratin tested was nt cmpetitive in either speed regime. Cmbining Figure Uk with the drag characteristics, Figure 1*5 presents the efficiency factr V&~ > where again the runded trailing edge was superir at H m * 0.5 and the elngated trailing edge was preferred abve M^ 0.5* The data fr the jet flap indicated a weakness f the frce-based /& parameter«the unexpected high efficiency 1 at M m» 0.3 was due t the large negative drag prduced by a mmentum cef- ficient f similar magnitude (but psitive), the sum f the tw appraching zer and inflating the parameter. The mre meaningful parameter (i/**) avided this difficulty due t the V./v^ term in the denminatr, and thus the curves f Figure ks were mre indicative f the trend in efficiency. Again the pure ellipse was the mst efficient abve M^ (with its 11

21 maximum at M *= 0.7) Lift cefficients assciated with these maximum 00 efficiencies (Figure kj) remained almst cnstant fr the pure ellipse up t M 0*7» while the runded cnfiguratin reached its maximum at M = O.k and drpped ff rapidly. Assciated blwing cefficients (Figure 1+8) were n the rder f C 0.02 fr the pure ellipse abve M w = 0.5 and C 0.03 fr the runded trailing edge belw M^ = 0.5, indicating a relatively lw maximum blwing requirement f C 0.03 thrughut the entire Mach number range. CONCLUSIONS Transnic tests cnducted ver the range 0.3 M 0.9 n a series f three circulatin cntrl ellipse airfils indicated that high speed perfrmance was heavily dependent n maintaining supercirculatin primarily by keeping the trailing edge Canda jet attached. Cmparisn f experimental results als gave the fllwing cnclusins: Belw M = 0.55> the runded ellipse cnfiguratin was the 00 mst favrable f the three, develping the highest lift cefficient, lift augmentatin, and aerdynamic efficiency. At higher Mach numbers a rapid drag increase with blwing, apparently resulting frm Canda jet detachment and lss f circulatin, caused cnsiderable deteriratin in verall sectin perfrmance f this mdel. The pure 15 percent ellipse with tangential blwing displayed superir high speed characteristics in the range 0.55 * M w * 0.9«Due t the elngated trailing edge, the mdel was relatively free f jet detachment effects up t H m 0.7 and generated greater lift and aerdynamic efficiency, plus reduced drag. The rearward mvement f the upper surface shck was beneficial in the latter respect. The 30 jet flap cnfiguratin was the least effective sectin f the three, shwing prmise nly in drag reductin (due t its thrusting ability) and lack f lift drp ff with increased blwing (althugh net lift augmentatin was small). 12

22 Fr the entire Mach number range, maximum aerdynamic efficiency was btained at C 0.03; this was reduced t C 0.02 by the pure ellipse at M > The results indicate that the elngated trailing edge was an effective high speed circulatin cntrl trailing edge, but that future wrk shuld be dne t ptimize the tangentially blwn cnfiguratin and extend its range f maximum effectiveness beynd M =0.7- Of primary imprtance is a need t understand the phenmenn f high speed Canda jet detachment and effects upn it f upper surface bundary-layer shck interactin and supersnic expanded flw dwnstream f the chked nzzle. Aviatin Department Naval Ship Research and Develpment Center Washingtn, D.C Octber

23 ACKNOWLEDGEMENT The authr wuld like t express his appreciatin t Mr. M. Stne and Mr. P. Mazzi, fr their assistance in instrumentatin, test setup, and data acquisitin and reductin fr the transnic tests at Aer Hypersnic Labratry, Rsemunt, Minnesta, 14

24 REFERENCES 1.Williams, R.M. Sme Research n Rtr Circulatin Cntrl. IK CAL/AVLABS Sympsium: Aerdynamics f Rtary Wing and v/stol Aircraft. 3rd, Buffal, N.T., Jun Prceedings, Vl Williams, Rbert M. and Harvey J. Hwe. Tw Dimensinal Subsnic Wind Tunnel Tests n a 20 Percent Thick, 5 Percent Cambered Circulatin Cntrl Airfil. Wash., Aug incl. illus. (Naval Ship Research and Develpment Center. Tech Nte AL-I76) 3. Kisils, A.P. and R. E. Rse Experimental Investigatins f Flight Cntrl Surfaces Using Mdified Air Jets. St. Pual, Minn., Nv I969. l$k p. incl. illus. (Hneywell, Inc. Dcument FR1. Cntract NOOOI9-67-C- 0200) (DDC AD 86V2716) k. Cngressinal Huse Cmmittee n Apprpriatins. Natinal Wind-Tunnel Summary (u). Wash., [132] p. (DDC AD ) CONFIDENTIAL 5. Hiltn, William F. High-Speed Aerdynamics. N.Y., Lngmans, Green, p. 6. Lck, C.N.H., William F. Hiltn and Sidney Gldstein. Determinatin f Prfile Drag at High Speeds by a Pitt Traverse Methd. Lndn H.M.S.O., n.d. 39 p. incl. illus. (Great Brit. Aernautical Research Cuncil. R & M *709, Sep 19^0) 7. Grahame, W.E. and J.W. Headley. Jet Flap Investigatin at Transnic Speeds. W-PAFB, Feb p. incl. illus. (Flight Dynamics Lab. Tech. Rpt ) (Nrthrp Crp. Cntract F C-1429) 8. Pearcey, Herbert H., C.S. Sinntt and J. Osbrne. Sme Effects f Wind Tunnel Interference Observed in Tests n Tw-Dimensinal Aerfils at High Subsnic and Transnic Speeds. Paris, l V» incl. illus. (Advisry Grup fr Aerspace Research and Develpment. Rpt. 296). 15

25 / -.05 t/c t/c t/c /c camber rati Karnann-Tslen Cmpressibility Crrectin f Ptential Flw Results u a u I. kt Critical Hach Number, M, rlt..9 Figure 1 * Critical Hsch Number f Ellipses at r - 0 C 16

26 r-l g «r4 i CO c H 4J id M 5 V 60 S s 1 *0 «3U»TOTJJ»O0 ajti e a w I CM I 17

27 m a* u U 1 4> I d m c 8 H en s t 18

28 -. ' (a) Internal view shving mdal, balance eyatem disc, and sltted flr & ceiling (b) External View, lking upatream Figure 4 - Trananic Wind Tunnel and Assciated Teat Equipment 19

29 3» a 5 s 3 U u 8 in s- 20

30 chfc«d Html tail*.». / P^ fr 0.01 BMk tl#t»if* 21

31 fcmwi Mile F. / P t? Jtt filmitf tt U Mtltiat FW».r tut t.9.2 ai V*rUtl«i 22

32 M U Frit Stra Muh lluabtr, n.9 Figur* 8 Ifcft lynidg ftnbr 8MM Bud n Mdal Chrd 23

33 < 2.0 I.I c ^*" 0.3 l.ft s /!^ *f~*& -^f *>«3 0.3 A.4 O,3.4 O.7.1 i.1 4 r 1 > J 1* 03 J *.c 0 U.i OMffteltafc. «t lift MrUttM vitk MHMHIII CmttUimt hrlmtmullih 24

34 \.05 >% 1.2 X \V.*.. 8 s u i n --^5jV\. 7\\s.8 1 \\\ 0 55 i\\v' 015 j N& t 4 1 v^ ^"TP 1_ 111 ^? C(l v^ !. i I Fraa Str K \ ^ Mich ftmber, H..8 9 Pignrt 10 Lift Variatin irith Itch tabar fr ftvadad Elllptt 25

35 s i.t i. tv ia n j.i is * j* ftuttty litte, f j/f«mpi II ttft iwtetlw «Uk J* *U«lty tar»»ill HllfM 26

36 4 I«2! J«t filclty Utl, WJl m Fitmra 12 farutlm la lift Anfmueln vftti J«t Valclty Pw t «t< llllptt 27

37 ,08.06 *tik ] * 9 M OB 0.3 A.1» O u 4) s (^j I v fr.6 y.5 \X \a r*jt ^< O.7.8 X.9.02 ^*^G M.= ( )2.< A.( *.08 Mmentum Cefficient, c u Figur«13 - Drag Variatin With Mmentum Cefficient Fr Runded Ellipse 28

38 0) H Ü H 0) I Free Stream Mach Number, J^.9 Figure lu - Drag Variatin with Mach Number fr Runded Ellipse 29

39 LQM» a, - c, d d 1 * d (c =0) ' f * < 4 6 act! - t a 0 H 1 «.U * / / I l.l 1 u h / i v 1 / \ / \ / *f -.1».'_ M.= Mmentum Cefficient, C 0U.05 Figure 15 Runded Ellipse Dreg Reductin 30

40 Pifvt 16 - FrMur«Mttributi fr R t.6.8 Mdiatni lnal CbrdvlM Statin x/ 31

41 k Drag Cefficient» C. Figure 17 - Runded Ellipse Drag Plar 32

42 MMtntuft Cefficient, c fttmrt If»if chh HUM** brutt«fr mamiti Uli* 33

43 32 A _rvm / L- ^^^*-"*^ z /.^^^ A f. 1 k 12 /// 0 \ X \ A O.I i lr**-*& i A.a 4.i X.I.t J 1 b.( n.( It.0, i.( H.< ö.c»4.07 CwfflcUat, c rigr«it PBTWBMC* ttvlttlmt Llft-t-Dr«t itfcl fr IlliH«34

44 ^* 9 10 I.! 13 Uft OMffUi««t. Cj rtfw«if It tu Wmu fill H»tl«at Uft-t-tnt tti* ft» H ill UUfM 35

45 Mmentum Cefficient, C Figure 21 - Lift Variatin with Mmentum Cefficient fr Pure Ellipse 36

46 c 0» * Free Stream Mach Number» H m Figure 22 - Lift Variatin with Mach Number fr Pure Ellipse 37

47 a» 0) u u 3 >-1>* s 4) u Ü I 2- s «3 «4 5 I M 60 *D l *WTWI* 0 'JTI 38

48 O 4J 2 e a (chked cm dc net»pplt **: H i 0.9 curve Jet Velcity, Vj/V, Flfttrt 24 VerUttcm la lift AufMnUCln with Jet Telcity fr Pure Ellitt 39

49 Tf Strsaa Mach ftnbcr, H m Figur«25 - Lift Cmparisn f Runded and Fur«Blllp«««40

50 T* O CM 8 a 1 Mmentum Cefficient, C r'icure 26 - Drag Variatin with Mmentum Cefficient fr Pure ellipse kl

51 .06.05, öli i.03 i *.02 v 8-01 r^ r^^^^l^i22l-.! -.01.<* i *-*w' y i / ; ^*^.01 ^ 1/ / J S i/ * i, i k Free Stream Mach Number, M \^y.8.9 figure 27 - *rag Variatin with Mach Number fr Pure Ellipse 1*2

52 *.v~r-.-v<''-*''^r- 1 " l^*l' ''.;** i 1 I I I L lt lcatin (V -.9*) t- -Li UO tr J L L wmwrtwtt CheardwiM Statin, a/e Plfurt 28 - Prttrar«Distributin««r tat tlllpm «t PU,^

53 . _i*a<r»^;''m ^*^!J-^ ylmphljlim k A V \.8. \ - \ -.8 i.6^ \ -.4 U ü < \< -1.2! #7 \ /.._. P<4 P _ 1 r 9 AC d M =) M -2.1».0V Mmentum Cefficient, C Mi..Oh.03 Figure 29 - Pure Ellipse Drag Reductin W)

54 l.of -.0? -.Ol <* Drac Cefficient, C, Ki.nuv i'r.r Kluppe I.ra.3 Plar v

55 Figur«31 Variatin la Pitching Mment with HMtntua CtfficUnt fr Furt Bllipi 46

56 m O 41 ä 9 t I I I Figure 32 Frcc-Baici Equivalent Lift-t-Drag Rati Fr Pirc Elllptt 47

57 "-'" Figur«33 - Kin«elc-Encrgy-&ascd Equivaltnt Lift-t-Dras Riti 7er Pur«Elllpat 4ö

58 vrr-r-tw-v^-t :r^»,,- TOI TÖ , OS Hmentum Cefficient» C Figure 34 - Jet Flap Lift Variatin with Mmentum Cefficient 49

59 ^mm^mmm^f^^s^s^^ i^ymmt^^^wwyw mmmmimmmmmmmmmamimm»mmmmm*mmmmm»> - ** U u n H I Free Stream Hch Nuber, ^ Figur«35 - jet Flap Uft Variatin with Hach number SO

60 -d t i I O rl ti Ü KmcnUsn Cefficient, C inure 36 - Drag Variatin with Mmentum Cefficient fcr -let Klap 51

61 t 0 a in Free Str^ar. ;-'ach Number I''i;;nrts 37 - «Tt Flap ;-ra.-- Variatin with."ach V::-.l'-r

62 -t '' -) a;.1 0 rl C) M -1.Ü Minentur. Cefficient, C Figure 3^ - Jet :-lap Dr.ic Reductin P3

63 ü!^55s?^»»r^?5«s» *e> 'WSTBWTOW»5W7Wf5W^^ -l.or 8 a *vbr\...-^- " --«* upper surface shck lwer surf ace s^ *s\ «hck >»*- cr^ slt lcatin n (x/c -.983) * h ' h» ic ' fe L -ry NndlAcnsinal ChrUvise Statin, x/c rigure 39 - Priture Distributin! fr Jet Flap at M 0.9»» nainal ' w ** c 54

64 T3T*^.^^-^ ^-- ~ ^ WWWV IJ : v-su^y,*.'^e^-ffl- CO O ) a O c. J! c \ ; ; u > f i -J g \ " -IS * \!/' \ 1/ en 3 a s ~4 Ü 0 C M 5 i ON d i- i»- 'r.f -! f/a l w 1 1 J i c 3 "D^U.^DTJJ^OO atwaua «u^is^til P^ip jjrj 55

65 «mmmmmmimmmmmmmmm^mmmmmmnm mmmm i.i. WS! i.i'i!mpimiillilj i,!!ii.py^'wwm^-w^y^'^" - j (^ ä m *sr «A v t- c 0\ <J - 0 x! i T\ i ) (V) ' ej n3 H C «i H H Ü H CM r-4 0) t H H ri cl b E Q 1 ( Q4 el H 8 i 4> m 1 i UN 5 r 0 'VJOTSyjja «n 56

66 I **^ÄSP55??^SPgppB"g! a^fw^wi^wpfj^w!^ 11 l ' Vt'.ä-''- Hacatu» Cefficient, C Figur«'42 - ftwbted Equivalent Uft-t-Dr«f JUtl fr Jet flap 5.

67 JtR: *rmmmmmmmmmmmm&^--m»»»»w««ptj^igaaffaf^iag^m A t ^ 0.» A.4 O.S V.6.y 0 C A /i fc >, «U.5 \0.4 4r 0 x» f /* 1^ * * ///-j A * tfy M JBKC / * * s /^ < Jp -1 " «05 <».«I I & i t IS.2 3 S.< b uft QMff ut«*, Cj fflfw» 41 - KI-CU mrty Ulli Hrt l«tt Lift-t*-Dru fed* farm ru*

68 8 V1 u -± «4 c J s Free Stream Kadi Number» H m Figure 44 - Cmparative Lift Characteristics i Hie Three Mdels 59

69 3 5 f t a i.3 * *.6 Free Strea«Mich Figur 45 - Cparisa f Maxleun Free»Baad EquivaUnC Lift-t-Prag Rati fr tha Ihrea Cnfiguratin«60

70 28 r~- /\ Runded Ellipse 0 H U a cd a i ij! '4-1 u G CO s Free Stream Mach Number, M Figure 46 - Cmparisn f Maximum Kinetic-Energy-Based Equivalent: Lift-C-Drag Rati Fr The Three Cnfiguratins 61

71 Ü H U H «-i til -i x.3 C H 0 u M-l Free Stream Mach Number, M Figure 47 - Lift Crrespnding t Maximum Aerdynamic Efficiency 62

72 !«MH^M<^^4«B^^ u Free Stream Mach Number, M Figure 48 - Mmentum Cefficients fr Maximum Aerdynamic Efficiencies 63

73 mmmmmmmm. m i!i i.. ' ".' UNCMSSIFIED S«^irilv Classificatin DOCUMENT CONTROL DATA.R&D (Security cleutiticatin l title, bdy l batrrt mud indenlng anntatin muni be entered when the verall reprt la ctmeellled) Zm. REPORT SECURITY CLASSIFICATION UNCLASSIFIED 26. GROUP I. ORIGINATING ACTIVITY (Crprate authr) Aviatin Department Naval Ship Research and Develpment Center Washingtn, D.C. 2003^ J. REPORT TITLE TWO-DIMENSIONAL TRANSONIC WIND TUNNEL TESTS OF THREE 15-FERCENT THICK CIRCULATION CONTROL AIRFOILS 4. DESCRIPTIVE NOTES (Type l reprt ml Inclusive dmtee) Technical Nte» AUTHOR(S) (Fltßt name, middle Initial, laat Rbert J. Englar «. REPORT OATE December 1970 M. CONTRACT OR «RANT NO. b. PROJECT NO. ^ 0n «. TOTAL NO. OF PACES _ M. ORIOINATOR'S REPORT KUMSCKIt) Technical Nte AL-182 7». NO. OF REFS 8 JKSRDC OTHER REPORT NOtSI (Any ther mmbere mat may be eelaned thle reprt) 10. DISTRIBUTION STATEMENT Distributin limited t U.S. Gv't agencies nly; Test and Evaluatin; December 1970.«Other requestes fr this dcument must be referred t Naval Air Systems Cmmand (AIR320). II. SUPPLEMENTARY NOTES It. SPONSORING MILITARY ACTIVITY Naval Material Cmmand (03lA) Washingtn, D.C ABSTRACT ^Tw-dimensinal transnic wind tunnel tests were cnducted n^hree fifteen percent circulatin cntrl elliptic airfils ver the range 0.3 m M * 0.9. Mdel cnfiguratins included a pure elliptical shape with bth jet flap asf tangential upper surface trailing edge blwings plus tangential blwing ver an elliptical shape with a runded trailing edge. Perfrmance f the runded trailing edge cnfiguratin was the best f the three at lw speeds, but abve M^«C5> detachment f the Canda jet caused rapid perfrmance deteriratin. Due t its elngated trailing edge and assciated larger effective radius dwnstream f the slt, the tangentlally blwn pure ellipse was able t extend the jet detachment Mach number t 0.7» where maximum equivalent lift-t-drag ratis f 22 at C r f O.Mr were >1 J achieved. The jet flap prved t be inferir t the tangentlally blwn cnfiguratins in all respects except in its ability as a thrusting, drag-reducing bdy. DD /rj473 S/w OI01.t07.ftOf (PAGE 1) UNCLASSIFIED