1、 NATIONAL ADVI.$0RY CO_I!:ITTEE FC_R .AErONaUTICS-TECHNICAL NOTE N0.: 412“TH_ AERODYNAh_IC CHARACTERISTICS OF _IRFOILS“ _ “ “ . .7._: ,“AT L_EGATIVE AI_GLE$ OF A_TACK “_; : _“,- .oBy Raymond F_ Anderson. :-. o . “.- . .- SU_IZARY .“. . , -.“:- A number of airfoils, including 14 commonly used air-foa
2、ls and I0 N.A.C.A. airfoils, were tested through the:negative angle-of-attack range in the N.A.C.A. variab.le-density wind tunnel at a Reynolds _umber of approximately3,000,000. The tests were made to supr_ly data to serve asa basis for the structural des ig_ of airplanes in the in-verted flight con
3、dition. In order to ,_:ake the results im-:._ediately available for this purpose they are presentedherein in preli:uinary form, together with results of pre-vious tests of the airfoils at positlve angles of attack.“!An analysis of the results made to find the variatioriof the ratio of the maximhm ne
4、gatlvelift coefficient tothe r,aximum positive lift coefficient led to the followingconclusions: I. For airfoils of a given thickness, the rati6-CL max/+OL max tends to decrease as the mean camber is.,increased. ,.“ :,2. For airfoils of a given mean camber, the ratio “ _-CL max/+CL max tends to incr
5、ease as the thickness In-ctoases.INTRODUCTIONThere is at present little information on the aero-d_,na_nlc characteristics of airfoils at negative angles ofattac:u. In the few tests which “ e een_av b _nade the Rey-nolds Number has been low. oProvided by IHSNot for ResaleNo reproduction or networking
6、 permitted without license from IHS-,-,-ERRATANATIONAL ADVISORY C0_iITTEE FOR AERONAUTICSTECHNICAL I_0TE NO. 412THE A_RODYNA._,:.IC CHAR.iCTERISTICS OF ._IRF01LS AT_EG.:TIVE A-_-_.S OF A_:TA3ZY i_.ure i0:Figure 20 :The c.p. at -7.9 should be 14.9 per centinstead of 4.9 per cent.The part of the c.p.
7、curve from-14 o extend-ing to and beyond -80 should be conc_.veupwards. The true form of these and otherc.p. curves ma_- be obtained more accurate-ly by computing c.p. values from the curvesof Cm c/4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 _
8、A,_A. Techncal,-Note ;!o.4.12 .: ,. _ . , The need for add._tlen_l. ds-ta-.,i11.t.hls range was re-cently experienced by the Bureau of Aeronautics, Navy De-partment, while they were“f6rn_lhting rationel proceduresto be fo!Ll-owe.d,i.n-designi.ng a.ir_-l_.ne_.,.fg.r.:_he Ldiv.e and in-verted flight c
9、onditions. Accordingly, a number of air-foils suggested:by_._tlhe Buree.u .o.f.Aeirgnau_ti_s and a numberof N,A,C.A, airfoils were tested at negative angles of at-tack in the N,A,C.A.: varlab.le.-dens$_, wlnd tunnel at aReynolds Number of approximately S,0O0,000. “_Pert of the results we r.9ipubllsh
10、ed in a preliminarynote (reference l) before the tests were completed, Thepresent report gives all the results, including those pub-_l,%-shed_i:_ referenc_l a_d the re%ult:s .of. lreviousl, y .un-pub.lish,ed, t:ests._f the :airf,oil_sa:t ,loqs.!t_y.eangles of at-tic/!(-.,6: _._.:+I_-.:,.3_.8! t40 7.
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