1、NASA Technical Paper 1498Low-Speed Aerodynamic Characteristicsof a 13-Percent-Thick Medium-SpeedAirfoil Designed for GeneralAviation ApplicationsRobertJ. McGhee and William D. Beasley _O=_/_ _I-,/_1,-, -,AI-)I _ r_,KIl_“f_Tl/“_ f-_l_“_,(“_4“laikl A“rl,_klAUGUST 1979Provided by IHSNot for ResaleNo re
2、production or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA Technical Paper 1498Low-Speed Aerodynamic Characteristicsof a 13-Percent-Thick Medium-SpeedAirfoil Designed for GeneralAviation Appli
3、cationsRobert J. McGhee and William D. BeasleyLangley Research CenterHampton, VirginiaNI ANational Aeronauticsand Space AdministrationScientific and TechnicalInformation Branch1979Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for
4、 ResaleNo reproduction or networking permitted without license from IHS-,-,-SUMMARYAn investigation was conducted in the Langley low-turbulence pressuretunnel to determine the low-speed two-dimensional aerodynamic characteristicsof a 3-percent-thick medium-speed airfoil designed for general aviation
5、applications. The results are compared with data for the 3-percent-thicklow-speed airfoil section. Also, theoretical predictions of the drag-risecharacteristics of the medium-speed airfoil are provided. The tests wereconducted over a Mach number range from 0.0 to 0.32, a chord Reynolds numberrange f
6、rom 2.0 x 06 to 2.0 x 06, and an angle-of-attack range from about -8 to 20 .The results of the investigation indicate that the objective of retaininggood high-lift low-speed characteristics for an airfoil designed to have goodmedium-speed cruise performance was achieved. Maximum section lift coeffic
7、ientsat a Mach number of 0.5 increased from about .70 to 2.06 as the Reynolds num-ber increased from about 2.0 x 06 to 2.0 x 06 . Stall characteristics wereof the trailing-edge type and were docile at the lower Reynolds numbers. Theapplication of a roughness strip near the leading edge of the airfoi
8、l resultedin only small effects on maximum section lift coefficients. Increasing the Machnumber from 0.0 to 0.32 at a constant Reynolds number of 6.0 x 06 decreasedthe maximum section lift coefficient about 0.08. The magnitude of the quarter-chord pitching-moment coefficient was decreased about 25 p
9、ercent for the medium-speed airfoil compared with the low-speed airfoil.INTRODUCT IONResearch on advanced-aerodynamic-technology airfoils for general aviationapplications has been conducted over the last several years at the LangleyResearch Center and reported in references to 6. This research effor
10、t wasinitially generated to develop advanced airfoils for low-speed applications.Emphasis was placed on designing airfoils with largely turbulent boundary lay-ers that had the following performance requirements: low cruise drag, highlift-drag ratios during climb, high maximum lift, and docile stall
11、behavior.More recently the general aviation industry indicated a requirement for air-foils which provide higher cruise Mach numbers than the low-speed airfoils andwhich still retain good high-lift low-speed characteristics. These medium-speed airfoils have been designed to fill the gap between the l
12、ow-speed air-foils and the supercritical airfoils for application on light executive-typeaircraft. The status of NASA low- and medium-speed airfoil research isreported in reference 7.The present investigation was conducted to determine the low-speed aerody-namic characteristics of a 3-percent-thick
13、medium-speed airfoil designed fora lift coefficient of 0.30, a Reynolds number of 4.0 x 06 , and a Mach numberof 0.72. This new airfoil is designated as MS()-0313. In addition, theresults are compared with the 3-percent-thick low-speed airfoil, LS()-043.Provided by IHSNot for ResaleNo reproduction o
14、r networking permitted without license from IHS-,-,-Theoretical predictions of the drag-rise characteristics of this medium-speedairfoil are also provided.The investigation was performed in the Langley low-turbulence pressuretunnel over a Machnumberrange from 0.0 to 0.32. The Reynolds number, basedo
15、n the airfoil chord, varied from about 2.0 x 06 to 2.0 x 0 6, and the geo-metric angle of attack varied from about -8 to 20 .SYMBOLSValues are given in both SI and U.S. CustomaryUnits.and calculations _re madein U.S. CustomaryUnits.CpcccCdcd c ZcmcnhMPqRxz2The measurementspressure coefficient,airfoi
16、l chord, cm (in.)p- p_q0osection chord-force coefficient,section profile-drag coefficient,point drag coefficientsection lift coefficient,SWake cd dlhlcn cos e - cc sinsection pitching-moment coefficient about quarter-chord point,- Cp - 0.2 d + Cp - d_f Csection normal-force coefficient, -(_,_, Cp dQ
17、 x)vertical distance in wake profile, cm (in.)free-stream Mach numberstatic pressure, Pa (ib/ft 2)dynamic pressure, Pa (Ib/ft 2)Reynolds number based on free-stream conditions and airfoil chordairfoil abscissa, cm (in.)airfoil ordinate, cm (in.)Provided by IHSNot for ResaleNo reproduction or network
18、ing permitted without license from IHS-,-,-zcztmeanline ordinate, cm (in.)mean thickness, cm (in.)geometric angle of attack, degSubscripts:maxo0local point on airfoilmaximumfree-stream conditionsAIRFOIL DESIGNATIONSketches of the low- and medium-speed airfoils are shown in figure I. Theairfoils are
19、designated in the form LS(1)-xxxx or MS()-xxxx. LS(1) indicateslow speed (first series) and MS() indicates medium speed (first series). Thenext two digits designate the airfoil-design lift coefficient in tenths, andthe last two digits designate the airfoil thickness in percent chord.AIRFOIL DEVELOPM
20、ENTThe intention of the medium-speed airfoil development was to combine thebest features of low-speed and supercritical airfoil technology. In order toexpedite the airfoil development, the computer program of reference 8 was usedto predict the results of various design modifications. The medium-spee
21、d air-foil is 13 percent thick with a blunt nose and a cusped lower surface near thetrailing edge. The design objective of the airfoil was to increase the cruiseMach number of the 3-percent-thick low-speed airfoil but retain good high-liftlow-speed characteristics. This type of airfoil is intended t
22、o fill the gapbetween the low-speed airfoils and the supercritical airfoils for applicationon light executive-type aircraft. The airfoil was designed for a lift coeffi-cient of 0.30, a Reynolds number of 14.0 x 106 , and a Mach number of 0.72.The medium-speed airfoil was obtained by reshaping the 13
23、-percent-thicklow-speed airfoil as indicated by figure I. The calculated pressure distribu-tions (fig. 2(a) indicate that increasing the Mach number to 0.72 for the low-speed airfoil at a lift coefficient of 0.30 results in a region of high inducedvelocities near the midchord on the upper surface of
24、 the airfoil. Note alsothat the low-speed airfoil is highly aft loaded and actually carries a smallnegative load in the forward region. Further increases in Mach number or liftcoefficient would result in a shock wave developing on the airfoil upper sur-face near the midchord. This airfoil has been r
25、eshaped to decrease the veloci-ties near the midchord and increase the velocities in the forward region on theairfoil upper surface. In addition, the camber of the medium-speed airfoil wasdecreased about 25 percent compared with the low-speed airfoil. Comparisonof the experimental low-speed (M = 0.1
26、5) pressure data for both airfoils at= 0 is shown in figure 2(b). The thickness distributions and camber linesProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-for both airfoils are comparedin figure 3. Table I presents the design coor-dinates for the
27、medium-speedairfoil.MODEL,APPARATUS,ANDPROCEDUREModelThe airfoil model was constructed with a metal core around which plasticfill and two thin layers of fiberglass were used to form the contour of theairfoil. The model had a chord of 61 cm (24 in.) and a span of 91 cm (36 in.).The model was equipped
28、 with both upper- and lower-surface orifices located 5 cm(2 in.) off the midspan. The airfoil surface was sanded in the chordwise directiowith No. 400 dry silicon carbide paper to provide a smoothaerodynamic finish.The model contour accuracy was generally within 0.100 mm(0.004 in.).Wind TunnelThe La
29、ngley low-turbulence pressure tunnel (ref. 9) is a closed-throat,single-return tunnel which can be operated at stagnation pressures from 1.0 to10.0 atm (1 atm = 0.3 kPa) with tunnel-empty test-section Mach numbers up to0.42 and 0.22, respectively. The maximum Reynolds number is about 49 x 106 permet
30、er (15 x 106 per foot) at a Mach number of about 0.22. The tunnel test sec-tion is 91 cm (3 ft) wide and 229 cm (7.5 ft) high.Hydraulically actuated circular plates provided positioning and attachmentfor the two-dimensional model. The plates are 102 cm (40 in.) in diameter,rotate with the airfoil, a
31、nd are flush with the tunnel wall. The airfoil endswere attached to rectangular model-attachment plates (fig. 4) and the airfoilwas mounted so that the center of rotation of the circular plates was at 0.25con the model reference line. The air gaps in the tunnel walls between the rec-tangular plates
32、and the circular plates were sealed with metal seals.Wake Survey RakeA fixed wake survey rake (fig. 5) at the model midspan was mounted fromthe tunnel sidewall and located chord length behind the trailing edge of theairfoil. The wake rake utilized 0.5-cm (0.06-in.) diameter total-pressuretubes and 0
33、.32-cm (0.125-in.) diameter static-pressure tubes. The total-pressure tubes were flattened to 0.10 cm (0.04 in.) for 0.61 cm (0.24 in.)from the tip of the tube. The static-pressure tubes each had four flushorifices drilled 90 apart and located 8 tube diameters from the tip of thetube and in the plan
34、e of measurement of the total-pressure tubes.InstrumentationMeasurements of the static pressures on the airfoil surfaces and the wake-rake pressures were made by an automatic pressure-scanning system utilizingProvided by IHSNot for ResaleNo reproduction or networking permitted without license from I
35、HS-,-,-variable-capacitance-type precision transducers Basic tunnel pressures weremeasuredwith precision quartz manometers Angle of attack was measuredwitha calibrated digital shaft encoder operated by a pinion gear and rack attachedto the circular model-attachment plates Data were obtained by a hig
36、h-speedacquisition system and recorded on magnetic tape.TESTS AND METHODSThe airfoil was tested at Mach numbers from 0.10 to 0.32 over an angle-of-attack range from about -8 to 20 . Reynolds number based on the airfoil chordwas varied from about 2.0 106 to 2.0 06 . The airfoil was tested both inthe
37、smooth condition (natural transition) and with roughness located on bothupper and lower surfaces at 0.075c. The roughness was sized for each Reynoldsnumber according to the technique in reference 10. The roughness was sparselydistributed and consisted of granular-type strips 0.13-cm (0.05-in.) wide
38、whichwere attached to the surfaces with clear lacquerThe static-pressure measurements at the airfoil surface were reduced tostandard pressure coefficients and machine integrated to obtain section normal-force and section chord-force coefficients as well as section pitching-momentcoefficients about t
39、he quarter chord. Section profile-drag coefficients werecomputed from the wake-rake total and static pressures by the method reportedin reference 11.An estimate of the standard low-speed wind-tunnel boundary corrections(ref. 2) amounted to a maximum of about 2 percent of the measured coefficientsand
40、 these corrections have not been applied to the data. An estimate of thetotal-pressure tube displacement effects on the values of cd showed theseeffects to be negligible (ref. 1).PRESENTATION OF RESULTSThe test conditions are summarized in table II. The results of thisinvestigation have been reduced
41、 to coefficient form and are presented in thefollowing figures:FigureSection characteristics for MS()-0313 airfoil . 6,7Effect of roughness on section characteristics . 8Effect of Reynolds number on section characteristics. Model smooth;M = 0.15 “ 9Effect of Reynolds number on section characteristic
42、s. Roughness on;M = 0.15 . 10Effect of Mach number on section characteristics. Roughness on;R = 6.0 06 11Comparison of section characteristics for LS()-0413 and MS(1)-0313airfoils Roughness on; M = 0.5 2Effect of angle of attack and Reynolds number on chordwise pressuredistributions for MS(1)-0313 a
43、irfoil Roughness on; M = 0.5 3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FigureComparisonof chordwise pressure distributions for LS()-0413 andMS(I)-0313 airfoils. Roughnesson; M = 0.5 . 4Variation of maximumlift coefficient with Reynolds numberf
44、orLS()-043 and MS(I)-033 airfoils. M = 0.5 . 5Variation of maximumlift coefficient with Machnumberfor LS()-043and MS()-033 airfoils. Roughnesson; R = 6.0 x 106 6Calculated drag-rise characteristics for LS()-0413 and MS()-0313airfoils. R = 4.0 x 06 . 7DISCUSSIONOFRESULTSSection CharacteristicsLift.-
45、Figure 9(a) shows that the lift-curve slope for the medium-speedairfoil in a smoothcondition (natural boundary-layer transition) varied fromabout 0. to 0.2 per degree for the Reynolds numbersinvestigated (M = 0.5).The angle of attack for zero lift coefficient was about -3 . Maximumliftcoefficients i
46、ncreased from about .70 to 2.06 as the Reynolds number wasincreased from about 2.0 x 0 6 to 2.0 x 0 6 , with the greatest increaseoccurring between Reynolds numbers of 2.0 106 and 4.0 x 06 . The stallcharacteristics of the airfoil are of the trailing-edge type, as shown by thelift data of figure 9(a
47、) and the pressure data of figure 3. The nature of thestall is docile at Reynolds numbers of 2.0 x 06 and 4.0 x 06 .The addition of a roughness strip at 0.075c (fig. 8) resulted in theexpected decambering effect because of the increase in boundary-layer thick-ness. For example, at R = 2.0 x 06 (fig.
48、 8(a) the angle of attack for zerolift coefficient changed from about -3 to -2.7 . No measurable change in lift-curve slope was indicated, and the lift coefficient at e = 0 decreased fromabout 0.35 to 0.31. These effects on the lift characteristics decreased as theReynolds number was increased and were essentially eliminated at R = 2.0 x 06(fig. 8(e). The roughness strip had only minor effects on the C_,ma x per-formance of the airfoil for the Rey
