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NASA Technical Memorandum 84245 USAAVRADCOM TR-82-A-8

.,o3- 17 5.)__

_,.7 17

An Experimental Study of DynamicStall on Advanced Airfoil SectionsVolume 3. Hot-Wire and Hot-FilmMeasurementsL. W. Carr, W. J. McCroskey: K. W. McAlister,S. L. Pucci, and O. Lambert

December 1982

fU/LS/National AeronautMcs andSpace Administration

REPRODUCED BYU.S. DEPARTMENT OF COMMERCENATIONALTECHNICALINFORMATIONSERVICESPRINGFIELD,VA 22161United States ArmyAviation Research Vnd DevelopmentCommand


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NASA Technical Memorandum 84245 USAAVRADCOM TR-82-A-8

An Experimental Study of DynamicStall on Advanced Airfoil SectionsVolume 3. Hot-Wire and Hot-FilmMeasurementsL. W. CarrW. J. McCroskeyK. W. McAlisterS. L. Pucci, Aeromechanics Laboratory

AV RADCOM Research and Technology LaboratoriesAmes Research Center, Moffett Field, California

O. Lambert, Service Technique des Constructions Aeronautiques,Paris, France

NASANational Aeronautics andSpace AdministrationAmes Research CenterMoffett Field California 94035

United States ArmyAviation Research andDevelopment CommandSt. Louis. Missouri 63166


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TABLE OF CONTENTS

LIST OF FIGURES .......... . ....................LIST OF TABLES ..............................

SYMBOLS ...................................SUMMARY , . * *

INTRODUCTION ................................

DESCRIPTION OF EXPERIMENTAL PROCEDURES ...................

DATA ANALYSIS AND INTERPRETATION ......................Skln-Frictlon Gage ...........................Hot-Wire Probe .............................Reverse-Flow Sensors ..........................Averaging Techniques ..........................Example of Signal Analysis .......................

RESULTS ...................................

REFERENCES .................................

TABLES ...................................

FIGURES ...................................

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LESTOFFIGURES

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Diagram showing installation of spar and airfoil shell in tunnel ....

Diagram of hot-film skin-frlction gage .................Response of hot-film skln-friction gages mounted on Ames A-01airfoil during airfoil oscillation in pitch (_ = 15 + i0 sin rot,k ffi0.i0, M_ ffi0.22) ..........................

Response of hot-film skin-friction gages at surface of NACA 0012airfoil during airfoil oscillation in pitch (s = 15 + i0 sin mr,k = 0.i0, M_ = 0.295) ........................

Diagram of dual-element hot-wlre probe .................

Response of hot-wlre anemometer probes on Wortmann FX-098 airfoilduring airfoil oscillation in pitch (_ ffi15 + i0 sin _t,k = 0.i0, M_ = 0.ii) ..........................

Response of hot-wire anemometer probe installed near trailingedge of the Vertol VR-7 airfoil during oscillation in pitch ......

Results obtained using trlple-wlre flow-reversal sensor:(a) Typical comparison of flow-reversal sensor and hot-wlreanemometer signal (from ref. 2); (b) Progression of flow reversalup airfoil during dynamic stall (from ref. 2) .............

Diagram of three-element, directionally sensitive hot-wire probe(from ref. 2) ............................Comparison of lO0-cycle ensemble average and slngle-cycle signalsfrom hot-wire anemometers for Vertol VR-7 airfoil during oscillationin pitch: --, i00 cycle average; ...... , slngle cycle ......

Response of hot-film skln-frlctlon gage and hot-wlre anemometerprobes on Vertol VR-7 during oscillation in pitch (a - 15 + i0 sin _t,k ffi0.i0, M_ = 0.185) .........................

Phase angle, _t, of flow reversal on NACA 0012 airfoil vs chordlocation for a range of Mach numbers at k ffi0.i, _ - 15 + I0 sin _t --Mach number effects ..........................

Phase angle, _t, of flow reversal on Ames A-OI airfoil vs chordlocation for a range of Mach numbers at k - 0.i, e = 15 + i0 sin _t --Mach number effects ..........................

Phase angle, _t, of flow reversal on Wortmann FX-098 airfoil vs chordlocation for a range of Mach numbers at k = 0.i, _ ffi15 + i0 sin _t --Mach number effects .........................

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Phase angle, _t, of flow reversal on Sikorsky SC-I095 airfoil vs chordlocation for a range of Mach numbers at k = 0.i, _ = 15 + i0 sin _t --Mach number effects . .........................

Phase angle, _t, of flow reversal on Hughes HH-02 airfoil vs chordlocation for a range of Math numbers at k = 0.I, _ = 15 + i0 sin _t-Mach number effects .........................

Phase angle, _t, of flow reversal on Vertol VR-7 airfoil vs chordlocation for a range of Mach numbers at k = 0.i, e = 15 + i0 sin _t --Mach number effects ..........................

Phase angle, _t, of flow reversal on NLR-I airfoil vs chord locationfor a range of Mach numbers at k = 0.i, _ = 15 + i0 sin _t -Machnumber effects .............................

Phase angle, wt, of flow reversal on NLR-7 airfoil vs chord locationfor a range of Math numbers at k = 0.i, _ = 15 + I0 sin _t --Machnumber effects ............................

Phase angle, _t, of flow reversal on NACA 0012 airfoil vs chordlocation for a range of frequencies at M_ = 0.295,

= 12 + 5 sin _t -- light-stall conditions ..............Phase angle, _t, of flow reversal on Ames A-01 airfoil vs chordlocation for a range of frequencies at M_ = 0.295,

= ii + 5 sin _t -- llght-stall conditions ..............Phase angle, _t, of flow reversal on Wortmann FX-098 airfoil vs chordlocation for a range of frequencies at M_ = 0.295,

= i0 + 5 sin _t -- light-stall conditions ..............Phase angle, wt, of flow reversal on Sikorsky SC-I095 airfoil vschord location for a range of frequencies at M_ = 0.295,

= ii + 5 sin _t -- light-stall conditions ..............Phase angle, _t, of flow reversal on Hughes HH-02 airfoil vs chordlocation for a range of frequencies at M_ = 0.295,

= i0 + 5 sin _t -- light-stall conditions ..............Phase angle, _t, of flow reversal on Vertol VR-7 airfoil vs chordlocation for a range of frequencies at M_ = 0.295,

= 15 + 5 sin _t -- light-stall conditions ..............Phase angle, _t, of flow reversal on NLR-I airfoil vs chordlocation for a range of frequencies at M_ = 0.295,

= i0 + 5 sin _t -- light-stall conditions ..............

Phase angle, _t, of flow reversal on NLR-7 airfoil vs chordlocation for a range of frequencies at M_ = 0.295,e = 15 + 5 sin _t -- light-stall conditions .........

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28 Phaseangle, wt, of flow reversal on AmesA-01 airfoil vs chord for arange of frequencies at M_= 0.295, _ _ 15 + i0 sin _t -- deep-stallconditions ...... ........................ 56

29 Phase angle, _t, of flow reversal on Wortmann W-98 airfoil vs chordfor a range of frequencies at M_ = 0.295, _ = 15 + i0 sin _t --deep-stall conditions ........................ 57

30 Phase angle, _t, of flow reversal on Wortmann FX-098 airfoil vs chordfor a range of frequencies at M_ = 0.185, e = 15 + i0 sin _t --deep-stall conditions ......................... 58

31 Phase angle, _t, of flow reversal on Vertol VR-7 airfoil vs chordfor a range of frequencies at M_ = 0.295, = = 15 + i0 = sin _t --deep-stall conditions ......................... 59

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LIST OF TABLES

i Summary of analyzed flow-reversal data .................

2 Phase angle of flow reversal: NACA 0012 airfoil ............

3 Phase angle of flow reversal: Ames A-01 airfoil ............

4 Phase angle of flow reversal: Wortmann FX-098 airfoil .........

5 Phase angle of flow reversal: Sikorsky SC-I airfoil ..........

6 Phase angle of flow reversal: Hughes HH-02 airfoil ..........

7 Phase angle of flow reversal: Vertol VR-7 airfoil ...........

8 Phase angle of flow reversal: NLR NL-I airfoil ............

9 Phase angle of flow reversal: NLR-7301 airfoil ............

10 Error-bound for flow-reversal measurements (deg): NACA 0012airfoil ................................

ii Error-bound for flow-reversal measurements (deg): Ames A-01airfoil ................................

12 Error-bound for flow-reversal measurements (deg): Wortmann FX-098airfoil ................................

13 Error-bound for flow-reversal measurements (deg): Hughes HH-02airfoil ................................

14 Error-bound for flow-reversal measurements (deg): Vertol VR-7airfoil ...............................

15 Error-bound for flow-reversal measurements (deg): NLR-Iairfoil ................................

16 Error-bound for flow-reversal measurements (deg): NLR-7301airfoil ................................

17 Notes pertaining to tables 18 to 25 ..................

18 Catalog of recorded data: NACA 0012 airfoil ..............

19 Catalog of recorded data: Ames A-01 airfoil ..............

20 Catalog of recorded data: Wortmann FX-098 airfoil ...........

21 Catalog of recorded data: Sikorsky SC-I095 airfoil ..........

22 Catalog of recorded data: Hughes HH-02 airfoil ............

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Catalog of recorded data:



Vertol VR-7 airfoil .............

NLR-I airfoil ...............

NLR-7301 airfoil ............

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SYMBOLC chord, m

CM moment coefficient

CN normal force coefficientFR flow reversal

HF hot-film

HW hot-wire

k reduced frequency

LS lift stall

M free-stream Mach number

MS moment stall

NFR no flow reversal detected

R tea ttachment

TI transition from turbulent to laminar flow

T2 transition from laminar to turbulent flow

t time, sec

u local velocity, m/sec

x distance along the chord, m

angle of incidence, deg

rotational frequency, rad/sec

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AN EXPERIMENTAL STUDY OF DYNAMIC STALL ON ADVANCED AIRFOIL SECTIONSVOLUME 3. HOT-WIRE AND HOT-FILM MEASUREMENTS

L. W. Carr, W. J. McCroskey, K. W. McAlister, and S. L. Pucci

U.S. Army Aeromechanics Laboratory (AVRADCOM), Ames Research Centerand

O. Lambert

Service Technique des Constructions Aeronautiques, Paris, France

SUMMARY

Detailed unsteady boundary-layer measurements are presented for eight airfoilsoscillated in pitch through the dynamic-stall regime. The present report (the thirdof three volumes) describes the techniques developed for analysis and evaluation ofthe hot-film and hot-wlre signals, offers some interpretation of the results, andtabulates all the cases in which flow reversal has been recorded.

INTRODUCTION

The study of dynamic stall of oscillating airfoils has demonstrated the need forobtaining detailed boundary-layer data during the stall process. Results from thepresent experiment show that boundary-layer characteristics can be signifi=antlyaltered by airfoil shape, and that the boundary-layer behavior is sensitive to manyparameters associated with the airfoil motion. These conclusions are based on analy-sis of signals from hot-wire and hot-film probes mounted near or at the surface ofthe various airfoils. However, evaluation of hot-wire data is very subjective, andpresents a formidable analytical task. The present report describes the techniquesdeveloped for analysis and evaluation of the hot-film and hot-wlre signals, offerssome interpretations of the results, and tabulates all the cases in which flow-reversal data have been recorded. An overview of the experiment has been presentedin reference I; a detailed summary of this test and the experimental conditions thatwere studied is presented in volume 1 of the present report; details of the pressuredistribution results, along with lift and moment data are presented in volume 2.The present report presents the corresponding details of the viscous flow measure-ments that were obtained.

DESCRIPTION OF EXPERIMENTAL PROCEDURES

The experiment was designed to allow accurate testing of various airfoils undervirtually identical operating conditions. Therefore each airfoil profile wasmachined into a shell which could be attached to the metal spar that contained allthe instrumentation. After each airfoil profile was tested, the instrumentation wasremoved from the shell; it then remained with the spar, ready for installation ofthe next shell. In this way, the various profiles could be tested using identical


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instrumentation and oscillation mechanisms; details of this system are presented inreference i; figure I is a diagram of the spar with a shell installed. Instantaneoussingle-surface pressure measurements were obtained for a wide range of test condi-tions. Hot-wire, hot-film measurements, or both, were made near the airfoil surfaceto determine the flow-reversal characteristics for each test condition. Three dif-ferent types of hot-wlre anemometer sensors were used during the oscillating airfoiltest: hot-film surface skin-friction gages, dual hot-wire probes, and trlple-wlreflow-reversal sensors. The most common configurations had either six hot-films alongthe airfoil upper surface, or one hot-film at the leading edge (x/C = 0.025) and fivehot-wires distributed along the upper surface. The data were recorded on 32-channelanalog tape, with a timing code that allowed comparison of hot-wire data and thepressure data, which were recorded separately for each test condition.

DATA ANALYSIS AND INTERPRETATION

Skin-Fric tion Gage

The skin-friction gage that was used during a major portion of the test programconsisted of an alumina-coated platinum surface element epoxied into a metal sleeve(see fig. 2). This sensor, which was very resistant to damage, was used for much ofthe oscillating airfoil test program. However, the characteristics of this probedesign must be taken into account when analyzing the output signals.

The output from the hot-film probe is related to the shear stress; when flowreversal occurs, the instantaneous value of shear stress passes through zero, andthere is a local minimum in the resultant signal. Unfortunately, a significant partof the energy supplied to the probe element is transmitted from the element to thesubstrate of the gage. This heat transfer results in a relatively high dcmoffset inthe output voltage of the probe. In addition, this heat transfer causes the minimumvalue of the hot-film signal to decrease slowly with time, even when the flow isfully separated (with a nominal shear-stress value = 0). These effects can make theinterpretation of the signal somewhat difficult.

Figure 3 presents an example of the output from skin-friction gages mountednear the leading edge of the Ames A-01 airfoil during oscillation. At the marker"TI," the flow has passed through transition from turbulent to laminar flow, with aresultant reduction in shear stress and decrease in fluctuation intensity. The flowremains laminar during the low-angle portion of the cycle; as the angle increases,transition to turbulent flow occurs (at "T2"), and the skln-frlction gage shows acorresponding increase in signal magnitude, as well as an increase in fluctuationamplitude. The next major event, marked by "FR," is the occurrence of flow reversal;this results in a drop in the magnitude of the shear stress. Note that the signaldoes not remain constant, even though the airfoil flow has separated; this continuingdecrease is associated with the heat-transfer effects outlined earlier. Finally,marker "R" indicates the point when flow reattaches to the airfoil (during the down-stroke), beginning the oscillation cycle once more.

Unfortunately, the relatively crisp delineation of flow conditions that appearsin figure 3 is not always present. Figure 4 shows an example of a less clear caseof leading-edge flow: here, the development of flow reversal is relatively slow,and the decreasing of thesignal to its minimum is difficult to separate from thedecreasing of the minimum itself. The estimated flow-reversal points are marked by"FR."


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Hot-Wire ProbeHot-wire anemometermeasurementswere performed using a dual-wire probe (seefig. 5); this dual-wlre approach was chosen to reduce the chance of interruption ofthe test as a result of wire breakage; since both wires were being recorded, the

loss of either wire would not mean the loss of flow-reversal information at thatx-statlon. The output signal from a hot-wlre probe is a nonlinear function of thelocal velocity; therefore, the signals were linearized and scaled such that theresultant signal was approximately proportional to the associated velocity. Figure 6shows a representative example of hot-wlre data for flow near the leading edge of theFX-098 airfoil.

As the angle of attack increases, transition to turbulent flow occurs atx/C = 0.025; this is observed at "T2" in figure 6 for hot-wlre probe HWI. Note thatthere is no dramatic change in the output signal magnitude. Transition on airfoilsoccurs at low angles of attack, for conditions where the boundary layer is thin. Inthese conditions, the hot-wlre probe is often near or at the edge of the boundarylayer. Therefore, the change of the velocity profile during transition has littleor no effect on the value of U; transition will mainly be marked by changes in thefluctuation level. The next major flow phenomenon is marked by "FR"; at this pointthe flow has separated from the airfoil, causing an abrupt decrease in the localvelocity. Note that the hot-wlre signal changes abruptly to zero, and then contin-ues at a well-defined constant value (compare with the hot-film output of fig. 3).Later, reattachment occurs (at "R"); as the minimum angle is approached, the flowbecomes laminar again, and the cycle repeats.

As was noted for the hot-film, the hot-wire results are not always clearlydelineated. Figure 7 shows a hot-wire signal measured near the trailing edge of theVR-7 airfoil which was difficult to evaluate. The turbulence level in this signalis very high, and is masking the development of the periodic component of the signal.Because this turbulent component is superimposed on the periodic part of the signal,the instantaneous value of the signal reaches zero long before and after flowreversal of the ensemble-averaged flow (marked as "FR" in the figure) would haveoccurred. Therefore, the error band for signals measured near the trailing edge issignificantly larger than those associated with leading-edge, or mldchord locations.

Reverse-Flow Sensors

A specially designed hot-wlre probe was developed for evaluation of the flowreversal on the VR-7 airfoil. This airfoil has trailing-edge flow reversal duringalmost all unsteady flow conditions, and a better method was needed for determiningthe reversal point under these conditions. The probe is described in detail in ref-erence 2; operation is based on the use of a highly heated center wire, with twoadditional wires, one upstream and one downstream of this heater, operated at lowoverheat ratio. These additional wires detect the heated wake of the center wire,and a comparison circuit is used to determine the instantaneous flow direction. Thisprobe system can detect both the magnitude and the direction of the local flow, andis especially effective in regions of hlgh-turbulence, low-veloclty flow. Examplesof the output from this probe are presented in figure 8; a diagram of the probe ispresented in figure 9.


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Averaging TechniquesEnsemble-averaging is often used to extract determinate signals from unsteadyturbulent flow data, and this approach was applied to the present hot-wire data.Figure i0 presents the results of an ensemble-average of i00 cycles of the hot-wiresignals on the VR-7 airfoil. It is evident in this figure that cyclic averagingsmears the flow-reversal signal (to the point where no approach to zero voltage is

observable in the averaged signal). In contrast, note the data for the last cycledigitized (shownas dotted in fig. i0). In this case, there are several instancesof zero velocity; there are also indications of vortex motion on the airfoil (in the40, 60, and 80 percent x/C wire outputs), which cannot be observed in the averageddata. There were small but significant variations in the angle at which flowreversal occurred between one cycle and the next; therefore, averages based onmechanical timing marks were not always able to capture the flow phenomena. In fact,this variation was sufficient in the present case to completely obscure the flow-reversal point in the data (in order to properly correlate these data, a true condi-tional ensemble-averaging technique would be needed, possibly triggered by a changein the character of the leadlng-edge pressure). Therefore, although someof the hot-wire and hot-film data were digitized and cyclically averaged, the analysis presentedin this report has been based on visual evaluation of the analog signals for each ofseveral cycles, after which the values of _t associated with flow reversal for agiven sensor were averaged.Exampleof Signal Analysis

Figure ii showsan example of a set of hot-wire and hot-film analog signalsobtained during one period of oscillation. The first three signals are the angle ofattack, the lift coefficient, and the momentcoefficient, showing the llft stall(LS) and the momentstall (MS). The next six signals comefrom anemometersensors:one hot-film near the leading edge (HFI), and five hot-wire probes (HWIto HW6).The markers on these signals refer to the various events that have an effect on thehot-wlre and hot-film readings: FR-- initiation of reversed flow; R -- reattachmentof flow; TI -- transition from turbulent to laminar flow; T2 -- transition from laminarto turbulent flow (as determined from hot-film signals).

RESULTSResults similar to these have been analyzed for all eight airfoils. In particu-lar, the phase angle wt, at which flow reversal first appears at the x/C locationof each hot-wire or hot-film probe, has been documentedfor a range of Machnumbers,frequencies, and stall severity for each airfoil. Thesephase angles, determined bythe techniques outlined earlier, have been recorded in degrees measuredthrough the

oscillation cycle, referenced to the meanangle, for ds/dt > 0. Table i presents asummaryof the analyzed flow-reversal data. TheMachnumber studies were performedfor e = 15 + i0 sin _t, k = 0.i, and cover Mach number conditions that range fromincompressible values (M_ _ 0.035) to ones that include small regions of supersonicflow near the leading edge (M_ = 0.30). The "llght-stall" frequency studies presentdata for a range of frequencies at M = 0.30, where the amplitudeand mean angle havebeen chosen to cause a slight overshoot of the static stall angle associated witheach airfoil during the oscillatory motion. The "deep-stall" study presents data fora range of frequencies at M_ = 0.30, _ = 15 + i0 sin _t (deep stall has beendefined in ref. i as a condition in which a fully developed vortex is formed during

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the oscillation cycle). The experimental data in deep stall were less amenable toanalysis -- the results were more subjective and in somecases inconclusive. There-fore, the results for only three airfoils are reported.

The results of these surveys are presented graphically in figures 12 to 31.Figures 12 to 19 present Mach number effects for deep-stall conditions; figures 20to 27 present frequency effects for llght-stall conditions; and figures 28 to 31present frequency effects for deep-stall conditions. These data are also presentedin tabular form in tables 2 to 9. The error bounds for these surveys are presentedin tables i0 to 16. Finally, a catalog of all the hot-film and hot-wlre data thatwere recorded is presented in tables 17 to 25, tabulated according to the correspond-ing pressure data (stored in digital form, as explained in vols. i and 2).

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REFERENCESlo

,

McCroskey, W. J.; McAlister, K. W.; Carr, L. W.; Pucci, S. L.; Lambert, O.; andIndergand, R. F.: "Dynamic Stall on Advanced Airfoil Sections," J. of theAmerican Helicopter Society, July 1981.

Carr, L. W.; and McCroskey, W. J.: "A Directionally Sensitive Hot-Wire Probefor Detection of Flow Reversal in Highly Unsteady Flows," in InternationalCongress on Instrumentation in Aerospace Facilities 1979 Record, Sept. 1979,pp. 154-162.

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TABLEi.- SUMMARYFANALYZEDLOW-REVERSALATAAirfoilNACA0012,A-01FX-098SC-I095HH-02VR-7NLR-INLR-7301

Mach No. a

Film dFilm dWiregFilm dFilm dComb. eFilm dFilm d

Light stall cFilm dFilm _C omh. eFilm dComb .eComb. e

Deep stall b

Comb .eWireg

Comb .f

aMach number sweep a = 15 + i0 sin _t, k = 0.I.bFrequency sweep, a = 15 a + i0 sin _t, M = 0.295.CFrequency sweep, a = ao + al sin _t, M = 0.29.dHot-film shear-stress gage."Hot film at x/c = 0.025; hot wire at all otherlocations.

fHot wire at 0.025, 0.i0, 0.25; reverse-flow sensorsat x/c - 0.4, 0.6, 0.8

gHot-wire velocity probe.

TABLE 2.- PHASE ANGLE OF FLOW REVERSAL: NACA 0012 AIRFOIL

MachNo.

0.036.076.ii0.145.185.220.250.270.280.290.295

0.025

i0.050.059.567.060.543.521.514.510.58.08.5

I O. i00

x/c0.250 0.400 O.6OO O. 80O

a = 15 + i0 sin _t, k ffi0.I

1.0 3.040.0 35.544.5 40.050.5 50.545.0 41.538.0 36.526.0 29.018.0 21.021.0 21.516.0 20.513.5 16.5

0.046.554.561.553.039.024.516.515.013.010.5

6.023.035.547.036.535.529.528.023.024.022.0

12.515.019.535.030.027.533.528.524.020.520.5

Reduced x/cfreq. 0.025 0.i00 0.250 0.400 0.600 0.800

Ref.frame

80138115232023142310220822042202220021032101

Ref.frame

a - 12 + 5 sin _t, M = 0.295

0.025.050.i00.200

NFRNFRNFR35.5

55.532.534.044.0

48.0 37.0 32.537.0 38.0 33.042.5 45.0 47.554.0 59.0 64.0

26.531.041.071.0

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ORIGINAL PAGE ISOF POOR QUALITY

TABLE 3.- PHASE ANGLE OF FLOW REVERSAL: Ames A-01 AIRFOIL

MachNo. 0.025

x/c0.I00 0.250 0.400 0.600 0.800

Ref.frame

= 15 + i0 sin _t, k = 0.I0.076.ii0.185.220.250.280.295

Reducedfreq.

48.556.556.553.529.518.012.0

48.547.553.046.529.019.516.0

32.535.531.532.526.019.517.5

26.533.534.033.029.523.019.5

25.537.538.039.032,027.023.0

22.543.544.528.533.531.528.5

x/c0.025 0.i00 0.250 0.400 0.600 0.800

= ii + 5 sin _t, M = 0.295

24400243162421924210242022411824108

Ref.frame

0.010.050.010

NFR 63.5 59.5 1 59.5 59.0 I 55.5NFR 96.0 72.0 68.5 65.5 56.5Data too irregular to be analyzed

302022521525217

a = 15 + i0 sin _t, M = 0.2950.010.025.05.i00.150

NFR12.512.014.523.0

12.015.516.017.528.5

6.511.512.017.523.5

5.0ii.014.519.028.0

5.0Ii.018.527.533.5

2.0ii.024.531.038.5

3002131016310183101931020


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TABLE 4.- PHASE ANGLE OF FLOW REVERSAL: Wortmann FX-098 AIRFOIL

Mach x/cNo. 0.025 . 0.i00 0.250 0.400 0.600

= 15 + i0 sin _t, k = 0.i

Refframe0.800

0.036.076ii0185.220.250280.295

Reducedfreq.

2.536.543.037.022.514.59.06.5

-1.234.539.537.024.515.512.012.5

-3.627.032.536.525.018.018.015.5

-2.018524.533.526.518.020016.5

-4.614.516.531.024.017.517.518.5

-8.64.5

10.524.021.521.515.521.0

16022161061611516 2011630116 3092220922202

x/c Ref.frame0.25 0.i00 0.250 0.400 0.600 0.800

= i0 + 5 sin _t, M = 0.295

0.010.025050.i00150.200

NFRNFRNFRNFR68.064.0

NFRNFRNFR72.076.069.5

67.095.069.077.582.079.0

67.093.566.075.576.068.5

66.582.061.570.081.075.0

63.049.057.066.085.0830

212012222322300223012230222303

= 15 + 10 sin _t, M = 0295

0.010 -99.9.025 0.0050 0.5.i00 i0.0

3753.51.5

12.5

4.53.54.5

14.5

2.53.56.5

15.0

2.53.58.0

19.0

a = 15 + I0 sin tot, M = 0185

0.0 211025.5 171189.5 17123

20.5 17201

0. 050.i00.150

14.020.528.0

15.521.530.0

17.525.032.0

16.024.032.0

I0.021.033.5

6.519.026.5

171021710817110


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TABLE5.- PHASEANGLEOF

O_'_,,_n' PAGE ;gOF POOR QUALIT'Y

FLOW REVERSAL: Sikorsky SC-I AIRFOIL

MachNo. 0.025

x/c0.i00 0.250 0.400 0.600 0.800

= 15 + i0 sin wt, k = 0.i

Ref.frame

0.076.ii0.185.220.250.280.295

Reducedfreq.

33.543.542.032.022.015.09.0

30.541.038.028.518.514.512.0

24.528.033.026.522.518.515.0

21.028.035.024.526.020.518.0

15.536.536.528.529.523.522.5

23.542.548.535.534.527.516.5

x/c0.025 0.i00 0.250 0.400 0.600 0.800

a = Ii + 5 sin _t, M = 0.295

33023331073311133206332083321633303

Ref.I frame

0.050 -99.9.i00 66.0

70.0 61.062.5 61.5

52.0 65.0 67.5 3722063.5 65.5 67.0 37222

TABLE 6.- PHASE ANGLE OF FLOW REVERSAL: Hughes HH-02 AIRFOIL

MachNo. O. 030

x/c0.120 0.250 0.380 0.560

= 15 + i0 sin _t, k -- 0.i

Ref.frame0.750

0.076.ii0.185.220.250.280.295

Reducedfreq.

40.048.552.525.015.07.05.0

40.045.042.025.016.09.09.5

32.54O.540.028.017.011.515.1

28.036.538.531.519.513.018.5

17.530.537.036.024.514.513.0

x/c0.025 0.i00 0.250 0.400 0.600

= i0 + 5 sin mr, M = 0.295

11.5 4211213.5 4232232.4 4230315.5 4231018.0 423145.8 42319

13.0 42211

Ref.frame0.800

0.010.025.050.i00.150.200

NFRNFR53.558.556.057.5

72.078.560.067.067.067.0

68.574.564.578.080.079.0

59.060.062.579.083.586.0

47.549.057.084.094.094.0

20.533.036.550.054.058.0

440204402244100441054410744113

i0


25/74

OF FSOR ,_U_'_-7_

TABLE7.- PHASEANGLEOFFLOWREVERSAL:Vertol VR-7 AIRFOILMachNo.

x/c0.025 0.i00 0.250 0.400 0.600 0.800

= 15 + I0 sin _t, k = 0.i

Ref.frame

0.076.ii0.185.220.250.280.295

Reducedfreq.

48.051.554.038.026.024.516.5

0.025

46.049.049.540.526.525.519.0

0.010 Ia = 15

37.0 30.044.0 32.545.5 37.839.5 36.029.0 29.530.0 33.026.5 26.0

xlc0.250 0.400

I0.515.025.025.025.523.519.0

0.600+ 5 sin _t, M = 0.295

-4.0-6.03.54.57.07.02.0

0.800

47200472074721447218473024730645100

Ref.frame

O. i00.025.050.i00.150.200

NFRNFRNFRNFR41.527.5

NFRNFR31.036.044.532.5

-3.015.026.536.049.548.0

-Ii .08.0

23.030.041.544.0

-14.0-Ii.0

2.517.539.530.0

-63.0-39.0-35.0-23.0

2.09.5

452044520645208452104521245214

= 15 + i0 sin wt, M = 0.2950.025.050.i00.150

NFR17.522.026.0

14.5 18.018.5 20.028.0 30.537.0 43.0I I

6.514.027.029.0I

-4.50.08.09.5Z

50021500195001750015

ii


26/74

ORIGINAL PAGE _3OF POOR QUALITY

TABLE 8.- PHASE ANGLE OF FLOW REVERSAL: NLR-I AIRFOIL

MachNo.

x/c0.025 0.i00 0.250 0.400 0.600 0.800

a = 15 + i0 sin mt, k = 0.i

Ref.frame

0.076.ii0.185.200.220.250.280.295

Reducedfreq.

17.029.036.030.520.59.51.50.0

17.526.032.030.517.512.5ii.06.0

18.023.026.027.018.515.514.59.5

21.526.028.533.521.021.018.012.5

25.530.033.041.021.524.021.517.5

32.536.038.041.029.524.527.024.0

x/c0.025 0.i00 0.250 0.400 0.600 0.800

6202162105621136211562209622116221862308

Ref.frame

= i0 + 5 sin _t, M = 0.2950.025I00.200

NFR45.052.0

43.550.055.0

44.047.054.5

42.049.055.0

36.555.061.0

35.559.066.5

631096311363115

TABLE 9.- PHASE ANGLE OF FLOW REVERSAL: NLR-7301 AIRFOIL

MachNo.

xlc0.025 0.i00 0.250 0.400 0.600 0.800

a = 15 + i0 sin wt, k = 0.i

Ref.frame

0.ii0.185.250

Reducedfreq.

84.098.569.5

78.593.558.5

75.0 66.582.5 76.055.0 52.5

x/c

56.050.548.0

24.035.038.5

0.025 0.i00 0.250 0.400 0.600 0.800

621056211362211

Ref.frame

a = 15 + 5 sin _t, M = 0.295

0. 010.025.050i00.150.200

NFRNFRNFRNFRNFRNFR

56.564.068.534.037.535.0

54.557.560.043.046.053.0

51.053.556.544.551.064.5

48.548.043.543.061.044.0

40.516.02.0

Ii.024.023.0

680206810168103681056811068112

12


27/74

TABLE0.- ERROR-BOUNDORFLOW-REVERSALEASUREMENTSdeg):NACA 0012 AIRFOIL

Mach x/c Ref.No. frame0.025 0.i00 0.250 0.400 0.600 0.800

Corresponds to table 2: _ = 15 + i0 sin _t, k = 0.i0.035.073.ii0.145.185.185.220.250.270.280.290.295

Reducedfreq.

4.02.01.55.00.52.53.00.02.02.00.50.5

0.00.00.52.52.03.01.00.02.02.02.51.5

1.51.50.54.01.02.50.51.52.01.01.51.5

1.02.51.03.51.01.52.52.02.52.02.50.0

1.55.03.03.53.54.02.50.51.52.01.00.0

2.03.03.03.52.09.03.01.50.03.01.52.5

x/c0.025 0.i00 0.250 0.400 0.600 0.800

810381152320231482212310220822042202220021032101

Ref.frame

Corresponds to table 2: a = 12 + 5 sin mr, M = 0.2950.025.050.i00.200

NFRNFRNFR5.0

5.00.02.01.0

4.02.02.03.5

2.05.02.55.0

2.02.04.02.0

1.52.04.61.5

7201720472067208

13


28/74

ORIGINAL PP--,GE |2OF POOR QUALITY

TABLE ii.- ERROR-BOUND FOR FLOW-REVERSAL MEASUREMENTS (deg):Ames A-01 AIRFOIL

MachNo.

x/c0.025 0.i00 0.250 0.400 0.600 0.800

Corresponds to table 3: a = 15 + i0 sin _t, k = 0.i

Ref.frame

0.076 1.5.ii0 1.0.185 1.5.220 2.0.250 1.0.280 0.0.295 0.5

Reducedfreq. 0.025

1.50.52.53.01.51.51.5

6.02.05.03.01.01.50.5

3.02.04.03.50.01.51.5

0.52.01.26.54.02.01.5

6.03.03.05.02.04.03.0

x/c0.i00 0.250 0.400 0.600 0.800

24400243162421924210242022411824108

Ref.frame

Corresponds to table 3: _ = Ii + 5 sin _t, M = 0.2950. 010.050i00

NFRNFR

I3.0 4.0 4.0 3.5 I6.5 2.5 2.5 2.0 I

Data too irregular to be analyzed

2.55.5

302022521525217

Corresponds to table 3: a = 15 + I0 sin _t, M = 0.295O. 010.025050i00.150

NFR2.01.01.31.5

3.02.51.01.03.0

2.03.00.51.02.5

3.01.00.01.51.0

1.01.02.54.01.5

1.51.03.52.00.5

3002131016310183101931020

14


29/74

OF POOR QU&L]3"_'

TABLE I 2.- ERROR-BOUND FOR FLOW-REVERSAL MEASUREMENTS (deg):Wortmann FX-098 AIRFOIl,

MachNo.

x/c0.025 0.I00 0.250 0.400 0.600 0.800

Corresponds to table 4: cx = ]5 + i0 sin ,_t, k = 0.I0.036.076.110.185220.250

Reducedfreq.

0.52.01.01.01.01.5

].53.02.01.01.01.0

0.0 l .51.5 ] .03.0 ] .01.0 3.0] .5 2.0] .0 0.5

x/c

1.0l. 0l. 03.02.01.5

1.02.01.02.03.02.0

0.025 0.i00 0.250 0.400 0.600 0.800Corresponds to table 4: a = i0 + 5 sin wt, M = 0.295

160221610616115162011630116309

Ref.frame

0.025.050.i00.150.200

NFRNFRNFR2.53.0

NFRNFR2.00.51.5

3.02.03.01.00.0

3.52.01.01.50.0

7.02.01.01.01.0

2.52.01.01.03.5

2222322300223012230222303

Corresponds to table 4: a = 15 + i0 sin wt, M = 0.2950.010 NFR.025 0.0.050 1.0.i00 1.0

2.00.01.52.0

1.00.01.00.5

2.00.00.52.0

2.00.01.52.0

2.50.00.55.0

22102171181712317201

Corresponds to table 4: a = 15 + i0 sin _t, M = 0.2950.050.I00150

14.020.528.0

15.521.530.0

17.525.032.0

16.024.032.0

i0.021.033.5

6.519.026.5

171021710817110

15


30/74

ORIGINAL PAGE I_OF POOR QUALITY

TABLE 13.- ERROR-BOUND FOR FLOW-REVERSAL MEASUREMENTS (deg):Hughes HH-02 AIRFOIL

MachNo.

x/c ! Ref.I l i i.030 0.120 0.250 0.380 0.560 0.750 frameI

Corresponds to table 6: a = 15 + iO sin cat, k = 0.10.076.Ii0.185220.250.280.295

Reduced

1.01.53.01.01.00.01.0

1.02.02.01.01.53.01.0

3.03.03.01.02.02.07.0

x/c

1.57.02.01.01.52.01.0

3.08.03.01.51.03.01.0

4.0 421222.0 423223.0 423034.0 423104.0 423141.0 42319i .0 42211

Ref.

freq. 0.050 0.i00 0.250 0.400 0.600 ] 0.800 frameCorresponds to table 6: _ = i0 + 5 sin _t M = 0.295

0.010.025050i00.150200

NFRNFR1.02.01.01.0

3.56.51.50.53.01.0

5.06.51.52.53.00.0

4.53.51.52.03.01.0

2.53.02.02.06.52.0

2.03.02.02.00.05.5

44020440224410044].054410744113

i

16


31/74


32/74


TABLE 15.- ERROR-BOUND FOR FLOW-REVERSAL MEASUREMENTS (deg):NLR-I AIRFOIL

MaehNo.

x/e0.025 0.i00 0.250 0.400 0.600 0.800

Corresponds to table 8: a = 15 + i0 sin u_t, k = 0.i

Ref.frame

0,076.ii0.185200.220250.280.295

Reducedfreq.

0.50.51.01.01.00.51.00.0

2.04.03/01.00.01.02.01.0

1.02.03.02.00.51.51.02.0

2.02.51.02.01.01.00.01.0

2.54.03.02.03.01.50.53.0

5.01.02.02.01.01.01.01.5

xlc0.025 0.i00 0.250 0.400 0.600 0.800

Corresponds to table 8: _ = 10 + 5 sin ut, M = 0.295

6202162105621136211562209622116221862308

Ref.frame

0.025 NFR.i00 0.0.200 2.0

3.50.50.5

3.05.05.5

3.52.02.0

0.5 O.52.5 2.00,0 2.5

631096311363115

TABLE 16.- ERROR-BOUND FOR FLOW-REVERSAL MEASUREMENTS (deg):NLR-7301 AIRFOIL

MachNo.

x/c0.025 0.i00 0.250 0.400 0.600 0.800

Corresponds to table 9: _ = 15 + I0 sin wt, k = 0.i

Ref.frame

0.ii0.185.250

Reducedfreq.

4.05.02.5

4.06.02.5

i0.0 13.07.0 7.01.0 2.0

x/c

ii.04.05.0

0.025 0.i00 0.250 0.400 0.600

Corresponds to table 9: a = 15 + 5 sin mr, M = 0.295

6.0 671211.5 67221I.i 67306

Ref.frame0.800

0.010 NFR.025 NFR.050 NFR.i00 NFR.150 NFR.200 NFR

1.02,03.51.01.50.5

,.J

1.53.03.51.01.04.0

0.52.05.52.04.54.0

1.5 2.0 680201.5 4.0 68101O. 5 2,5 681030.5 5.0 681052.5 5.5 68110

Ii,0 9.0 68112

PRECEDING PAGE BLANK NOT FILMED8


33/74

r',_" POO.q Qo_.I,'TY

TABLE 17.- NOTES PERTAINING TO TABLES 18 TO 25DATA LISTED IN ORDER A FRAMES STORED ON DIGITAL TAP[B FRAMES ARE ON ANALOG TAPE ONLY

A FRAME - CATALOG ENTRY FOR PRESSURE DATATRIP - TRIP %S PRESENT - (YIES. OR (RIOTYPE - TEST CONDITIONS (STIEADY. OR IUNISTEADYAO - MEAN ANGLE OF OSCILLATION. DEGREESA1 - AMPLITUDE OR OSCILLATION, DEGREESQ - FREE STREAM DYNAMIC PRESSURE. PSIM - FREE STREAM MACN NUMBERRE - FREE STREAM REYNOLDS NUMBER

FRE@ - DIMENSIONAL FRE@UENCY. HERTZB FRAME - CATALOG ENTRY FOR HOT-FILM AND HOT-WIRE DATA

19


34/74

ORIG!N;,L I:_.C_ _3OF POOR C,_' "_ "_"

,--I0

I--I

C-,l,-.-i0o

Z

0

[.=.w0o

,.Zua 30,,.iZ,


63/74

OF ?OOR _v ......

7O

6O

40..IOOZuJ 30.=IZ.ljzl.u,-IzI,u_czo.

70

60

5O

4O

3O

20 .....

I0

0

-10 -- 0

NLR-70

RED FREQ[] = 0.0100 '= 0.025A = 0.050+ = 0.100X = 0.1500 = 0.200

I ! t I.2 .4 .6 .8 1.0

x/c

Figure 27.- Phase angle, _t, of flow reversal on NLR-7 airfoil vs chord locationfor a range of frequencies at M_ = 0.295, e = 15 + 5 sin _t -- light-stallconditions.

55


70/74

ORIGINAL PAG_ _OF POOR QUALITY

5O

4O

_30-I>.j,zm 20.J_3Zu.I

z 10D.

-10

IAMES-01 | RED FREQmI [] = o.oloI o = 0.025I _ = 0.05o.... I + = o.'mo

.jsJ x = 0.150

+

o " .;, " ._ " ._, .e 1.ox/c

Figure 28.- Phase angle, _t, of flow reversal on Ames A-OI airfoil vs chord for arange of frequencies at M_ = 0.295, _ = 15 + 10 sin _t -- deep-stall conditions.

56


71/74

5O

40

WORTMANN FX-098RED FREQO " 0.0100 = 0.025A = 0.050+ = 0.100

+

.2 .4 .6 .8 1.0x/c

Figure 29.- Phase angle, _t, of flow reversal on Wortmann W-98 airfoil vs chord for arange of frequencies at M_ = 0.295, _ = 15 + i0 sin _t -- deep-stall conditions.

57


72/74

ORIGINAL P._G_ [


73/74

OHIL_,,AL PAGT- ,:_OF POOR QUALITY

50

40

BOEING VERTOL VR-7

+

RED FREQ[7 = 0.0250 = 0.050

= 0.100+ = 0.150

._ 3O--I).Jzw 20oz

mccroskey 3

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