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^j ^UNIVERSITY OF WICHITA NEW RESULTS IN INFLUENCING LIFT OF WINGS

by Albert 3etz as translated by Friedrich Wagner

I

Engineering Study No. 083

for the Office of Naval Eeeearch Contract Nonr-201( 01)

September 1952 University of Wichita School of Engineering

Wichita, Kansas

i-.-EW RESULTS IN I i :FLUEi 'C I ::C LIFT OF WINGS

DY ALBERT BETZ AS TRANSLATED BY FRIEDRICH WAGNER

ENGINEERING IJTUDY No. 0&3

FOR THE OFFICE or N;AVAL RESEARCH

CONTRACT ;,ONR-2Q I (0 I )

SEPTEMBER, I952

UNIVERSITY OF WICHITA SCHOOL OF ENGINEERING

WICHITA,.. .1A NS AS

KWVJLUUXXA. W \

\ ' \

\ FROM LOW CONTRAST COPY. \

V )

EW RESULTS !•- tr.'FLUPr'C R:G LIFT uF WI h'GS

A FEW YEARS A 1,0 !•• R . E-UME ADVISED US TO TRY TO REPLACE

THE USUAL MOVABLE RUDDER WITH SOME OTHER DEVICE, WHICH DID

NOT CONTAIN SO MANY SENSITIVE "ARTS. ! iiAVE TOLL OWED THIS

SUGGESTION. RESEARCH ON THE SUBJECT HAS UD TO VERY SATIS-

FACTORY SUCCESS. THERE WAS ANOTHER VERY SIGNIFICANT RESULT,

SINT DURING THE EXPERIMENTS THE LIFT COEFFICIENTS OF THE

WINGS EXCEEDED THE USUALLY OBTAINED RESULTS. I WANT TO REPORT

BRIEFLY ABOUT IT.

AT FIRST I PROPOSED A DEVICE, WHICH AFTER SOME PRELIMINARY

TESTS WAS SHAPED ACCORDING TO FIGURE I.

FIGURE I.- WING WITH ROUNDED TRAILING EDGE AND BLOWING SLOTS.

THEREBY THE TRAILING EDGE IS NOT SHARP, AS USUAL, BUT BLUNTLY

ROUNDED. FOR THE NORMAL PROFILE THE LIFT OF THE WING IS DETER-

MINED AT A GIVEN ANGLE OF ATTACK BY THE SMOOTH CONFLUENCE AT

THE TRAILING EDGE* THE POSITION OF THIS STAGNATION POINT AT

THE TRAILING EDGE IS DETERMINED BY THE SHIFTING OF BOUNDARY

LAYERS ON THE SUCTION AND PRESSURE SIDES. !T MUST BE POSSIBLE

TO CHANGE THE POSITION OF THIS STAGNATION POINT AND TO CHANGE

WITH IT THE LLI'"T OF THE WINGS BY INFLUENCING THE BOUNDARY LAYER

FOR THIS REASON THERE ARE TWO SLOTS NEAR THE TRAILING EDGE,

THROUGH WHICH THE AIR IS DISCHARGED THROUGH THE SLOT ON THE

SUCTION SIDE. THE FRICTION LAYER ON THIS SIDE PCCOMFS RICHER

+ CADO Mo. Zvm/]JAL/l047-42/S-21 R 2784 F 1027

IN ENERGY CAUSING LESS DIVERSION THAW o is i ri E. PRESSURE S I 0 E

SO THE POINT OF SEPARATION MOVES TOWARD THE PRESSURE SIDE.

THAT MEANS AN INCREASE IN THE LIFT, EXACTLY LIKE A FLAP AT

THE TRAILING EDGE IF THIS FLAP WAS DEFLECTED DOWNWARD. INVERSELY,

THE DISCHARGE ON THE PRESSURE SIDE CAUSES A DECREASE IN I ITT,

THE EXPERIMENTS DONE BY ONE OF MY ASSISTANTS, MR. CCHWIER,

SUBSTANTIATED THIS CONSIDERATION. WITH PROPORTIONALLY SMALL

DISCHARGE QUANTITIES, THE CHANGE IN THE LIFT COEFFICIENT CA

CAN EASILY REACH 0-5 WHTCH IS COMPARABLE TO THE EFFECT OF A

DTFLECTED AILERON. THE QUANTITY COEFFICIENT IS ABOUT .'JI2,

THAT MEANS, THE DISCHARGED QUANTITY EQUALS IN UNDISTURBED AIR

FLOW A THICKNESS OF .012 OR I .2'J OF THE MEAN CHORD.

INDEPENDENT FROM THIS DISCHARGE METHOD, MY ASSISTANT

,-;R . RCEGENSCHEIT DEVELOPED A SUCTION METHOD. THIS METHOD IS

SHOWN IN FIGURE 2. THERE IS A SUCTION SLOT AT THE TRAILING

EDGE CF THE WING WHICH IS SO SITUATED THAT THE END OF THE FRES~

SURE SIDE IS A LITTLE BIT LONGER THAN THE END OF THE SUCTION

SIDE. IF THE AIR IS SUCKED THROUGH THE SLOT, A CONSIDERABLE

LIFT INCREASE IS MEASURED: WITH THE OPPOSITE DEVICE OF THE

END OF SUCTION SIDE LONGER THAN THE END 0." THE PRESSURE SIDE

A DECREASE OF LIFT IS MEASURED.

THE EFFECT CAN BE EXPLAINED IN THIS WAY. THE STREAMLINE

WHICH SEPARATES THE SUCKED AIR QUANTITY FROM THAT WHICH IS NOT

SUCKED (IN FIGURE 2 THE HEAVIER LINE) CREATES A NEW CONTOUR

OF THE PROFILE, WHICH IS STRONGLY ROUNDED AT THE TRAILING EDGE.

3

FIGURE 2. - STREAMLINES FR C X SUCTION ON THE WING TRAILING EDGE.

BECAUSE THERE > S N 6 SURFAC'E FRICTION, AND THAT MEANS NO BOUNDARY

LAYER ON THE IMAGINED PROFILE LIMIT, THERE IS NO FLOW DIVERSION.

THE FLOW FOLLOWS THE VERY MUCH CURVED TRAILING EDGE AND THE

POSTERIOR STAGNATION POINT MOVES TO THE PRESSURE SIDE. WLTH

THIS DEVICE ALSO VERY GOOD EFFECTS CAN BC OBTAINED. THE SUCTION

QUANTITY, WHICH IS NECESSARY TO INCREASE THE LIFT COEFFICIENT

C A FOR C.5, IS GIVEN 3Y THE QUANTITY COEFFICIENT Cg = O.OO7.

IT IS ABOUT 40£J SMALLER T H A N FOR DISCHARGE.

rnor O — ^-' T o r » u A 0 f\ 1 1 %• 1 f \ uunc /) » J i KLnn .-. T* \s ^ it u

A WING WiTH TRA IL I NG-EDGE S U C T ION.

• IGUSL _) 3NCW3 A FLCw I i< A rilUKUUlNAMiC I A ri t\ . W t LAN UbitKVL

FROM THE STRONG DEVIATION OF THE STREAMLINES, THE LARGE LIFT.

AND BESIDES, THIS 'LIFT IS OBTAINED WITHOUT A LARGE ANGLE OF

ATTACK.

HIGHER LIFT COEFFICIENTS W E R E REACHED, W I ~. z N DURING D ISCHASGL

INSTEAD OF A SIMPLE ROUNDING OF THE TRAILING EDGE A V A K I A aL E

FLAP WAS USED AND DURING SUCTION A 5PLIT FLAP WAS USED,

FIGURE 4.- STREAM AROUND A WING WiTH A SPL i 7 FLAP

AND TRAIL IMG-EDGE SUCTION

A "I H IbM L iFT .

FlGUKE 4 SHOWS THE MENTIONED ARRANGEMENT AND THE CORRESPONDING

fLOW. WE SEE (HAT THE FLOW IS COMPLETELY SEPARATED AT THE

LEADING EDGE, DU1 IS ATTACHED AGAIN AT THE TRAILING EDGE. IF

WITH THIS DEVICE WITH ALMOST CONSTANT SUCTION THE VELOCITY OF

THE WIND T'iNNEL IS DECREASED THE LIFT IS NOT DECREASED PRO-

PORTIONALLY, BUT LIFT COEFFICIENTS WERE ODTA'^'ED WHICH WERE

COMPLETELY UNKNOWN FOR WINGS. WlTH BOTH THr SDCT IOIJ AND THE DIS-

CHARGE METHOD VALUES WERE OBTAINED. T0 GIVE AN IDEA OF THE

MEANING OF I H £ 5 E VALUES, I UKLY WANT TO MENTION THAT THE MAXI-

MUM LIFT COEFFICIENTS OF THF USUAL WING ARF AUOUT 1.5* WlTH

LANDING FLAPS' AND SIMILAR DEVICES LIFT COEFFICIENTS OF 2 ..• p CAN

3 E REACHED. WlTH THE PRESENT S30UNDARY-LAYER SUCTION IN CONNEC-

TION WITH FL.APS WE CAN OBTAIN LIFT COEFFICIENTS AROUND k a ONLY

l HE ROTARY CYLINDER GIVES A SIMILAR L ifT COEFFICIENT..

THE HIGH COEFFICIENTS OF THE WING ARE VFRY SURPRISING,

5 i NC E THE THEORETICAL MAXIMUM VALUE FOR A FLAT PL A T £, WHICH IS

OBTAINED WHEN THE FRONT AND THE REAR STAGNATION POINTS CONVERGE

ON THC PRESSURE SIDE, IS 2\7 OR AUOUT 6, SO NAT J RALLY WE MUST

ASK HOW SUCH A HIGH LIFT COEFFICIENT IS POSSIBLE.

in I n t v. « o t. w r\ w nioruAOfr ! C M ! C y. LIFT p A p *r j A i i_ v r A M or

EXPLAINED THAT THE REACTION OF THE BOTTOM DEFLECTED DISCHARGE

JET GIVES A PART OF THE LIFT; BUT IT DOES .MOT SEEM TO BE THE

MAIN PART. I N THE CASE OF THE SUCTION SUCH AN EXPLANATION IS

IMPOSSIBLE. THERE ARE IDEA* FOR A THEORETICAL EXPLANATION,

BUT I HESITATE TO DISCUSS IT BECAUSE TOO LITTLE IS KNOWN. I

WANT TO MENTION ONLY ONE THING: APPARENTLY THE HIGH LL»'L C 0 F F "

FLCIENTS APPEAR FOR SUCTION ONLY IF AT ALMOST CONSTANT SUCTION

WE DECREASE THE VELOCITY. WHILE STARTING AT HIGHER VELOCITIES

THE VALUES ARE NOT SO HIGH.

THE SUCTION AND DISCHARGE QUANTITIES AT WHICH THE UNUSUALLY

HIGH LIFT COEFFICIENTS OF CA = 10 WFRE MEASURED ARE VERY LARGE,

SO- THERE IS NO PRACTICAL USE AT THIS TIME FOR THE UNUSUAL VALUES,

I N ORDER TO OBTAIN LIFT COERICIENTS CA = 10 A REQUIRL'D DIS-

CHARGE QUANTITY COEFFICIENT OF CQ = -07^, BUT WITH SUCTION CQ-.23-

AT MEDIUM LIFT COEFFICIENTS (CA ~ 3 TO 6) THE CONSUMPTION IN

SUCTION IS STILL LARGE BUT TOLERABLE. LIUT AS THESE HIGH LIFT

COEFFICIENTS ARE USUALLY NEEDED ONLY FOR A VERY SHORT TIME AS

FOR I A M D I N G OR IN AIR COMBAT, WE CAN IMAGINE THAT THE SUCTION

OR DISCHARGE OUTPUTS COULD BE CREATED BY ROCKETS WITH SIM'LAR

RESULTS. REGARDLESS OF THESE PRACTICAL POSSIBILITIES, THE DIS-

COVERY THAT IT IS POSSIBLE TO REALIZE FLOWS WITH SUCH UNUSUAL

LIFT COEFFICIENTS SEEMED CF ENOUGH IMPORTANCE TO ME TO REPORT

ABOUT ii HERE.

*

The second configuration of the swept-wing, blowing-

duct raockup was fabricated and tested, The results were

very favorable. As a comparison with the first configuration;

1st Configuration

Q, = 9.85 ft3/sec

V = 338 ft/sec a^exit

P Duct iosses= 122.5 lb/ft

= 4.875 q

Avail.Energy = 178.0 lb/ft2

= 7.1 q

v avg.

2nd Configuration

Q, = 10.0 ft3/sec

= 409,5 ft/sec 3exit

Duct losses = 80.4 lb/ft2

= 3.2 q

Avail.Energy = 189.2 lb/ft

= 7.55 q

In these relations the tunnel dynamic pressure, q, was assumed

to be 6 inches of alcohol or 25.3 pounds per square foot,.

The velocity distribution improved considerably along

the entire span. From the root (Sta. 42.75) to approximately

Sta. 65.00, the velocity increased slightly and was generally

more stable. F^om Sta. 6b.00 to ST.H. 75.00 (Sta. 72.35 the tip),

"Caere was 25 percent less decrease in velocity for the second

configuration than for the first.

The above results required a design change in the

s^Bui wing 3Ir-C model v OiTR—KTI—5 ;. The uluwiu^,—davit iftwuiiup 1^

now being changed to a suction-duct mockup.

Jet mimo.- The steam Jet pump experimental oroerara

was temporarily discontinued until a steam superheater is re-

outlined the experimental results obtained from the present pump

'

firmed Services Technica eriC) Because o* ",jr limited supply,, you are requested to return tnis copy WHEN IT HAS SERVED YOUR PURPOSE so that it may be made available to other requesters. Your cooperation will be appreciated. •4

NOTICE: WHEN GOVERNMENT OR OTHER DRAWINGS, SPECIFICATIONS OR OTHER DATA ARE USED FOR ANY PURPOSE OTHER THAN IN CONNECTION WITH A DEFINITELY RELATED GOVERNMENT PROCUREMENT OPERATION, THE U. S. GOVERNMENT THEREBY INCURS NO RESPONSIBILITY. NOR ANY OBLIGATION WHATSOEVER: AND THE FACT THAT THE GOVERNMENT MAY HAVE FORMULATED, FURNISHED, OR IN ANY WAY SUPPLIED THE SAID DRAWINGS, SPECIFICATIONS, OR OTHER DATA IS NOT TO BE REGARDED BY IMPLICATION OR OTHERWISE AS IN ANY MANNER LICENSING THE HOLDER OR ANY OTHER PERSON OR CORPORATION, OR CONVEYING ANY RIGHTS OR PERMISSION TO MANUFACTURE, USE OR SELL ANY PATENTED INVENTION THATTKAY IN ANY WAY BE RELATED THERETO.

!f a ft T ? B !! ! ! ft ! K ff !^£VY**&i 1 AUIA ft PUS 5 i mm uiftb UAI i jjg. j. iinm

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