T4

TH. UNIVERSITY OF TEXASAT AUSTIN

ARL-TR-70-44 CoFy No. ,,6

December ')70TESTS OF VORTEX GENERATORS TO PREVENT

SEPARATION OF SUPERSONIC FLOW IN ACOMPRESSION CORNER

NAVAL AIR SYSTEMS 'OMMANDDavid K. 'Garting APL'JHU Subconract 2, 1734, Tcsk B

p.RCHL-J .. . ., . .

. I i-I , .. ,

NATIONAL TECHNICALINFORMATION SERVICE

.prngfo d, a/. 22111

Approved for publ,C r#eIeaOe

distriuvton j,,mi; ed

BestAvailIable

COPY

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Appled Research Laboratovies !CLASU~IEDThe University of Texas at Au~tiII KUA~ustin, Texas 78712 _ _____

TESTS OF VO7.EK GEliERAOpS To) P jM SEPARAjTIChl OF SUPMRCH~IC FLOW TN~ ACCRFSION CORNER

- - 4 btCtCftIPTIV9E NO1S(7I'p#olt4vtifand C*iVive42)

tedbuical report_47' ?#41tst fltpt r,00. alih, iI wal. tt name)

David K. Garting

6- "CWQRY CATC 70. TO&% MO. OF VA4Z bS, PN. or "itWs

-Decemnber 1-970 83 -C, ONY'IACT ON GRANdT NO . OetATOWO WSOO 4UuU~mIftl

APL/JJH subcontract LqT34,h. PhOJgEC T.

Task B ARIL-TR-7O-4C.' OFNSR PtOR OIS: (A'r *O n,4... that mi., boe S5I.d

Approved for Public release; distribution unlimited.

11 SOPLECTuAIV4Y NOTES 13. IS'ONSBMLtTLRf ACTIVITY

-aal Air Systems Commma: partment of the NavyWashington, D. C. 2036

iTests were ma.de on four vrortex generaLtors to determine their ability t--3 prevtuent.flow separation. The geiherators- were of rectangular planform vitha chor~d lengthsof 0.;5 and 1. 0 in:. and spans of 0.25 and 0.50 in. Generator section shape was as ynnetric double wedge. The generators were individually mounted at a 15 de~anele of attack on a-f-iat plate upstream of a 35 deg compresaion corner. Theteuts were nade in a wind tunnel at an avi'raire Mach Nuimber ofP 4+.67. Trhe bolundarylayer was turbu'Lent and approximately 1/4 in. thick at the te.st station. StaticPressure measurements- were taken along the. centerline of the plate and on therap fao Oi I and dye flows and schlierenphotographs were used to aid indeterin I1ng- the extent of separation.- Th.- vortex generators ve-e fnmd to preventseparation if placed suff'iciently close to the compression corner. The unseparatedcregion in each case was very narrov in spanvise extent. Separtiin was prevented16y increasIng the mom~enti of the boundtry layer through the action of the tip-vortex and- a secondary vortex. (U)

0I DO "'0?.1473 UNCLASSIFIEDS/_N14S74o ~c~t ~umf'to

f I IetR I t VILV aTurbule-nt FlInw IVc~rtex GeneratorsCompressible Flow

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DeeFbt17

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APPROVED FOR PLJRUC fi~ 4RELEASE; M!STRIUIIONUNLiMITED-

v ~APPLIED RESEARCH LABORATORIESS THE UNIV-ERSITY OF TEXAS AT AUSTIN

A&VJSTR, TEXAS -7 S-12

ABSTRACT

Tests were made on four voitex generators to determine their

ability to prevent flow separation. The generators were of rectangular

planform with chord lengths of 0.5 and 1.0 in. and spans of 0.25 and

0.50 in. Generator section shape was a symmetric duuble wedge. The

generators were individual-ly mounted t a 15 deg angle of attack on a

flat plate upstream of a 35 deg o!resaion c6rner. The tests were

made in a wind tunnel at an average Mach TH=ber of 4.67. The bloundary

layer was turbulent-and approximately 1/4 in. thick at the test *tation.

Static pressure zeasurements were taken along the centerline of the

plate 9nd on the ratp face. Oil and dye flows and siblieren photographs

were used to aid--in determning the extent of separation. Yhe vortex

generators vere found to prevent separation if placed sufficiently close

to the compression corner. The unseparated regio7. in eacb c&se was very

narrow ir spanwise extent. Separation was prevented by increasing the

momentum of the bo-undary layer through the action of the tip vortex and

a secondary vortex.

N-iii

PREAC E

The semaration, of a sup -rSonicg fl-re;. in co~sxresston0- cornmers is

a iffiul deig prodblem of imoderni flightr vehicles. The l i'o

prevent senaraetionk would be an, obvious aid in the .. Sc"lono nressure

distributions and hea*t t;raxisier.- rates for fligt syst-ez ." Vo rte x

generastors have proved useful in ontroflng separatio-n in msub so;.0 and

transonic flows. -This renor preSets tE eltsotssofvt

-generators "to prevent separationr:. a supersonic flow4 in a-comressionm

corner.

The current study is one of a series, devoted to high seed flc

-searation end its prevenqtion, conducted at Applied Besearc~h laboratories

-of The University of Tenas a~t Austin. This work has been sponredb

the N'atal Air Systems Couand under Ant/Jt! Subcontract 271173141 Task B

with th Applied Phyzsics Laboratory, The Joh. s Hon-kins U.niversity.

The author would -lke to express his anpreciation t

-Dr. John C. Westkaemaper, Research Engi-neer, Apn-lied Researchs Laborwtories,

for his continued guidance and az;sistance. Special appreciation is also

due Mr. W1liam Creamer and r.j. Gary Perser for their assi stance in

the eP=-erim-mentaI wor.

F::

Ti-tO COE

ABSTIRAC Tii

tIM OF no-UGU i

M N -- CLA I M-xii

n-. :-?.Af4EFTA IP'E~S AND PRO-CEDURE 5A. Wina unneL

B. Flt Pl-ate amd Rfaup5

C Vortex Generators7

D. Flow Visudalizatlion Teebrdc-ue BL. instrumentat ion" and Proce dure

i.- AA E 'CTVX4 AND ACC-UACYA~Data Rz2ecton I

3. Accurpayr 12

A Sepaaion Region 'ethu Gxenerators

~) Seraration Pae ters 1

~,Thrz-ee-inerasion-al1 Fects

_j7 3ej:nratod 1oato

T. S I4ARY ND COMWUJ TW 2

-vs 29SERiE

LIST OF fCU2

A#pitia Pagc

Flat Plate and iRa= w. 7.M444!1. --Generatohr

Vortex fl-Enrarors

Corner

Snawise r-ress- nCeffiintsz for Ccnresan '

Corne

Sen eren Puo a! ca 4nrr-n P'ornieiSktho Typical--~. Oi Fl- for.z; %-emu-e F

t~~a %Centsr'-ire F-assuwe teffic ents for-40

Generator '1o. 1I i ForwardPtsio

Soritw 4 1e Prssr 'oiiintz for -

Gentrator n. a o~r ozif

Geea o:.CJI ForwardAo:

CGenerator fl.2 in. _orved Psto

Ceniterline Pressure Cof~i sforGenerator No n Forwar-d Posit.ion

Generator No3i heti oiion

1±5 -nerline parure rt forGe~praorIN.. It rard ro-sitlo

i~~b Soanwise Pesr ofiin- o-Gweerator No. inFrard Psto

--kp r1, of Oil Flow for- Genieratocris in1 ForardPON t-rA.

ix

-UISrFnmum-(Cont'i

13a ;eter4-e Pressurxe C-efflcients for V

-lenerao i'o. in Aft Plht Position

=~~~~-r I h- fC 'u lef* 2 _-eats for 5

Germe3 aItor TAO. I in Aft Bih Pstio

V~a Ceterlire Pres-sure Coefficients for51GeeatrNO. -2 in Aft RMgt Posi-tion

Soanwise PreA aire Coeificlents focr >Generator NoM. 2 i.ns~ Pitlit Position

i~a Centerline Pressure -Coeffictenlts for 5Generator No. ]3 -in Aft -Right P7iii

15b SonvisePro sr're o'~iensforGenerator No14. 3' in- Aft Eight Position--

1-6a sCenterlin-e Pro vssuxra Coefficients for 5Generator no. 4~ inj Aft Bi4ght Pstu

lab Snanvwise -Pro ware Coefficienlts forGenerator Nlo. 4t in Aft REit Position

11aCenter1i- Prssr Coetfi ~as for 5Generator N~o. I in -Aft Lerft Position-5

I.b bnifl-1se Pressure ..oernfcients -forGienerator No. I in AfM Left Position

l~da Ceterline -Pressurale Cweffliers for 5Generator NO. 2 -:A Aft LeftPsio

Snpanwie IPressutre COef ficl its for 46Generator No. 2 iii Aft Left Position

netxi- Pressu~1re ;!1'aticits=w for

NO. 3 in-No. Aft left Position

h91 ISn~ese Pressur-e CofiinsforGenerati-m N 3 AinM Left PAt-Z-

L0 Centerlin me T Ctaa.'....nvs forDGenertor -Ho *

4 4 inrI AmE-m 'oiia

~.eentr R. Iin Aft Left positio

F' -EL-cP-

FNOMI CLArIRE

a =free interaction angle (see Fig. )

A= aspect ratio

b = vortex generator span

c = vortex generator chord

C = coefficient of pressure

= ratio of specific heats =1,40

I = length

NI Mach Number

P pressure

' = dynamic pressure

i SUBSCRIPTS

= free stream static

o stagnation or total

s = separation

XEL

I. INiTRODUCTION

The separationi of a viscous fluid 2"low due to an adverse pressure

gradient, can present a major problem to the designer of a modern flight

vehicle-. In the siibsoii flight regimep flow separation may cause large

R modifications in pressure distribution and aerodynemic loading. The

supersoni? regime adds the prolem of high local heaing rattes to the

problem of modified loading. In 'both cases the performaric of an entire

flight Yehicle system may become dependent on local flow, condit-ions iff

separation occuirs. Since separation causes a vrariety of design problems,

it is useful to investigate the po tsibilities of preventing zeparation.

The Aeromechanics D~ivision of Applied Eesearc tabaoiso h

Utiversity of Texas at Austin is coducting an extended investigcotion

-of flow separation nnd its prevention. It is the ob~ective ofl this

report to present the results of experimentz using vortex generators

to prevent sepiration of a sup0ersonic turbulent bo'.mdary layer in a

Compreasion corner.

The separation of a fluid flow in a compression corner is

caused by the continued depletion of the 1inetdc energy of the flid

ztream catesed by an adverse pressure gradient, ConsiLdering the imper-

sonic flow of an inviscid fluid in a comression corner, a s i~le

oblique shoek wave originating at the corner turns the flow parallel to

V ~ the downstream wall. Wrhen viscosity is included, the inviscid free

streami becomes coupled to the viscous boundary layer throu_h a pressure

interaction.

Due to viscosity the velocity and kinetiz energy of a flnid vE y

17from zero at a solici boundary to the inviscid free stream value at thE

edge of the boundary layer. At a compression corner the high pressure

resulting frm the turning of the flow diffuses upstream through the

subsonic portion of the boundary layer. The already low energy fluid

near thev wall is thus forced to exoend more energy to overcome the

additional pressure force. if the pressure gradient is sufficiently

large, the boundary layer will reach a point uhere St can no longer

overcome the pressure force and will separate from the vall.

As shown in Fig. I the separation of the flow upstream of a

compression corner establishes a new effective geometry for the

- oncoming -flow, At the separation point the fAlow is deflected through

an angle smaller than the original turning angle. This results in a

weak oblique shock wave emanating from the separation point. The

separated flow reattaches on the downstream wall, where it is turned

parallel to the wall through a second oblique shock vave. Between

the separated fluid and the compression corner a low speed vortical

flow is established by the free shear action of the boundary layer and

the upstream directed presswre gradieut.

The fundamental aspects of flow separation have been invest-igated

by numerous workers with a view toward correlating separation parameters

with local flow conditions (Ref. 1,2,3). Li the area of preventing

separation the majority of the work has been in the subsonic and tren-

sonic speed regimes. D-iing the late 1940's and early 1950's workers

2

i=at United Arcraft Compnany demontrated the use of vortex generators

to prevent separation. primarily in subsonic flows. British inves-

tigators during the ite ! 9 50's extended the use of vortex generators

to the transonic flight regime (Tef. 4,15).

Tbe mechanism by which separation was prevented in these cases

consisted of re-energizing the low momentum bun-dary layer. By placing

s nmiber of smeli, wing-shaped- anes or generators normal to the srrface,

a system of stream-wise vortices is ploduced. Th*ie vortex motion SweepS

high momentum fluid from the free stream into the low mOmentwn boundary

layer as Uhe vortex system procee", dowstream. If the boundary ls yer

momehtum is increased suff'iciently,, the adverse pressure gradient willbe overcome and separation prevented.

The utility of vortex generators in preventin separatiou in

subsonic and tnansonie flows has been demonstrate i. Some previous work

done at Applied Research Laboratories of The University of Texas at

Austin vas directed towara extending the use of vortex generators to

supersonic flows. %itten in Ref. 6 measured th- drag of several

genermtor shapes but did not demonstrate their use in preventing sepa-

ration. The work of the present report was ,ndertaken to obtain

better definition of the floa behind a vortex generator placed upstream

of a compression corner.

The experimental program consisted of two rain phases. The

first phase -onsisted of defining the separation geoxetry prou,.ced 3by

the compression corner. This vas accmelshed throough the use of static

pressure me'-surcments, oil and dy-e flows, and sehlIeren photogranhs.

3.

Therenindr o th exeriefla os ccetrated on determin-ing the

effect of a single vortex generator on thO separation regions rm-tng1 the

same techniques as in the Vlarnt phaZS

_ 2-

4

rI. EXEIMEIA AM P_ _'

Wind - -n

ThIetwr efre nx7i! idt-eIo

The test P= s ere .perohed itante prssr in .-ind unne of5 t

th0dig he test program, u was 4.7 h santonarssued varieom6 to

2Alsadrn h etprgabtwscnrle aunt~ratll et

within ±3 psi during any particular test. The stagnatioteprue

range for this program was ia-* to 79F'with an average of 176 8 Fr.

Th-is was sufficient to prevent mistumre condensation in the wind tunnelA..

For each particular test the suppl.y air was heated to the preset valuep

using electric resistance- beaters located - 0 -tr-am of11 the stillijng

chamber. The stagnation temperatulre -was constat within +-sF during

any One test.

-Flat late and RAWn-

The tests uere conducted with the. frlat plate, rampfl combination

sn-own in F ig. 2. The plate ea Ame fr om Tinthcalr nad

was 17.5-1 in-. long and 6 in. wi-de. A sharp lead1 ng eage was prvided b

-~i5deg chamifer machined an the side oppst thV etsrae

boirejary layer trip-per strip, mwae of' 80-grit eme-ry cltwas mounted

approximately- i/2- in- from the leafine edge.

The ramp was made from mild steel and macbined to provide a

35 deg turning angle frc the flat plate. The ramp test face was

1.08 in. long and rose 0.625 in. above the plate surface. When-mounted

on the plate, the turning corner was 1.2 in. from the leading edge.

A rubber sealant was used to provide an airtight joint at -the ramp-

plate interface.

The plate was manted norizontall- between the sidaealls of the

wind tunnel, with the test surface coincident with the nozzle center-

plane. A rubber gasket was placed between the model and wind tunnel

wall to prevent air flow through the manting-clearance gap.

The model contained static pressure -;aps arranged in a centerline

and soanwise pattern (Fig. 2). The taps wexe spaced every 1/2 in.

along the centerline of the flat plate from a point 7.65 iv. upstream

of the ramp to % point 4.65 in. from the ramp. From that point to the-

amp the tap spacing was 1/16 in. The quantity of taps on this portion

of the model proved more than necessary for this study. Thus, only

alternate pressure taps, beginning with the first, were used. This gave

a pattern of measurements taken 1 in. &part from 7. into 4.65 in.

upstream of the ramp, and 1/8 is. apart from 4.65 in. to the rap

(Fig. 3). A centerline nattern on the ramp provided taps 0.1 in.

apart beginnLng 0.1 in. from the compression corner. The spanwise

patten- consisted of tbree rows of taps located 0.3 in., 0.6 in., and

0.9 i Trom the compression corner. Each row extended I in. on both

sides of the center!Lne with taps spaced 0.1 in. apart in each r

( ..3).

(Fi.... :

The plate was also fitte_ witt a therrlcople, located ahe-i

of the separation region, to nmnitor plate temperatu-re. A recess

m-acLned in the back 01f the plate and O-A pro ae space for the

pressure azd thermcoue leaa A cover plate provided protection to

this area f the free -trem flow.

The flat plate was provided with three slots An t _

the vortex generators. The centerline of the forward slot was iocated

4-.9 in. upstream -ot the ramp on the centerline of the model. The

centerl ines of t to slots " 5 i upstream-

of the razp. One of these slots was located 3d46 in. to the right of

the cente-line aind the other slot was 1/'2 in. t the left of the center-

line (rig. 3). All three slots were inclined at a 15 deg angle to the

plate centerlina to provide the vortex generators w-ith a- angle of attack.

The fourth slot seen in Fig. 2 was not used in this inmestigation.

C. Vortex Generators

The vortex generators are shown in Fig. I an. their dim-nestons-and desinations are given in Table T. Te ge.tors ere made of

mild steel and were a'1 of rectangular plexiform. Four differpnt

generators were used, with chor lengths of 0.5 and 1.0 in a-nd spans

of O.P2S and 0.C in. Tiche section shape of each generator was a sym-

metric double wedge with the maxitm thiekness of W-064 in. occurring

at the mid-chord oin-t. Each generator was providei hn a mounting

tab 3/1 in. iong, 1/16 in. wide, amd If' in. -deep. The generator was

m-inted in the desired slot on the plate using a therm plastic adhestve,

Crystabond 509. All of the geeraters were mounted at an ankie of

attack of 15 der.

rvi z

D. o- Visuali zai Techniques

Ext-ensive use was made o v'arious fl- isulization techniques

to help defime tn finw patterns. Schileren photographs were taken of

each configuration. using' a sinale-pass schlieren system. The I-J4-t

so -ewas a -tungsten, ribcn-frlanerit lamp. This system alow either

black -.Lid white or color photog-raphs, t:iough.n itms proram color-was

used exclu-sively due to its increased defbnition.

Adye injection technique was also used to deine the flo on

the eilate b-rfae and- ramp face. An oil soluble dye disslved z--In -tha

was -ected throieh a resu- e orifice using the pressure differeII

between the inside of the wind tunnel enul the at-osphere.

ue to the large velocities p resent in the flow, tht dye

in- .3tion proved to be of 'iited vate and subsequently an oil flowteehuie was employed. -mixtue of 30 weight raor oil and titani-m

7- ; -dioxide powder proved satisfactory. _The oil 'as Ad'ibed on the plate.

the tunnel started, Lnd the pattern allwed to form. novever, az in

the case of the dye iLnjecticn, the entraining nalture of the flow caused

buildups of oil and d:e. Upon shut-dowm cf the tunnel, the pattern ra-

distorted by the flow of excess oil. Since the tunnel geometry precluded

use of phoogra-phic equip ent during operation, the patterns -w vere

obser ved and skctches made during each nnin,

S. instrmentation and Procedure

The =bodel static pressures were displayed on three multitube

ma- rcur y imIeter boads a nd were renrrded ph--oto PphieaLy. The pi7- e

the-coupe -- trut "' was, recorded on a Hone,-ifl-Brown strip. chart

0

recorader, as was, z ge cutiut of- the virnd t unnel~ s4 nts'qr tlefp-~Ae t ure

mhrocoupnle. The stftgchadlber *re)y- z--hSJi- WTs wtha

bor&ntype pressure gug Vail vas rercorae onotogranh-dcaly

For any partilatettetiinh br pressuire ea

tecpezrature cotrllers L'r rr, ~~4n~=A ~ifc

ieas t;hen- staet'-4 and the stagnatlon- Dre ssure Al-we to tbiI1Ze

benfore the static p-ressures 'were recorded. S- 1-ce %,h vlt as no,

betted to recovery te;erue pror toechrn the pl ate teprte

-as m~onitored peri4odccll - T1he nreselected stasnation t-enratur&-e

~~~*Aa~~~~~~ the Feovr -e-rnpr'rxn's"IeP e t-o the usuall

high ambient t-emnerature- (spproximatelvy 1-0-WOar)p the temmrature

diffterence betwgeen the plate at thec star-t of a ru ad the recov.ry

te - e was sm~all. As & result of the short rn tixtes C anproxi-

tel25sec), the plate teant-e-rature increased l-ess than A15 F during the

run monitoyred. This was felt 'to be revresentative of the enti re test

program, raidng t-he s 4 'd nearly caiabatic. Duingthe earlypae

of the testing at least fordupAlicate rn'were made ai eachcni~

ration. Good repeataility,1 during hasealowei th UM- e of rns

er cooflizuration to be reduced to t-wo in the ltrstages of the

IF

~~~g - W m. -- - -

ppm-_- - Olin-

- ?~- Z __ -- ~ ---VMS-

plotz~tt-r - --

sloyre mea,.urericriLtS were also mj,4-e 1sing the schlieren photographs.

Separation lengths and shlock wave angles were measured by projecting

the 35M.sieso screen and us-Ing a Gerber Variable Scale and a

pr.t rAor

The static pressures were displayed on three mercury manometer

boards having least scale divisions of 0.2 and 0.1 in. The photogra~Phic

records were founid to be of sufficient claritY to allow interpolation

to 0.05 in. Due to the Low pressures being recorded, an error in

manometer reading of ±0.05 in. corresponds to an error of 6.6% in static

-'pressure. H~owever, by red-action of the data to coefficienlt

form., the

variation in C was less than ±0.01, w~hich was deemed sufficient for

this sw6dy.

12

IV. RESULTS ANDi DlSCUSSI1014

The phenomenon of separation Jis hiehly deDendent or- the type

of boundary layer present and the nA~itude Of' the pressure gradient

retarding the flow. A turbulent boundary layer was assum-ed for this

program based on the presence of a boundary layer trip en-d a caloulted

6Reynolds Numtrber per foot o'& 141 x 10 The bcindar ae asaooi

rnately 1/4 in. thick in the -test, area as deduc-d from the schlieren

photographs.

A. Separation Region without Generators

The centerl-ine and suanwise pressure distributions obtained for

the compression corner without the generators are p-iotted in coefficient

form in Fig. 5(a) and (b).

1) Separation Parameters

The centerline pressure profile shown in Fie. 5Wa S -P ypce,

of the separation profile for a two-dimensional t-urbule-nt boundary

layer. Tne point o.& sepaxation is generally taken to be the first

inflection point in the p essure profile. T.hin occurs I..7 in.

upstream of the compression corner. Reattactment of the flow on the

doianstrenm wall c'orresponds to tChe third inflection point in the profle,-

which is 0.4158 in, along the rampy frice. The middle infleurtion point

is the plateau pressure rise, which is -due to the defLection. of the

external stream. The plateau pressure coefficient ani the loction of

separation and reattachment are sufficienttoalwccltin f

several separation parameters.

13

Tna free interacti-;. on angle or angle between the free stream

direction and the dividin streamline at separation was obtained by two

methos. 1he plateau pressure coefficient end free strt ach num'jer

permi itted use of the oblique shock relations or the charts of Ref. 7 to

obtain the corresponding deflection angle. This method yielded a free

interaction angle of 0*-8.7 deg. By use of the ramp geometry and the

location of separation and reat achment, a free interaction angle of

-78.-- deg was calculated. Measurements from schlIeren photographs

(Fig. 6) showed a turning angle of approxinately C--=i deg, verifying the

calculations.

The separatton length (Fig. i) was found by trigonometry using

the free interaction angle and the locaticn of separation and reattach-

ent. This yielded a value of 1 =1.77 in., while schlieren photog-raphss

showed 1 j=1.9 in. A comparison of these values for free interaction

angle and separation length with data obtained by Gillette (Ref. 3)

showed good agreement. A comparison of centerline pressure distributions

with those obtai.ed by , and Sterrett and !-ery (Ref. 8) also

showed good agreement.

It should be noted that the peak pressure on the ramp fallshrt of tb-at pedi t ed by ir'viscid 4heory. This phenomenon hat been

n-t-e ed by- a nm-er o'P irvestigators and is attributed to the p-:resn- of

the side-walls. The low speed reierae flow region of eepara-ion is

nprevented fr-m svanuise venting by t-e sidewalls. This causes a targer

seoaraton area than for -an ,Lnbounded flow The result is

1&

ftee interaidon angle, Pa s'r _nsger sM-c1k -wave at nepartion, and a

smaller' finaL pressure rise. Work by 'Kaftai et all (Ref' 9) supports

this Iynothesize

2) Three-DimenSional Zff'ec-

The ~ ~ -spnienesr itributions plotted in Fig. 5(b) show

the three-dimenisiornal effects ire flowi. SoDanwise variations in

pressure were observdo the ram face, inictganoniomfo

-'o aid in determining the ;haracter of the flow,~ a series of oil and dye

flo ests vwas made. Te flow pattern obtained fyom these tests is

sketched in Fig. 7. The separation line was essentia'.lly straight over

approximately 60% of the center portion o.f the plate. Near the side'wafls

thesepraton ine bec~ne curved and joined the cureved separation line

of the sidewalU boundary layer. Inthe center pozrtion of the plate the

flow in the separated region vwas -directed Amif ormly upstream. Close

to the sidewalls a spanvise vdlocity component, directed outward from

the centerline, caused a curvature of the streemlines, which cu~linated

in a surface vortex at the separation line near each sidewall.

In t-he reatt-achmment region on the ramp face. a series of

reualy spaced radial fliow patterns -was noted. he centers of eachI

paler 'Vem ere located at the reattachment Line a.nd -were snaced at 1 i4n.

intervals in the snanmwise direction. From each -'enter the flow was

radil i alldirctios -it a small distance from +he cienter tile flow

"became more streammise, resulting in higl curved strearni-nes At t ze

spanwise points 4here two patterns Joined, a heavier oil floW resulted

giving the appeararce of a striation parteft. This striatio f h

eprarc r mio- whr th Oi pate- 'wa llz- Mr

FZ- r- of- n -- ---zt --------- nmdre--l ------

i panrWa regiuwee the oi vratern oas tessteist.ez l

rn eeralce invesgat usin vries ae~re cs ino ik. li

andieostgaDtinof ainon ea-thretberd rerlar j stratin

oth weracconuaed by rhea vkariation inw thessreandn hea tranie

rauates d Gilette (Fe! 3 prandershk en-in those (Rtef 11nvetoedms the

flowrn for i tret ratacn!as deflows zThe :r-'s of Sezte sIa's

isutn Ierfly attruedstoth creatofsafstemie otcsi

th bunar layer, due tor thetri- the vo at entraton -Maumi

Lad a re ergt orerTePinle arey V nsedere s three-X-

intesi~onl cetraeios oned en oth-eniirex tato-dimennctal fl

on. . the traghtnsn of te sertn Hn an the'-e is ren ofy atimp

caluted sc-er atin ramet- -es wia those ofer: inetigtos, h

A fe inrodutor codt ts othvrte generator,, i cuirtio

mad rtesuts ae iodr prncpa in exerh Srl~tia- iSad

r

ctcuit;-fVA -el- tmntr 4t-ef thMn ahnfec fth

ce-reaedr*vi" te senantir=.aita. Also,-a the fiou.- ptter

creete by th gennerarvdki an ±s eztonre y C=P x,

a dt~iedan~yss s beyond thesoe of the present ivork. Thereore

Only a quai~t&tive decp~nof the! itanrrn od -- are

n"-eicte tinlit sotowinI y on ions

pr ur akw o-A -fs:U

-ice ~ ~ ~ ~ F '!6 tL ic tip *r.- rnz leM cu-wrn

vidsm3a .Hrweveri-- dtnls Zbe piresent ivtitinit tecsre vfn

that ttie: -P . -te -e~ f -was- 1Anadamate todeterr'irc- the-. extent 01P

aptj~ the presence of a vorex gemnerator. Th-e spsnwiuse- pressure

-distrbu tions vere essenlal 4-- def-r~ the region= afffect--d bay the

Etnawatorz l~4j, i ) ineit into t.a met'h'----v~ by whchsemara-

e alnae were not

s~fcttto Ateme iihte tepar-at-Lr-t 1had 1-~npreven=ted, snen

prvo crteria e.x r 4 talva ~e~o. theexeniv ve of

ct iot atarfaca mattern f or -each vormrto as def innc- *Mh'-se

the~~~I prtdcinst betue Cteno. =.re---ie that the

thirl the: bol-ia laver is otvalid. Taaid isl vitn±-ii tile

-am lthe wras ta eE2I:~ .ee-arnii e#4 L4t--0e 4n - rr t %Ar rnI

arnL ~ -ys- ass mides ~ ~anna- hcrm r s walj-- f ilJ(~

I .1) ?orward Location

The pessasure distributions for the four- generators in the forward

location are sho'wn in Figs. 8- to 11. The center!lne nrofile for each

generator shows a slight lowering of the plateau pressure though theprofile shape remains similar to the typical separation proftle.

In the spanwisa profiles all of the generators sho.ed some

deviation from the no-generator profile. Generators I and 4 had similar

patterns though they differed in the magnitude of the variations in

ooh cases the dowmstream develop-ment of two pressure peaks on either

side of the centerline was-noted. Separating each peak and outboard of

the peaks were regions of low pressure. Generator I showed a more

distinct davelovment of these variations than did the smaller chord

generator 4. 3owevei, in neither case were the changes in presesure

coefficient greater than 0.2 f1m the no-geherator values,

Generators 2 and 3 also shcwed a similarity in spanwise profiles,

though again the magnitude of the variations vas proportional to chord

length. For s short span generators a single pressure Deak. developed

to the leeward side of the generator. This peak was noted to be

unsteady fIr generator 2. To the winbtard side of the generators a

;r-y- low pressure regio;i developed.

Te sketch of t oiI flow patterns obtained for these

configations is shown in Fig. 12. None of the fl7o tests showed a

1lW of oil streaniise over the entire ramp face, indicating separation

was not pr-evented by the generators in this forward location. Tne basic

ifl

pattern in Fig. 12 was comron tlo all four generators, with' only th-e

positicen ofL the surface vortex varying from one generator to- another.

For generators -I and k the Pattern vas as- shown in Fig. 12; for genera-

tors 2 and 3I the vortex was centered on the mlodel -enterline.

Coimo 'toal four configur-atioJsEi the lxpressure area near-

the centerline in the searwv se prof-ilIes. T-he shock expanston analyjsis

tor the portio of the generato in the free strem anaicate& velocities

at the trailing edgee co-,-mparable to free stream veloci-ty. At th utr

edge o f thbe bondr layer, the hihvelocity flow would intersect-* the

ram-- a-t tie reattacbrment line or hi~ther. Since thc largest va1riations

i n pressure appear high on t-he rampq, it is; felt thrat the press-ure trough

ini the profile -is a resualt of the high vilJocity f'low off the tr_ au

edge of t15he genzerator.

The, flow hlear the surface also has- -, relatively b,:igt velo city

rgion S.the trailing edge 'wu is -cc lcated by the presence of a

streawise tortex ndthe separation Ira n the corner II'rnei by

th:,e windward stge of the generator and-ti plaste, a etrearyise vortex

As zori-ead due to the nonuniform turning-ot the boundary-- th

inerator. N-Vear thit surface the Zlowfr roing fl!i it t- wed t

a greater angle than the faster gann f 1L at the cu-er edge or th

'Nomdarr ~ ~ ~ I -er Itii..al~m g t 'xuaar~ lsnwr txt

teform~ation -of a stenievorte% ne.ar- the z-riae -~

vorex act to $nce0 the maretiz f_ thte fluid near the surfa-e at

M the ~gene-rator t.rmg edg-e. - sseen inthe oil- a- th e flrW in this

region has s'affitient mc~wentim to penetrate the sepmatlw region

cauing a cuszi the sep-a-rati line inieer. wit the 14r--+m-

to everItualWy retard the flo. n"us '- sc-pflatvfl "i farh

o:fa attache&Ad owmtTremn fla;w is ukebytime i4Orstresam edue of tine

surfawce vortex seen -

The ress.re rcearrk v-ra-i n =e-as~- I 1. 'a face a&M

asszcat ivih shr~ i*-ave = creat b he Jreewr4 side 0"1 t!he

£enenor. ot gneraors and 3- the nnres-r-n peak tz vt~~eri

thdtaien e il s r m-- w ex e -tlip mon at14t- A

the ;hitc-Lrti~

z. e =---. *IaE ztni et~k

time------------------ searae

iu -3- wave vin ---- pasm ai----

te-

*~ rlatsyl ~f&SILTl. ALb-ir 'be Um

_ ~ tr ~Urt~ atthe tj SZti tWsm

-- e-s

-I 4"-- sbm.3n~-- --

essurc --- v- -eut in-

irg e- - _ I __

_ -- n ---. cse- ~ -mtS

as- fl --- t

sksq - ag ' -- = __

___ ~tX wr~$ ~ .2 _ it

Z- tnZal,- *- -SSE

Mkltr~s ne

-he -b ms tc= l!

a 5119 m s

mr- - fl a

*Z - - -

-mom~

_ ft = -

ZrM:-

= 7 T -=z 24e=- -

-=nd= IM

40= Liam_ 4 _lw- f

a. ___ -= Am - ~ -

kt z- --w -= ~ T ~ N-

-- 4'.

[ of rotation of these vortices seem to be dependent on aspect ratio and

the trailing edge conditions for each generator. For generator 2, with

the lowest aspect ratio, the vortices rotate in opposite directions.

The remaining generators have co-rotating surface vortices and -higher

aspect ratios. The oil flow for generator 1 indicates a stalled condi-

tion at the trailing edge, while for generator 4 the pattern indicates

the onset of stall. in these two cases the surface vortex to the leeward

side of the generator was further upstream than for the unstalled genera-

tors. Stalling on generators I and 4 was believed to be the result of

the high downstream pressure, the lonC span of the generators, and the

high angle of attack.

At the outer edge of the b)oundary layer the generator is

influeni..ng a free stream flow. The shock wave system from the generator

is thus able to proceed downstream above the s-..parated area and intersect

the ramp. The two pressure peaks indicated in the spanwise profiles

correspond to the leading and trailing edge shock waves. In this aft

location there appears to be little effect due to the tip vortex,

perhaps because of the reduced streamwise distance over which the vortex

has to act. Outboard of each pressure peak the pressure tends roward

the no-generator valucs, indicating the narrow region affected by the

ogenerator.

in Fig. 25 is shown a schlieren photograph of generator 1 in

the aft location. Note that the shock wave emanating from the separa-

tion point is no longer a single compression -wave as in the no-generator

24

configuration. The breakdown of the Single shock wave into several

coripression waves is felt to be the result of the highly curved --epara-

tion line near the generator shock waves. Due to the narrow spanwise

extent of the unseparated region, schlieren photographs did not show

any detail in this area. The photograph of Fig. 25 'u, tYpia f h

for generators in the aft location.

LIM'.V. SI44NARY M~ID COICIUSIQNS

An experimental -Investigation vas made to determine the

usefulness of vortex generators in preventing the sepaxation of a

supersonic flow in a coaipreszion corner. The Nort generators were

mounted on. a flat pla~te at two stations upstream of a 35 deg ramp. The

I: average Mach Number was 4.67 and the Reynolds Numiber was 14 minlion

per foot. The boundary layer on the plate was turbulent and approxi-

mately k14 in. thick. Static press~ure measurements, oil and dye flows,[ and schlieren photographs were used to develop a qualitative description

of -the flow.

The following conclusions were made:

1) A vortex generator, if placed sufficiently close to a

compression corner, c&a, prevent the separation of a super-

sonic flow due to an adverse pressure gradient.

2) lthe vortex generator epnergizes the low momentum fluid of

the bo Nay layer by an expansion process around the

generator body, in addition to the energi2-ing action of the

tip vortex and the st-reazwl.se vortex formed along the base of

the generator. For this investigation the effects of the

two mechanisms were ztA separable.

3) Toe region of effeetiveness of the generator was limited

to a very narrow region directly behind the generator

trai'ling edge.

27

receding page blank

41 The perfonnanrce of each' geneTrator 'was related more to. Chor

lngt-h them tO generator pA-.

E) Vaticai thr - onsi al -perturbations iert found in

the turbrtent reittaching filow on the rcp- in the absence of

thhe generators.

28

wuerer, UE., and F. ia-Vtonl. rtcMl -d r lon in ragn zpe-e-arligh, -A Revie o he State-o- -the-_Artc - "epr M

2. kaufran, IL. G., atl.. !2 eview of Hlypersonic Flo-W Sepa-ration anIdControl Chraterisetics, Untd . ~Ai r Force, Aeronautical.Systeins Division., TDR6-~S 4l~ 1962

Gillette, W. B., "Sceparation- MI suretents of Sunoersonic Turbul-fentSmBoudary La-yers Over Cosuression Corners,. Defense Research LaboratoryFenortb Ncz. 51 3(n-3 ECR-26)-, Defense Research~ Laboratory,The University, ofTzs as 4 ~rxs ul-y 19665.

1.Parcyo H1. 4H., and C. IM. Stuart, *k14thcods of Boundary Lwyer Cont.rolfor Posinvcurng and Mlleviatins Buffeting and Other Effects ofShok-Thduced Separation, " AUt A FirhWI-d- rmi Pat per 22, * e 15

~,.Ed~arz, ... a,-Free Flig-lt Tests of Vortex G:enerator Ccnf-igu-rations at -Transonic Suaeds," A.A.Z. TLech. Hote-Akero 282December 19462.

6, Thitten, J. W., "T--e- Drag of Vaie-!Type Vormtex Generators inComjressibe T'"' .tt FoDefense Research Laboratory Report'oM 561DR056) Defense Researc-h Laburamcry., The Universityl ofTexas, Akutinz Texas, Augt 196-7.

y "Equationa, Tables end Charts for Comressible Flo,"AAReport 113:5, U. S. 'Governmerntit Office, Wasri.-ton, D. "

1953aSterrett, J. Ri. an J. . .=~r~ Drie Separation Studies

for Two-Dimensional Wedges and Curved Suarfaces at Mach Numbersof 4.8 tvo 6-2, HASA Vfl--1ol4, February 19 -_,2

9. Kaufm-an, L. S., ea, t ninvestigatio of Hypersonic Fo

-- Separation and Coentrol Characteristics," 1nited S tate Air Force,*Research and Technology Division AM1.TR-6-lk, January 196,5_

1-0. Ginoux, J.* J, "Thle Existence of T"'ee-D-ime'si-la' PrurA.osif teReattachment of a Tuo-Dihns-na SupeGmrsonic Boundar vlayer

after S-eparaetion," AGAPD Report A' -3.

1.Rosbko, A.,and nL J icl~r~e, "Obseriatofls of Turbulent ReattaChment

BehtndC an. Axisym etrit- Downstrean-F&CiflS Step in Supersonic P10%"

A IMk Journal '46), June 1966.

"Th T, ±.A -.i nsionas- ±nterac,-1u n Of. a. Sockav with

Turbulent BOun!dary, Layepr," m eoatclQartery Vo I VI

()August 1966.

30

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