ii f • .

NASA Technical Memorandum 4663

Water Tunnel Flow Visualization Study

Through Poststall of 12 Novel Planform Shapes

Gregory M. Gatlin and Dan H. Neuhart

March 1996

NASA Technical Memorandum 4663

Water Tunnel Flow Visualization Study

Through Poststall of 12 Novel Planform Shapes

Gregory M. Gatlin

Langley Research Center • Hampton, Virginia

Dan H. Neuhart

Lockheed Engineering & Sciences Company • Hampton, Virginia

National Aeronautics and Space Administration

Langley Research Center • Hampton, Virginia 23681-0001

March 1996
Available electronically at the following URL address:

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http://techreports.larc.nasa.gov/ltrs/ltrs.html

National Technical Information Service (NTIS)

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(703) 487-4650
Summary

To determine the flow field characteristics of

12 planform geometries, a flow visualization investigation was conducted in the Langley 16- by 24-Inch Water

Tunnel. Concepts studied included fiat-plate representations of diamond wings, twin bodies, double wings,

cutout-wing configurations, and serrated forebodies. The

planform models tested were 0.25-in-thick flat plates

with beveled edges on the lower surface to ensure uniform flow separation at angle of attack. A removable,

simulated balance housing also was tested to determine

the potential effects on the flow field characteristics. The

off-surface flow patterns were identified by injecting colored dyes from the model surface into the free-stream

flow. These dyes generally were injected so that localized vortical flow patterns were visualized. Photographs

were obtained for angles of attack ranging from 10 ° to

50 °, and all investigations were conducted at a test section speed of 0.25 ft per sec.

Results from the investigation indicate that the formation of strong vortices on highly swept forebodies can

improve poststall lift characteristics; however, the asymmetric bursting of these vortices could produce substantial control problems. The simulated balance housing

affected the vortex structure on some configurations, but

these effects were noted only at angles of attack of 20 °

and below. The vortices that formed on the additional

forebody and the wings of the twin-body and doublewing configurations probably account for the lift

increases noted when these configurations are compared

with the single-body and wing configuration. A wing

cutout will significantly alter the position of the forebody

vortex on the wing by shifting the vortex inboard. The

diamond-shaped cutout produced a vortex over the aft

inboard portion of the wing; however, this did not happen with a triangular-shaped cutout. Serrated forebodies

effectively generated multiple vortices over the configuration. Vortices from the 65 ° swept forebody serrations

tended to roll together, while vortices from the 40 ° swept

serrations were more effective in generating additional

lift caused by their more independent nature.

This report states that color photographs are presented. Most copies of this document were printed in

black and white; however, a limited number of color copies are available from the author. The color images are

also available in the electronic version at URL http://

techreports.larc.nasa.gov/Itrs/ltrs.html.

Introduction

As the demands to develop increased maneuverability are continually being pursued for fighter aircraft

(ref. 1), novel control concepts are receiving more attention. Multiple concepts, such as deployable strakes

(refs. 2 through 5), blowing and suction systems (refs. 5

through 10), and porous surfaces (refs. 11 through 13),

have been developed for a variety of applications. These

novel means of control could be incorporated into a

newly developed vehicle design, thus resulting in a configuration with substantial levels of maneuverability.

To develop such a vehicle, the appropriate initial

studies would include an investigation of various promising planform shapes. This type of investigation has been

conducted with 21 planform models that incorporate

twin-body, double-wing, cutout-wing, and serratedforebody concepts. The investigation was conducted in

the Langley Subsonic Basic Research Tunnel over an

angle-of-attack range from 0° to 70 ° at a free-stream

dynamic pressure of 30 psf. The results of this wind tunnel investigation, which include longitudinal force and

moment data and minituft surface-flow visualization, are

presented in reference 14.

The concepts investigated were chosen based on the

expectations that these particular planform shapes would

effectively generate high lift across the angle-of-attack

range. Double-wing and cutout-wing configurations

were expected to derive benefits from a forward and aft

lifting surface that would act independently at moderate

to high angles of attack. These lift improvements were

expected because previous research findings on

close-coupled wing-canard configurations (refs. 15

through 17) have shown favorable improvements in

maximum lift coefficient when a close-coupled canard

was added to the basic wing planform. The intent of

including the twin-body and serrated-forebody configurations was to investigate the effects of multiple forebody

vortices on the high-angle-of-attack characteristics. The

serrated-forebody concept was specifically designed so

that a vortex would form on each forebody serration, and

thus the multiple vortices that would extend over the

length of the configuration would enhance the liftgenerating capability at moderate to high angles of

attack.

As a follow-on study to the wind tunnel test, an offsurface flow visualization investigation was conducted in

the Langley 16- by 24-Inch Water Tunnel. The results of

this investigation are presented in this report. The goal of

the investigation was to develop a more thorough understanding of the flow fields associated with the planform

concepts under consideration. A water tunnel that operates at low speed is capable of providing high-quality,

detailed flow visualization of complex flows, which

include vortex generation, interactions between multiple

vortices and aerodynamic surfaces, and vortex burst. For

thin, sharp-edged configurations, the results obtained in a

water tunnel at low Reynolds number can be related in a

qualitative manner to high Reynolds number flow in air.
Theseissuesare fully discussed and supported in

reference 18.

Although 21 planform models were tested in the

wind tunnel investigation, only 12 planforms were examined further in the water tunnel investigation. Generally,

the configurations that showed the most promise in the

wind tunnel were also examined in the water tunnel.

Furthermore, insight from the wind tunnel investigation

indicated that several of the 21 planforms tested had very

similar off-surface flow field characteristics, and thus

further examination in the water tunnel was not

necessary.

The off-surface flow patterns for 12 planform models were identified in the present investigation by injecting colored dyes from the model surface into the freestream flow. The colored dyes were generally injected in

a manner so that localized vortical flow patterns would

be visualized. Specifically, colored dyes were injected at

the forebody apex, the wing/body junction, and any other

location where a vortex would be expected to exist. The

planform models were 0.25-in-thick flat plates with a

beveled lower surface on the leading edges to ensure a

uniform flow separation at angle of attack. Both topand side-view photographs were obtained for angles of

attack ranging from 10 ° to 50 °. All investigations were

conducted at a test section flow speed of 0.25 ft per

sec, which corresponds to a Reynolds number of

25 000 per ft.

This report states that color photographs are presented. Most copies of this document were printed in

black and white; however, a limited number of color copies are available from the author. The color images are

also available in the electronic version at URL http://

techreports.larc.nasa.gov/ltrs/ltrs.html.

Symbols

All measurements are presented in U.S. Customary

Units. All data have been reduced to standard coefficient

form, and lift coefficient data are presented in the stability axis system.

b reference span, in.

Lift

CL lift coefficient, --

q**S

CLm_, maximum lift coefficient

c reference length of planform, in.

q** free-stream dynamic pressure _pVZ, psf

S planform reference area, ft2

J=,

V.. flee-stream velocity, ft/sec

ct angle of attack, deg

p density, slug/ft 3

Model Description

This investigation was conducted in the Langley

16-by 24-1nch Water Tunnel, as illustrated in figure I.

All models were held in the test section by the offset

model support system that is shown in figure 2. Twelve

planform configurations were tested. The first seven

planforms were models that were specifically designed

and built according to predetermined specifications. The

remaining five planforms were generated by modifying

several of the original planforms.

Sketches of the original seven planform models are

presented in figures 3 through 6. These models include

55 ° and 65 ° delta wings, 30 ° and 40 ° diamond wings, a

twin-body configuration, and two double-wing configurations. The figures show a side and bottom view of each

model, as it was tested. As illustrated, the 0.50-indiameter sting was attached to the bottom surface of each

model and was inclined 5 °. In addition, a simulated balance housing was mounted on the top of each configuration. This housing was added so that the upper surface of

each model would be identical to that of the configurations tested in the wind tunnel investigation (ref. 14). The

simulated balance housing was cylindrical with a 0.50-in.

radius and a hemispherical front end. This housing was

also removable so that testing could be conducted to

determine if it produced any substantial effects. Each

planform model was 0.25-in. thick and had a fiat upper

surface. To ensure a uniform flow separation at angle of

attack, the leading edges were sharpened by beveling the

lower surface. The trailing edges also were beveled on

the lower surface for all configurations except the two

delta-wing planforms.

Five modified planforms also were tested in the

investigation, and they are identified in figures 7 and 8.

Each of these modified planforrns was generated by

attaching 0.0625-in. fiat plate pieces to the top of an

existing model to produce the desired planform. In all

cases, the edges of the fiat plate pieces were taped to

minimize the effects of any forward and rearward facing

steps.

The first set of modified planforms presented (fig. 7)

are referred to as cutout-wing concepts. The 30 ° diamond

cutout wing, as presented in figure 7(a), was not tested in

its original configuration in this investigation; however,

the side- and bottom-view sketches are presented to provide a complete description of the modified cutout configurations. The two 30 ° diamond cutout-wing planforms

that were investigated include one with a triangularshaped cutout (fig. 7(b)) and one with a diamond-shaped

cutout (fig. 7(c)). Both planforms were generated by

modifying the original planform, which was referred to

as the 30 ° diamond cutout wing (fig. 7(a)). Because all

the geometric details of the original unmodified
30° diamondcutoutwingarepresentedin figure7(a),

only the overallplanformshapesare presentedin

figures7(b)and7(c)for the modifiedplanforms.The

cutoutareaonthe30° diamondwithtriangularcutout

configurationwassetequaltothecutoutareaonthe30°

diamondwithdiamondcutoutconfigurationsothatthe

effectsofthecutoutshapealonecouldbeexamined.

Thefinal setof modifiedplanforms,presentedin

figure8,wasdesignedtoexaminetheeffectsof serrated

forebodies.Thefirstplanformis referredto asthe65°

deltawithdeltasawteeth, andit wasgeneratedbyadding

a deltasawtooth-shaped forebodyto theoriginal65°

delta-wingmodel.Anothersawtooth-shaped forebody

conceptalsowastested,asillustratedinfigure8(b),and

it wasgeneratedby adding3diamond-shaped sawteeth

thatwereswept40° to theforebodyof theoriginal40°

diamondwingmodel.Thefinalserrated-forebody configuration(fig.8(c))wasproducedbyaddinganosetip

to the 40° diamondwith 3 diamondsawteeth

configuration.

All theoriginalandmodifiedconfigurationswere

paintedwhitetoprovidemaximumcontrastwiththecoloreddye.Thecompleteplanformarea,length,andspan

for eachof the originalandmodifiedconfigurations

testedarepresentedintableI.

Test Conditions and Techniques

Water Tunnel Description

The investigation was conducted in the Langley

16-by 24-Inch Water Tunnel, as described in reference 19. This facility is a closed-return water tunnel that

is capable of test section velocities from 0 to 0.75 ft per

sec with flow through in a downward (vertical) direction

(fig. 1) through the 16- by 24-inch test section. The

velocity normally used for testing, which was used for

the present investigation, is 0.25 ft per sec. This velocity

produces the most uniform flow. The flow rate is also

slow enough to easily observe the flow phenomena, such

as vortex flow, with the unaided eye. The model support

system can be operated in the pitch and yaw planes of

rotation through +33 ° and +15 °, respectively. An offset

sting, as illustrated in figure 2, can be used to shift the

available pitch range to 62 ° .

To visualize the model flow field, red, green, and

blue vegetable dyes or fluorescent dyes can be injected

into the free-stream flow through a remotely controlled

probe that is mounted above the test section. These same

dyes can also be remotely injected into the flow through

orifices located on the model surfaces. The clear acrylic

test section walls and the location of the model in the test

section at approximately eye level above the floor produce an environment that is well suited for generating

photographic records of the flow patterns around the

model.

Test Conditions

All 12 planforms were tested at a flow velocity of

0.25 ft per sec with the model on the tunnel centerline.

This condition corresponds to a Reynolds number of

25000 per ft. Flow visualization photographs generally

were obtained at 10 °, 20 °, 30 ° and/or 35 °, and 50 °. In

some limited cases, additional angles of attack were

investigated. All testing was conducted at a sideslip

angle of 0°.

Test Techniques

Because the goal of the investigation was to gain a

better understanding of the off-surface flow field characteristics associated with each planform concept, the

investigation focused on flow visualization. Specifically,

when conducting flow visualization studies with colored

dyes in the Langley 16- by 24-Inch Water Tunnel, the

best flow visualization occurs when the dye gets wrapped

in a vortex. Because this was the desired condition, the

technique of injecting dye directly from the model into

the flow was chosen as the most appropriate method.

When this technique is used, dye generally can be

injected into the flow at just the right location so that it

clearly identifies a vortex in the flow field.

Therefore, dye injection tubes had to be attached

before each planform model was mounted on the support

system in the water tunnel. These tubes, which were

0.04 in. in diameter, were attached to the undersurface of

each configuration with the tube opening located such

that the dye would be distributed into the flow at just the

right location. The appropriate location for dye injection

generally was at the forebody apex, at the junction of the

wing leading edge and the body, and at any other position on the configuration where vortex flow would be

expected. These additional positions include wing cutout

and serrated-forebody locations. Because the end of the

dye tube would probably be very close to a significant

flow region, it had a steep bevel angle of approximately

20 ° to minimize any possible interference effects. A

sketch that illustrates a typical dye tube installation is

presented in figure 2.

The final data obtained in this investigation and presented in this report are color photographs. Top-view

photographs are presented for each test condition, and

side-view photographs are presented for selected cases.

Note that when side-view photographs are presented,

they were not taken simultaneously with the top-view

photographs.
Discussion

To further understand and interpret the flow visualization photographs, lift coefficient versus angle-ofattack data are presented for each configuration. These

data are taken directly from reference 14, and they were

obtained on the same planform models that were tested in

the water tunnel. These aerodynamic data were obtained

in the Langley Subsonic Basic Research Tunnel at a freestream dynamic pressure of 30 psf. Since these data are

analyzed in reference 14 and are presented in this report

solely to support the interpretation of the flow visualization, they will not be analyzed in detail in this paper.

To address the flow characteristics of the planforms

in a meaningful fashion, the discussion of the test results

has been divided into four sections. These sections are

delta and diamond wings, twin bodies and double wings,

cutout wings, and serrated forebodies. In each section,

the lift coefficient versus angle-of-attack data are presented first, and the flow visualization photographs for

each configuration are presented second. All color photographs that illustrate the flow visualization patterns

obtained and the graphical representations of the aerodynamic data are presented in the figures, as listed in

table II.

Delta and Diamond Wings

To establish a baseline set of flow visualization

photographs on a simple planform concept, initial testing

was conducted on 55 ° and 65 ° delta-wing configurations.

It was anticipated that first obtaining flow visualization

on some simple, well-known planforms would help interpret and understand the flow patterns later visualized on

the more complex configurations. In addition to the delta

planforms, simple 30 ° and 40 ° diamond wing planforms

were included in the initial investigations. Lift coefficient versus angle-of-attack data are presented in

figure 9 for these four configurations. The corresponding

flow visualization photographs are presented in figures 10 through 13. Examination of the aerodynamic

data indicates that for the 55 ° delta wing, maximum lift is

generated at approximately an angle of attack of 25 °. For

the 65 ° delta wing, CL,,_ occurs at approximately 30 °,

and for both diamond wings, CLr_ occurs at approximately 35 °. This information will help interpret the flow

visualization photographs.

The first set of photographs, presented in figure 10,

is for the 55 ° delta wing at angles of attack of 10°, 20 °,

25 °, 35 °, and 50 ° . Both top- and side-view photographs

are presented for each of these angles of attack. The first

photographs (in which tx = 10 °) clearly show the location

of the core of the primary vortices that are formed at the

apex. Although the exact location of vortex bursting is

not necessarily clear in these photographs, it is evident

that vortex flow will have a significant effect on the

majority of the configuration at this angle of attack. Also

note that a colored dye shadow is present directly on the

surface of the model. This shadow is easily seen on the

mid to aft region of the model, and the phenomenon

occurred on each configuration throughout the investigation. At an angle of attack of 20 ° (fig. 10(c)), vortex

bursting occurs at a location that is approximately

20 percent of the reference length back from the apex.

The side-view photograph indicates that the vortices are

now slightly farther above the model surface than at an

angle of attack of 10 °, as would be expected. At an angle

of attack of 25 ° (fig. 10(e)), the vortices appear to burst

just after they are formed at the apex. This result supports

the fact that the aerodynamic data indicate stall in the

vicinity of an angle of attack of 25 °. At angles of attack

of 35 ° and 50 ° (figs. 10(g) through 10(j)), the flow visualization photographs indicate separated flow over the

configuration. The dye present in these figures flows

more directly aft in the streamwise direction and farther

above the model surface than at an angle of attack of 25 °,

thus indicating a separated flow condition. This condition is expected because the aerodynamic data indicate

that angles of attack of 35 ° and 50 ° are well beyond stall.

Flow visualization photographs for the 65 ° delta

wing are presented in figure 11. Photographs were

obtained at angles of attack of 10 °, 20 °, 30 °, 35 °,

and 50 ° . In addition, photographs were obtained with the

simulated balance housing removed to determine if the

housing had any effect on the location of the primary

vortices. In general, the photographs presented indicate

that the vortices formed on the 65 ° delta wing extend farther aft before bursting than those formed on the 55 °

delta wing at all angles of attack. When the 65 ° delta

wing is at an angle of attack of 10 ° (figs. l l(a)

and 1l(b)), vortex bursting does not occur until aft of the

trailing edge. Vortex flow is present on the 65 ° delta

wing at the angles of attack tested up to 35 ° . At this

point, vortex bursting occurs relatively close to the apex,

thus indicating a flow condition near stall. At an angle of

attack of 50 ° , the flow visualization photographs indicate

separated flow over the configuration. When comparing

the photographs with and without the simulated balance

housing, no identifiable effects were observed in terms of

vortex location or vortex bursting. This observation

holds true for all angles of attack tested. If an effect had

occurred, it probably would have been seen at angles of

attack of 10 ° or 20 °, because the vortices are much closer

to the simulated balance housing at those angles of attack

than at the higher angles of attack.

Flow visualization photographs for the 30 ° diamond

wing were obtained at angles of attack of 10 °, 20 °, 30 °,

35 °, and 50 °, and they are presented in figure 12. For this

configuration, colored dye was injected into the flow at
theapexof theforebodyandatthejunctionof the forebody and the wing leading edge. At an angle of attack of

10° (fig. 12(a)), the forebody vortices extend completely

down the forebody and onto the main wing. The vortices

that are formed at the wing/body junction, which will be

referred to as wing vortices, also extend over the majority of the wing, but they do not interact with the forebody

vortices. The side-view photograph (fig. 12(c)) shows

that the wing vortices lie farther above the model surface

than the forebody vortices. This orientation is why the

wing vortex wraps over and around the forebody vortex

when the vortices interact at an angle of attack of 20 °

(fig. 12(d)). Although the wing vortex appears to be

pulled around the forebody vortex at an angle of attack of

20 °, the forebody vortex is pulled outboard because of

the influence of the wing vortex. Thus, both vortices

affect each other. At an angle of attack of 30 °

(fig. 12(g)), the bursting of the forebody vortices has

moved upstream far enough so that the wing vortices can

no longer interact with them. At an angle of attack of 35 °

(fig. 12(j)), which is approximately CLm_x, the forebody

vortices burst at the end of the forebody. Not only does

this prohibit any interaction with the wing vortices but

also it may hinder their formation. Although the flow

patterns indicated by the colored dyes at angles of attack

of 30 ° and 35 ° could suggest the presence of wing vortices, note that the definite existence of these vortices is

inconclusive. This statement generally holds true for all

configurations that will be presented with a wing

leading-edge sweep of 30 °. At an angle of attack of 50 °

(fig. 12(m)), no wing vortices are present; however, the

forebody vortices still extend halfway down the forebody

before bursting occurs. The existence of the forebody

vortices at this angle of attack causes a more gradual

dropoff in lift beyond stall than existed for the delta-wing

configurations. This forebody effect will generally be

found on all configurations presented with a forebody of

this type.

Flow visualization photographs were also obtained

on the 30 ° diamond wing without the simulated balance

housing. When the photographs with and without the

simulated balance housing are compared at an angle of

attack of 10 ° (figs. 12(a) and 12(b)), a difference in the

flow patterns is noted. The simulated balance housing

appears to delay vortex bursting for both the forebody

and the wing vortices; however, its presence generally

does not cause the spanwise location of the vortices to

change. At an angle of attack of 20 ° , the configuration

with the simulated balance housing appears to be producing a smoother, more uniform vortical flow pattern. It is

uncertain why the simulated balance housing has this

effect, but it could be related to the accelerated streamwise flow around the housing. Accelerated axial flow is

known to stabilize the vortices and move downstream the

vortex breakdown. Note that more dye was being

injected into the forebody and wing vortices in figure 12(e) than in figure 12(d). The greater dye intensity

on the configuration with the simulated balance housing

removed (fig. 12(e)) could account for the vortical flow

patterns not appearing to be as smooth and uniform as

they are on the configuration with the simulated balance

housing. Since it is difficult to set the dye injection rate at

exactly the same value for each configuration, it is

important that the flow fields not be misinterpreted

because of variations in the amounts of dye injection. At

an angle of attack of 30 ° and beyond, the simulated balance housing appears to have no effect on the vortical

flows.

Flow visualization photographs for the 40 ° diamond

wing are presented in figure 13. The photographs that

indicate the flow conditions at an angle of attack of 10 °

show the forebody vortices rolling around the wing vortices. This effect is very different from the flow conditions

noted on the 30 ° diamond wing. When the 30 ° diamond

wing was at an angle of attack of 10 ° (fig. 12(a)), there

was no interaction of the wing and forebody vortices.

The higher wing sweep on the 40 ° diamond wing produces a wing vortex that is swept farther aft than on the

30 ° diamond wing. This wing sweep positions the wing

and forebody vortices closer together, and therefore they

interact. At an angle of attack of 20 ° , the flow pattern on

the 40 ° diamond wing is very similar to that on the 30 °

diamond wing. At this angle of attack, the wing vortices

wrap around the forebody vortices on both diamond wing

configurations. The side-view photograph for the 40 °

diamond wing (fig. 13(e)) shows how the wing vortex

goes up and around the forebody vortex. At an angle of

attack of 30 °, the forebody vortices on the 40 ° diamond

wing burst in the vicinity of the junction of the forebody

and the wing leading edge, which generally eliminates

any interaction of the wing vortices with the forebody

vortices.

Additional observations were made at an angle of

attack of 30 °, and as a result, additional photographs of

these observations are presented. Although the model

was held fixed at an angle of attack of 30 ° and a sideslip

angle of 0 °, the forebody vortices did not always burst in

a symmetric fashion. This effect is clearly illustrated in

figures 13(g) and 13(h). One vortex would burst at the

wing/body junction, while the other vortex would burst

downstream over the wing. The bursting locations would

then move toward, pass one another, and end up in the

longitudinal location where the other had been. Ultimately this process continues, and the fore and aft forebody vortex bursting locations proceed to swap back and

forth. This phenomenon has been observed by other

researchers, and it is described in detail in reference 20.

The effect was also observed at an angle of attack of 35 ° ,
eventhoughonlya slightly asymmetric pattern is shown

in the photograph. Note further that the wing vortices are

also present in an asymmetric fashion (figs. 13(g), 13(h),

and 130)). This effect is most evident in figure 13(g)

where the vortex on the right wing is more coherent than

the vortex on the left wing. The asymmetric bursting of

the forebody vortices is probably directly producing the

asymmetries present in the wing vortices. At an angle of

attack of 50 ° (fig. 13(k)), the forebody vortices are still

present, and the bursting is still occurring in an asymmetric fashion.

The effects of the simulated balance housing were

also investigated on the 40 ° diamond wing, and photographs are presented with the housing removed for

angles of attack of 10 °, 20 °, and 30 ° (figs. 13(b), 13(d),

and 130)). These photographs indicate that the simulated

balance housing had little influence on the wing or forebody vortices.

The overall results of the delta-wing and diamond

wing investigations indicate that the flow fields are dominated by strong vortical flows. Strong vortices that form

off the forebody can interact with wing vortices, depending on angle of attack and wing leading-edge sweep.

Asymmetric forebody vortex bursting occurred on both

diamond wing configurations even though photographs

of this effect were only presented for the 40 ° diamond

wing configuration. These asymmetric vortical flows

could produce control problems; therefore, their location

and behavior are significant. The forebody vortices exist

for angles of attack up to at least 50 ° on the diamond

wing configurations, and thus they explain the reduced

poststall lift loss for these configurations compared with

the delta planforms. The simulated balance housing generally did not affect the vortical flows on any of the

configurations except the 30 ° diamond wing. On this

configuration, the shape of the vortices as well as the

vortex burst location were influenced by the simulated

balance housing only for angles of attack up to 20 °.

Twin Bodies and Double Wings

Because twin bodies and double wings produced

additional vortices in the flow fields, these configurations were of significant interest in this investigation.

Two additional 30 ° diamond wing configurations were

tested; one had twin bodies and one had twin wings. An

additional double-wing configuration, referred to as the

60 ° double arrow, was also tested. Lift coefficient versus

angle-of-attack data are presented in figure 14 for these

configurations, and flow visualization photographs are

presented in figures 15 to 17. The wind tunnel data indicate improvements in lift caused by the twin bodies and

double wings when compared with the original 30 ° diamond wing configuration.

The flow visualization photographs for the 30 ° diamond wing with twin-body configuration indicate

vortical flows on each forebody and wing at an angle of

attack of l0 ° (fig. 15(a)). The wing vortex wraps up and

around the outboard forebody vortex. This effect is

unlike that of the 30 ° diamond wing where the wing and

forebody vortices stay independent at an angle of attack

of 10 ° (fig. 12(a)). Evidence is also present (figs. 15(a)

and 15(b)) which indicates that the inboard vortices from

each forebody flow directly into the simulated balance

housing. This is evident in both the top- and side-view

photographs. No testing was conducted with the simulated balance housing removed; therefore, no direct comparisons can be made. At an angle of attack of 20 °, the

vortical flows are still similar to the case in which the

angle of attack equals 10°; however, now the outboard

forebody vortices are bursting near the wing trailing

edge. In addition, the side-view photograph (fig. 15(d))

indicates that the inboard forebody vortices are now

much higher above the model surface than the outboard

forebody vortices. This may be due to the simulated balance housing.

When angle of attack is increased to 35 °, the forebody vortices burst either on the forebody or near the

back of the forebody, and no wing vortices appear to be

present. Asymmetric forebody bursting is now seen on

each forebody, and the vortices are observed to burst

anywhere from halfway down the forebody to just in

front of the simulated balance housing. Typically the outboard vortices tend to burst farther upstream than the

inboard vortices; however, longitudinal movement of all

forebody vortex bursting does take place over time.

Two flow visualization photographs are presented at

an angle of attack of 35 ° to identify the presence of the

two classic types of vortex bursting. These two types of

vortex bursting, as defined and described in reference 21,

are referred to as bubble-type and spiral-type bursting.

The first photograph presented for the twin-body configuration at an angle of attack of 35 ° (fig. 15(e)) has

bubble-type vortex bursting on the outboard vortices of

each forebody. In the following photograph (fig. 15(f)), a

classic example of spiral-type vortex bursting is noted on

the outboard side of the left-hand forebody. The inboard

forebody vortices (shown in both photographs) generally

burst in a manner that is a combination of the two types.

Throughout the investigation, forebody vortex bursting

would slowly oscillate between these two types on every

configuration with this 80 ° swept forebody.

At an angle of attack of 50 °, forebody vortices are

still present; however, now vortex bursting occurs when

the vortices are approximately one-third of the way down

the forebody. These vortices stay relatively close to the
forebodyuntilburstingoccurs,asnotedintheside-view

photograph(fig.15(i)).

Thepresenceof four forebody vortices on the twinbody configuration at angles of attack up to 50 ° will generate more lift than that generated by the single set of

vortices on the 30 ° diamond wing with only one forebody. This would explain why the twin-body configuration generates a greater lift coefficient than the 30 °

diamond wing configuration at all angles of attack

greater than 20 °.

Flow visualization photographs for the 30 ° diamond

twin wing are presented in figure 16. Dye injection tubes

were again located at the forebody apex as well as at the

inboard leading edge of both wings. In addition, dye

injection tubes were also placed at the wing tips of the

forward wing.

When examining the flow visualization photographs

obtained at an angle of attack of 10 ° (fig. 16(a)), strong

forebody vortices extend down the configuration, with

bursting not taking place until aft of the trailing edge of

the forward wing. The forward wing vortex wraps up and

around the forebody vortices, while the aft wing vortex

stays independent. The dye injection tube located at the

inboard leading edge of the aft left wing was not placed

in the appropriate location for the dye to get caught in the

wing vortex; therefore, this dye does not show any significant flow characteristics at any of the angles of attack

presented. At an angle of attack of 20 ° (fig. 16(b)), the

flow patterns are similar to those noted at an angle of

attack of 10% however, now the forebody vortices are

bursting at the trailing edge of the forward wing. At an

angle of attack of 35 ° (fig. 16(c)), the forebody vortices

are bursting just aft of the forward wing leading edge,

thus hindering the formation of the vortices on the forward wing, or forward wing vortices may not be present

at this angle of attack. The aft wing vortices, however,

are still present, probably because of the reduced incidence as a result of the forward wing downwash. The

presence of these vortices indicates that the aft wing is

still producing considerable lift, and thus explains the

greater CLr_ produced by the 30 ° diamond twin wing

compared with the 30 ° diamond wing. At an angle of

attack of 50 °, only the forebody vortices still exist, with

bursting occurring approximately halfway down the forebody. The dye injected at the tips of the forward wing did

not reveal any significant flow characteristics at any

angle of attack.

A second double-wing configuration, referred to as

the 60 ° double arrow, was tested, and flow visualization

photographs for this configuration are presented in figure 17. Colored dye was injected in the usual forebody

apex and forward wing inboard leading-edge locations.

In addition, colored dye was injected at the wing tips and

at the inboard trailing edge of the forward wing.

At angles of attack of 10 ° and 20 °, strong forebody

vortices extend over the length of the configuration. In

both cases, the forward wing vortices roll over and

around the forebody vortices, and this combined vortex

pair flows over the aft, inboard portion of the space

between the two wings. In addition, an upward flow

exists in the space between the two wings. This upward

flow is most easily noted in the side-view photograph

presented for an angle of attack of 20 ° (fig. 17(t)). In this

photograph, the forebody vortex cores move abruptly

away from the upper surface of the model as they flow

aft over the space between the two wings. At an angle of

attack of 35 ° (fig. 17(g)), the forebody vortices burst at a

location approximately halfway between the leading and

trailing edges of the forward wing, thus hindering the

formation of the wing vortices as the colored dye from

this location rolls around the bursting forebody vortices.

At an angle of attack of 50 °, once again only the forebody vortices exist. The photographs that show the configuration with the simulated balance housing removed

indicate that the housing had essentially no effect on the

vortical flows across the angle-of-attack range presented.

The results of the twin-body and double-wing portion of the investigation indicate that the vortices that

form on the twin forebodies and double wings would add

additional lift when compared with the single component, 30 ° diamond wing configuration. The existence of

wing vortices on the aft wing of the 30 ° diamond twinwing configuration is probably enhanced because of the

aft wing being in the downwash from the forward wing.

This downwash effectively reduces the local angle of

attack of the aft wing, thereby allowing it to maintain its

lift-generating ability to a higher overall model angle of

attack. The simulated balance housing interfered with the

inboard forebody vortices on the 30 ° diamond wing with

twin-body configuration for angles of attack up to 20 ° .

No simulated balance housing effects were found, however, for the double-wing configurations.

Cutout Wings

The effects of wing cutouts were another area of

interest in which flow visualization was expected to provide valuable insight into understanding the flow physics. Lift coefficient versus angle-of-attack data are

presented in figure 18 for the original 30 ° diamond wing

configuration as well as for two cutout-wing configurations. The cutout-wing configurations consist of a planform with a triangular cutout shape and one with a

diamond cutout shape. Both these cutout shapes are

equal in area so that the effects of cutout shape alone

could be examined. The aerodynamic data presented

7
indicate that lift increases across the angle-of-attack

range for both cutout configurations over the original 30 °

diamond wing; however, the diamond cutout shape is the

most effective.

Flow visualization photographs have been obtained

for the 30 ° diamond with triangular cutout configuration

with and without the simulated balance housing, and they

are presented in figure 19. Colored dye was injected at

the usual forebody apex and inboard wing leading-edge

locations in addition to the forward inboard corner and

outboard corner of the cutout. At an angle of attack of

10% forebody vortices extend the length of the configuration, while they always maintain a position inboard of the

wing cutouts. The wing vortices extend across the forward portion of the wing; however, bursting occurs as

they cross over the outboard portion of the cutout region.

When compared with the 30 ° diamond wing at an angle

of attack of l0 ° (fig. 12(a)), differences in the flow patterns caused by the wing cutout are noted. The cutout

appears to cause the wing vortices to burst sooner, and it

also causes the forebody vortices to sit farther inboard

over the wing portion of the configuration.

At an angle of attack of 20 ° (fig. 19(c)), the wing and

forebody vortices now progress farther outboard over the

wing portion of the configuration, as compared with the

conditions noted at an angle of attack of 10% The wing

vortices no longer flow into the cutout region; however,

now the forebody vortices do flow over the aft inboard

portion of the cutout region. This phenomenon is very

different from how the wing and forebody vortices roll

together on the original 30 ° diamond wing configuration

(fig. 12(d)).

At an angle of attack of 30 ° (fig. 19(e)), the forebody

vortices now burst in the region between the wing leading edge and the cutout, thus tending to disrupt the wing

vortices similar to the effect that occurred on the noncutout configuration. At an angle of attack of 35 °, the

wing and forebody vortices behave similar to the way

they behaved on the original 30 ° diamond wing. The

forebody vortex bursting at the intersection of the forebody with the wing leading edge appears to drive the

wing vortex outboard, and the two vortices have no further interaction. As mentioned previously for the 30 ° diamond wing, at angles of attack of 30 ° and 35 °, wing

vortices could be present, but their actual existence is

inconclusive. At an angle of attack of 50 ° , the flow pattern is again similar to that on the original 30 ° diamond

wing.

The photographs obtained with the simulated balance housing removed indicate that the housing may or

may not interfere with the vortical flows, depending on

angle of attack. When the angle of attack is t0 ° or 30 °,

no obvious effects caused by the balance housing are

indicated. However, at an angle of attack of 20 °, the simulated balance housing appears to affect the vortical

flows (figs. 19(c) and 19(d)). When the simulated balance housing is on the configuration at this angle of

attack, the wing vortices flow outboard and away from

the forebody vortices. However, when the simulated balance housing is removed, the wing vortices flow aft and

interact with the forebody vortices. This phenomenon

also tends to draw the forebody vortices farther inboard.

The colored dye that was injected in the inboard and

outboard regions of the cutout did not reveal any additional significant flow characteristics at any of the angles

of attack presented.

Flow visualization photographs for the 30 ° diamond

with diamond cutout configuration are presented in

figure 20. Colored dye was injected in the same forebody

and wing locations as before; however, in the cutout

region, dye was injected at the most inboard and most aft

locations.

The photograph that shows the flow conditions at an

angle of attack of 10 ° (fig. 20(a)) indicates similar trends

to those noted for the 30 ° diamond with triangular cutout.

The forebody vortices extend the length of the configuration while they maintain a position inboard of the wing

cutouts. The forebody vortices move progressively outboard as they flow downstream over the configuration;

however, the cutout acts to redirect the vortices so that

they stay inboard of the cutout region rather than flow

over it. Once again the cutout region appears to cause the

wing vortices to burst sooner than they did on the original 30 ° diamond wing.

At an angle of attack of 20 ° (fig. 20(b)), the wing

vortices wrap over and around the forebody vortices similar to the way that was noted on the 30 ° diamond wing

configuration. A new flow condition, however, is also

noted. The dye that is injected at the inboard corner of

the cutouts reveals the existence of a vortex that flows aft

and outboard over the remainder of the wing.

At angles of attack of 30 ° and 35% the forebody vortices burst near the junction of the wing leading edge and

the forebody, thus hindering the development of the wing

vortices and also preventing the wing vortices from rolling around the forebody vortices. As before, this condition assumes that wing vortices are present at these

conditions. The vortices that form at the inboard corner

of the wing cutouts are still present. These cutout vortices are probably the reason why the 30 ° diamond with

diamond cutout configuration produces a greater CLm _

than the triangular cutout-wing configuration. The cutout

vortices produce a smoother, more well-behaved flow on

the aft inboard portion of the wing than would be present

without the vortices. Thus it appears that when the aft

$
edgeof thecutoutis sweptinthesamedirectionasthe

wingleading-edge, vorticesfromthecutoutareformed.

Onceagaintheforebodyvorticesarestill presentat

anangleof attackof 50° (fig.20(e)),andthebursting

occursapproximatelyhalfwaydowntheforebody.

Theresultsof thecutout-wingportionof theinvestigationindicatethatwingcutoutscansignificantly

alterthevortexstructureovertheconfiguration.Forebodyvorticeswill tendtobeshiftedinboardbecauseof

thewing cutout,whilewingvorticesmayburstprematurelywheninteractingwiththecutoutregion.The

diamond-shaped cutoutwill generateanadditionalvortexaftonthewing;thisvortexis notgeneratedby the

triangular-shaped cutout.Theadditionalvortexproduces

amorefavorableflowconditionontheaft,inboardportionof the30° diamondwithdiamondcutoutconfiguration,andthusexplainswhythisconfigurationgeneratesa

greaterCLm_ ,.

Serrated Forebodies

The final phase of the investigation was focused on

illustrating the effects of serrated forebodies. Lift coefficient versus angle-of-attack data are presented for the

serrated-forebody configurations in figure 21. Data for

the original configurations, which were modified to produce the serrated-forebody configurations, are also presented for comparison purposes. Aerodynamic data,

however, were not obtained for the 40 ° diamond with

3 diamond sawteeth and nose tip configuration.

The 65 ° delta with delta sawteeth configuration was

generated by adding a 65 ° swept serrated forebody to the

65 ° delta wing. Dye was injected at the apex of the configuration and at the inboard corner of each of the three

serrations. Flow visualization photographs, which are

presented in figure 22, were obtained both with and without the simulated balance housing.

The first set of photographs presented are for the

configuration at an angle of attack of 12 °. Photographs

were taken at this angle of attack, as opposed to 10°,

because an angle of attack of 10 ° was not high enough

for a vortex to form off each serration. This in turn

resulted in poor flow visualization. At an angle of attack

of 12 °, however, a vortex does form at each serration,

and as shown in the photograph, all the vortices on each

side of the configuration tend to wrap around one

another.

At an angle of attack of 20 ° (fig. 22(c)), the cores of

the apex vortices are shown to extend the entire length of

the configuration, and the vortices from the other serrations appear to roll right into the apex vortices. At an

angle of attack of 30 °, the same trend continues with all

the vortices rolling into one; however, now vortex bursting begins to occur before the trailing edge of the

configuration.

At an angle of attack of 50 ° (fig. 22(h)), vortices still

appear to form at each serration. The apex vortices are

clearly present; however, they now burst before they

reach the end of the first serration. Vortex development

is now more difficult to identify on the downstream

serrations.

When the photographs with and without the simulated balance housing are compared, no evidence is indicated that the simulated balance housing affects the

vortex structure or location at any of the angles of attack

presented.

Photographs for the 40 ° diamond with 3 diamond

sawteeth configuration are presented in figure 23. Dye

was injected at the apex and the inboard comer of each of

the three sawteeth, just as it was for the 65 ° delta with

delta sawteeth configuration. The photographs, which

illustrate the flow conditions at an angle of attack of 10%

indicate that vortices are beginning to form on the second

and third sets of sawteeth and on the main wing. At this

angle of attack, however, the vortices on the sawteeth are

not well defined. Also at this angle of attack, the dye

injected at the apex was flowing under but not over the

configuration so that no flow over the first set of sawteeth was visualized.

At an angle of attack of 20 ° (fig. 23(b)), separated

flow is indicated by the dye injected at the apex over the

first set of sawteeth, while vortices are indicated on the

second and third sets of sawteeth and on the main wing.

Each of these vortices appears to stay independent as it

flows downstream over the configuration.

The vortices on the second and third sets of sawteeth

and on the main wing appear stronger and more well

defined at angles of attack of 30 ° and 35 ° than they did at

an angle of attack of 20 °. Once again these vortices stay

independent as they flow over the model. (See

figs. 23(c) through 23(e).) This independence is clearly a

different vortex flow behavior than the way all the vortices roll together on the 65 ° delta with delta sawteeth configuration. The independent nature of the vortices from

the diamond sawtooth forebody appears to affect a significant region of the flow over the main wing, thus probably preventing flow separation on the aft part of the

configuration and accounting for the significant lift

increases noted in the data presented in figure 21. In

addition, the wing vortices on the diamond sawtooth configuration are much more well defined than those on the

40 ° diamond wing configuration. (See figs. 13(f) through

130). ) This better vortex definition may be caused by the

absence of the forebody vortices bursting in close proximity to the wing vortices as is the case for the 40 °

9
diamondwing configuration. It may also be due to a

lower effective wing incidence caused by the downwash

field from the upstream vortices generated by the

sawteeth.

At an angle of attack of 35 ° (fig. 23(e)), note that the

wing vortices are asymmetric. It appears that the vortex

on the right wing has begun to lift off the surface, but the

vortex on the left wing has not, which suggests that at an

angle of attack of 35 °, the wing vortex breakdown is

beginning to occur.

At an angle of attack of 50 ° (fig. 23(0), the flow is

still separated over the first set of sawteeth; however,

vortices do still exist over the second and third sets of

sawteeth and the main wing. The presence of these vortices continues to produce lift improvements when compared with the 40 ° diamond wing configuration, as

illustrated by the data of figure 21.

The 40 ° diamond with 3 diamond sawteeth configuration has effectively generated multiple vortices that

have improved the lift characteristics by significantly

increasing CL_,. The first set of sawteeth, however, was

not effective across the angle-of-attack range. Therefore,

to improve the effectiveness, a nose tip was added to the

40 ° diamond with 3 diamond sawteeth configuration (as

illustrated in fig. 8(c)), and a final set of flow visualization photographs was obtained. These photographs are

presented in figure 24.

At an angle of attack of 10°, vortices are visible on

the nose tip and the main wing; however, as before, the

vortices on the sawteeth are not well defined. At an angle

of attack of 20 °, the vortices on the second and third sets

of sawteeth become more defined, but the bursting of the

nose tip vortices may affect the formation of the vortices

on the second set of sawteeth.

At angles of attack of 30 ° and 35 ° (figs. 24(c)

through 24(e)), all the vortices are well defined and exist

independently. The nose tip vortices now burst before

they can interfere with the formation of the vortices on

the second set of sawteeth. The location of the nose tip

vortices certainly suggests that they would improve the

flow condition over the first set of sawteeth as compared

with the configuration with no nose tip.

Although the nose tip vortices burst before they

reach the second set of sawteeth at angles of attack of 30 °

and 35 °, the nose tip vortices still affect the vortices on

the second set of sawteeth. This effect is clear when the

photographs with and without the nose tip are compared

at these angles of attack. The vortices on the second set

of sawteeth are located farther inboard on the configuration with the nose tip than they are on the configuration

without the nose tip. The vortices on the third set of sawteeth are located in the same position on the configuration whether the nose tip is on or not.

Finally at an angle of attack of 50 ° (fig. 24(f)), all the

vortices are still present and exist independently on the

configuration with the nose tip. Since the nose tip vortices are still present, it is implied that this configuration

would have better lift characteristics at this angle of

attack than the configuration without the nose tip.

The results of the serrated-forebody portion of the

investigation indicate that multiple vortices can be generated on a configuration by a serrated forebody. The vortices generated by the 65 ° delta sawtooth forebody tend to

roll together as they flow over the configuration, whereas

the vortices generated by the diamond sawtooth forebody

tend to stay more independent. The more independent

nature of the diamond sawtooth vortices is probably the

cause for the significant lift improvement that is generated when the diamond sawtooth forebody is added to the

40 ° diamond wing configuration. The addition of a nose

tip to the diamond sawtooth forebody eliminates the separated flow condition that would otherwise exist on the

fLrst set of diamond sawteeth and thus further improves

the flow characteristics over the 40 ° diamond with

3 diamond sawteeth configuration.

Summary of Results

The results of a flow visualization investigation of

12 different planforms tested in the Langley 16- by

24-Inch Water Tunnel are summarized as follows:

1. As expected, the formation of strong vortices on

highly swept forebodies will improve poststall lift

characteristics. The asymmetric bursting of these vortices, however, could produce substantial control

problems.

On the configurations where the effects of the balance

housing were investigated, it was found that the simulated balance housing did affect the vortex structure

on the 30 ° diamond wing, the 30 ° diamond wing with

twin body, and the 30 ° diamond with triangular cutout. These effects, however, were only noted at angles

of attack of 20 ° and below.

The vortices that form on the additional forebody and

the wings of the twin-body and double-wing configurations would account for the lift increases noted

when these configurations are compared with the

single-component configuration.

For the cutout-wing configurations investigated, it was

found that a wing cutout can significantly alter the

vortex structure over a configuration. Specifically,

forebody vortices are shifted inboard in the vicinity of

a wing cutout. The formation of a vortex over the

.

.

.

10
inboard portion of the wing aft of a diamond-shaped

cutout explains why this cutout shape generates a

greater maximum lift than a triangular-shaped cutout.

5. Serrated forebodies will effectively generate multiple

vortices over a configuration. Vortices from a 65 °

delta sawtooth forebody will roll together, while vortices from a 40 ° swept diamond sawtooth forebody will

stay more independent. The addition of a highly swept

nose tip to a 40 ° swept diamond sawtooth forebody

will improve flow conditions by producing vortical

flows over the first set of sawteeth, which would otherwise generate a separated flow.

NASA Langley Research Center

Hampton, VA 23681-0001

August 21, 1995

References

1. Chambers, Joseph R.: High-Angle-of-Attack Technology--

Progress and Challenges. High-Angle-of-Attack Technology,

Volume I, Joseph R. Chambers, William P. Gilbert, and Luat T.

Nguyen, eds., NASA CP-3149, Part 1, 1992, pp. 1-22.

2. Murri, Daniel G.; Biedron, Robert T.; Erickson, Gary E.;

Jordan, Frank L., Jr.; and Hoffler, Keith D.: Development of

Actuated Forebody Strake Controls for the F-18 High Alpha

Research Vehicle. High-Angle-of-Attack Technology, Volume I, Joseph R. Chambers, William P. Gilbert, and Luat T.

Nguyen, eds., NASA CP-3149, Part 1, 1992, pp. 335-380.

3. Erickson, Gary E.; and Murri, Daniel G.: Forebody Strakes for

High-Angle-of-Attack Vortex Flow Control: Mach Number

and Strakes Planform Effects. High-Angle-of-Attack Technology, Volume I, Joseph R. Chambers, William P. Gilbert,

and Luat T. Nguyen, eds., NASA CP-3149, Part 1, 1992,

pp. 381-480.

4. Mum, Daniel G.; and Ran, Dhanvada M.: Exploratory Studies

of Actuated Forebody Strakes for Yaw Control at High Angles

of Attack. AIAA-87-2557, Aug. 1987.

5. Malcolm, Gerald N.; Ng, T. Terry; Lewis, Liane C.; and Murri,

Daniel G.: Development of Non-Conventional Control Methods for High Angle of Attack Flight Using Vortex Manipulation. Technical Papers--7th AIAA Applied Aerodynamics Conference, 1989, pp. 249-267. (Available as AIAA-89-2192.)

6. Ng, T. Terry; and Malcolm, Gerald N.: Aerodynamic Control

Using Forebody Vortex Control. High-Angle-of-Attack Technology, Volume I, Joseph R. Chambers, William P. Gilbert,

and Luat T. Nguyen, eds., NASA CP-3149, Part 1, 1992,

pp. 507-531.

7. Ng, T. Terry; and Malcolm, Gerald N.: Aerodynamic Control

Using Forebody Blowing and Suction. AIAA-91-0619,

Jan. 1991.

8. White, E. Richard: Effects of Suction on High-Angle-ofAttack Directional Control Characteristics of Isolated Forebodies. High-Angle-of-Attack Technology, Volume I, Joseph R.

Chambers, William P. Gilbert, and Luat T. Nguyen, eds.,

NASA CP-3149, Part 1, 1992, pp. 533-556.

9. Schreiner, John A.; Erickson, Gary E.; and Guyton, Robert W.:

Application of Tangential Sheet Blowing on the Forebody of

an F-18-Like Configuration for High-Angle-of-Attack Maneuverability. High-Angle-of-Attack Technology, Volume I1,

Joseph R. Chambers, William P. Gilbert, and Luat T. Nguyen,

eds., NASA CP-3150, 1992, pp. 1-25.

10. Roberts, Leonard; Tavella, Domingo A.; and Celik, Zeki: Controlled Vortex Flows Over Forebodies and Wings. High-Angleof-Attack Technology, Volume I, Joseph R. Chambers,

William P. Gilbert, and Luat T. Nguyen, eds., NASA CP-3149,

Part 2, 1992, pp. 659_571.

11. Bauer, Steven X. S.; and Hemsch, Michael J.: Alleviation of

Side Force on Tangent-Ogive Forebodies Using Passive

Porosity. A1AA-92-2711, June 1992.

12. Wood, Richard M.; Banks, Daniel W.; and Bauer,

Steven X. S.: Assessment of Passive Porosity With Free and

Fixed Separation on a Tangent Ogive Forebody. AIAA-92-

4494, Aug. 1992.

13. Modi, V. J.; and Stewart, A. C.: Approach to Side Force

Alleviation Through Modification of the Pointed Forebody

Geometry. Technical Papers---AIAA Atmospheric Flight

Mechanics Conference, 1990, pp. 349-358. (Available as

AIAA-90-2834.)

14. Gatlin, Gregory M.; and McGrath, Brian E.: Low-Speed Longitudinal Aerodynamic Characteristics Through PoststaU for

Twenty-One Novel Planform Shapes. NASA TP-3503, 1995.

15. Gloss, B. B.: Effect of Wing Planform and Canard Location

and Geometry on the Longitudinal Aerodynamic Characteristics of a Close-Coupled Canard Wing Model at Subsonic

Speeds. NASA TN D-7910, 1975.

16. Yip, L. P.; and Paulson, John W., Jr.: Effects of Deflected

Thrust on the Longitudinal Aerodynamic Characteristics of a

Close-Coupled Wing-Canard Configuration. NASA TP-1090,

1977.

17. Paulson, John W., Jr.; and Thomas, James L.: Summary of

Low-Speed Longitudinal Aerodynamics of Two Powered

Close-Coupled Wing-Canard Fighter Configurations. NASA

TP-1535, 1979.

18. Erickson, G. E.: Vortex Flow Correlation. AFWAL-TR-80-

3143, U.S. Air Force, Jan. 1981. (Available from DT1C as

AD AI08 725.)

19. Pendergraft, Odis C., Jr.; Neuhart, Dan H.: and Kariya,

Timmy T.: A User's Guide to the Langley 16- by 24-1nch

Water Tunnel. NASA TM-104200, 1992.

20. Ayoub, A.; and McLachlan, B. G.: Slender Delta Wing at High

Angles of Attack--A Flow Visualization Study. AIAA-87-

1230, June 1987.

21. Payne, F. M.; and Nelson, R. C.: An Experimental Investigation of Vortex Breakdown on a Delta Wing. Vortex Flow Aerodynamics, Volume 1, J. E Campbell, R. F. Osborn, and

J. T. Foughner, Jr., eds., NASA CP-2416, 1986, pp. 135-161.

11
Table I. Geomewic Characteristics of Planform Models

1

2

3

4

5

6

7

8

9

10

11

12

Planform description

55 ° delta wing

65 ° delta wing

30 ° diamond wing

40 ° diamond wing

30 ° diamond wing with twin body

30 ° diamond twin wing

60 ° double arrow

30 ° diamond with triangular cutout

30 ° diamond with diamond cutout

65 ° delta with delta sawteeth

Reference area S, ft 2

0.3236

0.3236

0.3140

0.3565

Reference length c, in.

8.16

10.190

11.90

13.67

Reference span b, in.

11.42

9.32

11.80

10.52

0.3421

0.2942

0.3067

0.2909

0.2909

0.3696

11.33

12.89

14.96

11.90

11.90

13.56

11.80

8.34

7.36

I 1.80

11.80

9.32

40 ° diamond with 3 diamond sawteeth 0.3998 13.67 10.52

40 ° diamond with 3 diamond sawteeth 0.4012 14.67 10.52

and nose tip

Table II. Presentation of Results

1

2

3

4

5

6

7

8

9

10

11

12

Figurein which lift coefficient Figureinwhich flow

data are presented visu_ization is presented

55 ° 9 10

65 ° 9,21 11

30 ° 9,14,18 12

40 °

30 °

9,21 13

14 15

30 ° 14 16

60 ° 14 17

Planform description

delta wing

delta wing

diamond wing

diamond wing

diamond wing with twin body

diamond twin wing

double arrow

diamond with triangular cutout

diamond with diamond cutout

delta with delta sawteeth

diamond with 3 diamond sawteeth

diamond with 3 diamond sawteeth

nose tip

30 ° 18

30 ° 18

65 ° 21

40 ° 21

40 ° Not obtained

and

19

2O

22

23

24

12
Figure1. Langley16-by24-InchWaterTunnel.

L-87-03479

Dye tube -_

Dye tube attached to underside of model

Free-stream direction flow

Top of model

Pitch drive

slot

Offset sting

Slider block

Pitch arc

Lead screw

Figure 2. Offset model support system used in Langley 16- by 24-Inch Water Tunnel.

13
Simoate00a,ance so 400

I

20 °

Section A-A

, , I_°.s°_°

o.85_J _ -3/_o.5o 8.16

0.25

11.42

_----- -_S "r- I 1.00

ting

(a) 55 ° delta wing.

Figure 3.

4.00

Simulated balance housing _ i--

_I_

l 0.85 ----.--I I_

0.25

20 °

Section A-A

10.00 "-

-5

Sting

I 1.00

(b) 65 ° delta wing.

Side- and bottom-view sketches of delta-wing configurations. All linear dimensions are given in inches.

14
Simulated balance housing

Section A-A

- 11.90

- 8.50 -I

- 5.67 • A_/A_,_n '

I// \'£y _

, _._7_ -- --i--_-- --, - _--

tmg

(a) 30 ° diamond wing.

1.00

11.80

Figure 4.

Simulated.......=balance housing _--_L

0.50

13.67

9.25 -I

I

A

1.00

I1.00

Sting

(b) 40 ° diamond wing.

Side- and bottom-view sketches of diamond-wing configurations. All linear dimensions are given in inches.

15
Simulated balance housing _ I 5°_

• -._.._j,t__TO.5 o

_._._- ._-- _ _ __

--5.67-- 30° A

20.0_/_._.. _ _- Sting 11/80

Section A-A

Figure 5. Side- and bottom-view sketches of 30 ° diamond wing with twin-body configuration. All linear dimensions are

given in inches.

16
Simulated balance housing _ 5 °

20"0°/1. j

Section A-A

12.89

10.49

8.99

7.5o •I

1

3.18

f

(a) 30 ° diamond twin wing.

I1.00

8.34

Simulated balance housing ___3_i__L__ r

3/L___o.5o

14.96

12.19 1

11.51--

lO.31--

912--- I 1 I _ -Cut°ut

8_ 1" _ area

5 67 --------_ 3.68 ,,I,'V/ I _1"4,__ 60 °_

o 1.00 I,,>"L_T_ t.___A,_-_ -0.62

20 0 °/d _\ ._// "_ Sting

/U Cutout

Section A-A area

I1.00

(b) 60 ° double arrow.

Figure 6. Side- and bottom-view sketches of double-wing configurations. All linear dimensions are given in inches.

17
Simulated balance housing

----_.f__

I ! i

11.90

10.04

8.50

6.96

5.67 --

1.00 I-0.64 7X

Cutout

area / \

_-- Sting

11.80

(a) Side and bottom view of original 30 ° diamond cutout wing.

11.90

10.04

8.50

Original planform

6.96

Cutout area

80 °

5.67

Cutout areaOriginal planform

11.80

:; 1//

i_,/

/

(b) Planform of 30 ° diamond with triangular cutout.

Figure 7. Sketches of 30 ° diamond cutout-wing configurations. All linear dimensions are given in inches.

18
11.90

8.50

Cutout area -_

Original

5.67

Original

Cutout area

7.80

I 11.80

(c) Planform of 30 ° diamond with diamond cutout.

Figure 7. Concluded.

19
13.56

1.89, 1.89 /-_65 °

All leading_

are 65 ° from vertical J _--\ Original planf _orm_

(a) 65 ° delta with delta sawteeth.

13.67

9.25 -1

5.67

'_' _' :o_,oo/ \

are40°fr°mvertical _ _ / 10.52

Original planform -_ _

(b) 40 ° diamond with 3 diamond sawteeth.

Figure 8. Planform sketches of serrated-forebody configurations. All linear dimensions are given in inches.

2O
13.67

9.25 I

5.67

_oo-_-__°l ,o;h_oo/ \ o

,.°° ° __ -_.-._.

All sawtooth edges _ /

are 40 ° frOmoii_irti_ilplanform _ \_ 10.52,

(c) 40 ° diamond with 3 diamond sawteeth and nose tip.

Figure 8. Concluded.

21
.8

C L .6

.4

.2

0

Figure 9.

55 ° delta wing

65 ° delta wing

_<_-- 30 ° diamond wing

40 ° diamond wing

10 20 30 40 50 60 70

e_, deg

Lift coefficient versus angle of attack for delta and diamond wings (ref. 14).

22
(a) Top view; ot = 10°.

Figure 10. Photographs of 55 ° delta wing.

23
(b) Side view; _ = 10 °.

Figure 10. Continued.

24
(c) Topview;t_ = 20 °.

Figure 10. Continued.

25
(d) Sideview;t_ = 20 °.

Figure 10. Continued.

26
.......3 ! ̧!

(e)Topview;o_= 25°.

Figure10.Continued.

2"/
(f) Sideview;ct = 25 °.

Figure 10. Continued.

28
(g) Topview;a = 35°.

Figure10.Continued.

29
(h) Sideview;o_= 35°.

Figure10.Continued.

3O
(i) Topview;t_ = 50 °.

Figure 10. Continued.

31
(j) Sideview;_ = 50°.

Figure10.Concluded.

32
(a) or= 10%

Figure 11. Top-view photographs of 65° delta wing.

33
(b) Simulated balance housing removed; tx = 10°.

Figure 11. Continued.

34
(c) tx = 20 °.

Figure 11. Continued.

35
(d) Simulated balance housing removed; tx = 20 °.

Figure 11. Continued.

36
(e) _ = 30 °.

Figure 11. Continued.

37
(f) Simulated balance housing removed; ot = 30 °.

Figure 11. Continued.

38
(g) a = 35°.

Figure11.Continued.

39
(h) Simulated balance housing removed; _ = 35 °.

Figure 11. Continued.

4O
(i) _ = 50°.

Figure 11. Continued.

41
(j) Simulatedbalancehousingremoved;t_ = 50 °.

Figure 11. Concluded.

42
l

/

(a) Top view; ot = 10 °.

Figure 12. Photographs of 30 ° diamond wing.

43
/

i _i_i_•_i_  ̧

(b) Simulated balance housing removed; top view; tx = 10 °.

Figure 12. Continued.

44
ii_iiiiiiiiii_i

iiiiiii!ii!iii,!!i

(c) Side view; t_ = 10°.

Figure 12. Continued.

45
(d) Top view; t_ = 20 °.

Figure 12. Continued.

46
J

(e) Simulated balance housing removed; top view; ot = 20 °.

Figure 12. Continued.

47
(f) Side view; t_ = 20 °.

Figure 12. Continued.

48
o

(g) Top view; tx = 30 °.

Figure 12. Continued.

49
(h) Simulatedbalance housing removed; top view; tx = 30 °.

Figure 12. Continued.

5O
(i) Side view; ¢t = 30 °.

Figure 12. Continued.

51
_ i_!_!_i_i!i_!_i_i!i!iiii!i_!!_!_!i_!i!_i!!_i_i!i_i_i_i!i_i!!ii!_i_!i!_ii_i_ _

(j) Top view; _x= 35 °.

Figure 12. Continued.

52
(k) Simulatedbalancehousingremoved;topview;tx = 35°.

Figure 12. Continued.

53
(1) Side view; t_ = 35 °.

Figure 12. Continued.

54
55
(n) Side view; t_ = 50 °.

Figure 12. Concluded.

56
(a) Top view; _ = 10 °.

Figure 13. Photographs of 40 ° diamond wing.

57
(b) Simulatedbalancehousingremoved;topview;o_= 10°.

Figure13.Continued.

58
(c) Top view; tx = 20 °.

Figure 13. Continued.

59
(d) Simulated balance housing removed; top view; tx = 20 °.

Figure 13. Continued.

6O
iiii_i_ii!i!_!iii!iiiii_iiiiiii!i

(e) Side view; t_ = 20 °.

Figure 13. Continued.

61
(f) Symmetric forebody vortex bursting; top view; _ = 30 °.

Figure 13. Continued.

62
(g) Left-hand forebody vortex bursts first; top view; ot = 30 °.

Figure 13. Continued.

63
(h) Right-handforebodyvortexburstsfirst;topview;o_=30°.

Figure13.Continued.

64
(i) Simulated balance housing removed; top view; tx = 30 °.

Figure 13. Continued.

65
iii_ii_ii_ii!i!ii

(j) Topview;_ = 35".

Figure13.Continued.

66
(k) Topview;_ = 50°.

Figure13.Concluded.

67
1.4

1.2

1.0

i i i

--0-- 30 ° diamond wing

30 ° diamond wing with twin body

30 ° diamond twin wing

60 ° double arrow

.8

C L .6

.4

.2

0

-.2

0 10 20 30 40 50 60 70

_,deg

Figure 14. Li_ c_fficient versus angle of attack _r twin-_dy _d double-wing configurations (ref. 14).

68
_J

_ i_I

(a) Top view; ot = 10 °.

Figure 15. Photographs of 30 ° diamond wing with twin body.

69
(b) Side view; tx = 10°.

Figure 15. Continued.

7O
ii_iil

!iii!il

/

o

(c) Top view; tx = 20 °.

Figure 15. Continued.

71
(d) Side view; t_ = 20 °.

Figure 15. Continued.

72
Bubble-type

vortex bursting

i !i:iii i

(e) Bubble-type vortex bursting; top view; o¢= 35°.

Figure 15. Continued.

73
Spiral-type

vortex bursting

siiiii!iiiiiiiiiiiiii!iiiiil,iiiiii_i_i

(f)

35 ̧

Spiral-type vortex bursting; top view; o_= 35 °.

Figure 15. Continued.

74
(g) Sideview;tx = 35 °.

Figure 15. Continued.

75
(h) Top view; tx = 50 °.

Figure 15. Continued.

76
!iiii!i i

(i) Side view; o_= 50 °.

Figure 15. Concluded.

77
\

IiO

(a) _x= 10 °.

Figure 16. Top-view photographs of 30 ° diamond twin wing.

78
(b) o_ = 20 °.

Figure 16. Continued.

79
(c) t_ = 35 °.

Figure 16. Continued.

8O
\

(d) ot = 50 °.

Figure 16. Concluded.

81
/

/

/

(a) Top view; et = 10 °.

Figure 17. Photographs of 60 ° double arrow.

82
(b) Simulated balance housing removed; top view; ot = 10°.

Figure 17. Continued.

83
(c) Side view; tx = 10°.

Figure 17. Continued.

84
J

r/

/

I

/

I

I

!

\

20

(d) Top view; o_= 20°.

Figure 17. Continued.

85
(e) Simulated balance housing removed; top view; ct = 20 °.

Figure 17. Continued.

86
(f) Sideview;et=20°.

Figure17.Continued.

87
(g) Topview;ot= 35°.

Figure17.Continued.

88
(h) Simulated balance housing removed; top view; _ = 35 °.

Figure 17. Continued.

89
5O

(i) Top view; a = 50 °.

Figure 17. Concluded.

9O
1.4

1.2 3O°Oamon w

30 ° diamond with triangular cutout

30 ° diamond with diamond cutout

..... i • t .........

.8

CL .6

0

0 10 20 30 40 50 60 70

e_, deg

Figure 18. Lift coefficient versus angle of attack for cutout-wing configurations (ref. 14).

91
iii!iii_ili:il

(a) ix= 10°.

Figure 19. Top-view photographs of 30 ° diamond with triangular cutout.

92
\

(b) Simulatedbalancehousingremoved;ot= 10°.

Figure19.Continued.

93
2 i)'

(c)_= 20°.

Figure 19. Continued.

94
!

(d) Simulated balance housing removed; _ = 20 °.

Figure 19. Continued.

95
/i

i •

(e) tx = 30 °.

Figure 19. Continued.

96
I

LJ

i _ : t

(f) Simulated balance housing removed; et = 30 °.

Figure 19. Continued.

97
(g) _ =35°.

Figure19.Continued.

98
(h) ot= 50°.

Figure19.Concluded.

99
i

i

/

J

Figure 20.

i_i!}!iii_ii!iii

(a) o_= 10%

Top-view photographs of 30 ° diamond with diamond cutout.

100
%

(b) tx = 20 °.

Figure 20. Continued.

101
/J

/

i

/

(c) _ = 30 °.

Figure 20. Continued.

102
(d) _x= 35 °.

Figure 20. Continued.

103
(e) o_= 50°.

Figure20.Concluded.

104
1.4

--0-- 65 ° delta wing

65 ° delta with delta sawteeth

40 ° diamond wing

40 ° diamond with 3 diamond sawteeth

C L

1.2

1.0

.8

.6

.4

.2

0

-.2

Figure 21.

0 10 20 30 40 50 60 70

_,deg

Lift coefficient versus angle of attack for serrated-forebody configurations (ref. 14).

105
\

Figure 22.

(a) Top view; tx = 12°.

Photographs of 65 ° delta with delta sawteeth.

106
,\

t

ii ̧ ̧ _

2  ̧ ,

ii!iii_!iiii!iiiii_i iiiiiiiiiii

(b) Simulated balance housing removed; top view; o_= 12 °.

Figure 22. Continued.

107
/

/

(c) Top view; cx = 20 °.

Figure 22. Continued.

108
it i

ii

(d) Simulated balance housing removed; top view; t_ = 20 °.

Figure 22. Continued.

109
0

(e) Top view; tx = 30°.

Figure 22. Continued.

110
(f) Simulated balance housing removed; top view; tx = 30 °.

Figure 22. Continued.

111
(g) Side view; o_ = 30 °.

Figure 22. Continued.

112
(h) Top view; tx = 50 °.

Figure 22. Concluded.

113
(a) Top view; ot = 10 °.

Figure 23. Photographs of 40 ° diamond with 3 diamond sawteeth.

114
iiiii_iiiiii_i

20

(b) Top view; o_= 20 °.

Figure 23. Continued.

115
(c) Topview;a = 30°.

Figure23. Continued.

116
ii_iiii_!! ,

ii!'i

iii!iiiil

(d) Side view; tx = 30 °.

Figure 23. Continued.

i:!i::

i_!__

117
_ 5  ̧

(e) Top view; ot = 35 °.

Figure 23. Continued.

118
ii!=

,iiiil

_iiill

0

(f) Top view; ct = 50 °.

Figure 23. Concluded.

!!i7

119
(a) Top view; o_= 10 °.

Figure 24. Photographs of 40 ° diamond with 3 diamond sawteeth and nose tip.

120
/

(b) Top view; tx = 20 °.

Figure 24. Continued.

121
(c) Top view; ot = 30 °.

Figure 24. Continued.

122
(d) Side view; ct = 30 °.

Figure 24. Continued.

123
(e) Top view; _ = 35 °.

Figure 24. Continued.

124
(f) Topview;t_ = 50 °.

Figure 24. Concluded.

125
REPORT DOCUMENTATION PAGE po_ Approved

OMB No. 0704-0188

Public r_;ng burd(m for this _T.,;;_i;vfi of ;_-,;o,-rr,=tlu_is estimated to average 1 hour per response, including the time for reviewing inatructions, searching existing data sources,

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

March 1996 Technical Memorandum

4. TITLE AND SUi¥iT-E 5. FUNDING NUMBERS

Water Tunnel Flow Visualization Study Through Poststall of 12 Novel

Planform Shapes WU 505-68-70-04

S. AUTHOR(S)

Gregory M. Gatlin and Dan H. Neuhart

'7. PERFOR:,',:;:,._ ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-0001

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

11. SUPPLEMENTARY NOTES

8. PERFORMING ORGANIZATION

REPORT NUMBER

L-17418

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM-4663

Gatlin: Langley Research Center, Hampton, VA; Neuhart: Lockheed Engineering & Sciences Company, Hampton, VA.

Most copies of this report were printed in black and white; however, a limited number of color copies are available from

the author. Color images are available in the electronic version at URL http://techreports.larc.nasa.gov/ltrs/Itrs.html.

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Unclassified-Unlimited

Subject Category 02

Availability: NASA CASI (301) 621-0390

13. ABSTRACT (Maximum 200 words)

To determine the flow field characteristics of 12 planform geometries, a flow visualization investigation was conducted in the Langley 16- by 24-Inch Water Tunnel. Concepts studied included flat plate representations of diamond wings, twin bodies, double wings, cutout wing configurations, and serrated forebodies. The off-surface flow

patterns were identified by injecting colored dyes from the model surface into the free-stream flow. These dyes generally were injected so that the localized vortical flow patterns were visualized. Photographs were obtained for

angles of attack ranging from 10° to 50 °, and all investigations were conducted at a test section speed of 0.25 ft

per sec. Results from the investigation indicate that the formation of strong vortices on highly swept forebodies can

improve poststall lift characteristics; however, the asymmetric bursting of these vortices could produce substantial

control problems. A wing cutout was found to significantly alter the position of the forebody vortex on the wing by

shifting the vortex inboard. Serrated forebodies were found to effectively generate multiple vortices over the configuration. Vortices from 65 ° swept forebody serrations tended to roll together, while vortices from 40 ° swept serrations were more effective in generating additional lift caused by their more independent nature.

14. SUBJECT TERMS

Planform shapes; Water tunnel; Flow visualization; Twin wing; Twin body; Cutout

wing; Serrated forebody

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

NSN 7540-01-280-5500

18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

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Unclassified

15. NUMBER OF PAGES

126

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A07

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