Longitudinal splitting of a wind tunnel moving ground belt and its effect on a jet flap model

January, 1972

e( ONGlTUDINAL SPLITTING OF A WIND TUNNEL MOVING OUND BELT AND lTS EFFECT ON A JET FLAP MODEL

by A. Berg

•

LONGITUDINAL SPLITTING OF A WIND TUNNEL MOVING

GROUND BELT AND lTS EFFECT ON A

JET

FLAP MODEL

by

A. Berg

Submitted January, 1972.

ACKNOWLEDGEMENT

This project was undertaken as part of a co-operative UTIAS - NRC programme under the ~oint supervision of

Mr.

J. Templin, Head of the Low Speed Aerodynamics Section of the National Aeronautical Establishment, and Professor P. A. Sullivan at UTIAS. The author would like to express his gratitude to both for their advice, assistance and cooperation. The special assistance given by

Mr.

Peter South of the NAE is gratefully acknowledged. The work was under-taken with the financial support of the National Research Council 0f Canada.

SUMMARY

This report describes an experiment unàertaken to examine the effects of variation in the geometry of moving ground boaràs useà in the testing of high lift aircraft models in winà tunnels. A high lift STOL moàel with a blown flap was àesigned and constructed at UTIAS anà testeà in the NRC

3

x

3

pilot tunnel in ottawa. It was found that if the rooving ground belt was split into two, and the gap was of the order of the fuselage width or smaller, that no effect was

.. _ observed on the tested aerodynamic properties of CL' CD' NT. However, if the

split or dead band was increased to a width much greatet than that of the fuse -lage, significant decreases in CL were observed. It was also founà that the eelt velocity useà in the test required only to be matched to the tunnel speed

to within ~

8%

to ensure no error in the rreasureà aerodynamic parameters.

TABLE OF CONTENTS

Acknowledgement Symbols

INTRODUCTION

EXPERIMENTAL METHOD

l(a) Moving-ground Belt

l(b) Model Construction and Mounting

RESULTS AND DISCUSSION

Boundary Layer Profiles Model Investigations

Ground Effect Measurements Simulated Belt Splitting

CONCLUSIONS REFERENCES APPE~X I FIGURES iv PAGE 1 1 1 2 2 2 2

3

3

4

5

b C I-l c h S y

wing span. feet drag coefficient, lift coefficient,

SYMBOLS

, Lift ~S

V

b

maximum "in ground" lift at

V

=

1.0, ex

=

00

momentum coefficient, statie thrust (flap off)

q S

00

wing chord, feet

wing ~eight above floor, feet

tail normal force lb.

free-stream dynamic pressure, psf

wing area, .ft2

lateral distanee across belt, inches free-stream velocity, ft./sec.

belt velocity, ft./sec.

angle of attack of wing, degrees flap deflection angle, degrees angle of attack of tail, degrees

INTRODUCTION

It has been well documented (Ref. land 2) that airplanes flying close to the ground experience aerodynamic force and moment changes due to their proxi-mity with the ground. This ground effect, as the influence is called, is of ten quite difficult to simulate accurately in wind tunnels and one of the most ob-vious and simplest, but not strictly correct methods tried, has been the use of a "fixed ground board" or tunnel floor to simulate the ground. This fixed ground board simulation has led to much criticism (Ref. 3) and more complex alternatives have been tried. The prQblem has become especially acute with the growing interest in high lift models. A boundary layer growth develops on the fixed ground board and it accounts for a major porti on of the lift lost as "ground" is approached. In order to produce the correct simulation, this boundary layer must be eliminated, and one method is the use of a large ground plane moving with a velocity apJ2roxi-mately equal to the tunnel free stream velocity.

Under a joint program between UTIAS and the Low Speed Aerodynamics section of the National Aeronautical Establishment (N.A.E.) a scale model study

was carried out to investigate if a moving ground belt system, used primarily for STOL aircraft ground effect testing could be split with minimal effects on aerodynamic characteristics. This information would assist in determing the feasibility of installing a split moving-ground belt system in the 30 x 30 ft.

wind tunnel at Uplands Airport, Ottawa. STOL aircraft tested in this tunnel would most conveniently be mounted from the floor and hence two moving ground belts would be required - one on either side of the centre ground strut support. This investigation attempted to determine how wide a gap could be tolerated without adversely affecting aircraft aerodynamic forces. Also we are interested in

investigating the effects of a variable moving ground belt speed on aircraft lift, drag, and tail normal forces, near ground, to determine whether the ratio of belt speed to free stream tunnel speed must be accurately fixed for accurate results. Accurate belt speed control would entail the design and implementation

of a complex and costly feedback system in the 30 ft. x 30 ft. tunnel, to

synchronize the belt velocity with tunnel free stream velocity. At our disposal, in Ottawa, was the NAE 3ft. x 3 ft. pilot tunnel and a moving ground rig that

-required some modifications. The high lift STOL aircraft model mounted in this tunnel was designed and constructed at UTIAS (Fig. 1).

EXPERIMENTAL METHOD l(a) Moving-ground Belt

The moving ground belt rig, shown in Fig. 2 out of the tunnel, was capable of speeds up to 1201sec. A be:rt speed of 70'/sec. was used in most of this work, however, to reduce the large vibrational problems associated with higher speeds. During the entire duration of this study 3 belts were used. The first one, a thick polyurethane "habasit" belt with an anti-static coating, ran

over two positive cambered rollers. This cambering effect, necessary for lateral

stability, produced longitudinal wrinkles in the belt at very high speeds and it was replaced by a 10 mil thick teflon coated fihreglass belt. Although the

fibreglass belt was quite strong and did not stretch longitudinally, laterally it tore easily and it ripped during its first few weeks of operation. We thus dis-covered that this belt was not durable enough to meet the operating conditions of even our simulation study and consequently was not the right belt for a large moving ground belt system in the 30 x 30 ft. tunnel. The final arrangement, and the one used for all the experimental data in this report was a "habasit" belt, 22" wide, between 2 no-camber rollers with large metal guides, necessary for lateral stability, attached to the sides of the rig. Previously, the cambering of the rollers of the rig had produced large unequal longitudinal stresses on

the ~elt at high speeds, and distorted the flat belt surface. l(b) Model Construction and Mounting

The model utilized a jet, flap wing of aspect ratio 6, with a thick

heavily cambered NASA 4418 section. This section was machined out (Appendix 1)

to accommodate an air manifold necessary to provide a uniform blowing along the

15" wing span over the 0.5" trailing edge flaps. As in most STOL aircraft, a

high wing and tail plane position was employed. The adjustable tail plane beam

(see Appendix 1) was strain ga~ged and the tail plane normal force was calibrated

unde~ the 1/4 chord position. For more detailed information Appendix 1 is inser-ted.

The model was mounted (Fig. 5) over the moving ground belt from the

test section roof by a partially shielded adjustable str~t. Attached to this

strut were 3 plastic air supply tubes running from the air manifold to the

hollow small fairing that supplied air to the wing cavity. For this experiment

the 00 ref. angle of attack of both wing and tail plane was held constant and

the only movement of the model was in the vertical direction with height being

measured from the wing chord line to the belt. The data obtained were not

cor-rected for drag of the exposed mounting and air tubes since we were not interested

in absolute drag forces, but only in change in drag with variable belt speed.

RESULTS AND DISCUSS~0N

Boundary Layer Profiles

Boundary layer traverses over the moving belt were made to check that

the rig was performing adequately in removing the ground boundary layer. The

belt speed for these profiles was set at 5% more than V , a value recommended

(Ref.4) for satisfactory results. 00

It can be seen from Fig.6, a three-dimensional plot of velocity profile

vs. V /V ,that the boundary layer thickness is greatly reduced with increasing

V_b ang

t~nds

to disappear as Vb/V

oo approaches unity. Unfortunately, an unayoidable

boundary layer growth develops on the flat metal plate (see Fig.5, insert), that

comprises the top of the ducts :used to remove the upstream boundary layer of the

wind tunnel and the residue of the boundary layer on this fixed surface adversely

affects the profile over the moving belt (Ref.3).

Next the simulated splitting of the belt was investigated. This simu-lation involved placing .005" thick steel strips of widths 2", 3" and 4" on top

of the moving belt and measuring the lateral variations of velocity profile, using

the traversing gear shown in Fig.3. Figures

7,

8 and

9

ar,e three-dimensional

plots of velocity profiles versus y, the lateral distance measured from the centre of the strips. Note that the velocity profiles taken across the strip

(centre and 1/4 width position) are similar to the velocity profile in Fig. 6

at zero belt velocity. Thèse "dead strips" adequately simulate a gap between

two moving ~ound belts. It is also worth commenting that the lateral effect

of the "dead_ strip" in the tunnel disappears within about one-half-strip width

from the strip edge.

Model Investigations

mainly determine an optimum jet flap angle that produced a high lift. Figures 10,

11, 12 and 13 show variations of

CL' Cn'

Nt with C~ at standard free stream tunnel

velocity of 67'/sec. It can be seen, by comparison of Figures 12 and 13 that a

distinct drop in lift occurred when flap angle was increased from 400 to 600,where

a further increase of lift might have been expected. On closer examination of the

model it was found that the flap leading edge was only partially rounded and the

Coanda effect, responsible for the attachment of the jet sheet to the flap, due

to the rounding of the flap leading edge, was probably destr.oyed at high flap

angles. The insert drag curve for this case also was irregular due to separated

flow over the flap. The insert Nt vs. C~ graphs all showed negative tail normal

force, because the downwash associated with a jet blown wing induced a negative

angle of attack at the tail plane. From these graphs a flap angle

aF

=

400 and

C~

=

1.6, producing an out of ground

CL

of 5.3, was chosen for our standard

configuration to test "ground effects".

Ground Effect Measurements

Figure 14 shows that for h/c

=

.6 there is an apparent lift loss of

27% without the moving ground belt and it was obviously needed for ratios of

h/c :::. 1.

The most significant ob s ervat ion , however, and the one later confirmed by other data in this report, was the flatting of the lift curves around

Vb/V_oo

=

1. This provided experimental indication that the belt speed did not

have to be set accurately and hence a costly velocity feedback system is probably

not required. It was noted also that the data in Figure 14 were consistent with

data obtained by Turner (Ref. l) in which he establishes a criterion for the

need to use a moving ground belt, based solely on

CL

versus h/b. When the data

points are inserted on his graph (see Fig. 15), they lie in the expected

relation-ship to his boundary curve. However, in his report he does not mention how large

an interval around Vb/V_oo

=

1 is acceptable without adversely affecting aerodynamic

forces and moments. We have found from Fig. 14 that the belt speed does not have

to be set accurately; in fact, an interval of

+

8%

about Vb/V_oo

=

1 seems

satis-factory for belt operation.

There is a small negative tail force change from an initial start of the belt but once the belt is moving Nt is constant (Fig. 16). The effects of

belt speed C

_n

exhibit similar characteristics. The upper curve in Fig. l7 is a

plot of C

n

as a function of belt speed at the most sensitive position. Again,

throughout a large interval about Vb/V

oo

=

1. C

n

remains constant. The small

variations of CD with Vb/V_oo at 0 and 1 values are also quite notable on Turner's

model (aspect ratio 7, ~

=

450) (Ref. 4).

Simulated Belt Splitting

The dead strip was inserted centrally, under the fuselage (Fig. 4) and the belt speed varied: then, the strip was removed and the measurements were taken again. This was done for each belt width and each value of h/c (0.6, 0.8, 1.0 and 1.4). At the lowest vertical position of the model (Fig. 18) insertion of the

2" strip had little effect on

CL/CL

measurements; whereas for 3" and 4" strips

g

there was a noticeable decrease (5-1/2%) in CL ' the maximum "in-gro~d lift"

g

occurring at Vb/V_oo

=

1.05. Similar results occur at h/c

=

.8 (Fig. 19) except that the decrease is a little less dramatic; but at h/c

=

1.0 there is virtually no effect of the strips (Figs. 20 and 21). The comparatively large effect, at the lowest model heights, of increasing the dead strip width from 2" to

3",

with smaller effects below and above these widths, demanded further investigation. The 2" strips, when centrally located under the model fuselage, is largely sheltered from direct jet impingement, and further measurements were carried out af ter moving the

2"

strip under one wiDg. In this case there was complete jet sheet impingement on the 2" strip width rather than a partial impingement. AP will be seen from Fig. 22, the lift was substantially decreased by the presence of the 2" strip.

The presence of dead strips has no not~ceable effect on Nt' but CD measurements were slightly lower (Fig. 17). However, these small variations may be within experimental error. In ~ny case, the dominant force affected was lift. The simulated splitting of the moving belt also substantiated the fact that a

+

8% interval about Vb/V

oo

=

1 had very little effect on lift measurements

even at very low h/c values; the data of Figs. 18, 19, 20 and 21 were consistent with the earlier graph, Fig. 14, in this respect.

CONCLUSIONS

A small-scale moving belt ground plane has been tested, and put into operation at N.R.C., ottawa, af ter its mechanical difficulties were overcome.

A study of the longitudinal splitting of the ground belt, with a non-moving strip between non-moving segments and the effects of variable belt speed on lift, drag, t~~ll normal force on a jet flap aircraft model was carried out, with a view to using this data to aid in designing a belt system for the 30 x 30 ft. V/STOL tunnel, and the following results were obtained.

It was found that the moving belt could be run within a range of about

+

8% rrom free stream velocity without affecting model lift, drag and tail normal force. Thus a costly feedback speed control system need not be devised. Secondly, it was found that model lift could be adversely affected by belt splitting. The magnitude of this effect depends upon the location and width of the "split" beneath

th~ model. If the non-moving strip beneath the model centre-line was confined to fuselage width so that there was no high-lift jet sheet impinging directlyon the strip, then the lift was not significantl~affected by it. However, if the gap was located under the high lift wing for instance, it pro~uced a noticeable de-crease in lift. This dede-crease of lift was also noticeable even it there was only partial jet i~pingement on the strip, simulating the gap, as in the case of 3" and 4" beUs beneath the model centre-line.

This lift loss can only partly be explained by jet sheet impingement since if it was purely associated with imping,ement, the change in loss in going from a 3 inch to a 4 inch strip should be approximately the same as from going from 2 inch to a 3 inch strip. The answer lies in complex 3-dimensional flow effects generated at the wing body junction. It was felt that the interaction of the vortex flow, at this Qunction, and the metal strip accounted for some of

this lift loss. Tl}is is supported by the measurements of loss in CL obtained from 2 inch strip mounted under the middle of one wing. The magnitude of the loss is only very slightly greater than that for a centrally mounted 4" strip which wquld have á little more than 2" under the jet sheet.

1. Butler, S. May, B. A. Glover, G. 2. Turner, T.

3.

East, L. F.

4 •

Turner, T.

5.

Abbott, I. H. von Doenh0ff, A. E. REFERENCES

Low Speed Tunnel Tests of a Low-wing Subsonic Jet Transport Model with Ground Simulation by Moving-Belt Rig.

RAE 65111, 1965.

Ground Influence of a M0del Airfoil with a Jet Aug-mented Flap as Determined by Two Techniques.

TN

D-658,

1961.

I

The Measurement of Ground Effect Using a Fixed Ground Board in a Wind Tunnel.

RAE 70123, 1970.

A Moving-Belt Ground Plane for Wind Tunnel Ground

~imulation and Results for 2 Jet-Flap Configurations. TN

D-4228, 1967.

Theory of Wing Sections, McGraw-Hil1,

1949,

First Ed.

DIMENSIONS OF MODEL WING BODY TAIL APPENDIX I NACA No.

4418

Span 15" Chord length 2-1/2" Thickness/chord

.18

Min. wall thickness

1/16"

Slot width .015"

Spacers

6

evenly spaeed

(1/8"

wide) Material-Aluminum, brass

Max. length 13"

Diameter of wood section 1.33" Length of wood section

8"

Length of steel bar section

4.5"

(from strain gauge to

1/4

chord position) Width of steel bar section .250"

Height of steel bar section .125" Material of fuselage - Oak

NACA No. 0012 Span 5"

Chord length

.45"

Height of Tail 2.40"

(abave cylindrical body) Material - Oak

NACA 4418 WING SECTION (Ref. 5 )

Chord Line

Air Cavity

.015"

Slot

Leading Edge Radius = .089"

Slope of Radius Through

Leading Edge

=

.20

FIG. 1 STOL

MODEL

FIG. 3. TRAVERSING GEAR AND BOUNDARY LAYER RAKE (IN 3 Ix3 I

PILOT TUNNEL) •

Tunnel

To Betz Manometer

Strain Gauge

la

Balanee

17

11

.--- Adjustable Aluminum

St rut

Air Manifold

Air Supply Tube Perpendieular to

Balance Lift

a

Drag Components

Air Hoses

Large Fairing

Pitot -Statie Tube

~I

-~

Idle

Roller

•

-Is

Metal Plate

~

3.5'

~

Adjustable Flaps

G4t---~

S'

---1,»0

Metal Guide

FIG. 5. DRAWING OF THE MOVING GROUND BELT RIG AND MODEL

IN POSITION INSIDE TUNNEL.

3'

Drive Roller

Movino Ground

Belt RiO

0.1

0.3

0.5

Vb/VCX)

0.9

FIG. 6. BOUNDARY LAYER PROFILE VS. BELT SPEED, 3.5' FROM BELT LEADING EDGE, Voo = 67'/sec.

3.0

2.0

h

V/VCX)

3.0

2.0

y

FIG. 7. VELOCITY PROFILE VS. LATERAL DI STANCE , Y, OVER 2"

STRIP (MEASURED FROM STRIP CENTRE) , V_b

V - 67'/ 00 - sec V--00 = 1.05,

3.0

2.0

h

1.0

1.0

V /

VaJ

3.0

FIG. 8.

y

VELOCITY PROFILE VS. LATERAL DISTANCE, Y, OVER 3"

STRIP (MEASURED FROM STRIP CENTRE), V

b Voo = 1.05, Voo

=

67'jsec

3.0

2.0

h

1.0

1.0

V/V(D

3.0

y

1.0

FIG. 9. VELOCITY PROFILE VS. LATERAL DISTANCE, Y, OVER 4"

STRIP (MEASURED FROM STRIP CENTRE) , V

b V~ = 67'/sec V oo,= 1.05,

3.0

2.0

h

1.0

V/Vf1:)

·05

6.0~

Nt

I

'"

0.01

0 ... '<

CL

--.05

I

4.0

I

-.10

0.0

0.5

1.0

CfL

2.0

.5

.

~~-Co

I ~

-CfL

-.5

1.5

2.0

FIG. 10. VARIATION OF AERODYNAMIC CHARACTERISTICS OF MODEL

WITH C "OUT OF GROUND" Cl

=

0° V

=

67'/sec

l.I'

' F '

00 Cl _t = 0°

2.0

O·

'

0.5

1.0

1.5

2.0

Cf'

6.0

CL

4.0

2.0

o

.05

Nt

-.05

- 10 '

_.

,

,

U:"" ₀

0.0

0.5

1.0

CJL

0.5

1.0

FIG. 11. VARIATION Of AERODYNAMIC CHARACTERISTICS OF MODEL

WITH C "OUT OF GROUND" Cl = 20°

~' , F

2.0

CJL

1.5

2.0

6.0

CL

4'°1

-.101

_I

0.5

~J.L

_/

.5

v _ft

·

2.

I

I-==-~

_CJ.L

Co

I

2.0'

JII"

-.5

o ·

,

0.5

1.0

1.5

2.0

FIG. 12. VARIATION OF AERODYNAMIC CHARACTERISTICS OF MODEL WITH C _lJ' "OUT OF GROUND" _, ex

=

40°

F

6.0r

.05

Nt

0.0

CL

4.oL

-.05

-.10 ...

' - - -... - - - - ' - - - ' - -_ _

....

0.0

0

.5

_{1.0 C}

_1.5

fL

2.0

1.0

CfL

2.0

o '

I I I I

0.5

1.0

1.5

2.0

FIG. 13. VARIATION OF AERODYNAMIC CHARACTERISTICS OF MODEL

WITH C "OUT OF GROUND" Ct

=

60°

ll' , F

CL

h

c=

0.6~

aF

=40

0

Cf'

=

1.6

0.8

6

-1.0

0 -1.4~

1.8

----at

=0

0 I

V

Cl)

=

67l'sec.

301

1

1

I

o

0.5

1.0

1.5

~/~

h/b

0.6

0.5

_Sweep

[J

0

A

35

0.4

r-

0

0

Double-slotted Flap, Ref.2

~

0

Tilt Wing,

Ref. 2

• Data Points trom Fig. 13

0.3

Conventional

0.2

0.1

o

1<1' .•... '1 ..•....•.•.• "" .•..

o

2

3

4

CL

FIG. 15. T. TURNER'S GRAPH (REF. 4)

h

c=·6

.06

-N

_t

.04

·02

, , ,

.00 •

04

0.8

1.2

.00

. V

b

/V(1J

FIG. 16.

TAIL NORMAL FORCE VS. BELT SPEED FOR VARIOUS

HEIGHT POSITIONS, aF

=

40°

Voo

=

67'/sec

C~=

1.6

at = 0°

. 8

1.4

1.8

•

El

A

0

O.O.

•

•

•

•

Co

• No Strip

-0.1

• 3" Strip

-0.2

aF

=40

0

a

t

= 0

0

Cf' =

1.6

V(/J=

67

I/sec.

-0.3~'---~---~---0.0

0.4

0.8

1.2

1.6

Vb / Vet)

FIG. 17.

VARIATION OF CD

vs.

~b

(NOT CORRECTED FOR

00

1.0

CL /C Lo

0.9

FIG. 18.

0.8

D

No Strip

6

2"

Strip

• 3"

Strip

o

4" Strip

c

V

CL _L

vs.

~

_Voo FOR VARIOUS STRIP SIZES UNDER

g h FUSELAGE AT - = .6 c

aF

=

40°

.

at

=

0°

C

fL

= 1.6

,

VfI)= 67

~sec.

0.7L, ______________

~

____________

~

______________

~_

00

0.5

1.0

1.5

Vb/VfI)

~

1.0

CL/CLQ

0.9

FIG. 19.

0.8

o

No

Strip

6

2"

Strip

• 3" Strip

o 4" Strip

c

V

CL L _g

vs.

~ Voo FOR VARIOUS STRIP SIZES UNDER FUSELAGE AT h C = ·B·

aF

=40

0

at

=0

0

CJL

=

1.6

Vf1J

=

67~sec.

0.7~1

______________

~

______________

~~

______________

~

__

0.0

05

1.0

1.5

V

_b

/Vf1J

1.0

CL/CLQ

0

.

9

c

V

FIG. 20. CL VS. Vb FOR VARIOUS STRIP SIZES UNDER

Lg 00

0.8

FVSELAGE AT

~

=

1.0

o

No

Strip

6

211

Strip

• 3

11

Strip

o 4" Strip

aF

=40

0

at

=0

0

CJL

=

1.6

•

•

V(/)= 67

/sec.

0.7 ... _ _ _ _ _ _ _

---11...-_ _ _ _ _ _ _ ....1.-_ _ _ _ _ _ _ - - - 1 . _

0.0

0.5

1.0

1.5

V

_{b /}

V(/)

•

1.0

CL/C Lg

0.9

FIG. 21.

0.8

A

c

V CL VS. V b

FOR VARIOUS STRIP SIZES UNDER Lg co FUSELAGE AT

~

=

1.4 c

o

No

Strip

A

2"

Strip

• 3"

Strip

o 4" Strip

aF

=40

0

Cf'

=

1.6

at

=0

0 I

VaJ

=

67/sec.

0.7

L ' _ _ _ _ _ _ _ L -_ _ _ _ _ _ _ ..L...-_ _ _ _ _ _ - - - ' - : _ _

0.0

0.5

1.0

1.5

Vb/VaJ

CL/C

_Lg

0.9

0.8

c

V

FIG. 22. CL VS. Vb FOR VARIOUS STRIP SIZES UNDER ONE WING LG 00 h AT

c

=

.6

aF

=40

Cp,

=

1.6

0.7

i

I

'

I

0.0

0.5

1.0

V

_{b /}

V(l)

•

•

• No Strip

02"

Strip

(under one wing)

o

1.5

a

_t

=

_·

0

0

, . , ' I

•

tnr;.s TEC!!NICI.L NarE NO. 173

Institute for Aerospace Studies, University of T oronto

LO)XSITUDD:r.l. SPLITTIl\(, OF A vlIND Tl..'!fflEL r-nVING GRO!.RID BELT AND lTS EFFECT ON A

JE-l: 7LJ.2 ~:OOEL

Berg, A. 6 pages 22 f1gures

1. Pc.,'ere:i L1f~ Te5~i!ló 2. t.1oving ûround. Belt j. Split Ground Belt

I. ijerg, A. Ir. tnIAS Teciln1cal Note :io. 173

Thls re:ç.ort descrlbe!i lUl exper1.Jnent und.ertaken to exa:nine the eff'ects of variation

in tee gecr.-.e,:!"y of' n::.:>ving grcu.."ld boards used in the -.:.esting of high 11ft aircraft =:;.iels ~r. :·:1nd tu..'Ulels. ft high lift STOL I:lOdel wi."r.'t:. a blown flap was designed and

ccn~-cru.:~ed A-... ;"jTIAS e!ld tested in the liRe 3 x 3 pilot tUImel in Ottawa. It "'as

fOi.:. ... ..c. t.ha:. if ï:.ne ltovi:.~ ground belt was split into t;.ro, and the gap was of the

craer of ~he fuselage w!.à'th or smaJ..ler, that no effect was observed on the tested

e.e~oiynem1c propertie. of CL' CD' NT' However, 1f the split or dead be.nd was

in-crea~ed. te e. -,'!i:it!t r:uch greater t}1..e.n that of the fuselage, significant decreases in

CT ',:ere observe:!. It .,:es a150 found. that the belt velocity used in t!le test re

-G,u:"!"c..i c!:ly to 'Oe ... ~":.che:i to the t.unnel speed to wl:'hin + &f, to ensure na error in

the lteasured aerodyna.c:dc pa.raJteters.

-~

tJrIAS TECHNICAL NarE NO. 173

Institute for Aerospace Studies, University of T oronto

LO~ITUDINAL SPLlTTll\"G at A WIND TUIlNEL MOVING GROUND BELT AND lTS El'l'ECT ON A

JET FLAP MODEL

Berg, A. 6 pages 22 f1gures

1. PO'dered L1ft Testir.g 2. Movir.g Ground Belt 3. Split Ground Belt

r. Berg, A. Il. IJrIAS Technical 1I0te No. 173

This report describes an experiment undertaken to examine the effects of variation

in the geometry of moving ground boards used in the testing of high lift aircraft

models in wir.d tunnels. A high lift STOL model w1th a blo,fO flap was des1gned and

cCDstrt:cted at UTIAS e.nd tested in the NRC 3 x 3 pilot tt:nnel in Ottawa. It was four..d that if the moVifl.g ground belt was split into t,,·o, and the gap 'VJas of the

order of the fuselage w1dth or sme.ller, that no effect was observed on the tested

aerodyne.mic properties of CL' CD' NT' However, 1f the split or dead be.nd was in -creased to a w1dth Ir!Uch greater than that of the fuselage, significant decreases in

CL we;re observed. It Has also found tbat the belt veloc1ty used in the test re

-qt:.i.reè. only to be :::i8.tcheà. to the tunnel speed to within + Sj to ensure no error in

the ~asured aerodynamic para.rceters.

-~

Available copies of this report are limited. Return this card to UTIAS, if you require a copy. Available copies of th is report are limited. Return this card to UTIAS, 'if you require a copy. IJrL'.S TECHNICAL NarE NO. 173

Institute for Aerospace Studies, University of T oronto

LOlCITUDINAL SPLITTING OT A WIND TUNNEL MOVING GROUND BELT AND ITS El'l'ECT ON A

JET FLAP ~lODEL

Berg, A. 6 pages 22 f1gures

1. Powered Lift Testing 2. Mov1ng Ground Belt 3. Split Ground Belt

1. Berg, A. Il. IJrIAS Technical Note No. 173

'rti3 report describes an exper1ltent undertaken to examine the effects of variation

in the geo:letry of mo\'ing ground boards used in the testing of high 11ft aircraft

t'.O<!els ;'n ~1nd tt:nnels. A high lift STOL model ~1 th a blown flap was des1gned and

cmstructed at ljTIAS and tested in the liRC 3 x 3 pilot tunnel in Ottawa. It was

fCu:ld tha-; if the moving ground belt was split 1nto twoJ and the gap was of the

arc..er of the fuselage .".idth or smaller J that na effect ""as observed on the tested

aero-.iynaJ"".ic propertlef: of CL' CD' NT- However) if tne split or dead band was

in-creased. ~o a width mud, greater tr.ar. that of the fuselage, significant decreases in

CL \-:ere observed.. It we.s also found that the belt velocity used in the test re

-Q.\ár~.:i only to be matched. to the tunnel speed to witbin + ~ to ensure no error in

the measureè. ae!"oè.ynamic parameters.

-~

Available copies of this report are limited. Return this card to UTIAS, if you require a copy.

lIrIAS TECHNICAL NOTE NO. 173

Institute for Aerospace Studies, University of T oronto

LOl\GITUDINAL SPLITTING at A WIND TUliliEL MOVING GROUND BELT AND lTS El'l'ECT ON A JET FLAP MODEL

Berg, A. 6 pages 22 f1gures

1. POlo/ered Lift Test'ng 2. MoVing Ground Belt 3. Split Ground Bel.t

l. Berg, A. Il. IJrIAS Technicel Note No. 173

This report descrlbes an experiment undertaken to examine the effects of variatiO:l

in the geometry of "",ving graund boards used in the testing of high lift a1rcraft

models in wind tunnels. A high lift STOL model w1th a blown flap "as des1gned and coostructed at UTIAS and tested in the NRC 3 x 3 pilot tun..'"1el in otta' .... a. It "r,'as

found that if the !!laving grol.:..'1d "::lelt was spli:' into t·,oIO, ani the gap ',,'~s cf the

order of the fuselage width or smaller, that na effect · .... as observed on thc teste.:i

e.eroiyn8.!l"dc propertie~ of CL' C

n, NT. Ho\ ... ever, if the split or dead band was

in-creased to a width mut:h greater than that of the fusel&ge, significant decreases in

CL were obscrved. It was also found that the belt velocity used in the test re

-quired only to be matched to the tunnel speed to within.:!: &,k to ensure na error in

the :neasured aeroà.ynamic para.oeters.

~