&P, No. 38

MINISTRY OF SUPPLY

AERONAUTICAL ,RESEARdH COUNCIL

CURRENT PAPERS I

The Air Towing

R.A. E.

Flow under the Carriages in the Seaplane Tank

K. M. Tomaszewski, lnz.Iotn. Warsaw , ( >

’ S. Raymond, B.Sc.(Tech.) and G. F. Chalmers

Crown Copyright Reserved

LONDON: HIS MAJESTY’S STATIONERY OFFICE 193

Price 4s. Od. net.

G,.?, Chakllers

By suitably adjus-Gin,g -tihe se-~-~i~, OS' f;l:e ~YXIX- fla?, i-t was found possible to obzain iI mean air :;geed under pi-chier carriage the s.ane as the carriage speed, The flap ;il;;o served ‘io stak.zini: c11e flow,

Page _ - -^-“-

‘I Incrodilcxion 2 Ran;c oi' Investjq~-iioll 3 De s~ripti on of A;qara-tus 4 HeSUlTS

4.“1 Air Speed l;ti-ch no screen 4 2 Nature of' the Air Flow

;I; Effcc-2 or' i'lz~ se-6tin2; on Air i'lo~-; under No 2 carriage Xffecr, of balance posii;ion on rcsis-kance measurements

on Ko.2 carriage 4.5 Effect of flap setting on Air Plo-il under i3o.l carriage

5 Conclusions

References 7

Table _-_

IV

h 1 InxxoducKon --- . - . - - . " .~ .._

l

3 Description of A;xJaratus II---_--_. _- _ . i Fe _ - .--_

For the major invecti~ation of tlw air flo;7 in the rqion of resistance models, a stack of five ;3i-ioi; s~;~~tic tubes was used, and the five gauges ;-reri: read ;)hotographicalPJ-. Vizxs or the auto-observer, and the pitot-ski-tic mountings arc siven in F-L:;,I:- ad. Fhzp5.

The %wo ;roodcn fla:~s for modi;yins Gh:; :,.ir i”1.~~ -,rcre mounted as shown in Pi,zs, 1 s 2 and 6. fhcse screens ;.;x, I,ivo;;cd at their connection With thi: carriage 3 the rango 0" co 40’

and could ‘Ix SC-~; a-1; any an,&i to the horizontal over For the final conl;rol. of air spozds, only the rear

flap T7a.s used, the froxc flap bcinq lxkcd in 51~ horir;ontal position.

4 Results E--- _ I

4.1 Air flo-:: with no screens I_ _ -._ _. _ _ _-_ _I. -- - -, -.

The results of rneasuremerxs made under No.2 carriage vsith a siny,le pi-to-t in the 1oni;itudinX. ilosftion normall:- occupied by the bow of the mcdei, are Liven in Table I.

The velocity field interpolated from -chest results is given 5-n Pig,i<, and the tests shop &.a~:-

(0 Whilst the drag balance was in its ilOlXlZ1 posi;,ion nea1' the water su-rface, the air f10r behind ii; was unsteady and non- uniform;

11; vas decided f'rcm th~x rc;v.lts to test models in air flow -&.th the drag bala.ncL 2-G a lizi@-t of 18 inches abovc :;Ja-ccr stir-face.

402 Nature of the air ?loi; _l_--_l_l-__ _- -I.-. .---

The front a:xd reLar fla~)a ;~ere fitted on Yo2 carriage and the steadiness of the .air floV ;TRS ascertained usinG :;oc:l tufts, Runs were made trith both flaps do:~n, rwr fla:, *only do-,n, and front 1.'la;l only

down, and photoj-graphs were taken of the wool tufts. Eesul-GS are given in Pi$,7, and show that the steadiest flo:,; is obtained when the rear flap only is used to slew Down the air -under the marriage,

An attempt :;r;ts made to measure i;he air spocd rcla~iv~ to the carriage when both screens -jert fully down, Whils-6 not being very consistent, the mcaaurtimcnts she<? that the air speed is reduced to about 10% of the carrisgc speed up to 30 f ,~?‘S,

4,3 Effect of flap setting on air f'lo:~ u&or 1\io,2 carrin~e ----- --_--__- -_- _.__-___-_ _--._ -.-.-----_I.

Moasurcmcnts 0

of air flil;-i i;ioro madc t-pith the ?ruur flu;) set at 20 , 30' and 40" to the horizontal - thi fmn-t .Fl:~p king :;et horizontally throughout, Co~mplctc results are given in Table II, The readings shoTrod that there XX only ;i small. variaci on in air spczd transversely. The t:To outcr @lo-is __ ~~~vc: consistently high readings -and were ncglectcd t-ken evaluating tli;: ml;'an air spcirl. Rondings made in the forward position diffcrcd from those made in the aft I,osi.t;i on. b-d-2 no consistent variation was found.

T'ne results obtained for a given flap setting and speed were meaned and the points are ShOTKl plotted in Fig 5. Individual readings may be IV& different from the mean rcadingo, but the majority 3r.z within 44% of the mean,

3

A working ~curve showin&: the fla-,? scttins required over a range of air speeds to give correct mean air i'lo;j is deduced from Fig,9 and shown in Fig,lO;

TO check these results furtlier moasuromcnts 7.;erc made later at the

. r step position of the ventilated model, The rcuultc arc given in Tablc III Variation ~5th height of the ratio, c1i.r speed -co krriagc speed,for the bog, stern and ste-i_? positions arc' given in F1g;~ll for 20 and 20 J?.~>~s~ carriage spocd.

4*4 Effect of balance position on resistance measurements on .------ . ---- ------ -..-.- -- ----- _ . - . _ . _ - . _ - -. . _ -. _ __.. No,2 carriage

-.-__- .-- - . _ _ --“.:.- _ - _._ I . _ . . ^ _ . - . _ - . - -. -_---__- - ..-._ --.. . -__.- . ^

The results arc plotted in Ffz 12 IGC: @-c<, curves for the correction to rcsistancc readings over th: whole: s>~,cd rr~i~g, and for three positions of balance,

- iI -

4.5 Effect of flap setting on air flow under No,1 carriage ----__I---- l_--_ _- .__- --.-_-_ _ _.. _. _- ._--- --

Air flow measurements were made xith the folloxing settings of the rear flap, 20°, 25O, 30' and 40' to the horizontal - the front flap being set horizontally throughout-, 4 diagram of the flap arrangement is given in Fig.2 and a view of the rear flap used to control the air flow is given in Fig,6,

Complete'results are given in Tablo IV. In the evaluation of the mean air speed the two outer pitots were neglected. In the forward position the speed of the air flow even at a 400 flap setting was higher than the speed of the carriage. Fig,13 sho$rs the flap setting as a function of

carriage speed for constant values of Va VC at the bow, step and stern

model positions, A flap setting of 32' Va gives the folloxing values of E

over the range of carriage speed 16 co 40 f.pOs,

I -- -._ ---_.--- ---.- -- - . - . . - . . - ---.-.+-.----l

Distance of tr,ansvcrsl: plane from datum (Inches) - -.-.

43.5 (box) 57.0 (s-q) ?4.5 (stern)

Variation of th- ratio of air speed to carriage speed with height for transverse vertical planes at the same positions are given in Fig.14 for 16, 20, 28 and 36 f,pOs, carriage speeds,

5 Conclusions -I- -1--11-

It is possible to considerably improve the air flow under both the R.A,E, towing tank carriages by means of a large flap positioned at the rear of the working section, Lowering this flap about its upper edge working line enables the mean air speed in th e region of the model to be reduced to that of the carriage. The air flo~-r is also made more steady,

Under No.2 carriage the present drag balance has also to be raised so that interfcrencc irith the air flew over the model may be avoided,

There is however a resultan; fore and aft pressure or velocity gradient which is considerably larger under No,1 than No.2 carriage, possibly because of the presence of the retracted screen used for fully screened tests. It is hoped to reduce this gradient in the future by transferring the balance on No,1 carriage, the better one, to No.2 carriage. Then all force measurements, with and without air flow till be done on No,2 carriage and dynamic model tests on No,1 carriage. The present drag balance design on No.2 carriage, by which the model is tomd by a long tow bar, is not considered satisfactory for tests in air flow because of air flow and air drag interference.

- 6 -

No o flUthOr -- -.. - . . . .._

I C-0?;-;;

2 Clark, Hills

3 Gotz

-7-

I

I I-

I I I

-o-

I’

TABLE I (Continued)

- - - - I - - ~ - . - _ I . - . - - - - _ - - - .-___

Balance ht. Pitot ht. Carriage Ratio of air speed to carriage speed above water above water speed f.-9-s.

--I-- --- --e- --- ----__ -; _____- -----___ i?itot ll$' port Pitot 6" port Pitot central Pitot 6" starbd. Pitot IO"' starbd. B - _-- --_----__--- --_-------- --I_--L_ - -----.---- -_.-_l--l -- .--- --. - _ _....I._ ---. I - .._-- ._.--- -_-_ ___ _____ _

IO 1.24 .1.12 1 .I0 1.10 1.12 2 in, 20 1 .23 1.24 1.17 1.20 1.25

3': 1.28 1 .21 1 1.21 21 1.21 1.20 1.19 1 .21 1.25 1.22 .

lo- ^_--_-.-- -.-__~--_____-_-_.--_-- -- - ______ -

1.15 1.20 I .I0 1.14 1 .I0 18 in. c; in. 20 1.22 1.23 1.17 I.25 1.17

30 1.23 1.23 1.17 1.24 1.17 34 1.20 1.19 1.18 1.22 1.13 : -------- - -- ----i. --I_.-- _ _I-- .--__ --____- - -- __ 10 1.20 1.15 0. 91 1.00 1.20

I 12 in.

20 1.20 1.18 0. 96 I . 04 A.24 W 30 1.23 1.17 1 00 I-07 1.25 .

I 34 1.19 1.15 I 02 1.04 1.19 . _-__I_--.-----)_._--_-______ ____ -- -c-P---- .-..-- -- --- -- -- - -_--_ __.__~__ --- .--- _ .

Pitot set perpendlculxr to the vertical plane through a point 84 imhes forward of the datum (Fig.1)" '

I .- ._ ’ , I I

I , , t I r I I

- 11 -

I I

- 12 -

- 14 -

--I

i s E J--l-l-

I-

2 / I s l- i

I i ; L-

-+- -

I i

l-

Q T-

I .I - -

- 15 -

. .I . . .) 0 0:-T- 0 “I

I i / i I I I I

---+---

! / I 1 I

I #

i I

Q’cu I

-!-

- 16 -

TAB.L?Z IV (Contimed) __---

I Carriage

Speed = VC (f.p.s.)

I----- . _ . .___

12

.._- -. -- .

1_--1.-- ___ -_____ _ _ -I_ - ._ __ __- -__ -.-- . _ --~__----- .-.--~- I Va Angle Zeight

----I of pitots

I---

E in Transverse Vertical IZlane 94.5 ins. forward of Datum !

--T

- - - - -_- -~- __ _ - - . - I - - “ - - - . , - - . - - * - - .

of flap above water hvel .X-Lot I Ztot IIT2itot IIITPitot IVT2itot V- Of l!:Iean over 1 (de& > (ins.) / 12"port

-+.--- I -.- - -- _.- ---,- . - 20

-.----_ i- .---_.-- ‘-2

6 1 l-Id3

l.l"s3 -. .----__-1 2

- -t 1-----1--- 1 ” Xj

6" stkd. lZi'stbd . __- _--- ^.-- -- - -- --_- _ ..-.. " ----

i-q92 I " 20'3 1.146 I.133

ye-,&j j- $f -/ - . 1 1 4 n- - --f

I.150 -_----.- - - , ̂0. 391 1.066 _ ._-_ _-- _-____ -- _ --_I I.203 1.222 “- -- ------ ._. _ 1,125 I.152 --- -- .-.-_._-I-- -- -- 1 4.119

1.14s ___.-_-- _ I.041 1,116

6 -- -- .-.--I " .-.--I " _- _ ___.- 2 6 - __. _ _.. ._ __-.----- -- __. _ _.. ._ __-.----- -- ---.-- ---.--

dY I

2 6

1,115 1.125 _------ I.100 1.097 -I- ---

6 -----.---

2 L

t I_ -__-^- 2 6 ----_- 2

I. 110 ---I - _ _ I. 06.!+ 1.087 - ----- _ . 1,182 :.194 -_ -- 1.107 1.102 --- 1.046

t

1 116 - -.I----- - I-071 1.089 .--.I_.- 1.186

TABLE IV (Continued) _

in 'i'ransverse Vertical Plane 94.5 ins. forward of Datm

- -+- ------ -----I---;.li-3 20

ii I.184 1.178 I.183 1.192 _ I.184

32 30 2 - I.109 1.106 1.100 6 1.118 1.114

40 -

1.114 _ 2 I.047 1.037 I.039 6 -lll_---- -_-_ ---- -- _.. ------_ I.056 1.051 1.053 ---_---_-

20 2 1.152 1.152 1.151 6 .----... 1.154 I.157 - 1.155 ._-__---------------- ----- ---~ ---. --

36 30 2 1.111 1.111 1.105 6 1.111 1.114 1.105 --^_---_-_.--"-------.----^--_ --._ .- ..--.- -------------.- .-.__ -_.

40 : I.035 1.033 1.025

-_---.-_._-_. _-._- _ 1.050 1.050 1.046 _--___-_ . .- -----_-__--_-__ -._--.----.__. ^___- 20

2 6

.-- -- - .

- _

Pitot IV 6" stbd. I--__

1.179 1.195 1.108

_ *-1,'120 1.050

-Lez-. 1.158 1.162 ---,- ----- 1.11-l 1.115 ---- .-- _-. I. 044 1.050 ---A I- --

.--- -~- 1.100 1 107 .----L- 1.040 1 . 0.46 -- - _-

-

--

.- -

, --

--._ - --- -.___ Pitot V

Xean of

12'stbd. pitots

--- - LLGZ 2 -_- 1.181 I.177 1.156 1.190 .-- -_._--_.---I_._-_ 1.094 1.105 1.089 .-- 1.116 1.005 1.042 1.020 -I._ -- - --_- - I.055 ---_-- 1.152 1.154 -1.115 1.458 .-_- . I _-_.. . ..--- -_-- I.-IO5 1.138 1. 074 1 III - -.- -_-_ - _. - _ _--__ _ -_- 1.978 1.034 I.016 1.049 ---- _._ _.__ -- -. -- .- -

-_- __-___ -~_-.*_--. . I.087 1.095 1,042 e-_lto_s_5e- 0.980 1.032 0.990 1 036 - -- -- -..-.-.- I_ --- --._ - --.

---

Mean over the area --- --

1.183 -- _l_l_

1.110 ~- --

1 a-8 -__ ._----~

1.156 -̂ _-_--- -.

1.110 I- ----- --.

I. 042 --- .--_---.

-- .- .--._ -.

1.095 --__-_.

I.034 ._.- --i

Wt.2078,E'38.g3. ?7-inted in Grw t Bri tan.

--.----.-- --- DIRECTION OF MOTION

PO9TlONS FOR

DATUM FOR LONC;ITUDlNAL MEASUREMENTS

Al RSPEE D MEASUREMENl++

DRAG BALANCE 1 SPAR OF CARRI.

SJUSTME.NT

” WATER iEVEL! ’ \ - -_-_____ -- - __I_-- _-__. ._ I _---L I__-- - II- -..------ - --- -.- --- _- -~ - -.--- -.. ---._ I --.- _-..___ __ - -.- - ~-I -____ -- - - I_-- I__ ~ - -

DIAGRAM SHEWING FLAP ARRANGEMENT AND P FOR AIR SPEED MEASUREMENT ON THE No.2 TOWING

CARRIAGE IN THE R.A.E. SEAPLANE TANK.

DIRECTION OF MOTION ---

DATUM FOR LONE,lTUOINAL I

POSITIONS FOR _

AIRSPEED MEASUREMENT

FRoNT SCREFN t

!/AFT

N .

SPAR OF CARRIAGE

FLAP ADJUSTMENT

WATER LEVEL I \ -- -- - -- -- ----- -- ----- ----_I___ -- -- ___- ~- -- --- -- -

DIAGRAM SHEWING FLAP ARRANGEMENT AND POSITIONS OF AIR SPEED MEASUREMENT ON No.1 TOWING CARRIAGE

IN R.A.E SEAPLANE TANK.

‘

FIG. 3.

PITOT CONNECTION /

STATIC CONNECTl,?hJ

BRASS TU&N$

GLASS STOP COCK

IN. PLY BASE BOARD .

HOLE’ FOR PIVOTING BASE. $3

SIDE VIEW OF PRESSURE GAUGE USED IN AIR SPEED MEASUREMENT

F PI MOU U ET

SPEED

F

IAGE

FIG. 8.

@ OF TANK

PORT ‘P

STARBOARD I

HEIGHT ABOVE WATER LEVEL,

AIR VELOCITY A5

.- IS IO 5

DIST.

0

FROM CENTRE

5 LINE, IN.

BALANCE: 6” A6OVE WATER %JRF/iCE B-B- -7 I2”ABOVE WATER SURFACE: -. . Is” ABOVE WATER SURFACE

VELOCITY FIELD UNDER No 2 TwlNG

CARWAGE IN PLANE OF MODEL.

BOW - DRAG 8ALANCE AT DIFFERENT HElC$dTS - NO FLAPS

FIGS.9 & IO.

MEAN RATIO OF AIRSPEED TO CARRIAGE SPEED- ;“+) MEAN

I

=L

IO 20 FLAP AN@E DEGREES

30

VAR CAR

-FIG.9.

IATION OF MEAN RATIO AIR SPEED TO RIAGE SPEED WITH FLAP ANGLE. .

A&E OF

REAR FLAP

TO HORIZONTAL

(W 2 CARRIAGE )

,

FIG. IO. *

CARRIAGE SPEED f?F?S.

FLAP ANGLE FOR”CORRECT” MEAN AIRSPEED AT DIFFERENT CARRIAGE SPEEDS. ’

(Ng. 2 CARRIAGE)

3

I HE&HT A.W.L

1

CARRIAGE SPEED 20 Fl?S

VARIATION OF 2 WITH

FIGS. I I QIZ.

t HEIGHT AWL

FIG. II.

I I Ilrn”” I II

\,- BOW

I \ \ \ AFTER

I I Ii I

,- BODY, Y I

t--tiiw ”

I\

-CARRIAGE - SPEED - - 28 FOPS.

HEIGHT ABOVE WATER SURFACE No. 2. CARR IAGE. ’

LB t

AIR DRAG, INDICATE0

FIG. 12.

BALANCE POSITION ABOVE - - -

j

- *’ .-

+’ d

,/

Rd

/- /- A’-

20 30 CARRIAGE SPEEO , FYI? S,

EFFECT OF BALANCE POSITION ON RESISTANCE MEASUREMENT ON No. 2 CARRIAGE

- -

FIGS. I3 &I4

vo -= o.g---$ VC =I0

VP FIG.13 va 0 95-s--- va VT= ‘*I -‘- .T = e =10.5 -II-

FLAP SETTlNq

VC VC .-- 1 b

to” I

TRdS”ERSE VERTICAL PLANE 57 INS FORdO OF DATUM i I I I I

RANSVERSE VERTICAL PLANE 94.5 INS. FORWARD OF DATUM.

I I I I I

I \++

TRANSVERSE VERTICAL PLANE 43 5 INS. FORWARD OF DA-T”&

+ I I 1 VC =CARRIAkESPE;FD

VARIATION 0; AIR SPEED W;” FLAP SETTkG No.1. CARRIAGE.

A 1 I HElQ+T A.W.L.

-0

CARRIAGE SPEED I6 ANDvJ3 F.F?S.

VARIATION OF K WITH

o-9 I.0 CARRIAGE SPEED 20 AND 36 &.k.

HEIGHT ABOVE WATER SURFACE FLAP SETTING 32” No.1. CARRIAGE.

C.P. No. 38 10010

A.R.C. Technical Report

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