NACA RM L55F20 Hydrodynamic Pressure Distribution Obtained With a Streamline Body Equipped With...

7/27/2019 NACA RM L55F20 Hydrodynamic Pressure Distribution Obtained With a Streamline Body Equipped With Chine Strips

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-6CODYRM L55F20

RESEARCH MEMORANDUM

HYDRODYNAMTC PRESSURE DISTRIBUTIOK OBTAINED WITH ASTREAMLINE BODY EQUIPPED WITH CHINE STRIPS

By Bernard WeinflashLangley A e r o n a u t i d Laboratory


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ICNACA REI L55F20

NATIONAL ADVISORY COMMITTEE FOR AERONAZTTICS

RESEARCH MEMOFWIDUM

HYDRODYNAMIC PRESSURF: DISTRIBUlCION OBTAINED WITH AS " L I N E BODY EQUIPPED WITH CHINE STRIPS

By Bernard Weinfflash

A l i m i t ed i nves t i ge t i on was d e o determine the nature of thepressu re dis t r ib ut ion and the order of magnitudeof th e pressures on as t re an l ine bodymoving on a wate r surfa ce. The body of revolut ion wasequipped w i t h chine s t r ips and had a f i n e n e s s r a t i o of 9. Pressures. were neasured a t selectedalues ofpeed, t r i m , an6 wettedength.These parameters were se lec ted to ob ta in pres sures in r eg ions wherenegative forces were indic ated by force data previously obtained and t oobtain some e f f e c t s of ind iv idua l paramter s .-

The r e s u l t s f r o = t h i s i nves t i ga t i on i nd i ca t e t h a t t he r e i s a chaxac-t e r i s t ic p a t t e r n of hydrodynamic pressure d i s t r ibu t ion for s t r eaml inebodies equipped with chine strips and movingon a water surface. In along i tudin al di rec t ion moving a f t , t'ne pr es su re r is es to a pos i t iv e peaka t the s t agna t ion l ine , then decreases usual ly t o a negative value andf ina l ly i nc rea s es t o a small posi t ive value. I n a t r ans ve r s e d i r ec t i onfromthe lower prof i l e line , the pos i t ive pres sures genera l ly decreaseda t f i r s t and then increase d to a peak j u s t inboard of the chi ne s t r ip s .Negative press ures gen erally aec rease d transv ersely from the p r o f i l e l i newithout a pronomced peak a t th e chine st r i p . Themeximum ne ga ti ve pr es -sure ueasured was about 0.25 pound pe r s q m e i nch .

IJPTRODUCTION

Hydro5ynamic f o r c e te st s of reference 1on models of s t r e d i n ebod ies nod ified by narrow chine st r i p s have indicated. t h a t such forms m ybe s u i t a b l e f o r h u l l s of water-besedairplanes. They are o f p a r t i c u l a rin te re st wher- used i n conjunction wi th hydzo-skis or hydrofoils. Stream-l i ne bod i e s are also of hydro&ynemic ifiterest for use as wing- t ip f loatssn& s s containers orexternel stores. Bowever, th e presence 03 negativepressures was detected during th e force t e s t s of these streamline bodies.Ekowledge of the magnitude and dis t r ibu t ion of these pressures and of the


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2 L NACA RM L55F20pressure di str i but i on n general i s essent i al ton underst andi ng of thef orces acti ng on such bodi es. rAccordi ngl y, thi s paper gi ves the resul t s ofn i nvest i gat i on mdew th a s t r edi ne body t o obtai n hyf i romamc pressure di str i but i ons f ora f ew sel ected test condi t i ons expected to be ofost i nterest based onthe f i ndi ngsof t he i nvest i gat i on repor tean ref erence 1. The mo&eltest ed hzd theame di nensi ons as ti e f i neness-rat i o- 9del used i n thef orce tests reported i n ref erence.

SYMBOLS

cvsl

9

P7

speed coef f i ci ent basedn hul l vol ume, /& = 0.211vdi mt er of nodel , i n.wetted l ength, i n.overal l l ength f nodel , 46.75 i n.measured dynamc pressure on model (does not i ncl ude st ati cdi spl acement) , lb / sq i n.dynamc pressure at st agnat i on poi nt ,, l b/ sq i n.144

speed, f p sst ati on measured r o n nose of mcdel al ong centerhe, i n.cent ral angl e measured outboard f rom l ower prof i l e l i ne,iegl i near di stzcce measured al ong center l i ne f rom rear ofnodel , i n.value of h for maxi m posi t i ve pressure on l ower prof i l el i ne, i n.mass densi ty of tow ng- tank water ,1.97 sl ugs/ cu f ttr i n; , angl e between center l i nef model an& hori zontal ,ieg


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NACA RM L55F20

The =ode1 wa.S-DESCRIPTION OF MODE&

lody of revoluti on defined b:b

3

the o f fse ts g iven intable I. A photograph o? the model i s shown i n f i g u r e 1 and some con-s t r uc t ion de ta i l s a re shown i n f igure 2 . The model was constructed byforming a c l e a r p h s t i c s h e l l pa rt ed in to two halves along a hor izon ta lplane of symmetry an&assembling the two halves around a brass frame.Nerrow full -le ng th chi ne str ip s were locate d on the lower half of th emodel alo ng th e lin es of in te rs ec ti on formed by passing planes throughth e model c en te r l i ne a t a n angle of 45O from t h e v e r t i c a l as ind ica tedi n f i g u r e 2 .

There were 246, 0.024-inch-diameter or if ic es lo ca te d on th e bottomof t he model in fiv e lo ng it ud in al rows deFined by pessing planes throught h e c e n t e r l i n e of the Eodel a t engles of Oo, l 5 O , 30, 45O, and 600 t op o r t of the lower p rof i le l in e . The 45O l l n e of o r i f i c e s was plzced justa lo n g th e se p ro z i l e l i n e s a r e g iv e n in table 11. Tie o r i f i c e s wered r i l l e d p e rp e n d ic u la r t o the sur face of th e p l a s t i c h u l l and sp e c ia l c a r ewes t aken to insu re c lea n sharp edges. T h i s w a s i n accordancewitn th efilzdings of references 2 and 3 where it w a s shown that such precautionse re n e c e s sa ry o make accuratepressur e measurements. St ai nl es s- st ee ltubes of 0.0625-inch insi de dia met er were inser-led i n th e model a t eacho r i f i c e lo c a t io n as shown i n f igure 2 t o produce a connection fo r th ef le xib le pla st i c tub ing lea din g to the manometer.

- inboerd of thehine s t r i p . The spacing and loc ati on of th e ri fi ce sI

APPARATUS AND PROCEDURETests were =de with t h e small m & e l owing gear of Langley tenk

no. 2. The Eodel was towed a t fix ed speeds, trims, an& drafts. The con-d i t i o n s t e s t e d are given i n t h e following schedule:

RUE"2L34567

Speed, V,f p s305065

I 30, 3020~ 20

Wetted-lengthr a t i o , Z/L0.58.. 858588379- 79

Chines t r i p sO nOnOnOnOnOnO f f


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4 NACA RM L55F20Runs 1 and 7 were se le ct ed because t he for ce t e s t data of reference 1i l ld icated argenegat iveforcesact ingmder hesecondi t ions . R u n s 2t o 6 were selected to give the wides t var iat ion poss :ble i n the paran-et er s be in g comparred wi th in th e scope of the f o r c e t e s t s of r e fe r ence 1.

The method of measuring th e pr es su re i s shown sch em atic ally in f ig-ure 3 and was developed for the t es t s r epor te d in r e l ' e rence 3 . The pres-sur es were t ran sm itte d from the model o ri fi ce s to th e xe rc ur y manometertube s by fre sh water. In orde r o .orevent the pos i t iv e pressu res on the=ode1 from for ci ng th e sa lt water of the towing tan k in to th e system asthe towing carriage WES brought xp t o speed, th e re se rv oi r of mercury wesr a i s e d i n a manner t h a t would cause some flow of th e f re s h w.zter out oft i e model o r i f i ce s . In oraer o cow ensa te for he water l e g on t he manom-eter tubes comected to the model or f f i ce s , the two re fe rence tubes a t th eends of t he nanometer board were connected t o a f resh-water reservoir w i t han open surface 2.6 inches above th e fr ee water le v el of the t ank .

Sin ce the re were only 100 t ub es i n t h e m o m e t e r board, only a p a r t ofth e 2k6 or i f i ce s in the nod el coultibeconnected on any one run. The ori-f ices connected to he mo ze ter were se lec ted s o a s to cover thewetted L.m e a d u r i n g t i e run.The vertical manometer board was placed about 8 feet from the modeland the pre ssu res were recordea wi th a canera. A second cmera w a s locateda t the bottom of th e towing tank t o ta k e underwater photographs as thenodelpassedover it a t t e s t speed. The wo cm er& svereoperated s f m l -taneously by nezns of a photoelect r ic re lay zr rangenent . Typical photo-graphs aken by th e two caq ers s are shown i n f i gu r e s 4 and 5.The hydrodynamic pressure st a pa r t i cu la r o r i f i ce in pounds per squareinch was ob-dined asfo llo ws . The hei gh t of th e mercury column co rre-

sponding t o tha t o r i f i ce was subt rac ted f ron the he igh t of the mercurycolumn in the refe ren ce tub es; and th is di f fe rence wes mcltirrlied by thediff ere nce between th e sp ec if i c weigkts of xercury and fr esh wate r ,0.453 pound perccbic nch. To this pro du ct WE?S adtied elg eb raic ally thecor rec t ion for the he igh t of the reference- tube water re se rv oi r lev el &bowt i e f r e e water l ev e l o f the enk (0.094 pound persqua re nch) . Themeasured pre ssu res , the refo re, did no t inclucle the s t a t i c p r e s s w e s due t ot he d r a f t of t h e o r i f i ce s .Wetted le ng th s were ob tsin e& from th e underwater photographs and were

neasu red f r o n t he a f t end of the model to th e in te rs ec t i on of the heavys p r ay l i ne wit'r- th e lawer pr of i le as shown on figure 4. Trin - a s measuredas the ang le betx een the cect er l ine of t ne model and the hor izontal .


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7- WtklOUt a pronow- ced peak t the chi ne st r i p. Theax imum negat i vepressure measured vas about.25 pound per square i nch...

Langl ey Aeronaut i cal Leboratory,Nat i ocal Advi sory Commttee for Aeronaut i cs,Lengl ey Fi el d, Va. , J une, 1955.

RETERENCES

1. Wei nzl ash, Bernard, and. Fontana, Rudol ph.: The Qrdrodynamic ForceChzracter i sti cs of Streami ne Bodi es f Revol ut i on Havi ng Fi nenessRat i os of 6 , 9, and 12 WFth end Wthout Chi ne St r i ps.ACA- RM L54Q2, 19552. Rayl e, Roy., J r . : An hvest i gat i on of the I nf l ueoce of Or i f i ce- GeometryonStat i cPressureMeasureznents. M S. Thesi s, M I. T.,

I9493 . Khpryzn, Wal terJ., and Boyd, George., Jr.: Eydrodynamic PressureD str i but i ons Obtai ned Dur i ng Pl m i ng I nvesti gat i on of Fi veRel ated Pr i smat i c Surf aces. NACA TN 3477, 1955.


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8

TABLF: IMODEL OFFSETS

~Station, x, in.0-4 7981.962 .go3.847.819 -7211.6915.5719 4923.38

27.2631.1835.0633.9444.7945.7646.75

3.88

40.9142.87

Diameter, d, in.01.111.502.092.512.873 - 4 43.884.224.494.905.125.205 .or:4.593.812.671.38-70.352.04

0

NACA RM L55F20


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2cNACA RM ~ 5 5 ~ 2 0 9

TABLE I1LOCATION OF ORIE'IGES

123456a217758sr29 to 30a3 9 to 35$b

3637383940414243444546

Region covered by orificese = 150

_IA

Y

Station, x, in. e = 00 e = 60

"1-inch longitudinal spacing.bl/2-inch longitudinal pacing.


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Figure 1.- Photograph of model.

I a


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r* A1""" Solid plastic

o 25" clearplastic shellSection A-A

L ASide view

dd - .125" 0 D .- .062gt1 I.D.Stainless

pr steel tube

-I+ .024." .D .Ty-plcal orificeinstallation

0 '* Stainless steel zube.dtO" O.D..030" I D.L . I

Alternate orifice installationused in aft portionf model

Location of longituainnlrows of oriflcesFigure 2.- Model detai ls .


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12

100 pressure tcbes

. I I Wirch-I I 9P

F-exible tcbeI

Ekesh-water reservoir1

Figure 3.- Schematic i l l u s t r e h i o n of method of measuring pressures.


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L-89 49Figure 4.- Underwater photograph il lu s t r a t in g method OP obtaining wetted

Ilength.


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14 NACA IIM L55F20

Figure 5.- Typical t e s t record ( r u n 3) .


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j e = o o ItI I I I I I I I I I I I

I I I I I I I I I I I 1

1.6 I f I 1 I I I I I 1 I8 = 60

.s - -

- 3 I I I I I I I I I I I0 I: S 12 16 20 24 26 32 56 40 k4 4Distar-ce *om af' end of model. X , In.(a) v = 30 feet Der second; T = 4; Z/L = 0.58; strips on; l zul 1.

Figure 6 . - Pressure data.


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16 - AC4 RM L55F201 r

.8

0

-.8

e = oc

1.6 I I I I I I I I I I I I 1

1.61 I I I I I I I I 1 I I 1

(b) V = 50 f ee t per s.econd; T = 4O; Z/L = 0.58; strips on; run 2.Figure 6 . ContinLted.

3c


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."2 4 I I I I I I I I I I I

I

i-.8 I I I 1 I I I I I I

0

J

( c ) v = 65 Peet per second; T = 4O; Z/L = 0.58; strips on; run 3 .Figure 6.- Continued.


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Wetted ler4:h -4I I I I I I I I I I I 1

(a ) V = 30 feet per second; T = 8 O ; Z/L = 0.58; strips on; 4.Figure 6 . - Continued.


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1.6 I I I I I I I I I I Ifa = 150

- 6 - -0

!z.-Ie$ m s I I I I I I I I I I I

"y-v"

(e) v = 30 feet per second; T = 4O; 2/L = 0.83; strips on; run 5 .Figure 6.- Continued.


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20 NACA FM L55F20

I


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EACA m ~ 5 5 ~ 2 0 21

Net t ed length -1.6 I I I I I I I I I I I 1


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22 - NCICA EM ~ 5 5 ~ 2 0.16 I I t I I I I I I I Ii Code Speed Run no. I, 2 8 1 e = 00 12

3 P t .

-.a81 I L I I I I I I I I I I. = E , I I I I I I I I I I I I

-- "" -__0 - -"" - "-Ii- 3a. I I I I I I I I I I I

.15 I I I 1 I I I I I I I I0 = j O o

0

. a I I I I I I I I I Ie = 600 I0. " "" "".

-.030 .I .2 .3 .4 - 5 .o .7 .a .9 1.0 1.1 1.2".h

(a)Longi tud ina l d i s t r ibu t ion of pressure.Figure 7.- Eff ect of speed. T = bo; Z/L = 0.58; strips on.

NACA FML55F20


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23

.16 * Code Speed ~ u no.50 20-- ch in e s t r ip-\5 30 30 1 Location of0""" t-.08 - - -- - - - - -- """""

Ph i """"----- c II d0" 08 I I0 15 30 LS 60Transverse location, 8 , deg(b) Trznsverse distribution f peak pressures in v5cinity of stagnationline..I6 I I I-08 -

P A0 """ " " - - - - - - - - - - 9-"-08 I 10 15 30 45 60

Twnsverse ocation, 8 , 8eg(c> Transverse distribution f largest negstive pressures ft of the peakpressures.

Figure 7.- Concluded.

.


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- .e l I I I I f I I I I I I I

LF

1.6 I I I I I 1 I I I I I II.a- '\/= 450 ' \/ \,@ ""- ""_" -""" - \

(a) Longitudinal distribution f pressure.Figure 8.- Effect of t r h . V = 30 feet per second; t / L = 0.58; strips on.

4cWACA R!! L55F20


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( c ) Transverse distribution of lazgest negative pressures aft of the peakpressures.Figure 8.- Concluded.


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26 NACA RM L55F20

-." -

."1.6 I I I I I I I I I - --r- - 1

-."e = boo I I I I I I I I I I

0 1" "_ "" """"

-.e0 I I I I I I I I I I I.1 .2 - 3 -1: .S .6 .7 .e .9 1.0 1.1 1.2h l b

(a) Longitudinal distribution of pressure.Figure 9.- Effect of wetted length. = 30 feet per second; T = 4;strips on.

NACA FN ~ 5 5 ~ 2 0 2'1


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Lc 2 .h I t / L R d o. I0- 0.58 1* 8 3 5 Location of

-51.6 * hine strip -*3 //---"I \ /"\ //2 . 8 -..E ""E - I R\ // -u)sID -& O

-.8 - 1 10 15 30 r;S I60Transverse location, 0 , deg(b) Transverse distribution f peak pressures in vicinity of stagnationline.

2.&

a 1.6*


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28 - NACA FM L55F20.a I I I I Stripa zun no. I I I I Ie = 00 on 6"" "_ off 70 " - """""".8 I I I I I I I I I L -7-= 1500

.-E:

I I I I I I I I I t I t.8 I I 1 - 1 I I I I I I I

0 = lL50-0 --" --.8 I f I I I I I I I I I

8 I I I I I I I I I I9 = 600 I

0 ---8, I I I I I I t I I I I.1 .2 .3 -4 .5 .6 -7 .s .9 1.0 1.1 1.2

(a) Longitudinal distrtbution of pressure.Figure LO.- Effect of chine strips. V = 20 feet per second; T2/L = 0.79. = 40;

5cNACA RM ~ 5 5 ~ 2 0 29


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-2 .lI 1 IS tr ip s Run no.- 0 on 6

0"- of f 7F:-r i1.6 -

Location of< t2schir.e strip

.a -*5 " """"""-


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NACA RM L55F20 Hydrodynamic Pressure Distribution Obtained With a Streamline Body Equipped With...

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