Variation of hydrodynamic impact loads with flight-path angle for a prismatic float at 12° trim and with a 22 1/2° angle...

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Material Information

Title:
Variation of hydrodynamic impact loads with flight-path angle for a prismatic float at 12° trim and with a 22 1/2° angle of dead rise
Alternate Title:
NACA wartime reports
Physical Description:
6, 3 p. : ill. ; 28 cm.
Language:
English
Creator:
Batterson, Sidney A
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Seaplanes   ( lcsh )
Airplanes -- Landing   ( lcsh )
Aeronautics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: Tests were made in the Langley impact basin to determine the relationship between impact normal acceleration and flight-path angle for seaplanes landing on smooth water. The tests were made at varying resultant velocities with the model at 12° trim. The model had a 22 1/2° angle of dead rise and a total weight of 1100 pounds.
Bibliography:
Includes bibliographic references (p. 5).
Statement of Responsibility:
by Sidney A. Batterson.
General Note:
"Report no. L-68."
General Note:
"Originally issued February 1946 as Restricted Bulletin L5K21a."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003638594
oclc - 71837566
sobekcm - AA00006239_00001
System ID:
AA00006239:00001

Full Text

RB No. L21a


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WARTIMEll RIIEPORT
ORIGINALLY ISSUED
February 1946 as
Restricted Bulletin LK21a

VARIATION OF BHYIODYIAMC IMPACT LOADS WITH FLIGHT-PATH
ANL FOR A PRISMATIC FLOAT AT 120 TRIM AND WITH A

220 ArGLE OF IEAD RISE
By Sidney A. Batterson

Langley Memorial Aeronautical Laboratory
Langley Field, Va.







NACA


WASHINGTON
NACA WARTIME REPORTS are reprints of papers originally Issued to provide rapid distribution of
Advance research results to an authorized group requiring them for the war effort. They were pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.


L- 68


DOCUMENTS DEPARTMENT







--I


NACA RB No. L5K21a R.: RICTED

fNATI^';AL ADVISORY C0.2TIT-I. 20.. IC'--'"-C.-


?3TICTErD 3J-TT L.7TI


VARIATION OF HYDRODY"AI'TC IIF-D.CT LC .S I.12 .L. T-PATi

A'n-LE AOP A P-13'L,-TIC 'LCAT AT 120 TRI'"! AiD ..IT' A
1o
22- ANGLE OF D:.rD RIS-
2
By Sidney A. Batterscn





Tests were made in the Lanriljey insect basin to deter-
n.ine the r lationship between impact normal acceleration
and flight-path ar.le for sealar.es landin, on smooth
water. The tests were rr.ae at varying resultant veloci-
ties with th-e inmoel at 120 trim. The nodel had a
1
22- arrrle of 'ead rise and a total 'fei 1it of lln ',ourid..
The results cf the tests indicated tiht the :-:i'..';-.I:
impact normal accele-ation v.as proii'.tical to v '-2
over the test r-an r of fll:ht-path anp4le y a-.n th: ;
maxi-nimu ir;act :ncr-r:al acceleration occ: rred prior to or
at the instant of chi:ne i:!:ters3in.


IT% "TQ.ODUCT I'".


Th.e initial phase cf the research p rr at the
Lanple-% impact L.sia hats Iaen centered upon dete.rr-ining
the variation of hydrodynm',ic ir:;.act loads with -he prin-
cipal flight pararieters: velocity, flii:ht-h..th a,-e,
and trim. The variation of impact norrial acceleration
with resultant velocity is presented in reference 1. 'he
variation '.vth fl~.ht:t-path anal- and trim is being .ieter-
mined from data secur_.d by mr.akinC a series of rune at a
fixed trim and varying, flight-path angles n and then
repea:ing the runs for a different trim. Reference 2
presents data obtained for 30 trin: and reference ;, for o6
and 9 trim. The present report sives data obtained in a
similar manner at 120 trim.

The present tests were made over a larger range of
flight-path angle than those of references 2 and in


RZSIR ICTDZ








2 -.'OA .'3 "-. L5K21a


order to secure values i3ndcative of rcugh-water land'nrs.
This increased r:.rrs cf 2l':r.t-:a;th a ,;-le also pi:.rmitted
observations re- ridingg the effect of chine inrnersion on
the impact ncrnal acceleration.


SYTLCL3


V resultant velocity of float, feet 1.:r second

Vh horizontal velocity component of float, feet
per second'

V, vertical velocity coriorent of float, feet -er
second

g acceleration of gravity (32.2 ft/sec2)

Fi i.ipact force normal to water surface, p'Ou-:s

V; total model weight, pur-ids

w\
ni maximum i:noact load factor (-w)
imax

T float trim, degrees

v fli-hit-;.:th angle, degrees tan y = )

7 vertical di placement of float, i:-ches

Z 'TP, -'T' AITD I"S -'"T.7''"' n" O


TheM lines and p.-,tine'nt dimensions of t-.he T L..-l-y
m!r et basin float r.ode:.l i-l tested are shown i.i fi-ure 1.
The rioleI was the foretLod of the float describ,-d in
refer-'nc'e 1 and has a 22- angle T'f d:ad rise with no
2
chine fCa-e. Th modelll was tested at a total .-.eiCht of
1100 :'oi.inI,. The.' test equiLpmen1l ;nd -nstr:nUentatlon '.rere,
with thc exception of the accelercm.t, tr, the same as
th.cze described' in rcferriancu 1. An "ACt rlir-daim[..d accel-
troireter with a natural frequency of approximately
21 ccles per second :*.s usud to r,asure ir'-act .:or,:nl
accele ration.









rACA RB Po. L5:U2la


TLST ?ROCZDUFiE


The tests included riuns at 1,orizirntal velocities
ranging- from aoproxrinatcly 2 feet p3r s:z ona to ap_.pr-x1i-
mately D00 feet per second, and t!e v.Urtical velocity
1
ranged from approximLntcly 1- feet per second to 12 fret
per second. The ran-e of flight-path angle resulting
from the combination of vertical a..d horizontal velocities
was from approximately 10 to J0. The trimind d ai1-e of
yaw were held constant throughout the tezts at C!.c and 0,
respectively. "he denth of irmnersion vwas :me.siued at the
stern perpendicular to the level w-ater surface. Daring
the impact process a lift equal to the total weight of
the m-odel ';as exerted on the float by r.:ea.is of the bucy-
ancy engine described in reference 1. All test r:easure-
ments were recorded as time histories.


PRECIS IOI


The apparatus used in the present tests rive rieas-
urements that ar:e believed correct withinn the fo.ic.ing
limits:

Horizontal velocity, foot per second ..... 0.5
Vertical velocity, foot per second . 0.2
Vertical displacement, inch . .. .2
Acceleration, g . . t
.'ei. ht, pounds .. ... .... .. .. 2.0


RESULTS A/D DISCUSSION


The independent flight para-ieters, the maxir.:um
normal load factor for each i:npact, and the immersion
depth are tabulated for each run in cabl T. Because
the maximum impact normal acceleration vas shown in
reference 1 to be proportional to the square of the
resultant velocity, the hydrodynaric load Zactoir was
divided by V2 to eliminate the efftots of velocity.
The values of nmax 2 thus obtained are plotted in

figure 2 against the fliigt-path angle at the instant of
water contact. .ithlin the scatter of the tst points









':2A '3 LC( L5:21a


the variation of n, with y is a simple p':'..ur
J*' ay.
function over th:. test ran, e. Ivaslution of the slope
of the curve in figure 2 shoves uh-t for 120 trim


ni1.22



"a-x:imu; depth of i.rrlne'rion r.nd depth of immersion
at the time of nlw are plotted against the fliht-
path .ngle in figure 3. The distance irom the keel to
the chine at the stern of the model is 8.0 inches (fiC. 1).
Since the miod-el was tested at a trim of 120, an inr.tiersion
of 7.8 inches would cause the level :ater line to inter-
sect the chine at the model stern; farther immersion
would serve to move the water line and chine intersection
fo-';ard. -igure 5 shows that for flihtt-poAt airles up
to 150 the maxnimu, impact normal acceleration occurr-'
b:-fore a depth corresponding,. to chine immersion :at the
stern in level water :'as reac'.~. For I-.;'acts occurr'.r.g
at fliiht-path angles exceeding 150, ,however, th.e- curve
leveled off cbi'..:-'tly and the a.;:',t.n acceleration occurred
at a denth corros:-ondi-. a ro::i: 'tely to :'-. i-mersion
at the stern. M:ost of the scatter in the test points is
believed due to inaccuracies in ti-,e correlation between
accelerometor and displacement records.

The re.ai'i]ne curve in figure 3 shows t at the maxi-
mum depth of imiersion continues to increase as the fl1iht-
path :-l.le increases. Since this curve presents the
results of a slnrle inrst"i.'-.Z:t, time correlation cannot
be a source of error; however, t'L}se runs were made at
widely different values of Pr17r' nu'f.L'-rr. In the tesLs
of reference 2 different iaxi:.um imersions .'ere obtl'ned
for similar fl I-t-:ath an-lcs w~en the vsl.- of Froade
i,'r.:;-r was varied. 3'nce the present test rur.s v.'ere n:de
at va -yin- resultant velocities, the scatter of the t;st
points is beliov..d to I'e a result of this effect.

It should be noted in figure 2 that t'-.-r.2 is no
apparent c:..an.c in the variation of niw 'with flitht-
Wwax
path angles extunv.;in, well Lcuond those r.;-lttitg im
C inr'; immrsion.








"^CA R. :o. LS""2la


CC'iC I:SI (02


Tests were made ir. tLhe La::: 1:;, .pat : fsii to ':tJr-
nmine the relationship tp'tw'een i",.c: 1.orr'..1 ccce:-".tiL.. c
and flilht-rat'. anrle fo. seapi:;r.c-s .rdii; on i:coTh
'ate:'. r.e results of thie testL, ..r.ic 'h w. :r maoc fr
const -t .r.,e.el I**'c- t'. n. I moi l L:"i of 12."' '..n. c .-te
the followrn:'.- -nclu3ircns

1. Th'- .axYmu.n I ..at noriml aicc.l':rQtlc s 2- '-
1.22
port>onal to y o'er the tost runr 6 of fliht-pach
angle E .

2. T'e ,.arl,:"un uir.acG noi ..r:al a..:ee~a.tion uccurrei-
prio" to cr at the in riant of c'..;r ine Il Iu."isicfn.


Langley "e:-norial Aeronautical Lab or.tcry
rational Advisory C(,.;mittee for ,eronultties
LangleyI Fiel d, s .














1. Batterson, Sidney A.: The :TaIA I:u.act Casin and ..ater
LIinding Tests of a Float i;cJ3 l at V:.arious V'elocities
and WVieights. ITACA ACTI No. 1il{!, 19)4!.

2. Batterson, Sidne- A.: Variation of I'ydrody;-na.ic Impact
Loads with Flipht-Path Angle; for a Prismatic Float
'0
at 36 Trim and with a 22 Aniile of Dead Rise. ilACA
RB IJc. LA24, 1945.

3. B"tterson, Sidney A.., and Stewart, Th!lma: Variation
of Kydrodynamic Impact Loads 'with Fliht-PaLth uAgle
for a PrismatIc Float at 60 and ;o Trim and a
1 Angle of D
221 Angle of Dead Rise. IJACA RE ;To. L51121, 195.






































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NACA RB No. L5K21a 6
TABLE I
DATA FOR ?.iODEL I-1 TESTED I:' LA:nGL' I.:PACT BASI;:
[.I = 1100 1b; T = 12c]
I-

Run V Vh V I, Ymax at i",ax
(fps) (fps) (fps) (deg) __iaxI (in.)! ( .)
--- ---- ....-- t ---- -
I 1.. 96. 6 1.1 1. 2.0 1i.


[:112 1 1 51 I .1 7 .
.2 0.i 6.6 ,96.7 2.2 -. -.2 ".2

4 1.c 4.5 12.6 6i.j 2.4 20.0 7.9
5 12.1 5.1 I~.2 6c..'. 2." 20.1 7*.0
6 ill.$ 5 .6 12.9 64.1 2.5 20.2 ;7.
S 111.1 i 11.6 2.. -I 17. .5
12 .2 .6 .2
S 1. e..7 1 .8 5o 2.6 0.r ..5

10 .l2.1 12.5 17.4 2.8 1 .o -.
1! 5 1 Z 'I I.
11 !2. 1 .5 1 .- 0 .9 2.7 1 7.5
12 11.2 6.3 1 .2 5 1 2.5 .
1 L .5 11 .1. 7 2 7.4 4.
L+ 12.2 1 .6 .2 41. .0 l .' .
15 12.1 '1.7 1 5I0 .' 7.

-.,7 121 3. l
16 i .7 12.. 69. 2. 1.7 .
1 .6 5.7 '1 .0 b5.5 2. 2 i.
1 1.6 | .9 l-... .7 2. 2 .1
19 :!1 .S 2 ,.- 1 .7 5 .5 2.6 ,... .1
20 11.2 1..s .- 6.1 1 52.5 2.7 i1 .2 6.7



7 '0 59 .
l.1 7 5 .o 152.7 o.9 .5 111.5 ".
26 12.5 1 C.9 22.6 0 .0 1.1
27 11. : = .5 o0. 11.2 6.7 7.4 6..
2b. 7.2 .5 1I 2.7 6.2 '.
29 2. |1,4.6 .7 i .0 .6 p.5 5.S

51 4.6 .7 45.0 5i '.6 7
52 5.2 ,L1.2 45 1.2 '.2
52 5.2 i49 5.2 0.6 1.9 I .0 4.
S9.6.2 11.2 .7 7.5 5.1
:4 :1l.5 1. l 46.5 L1 .1 5.1 t.0 7.1
'AT, IO 'AL ADVISORY
COLT.iITT.-E FOR AL0!:A'U!ICS







NACA RB No. L5K21a Fig. 1











C2 Q P58 /7


CH/NE
HALF-BREADTH
-/19 4"-
9








BODY PLAN


5TATION 259 2/ 8,20 /ao5


NATIONAL ADVISOY
PROFILE nuT m CS


FIGURE I- L/NES OF FLOAT MODEL M-1 TESTED /N LANGLEY IMPACT BASIN.






NACA RB No. L5K21a


iF/ght -pa/h any/e, 7,deg

fyLgure 2.- Var/at/on of the parameter n,,;/v
wi/h f/gyhf-pa/h angle. 7r--/; W=//00 pounds


Fig. 2






NACA RB No. L5K21a


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,.' ..::s'--;C SCIENCE LIBRARY
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...-lNE'L LE. FL 32611-7011 USA










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