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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
February 1943 as
THE BELT METHOD FOR MEASURING PRESSURE DISTRIBUTICM
By Blake W. Corson, Jr.
Langley Memorial Aeronautical Laboratory
Langley Field, Va.
UNIVERSITY OF FLORIDA
120 MARSTON SCIEC E ULBRARY
," '. E ;,i *i 1 7011
C-: .'./LLE,- FL 32611-7011 USA
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.
HATIOIAL ADVISORY COhMiITTEE FOR AERlOIAUTICS
THE BELT METHOD FOR IMEASURI:hG PRESSURE DISTRIBUTION
By Blake IW. Corson, Jr.
The measurement of pressure distribution may be
accomplished ra.'idl-. for -n;;, n"..boar of locations deemed
necessary in model or full-scale invustigatios by use
of Thu "bolt" m,.thod. Reaso-jqLle -ccuracy may be ob-
tained by careful use of this methoa.
ITTiRDU CTIO 0T
In wind-tunnel i..vest igation of engine corlings it
is desirable to obtnin a clenr ;:'icture of ,r-ssure dis-
tribution every'-her, in th, vicinity of the eni ine instal-
lation. The iLinortance of pressures within the cowling
which bear directly on en;ine coolin-, is obvious. Of
equal interest are tLe orussur'.s .vjr variu"s regions of
the cow11i ,- exterior in that ticse effect the internal
oressures availpbie for ej inj coolii,.-, i..dicate dri
qualities associated with .--t-rni l flo',. ai.d determine the
critical comoprc .sioii t'- soed.
Full-scale eni-6ne -ceill iis, ta li1t iorn r cen t 1,
tested 'vere hnot provided, wit.: stL.rface O)r-cFurL orifi.cEs.
If such orovistios had bear. niue, the time and expense
for in.stalling a satisfactor'r nur, er of ,i ensure orifices
woulj. have been exceFsire and t"Le t i.e r-equired for con-
nectirt: and disconnecti. their leads wjnCEVer the cowling
had to be r6njov.d wolld have m?.ad tLeir use imprpctical.
If external pressure distri but ions were t.' C e measured,
it would have to be b; a q.ic'l.y a li .caL' e .[ethod.
Since pressure i ea .re..tnt s were desired at q large
numal er of roiLts, and iniqs.u:>J as surface 'rcEssure orifices
were missing, these ri.easurement s could IhAve teen madt by
the use of a "i.iouse. Honw ver, the time lost during the
shutdowns that would have been necessary for the relocation
of the mouse made tLiis method prohibitive also.
DESZRIPTIO: CF "BlLT" L..ET:OD
The construction of e .oue s'ugested the use of a
belt of smaeli-auiA er cotpe:" tuoojs, s-vted to-ether,
each of ,-r.i>.I is "-'ov a.c'. with a si.n le orifice at a point
where the pressure L.ea sur -.at is to be uade. All of the
tu':es are sealed v-i o.,' CLa ea..d co.:nEcta to mano ieter
leacs at the other S.e a oclt iay readily be onIced at
any location that t..e ieasu.re-ent of a )ressur( distribu-
tion is desirt-L.
Since the a nlicat io of a ceit to the s,.'rface of a
body in effect c.iviy.fe-s -'i.pe of the body, it is reil-
ized taat the Tre-3s'lre aistribut -o: over t.he body near the
belt will be alte:'-.c. ; its rese':ce. On the other hand,
th.e use of the bdlt ..tadt per,..i s a iaeans for obtaining
a pressure distrio,-ti n over a 1ir:e area du'.ring a single
run. Alteration to the nodel is inconsequest iael. The
belt may be easil- .oved fro.u one rc ion to .i.ot..er on the
-.odel and may be '.isce:aed ctirel. u:o., comnletion, of
pressure-distribution -esasureents, la s.i no im.edim enta
on the model to i.iterfere witii subseoue!.t tests.
ZESCRIPTIOi OF TEST
In order to .scer c'-i. t '. sibili?'. n-id reliabil-
ity of Lhis method for mes':ri ress- re distribution,
a brief test was r.? e to det~r!..i the e:-.te.t of nL.reement
between a pressure distri-iation mu ,s're~ t", the b:it
metl.oi -rnd one me:-.. re," bI t e use of surface orifices.
These tests were coi.ducted in the .:ACA pro-peller-research
tunnel usi,.-: a boc- of revo.ltio., as t 'e Moriel oni whisn
the pressure distributions were iimas.irei.
A photograph of the belt iiInst~led on the model is
shown in figure i. Figure 2 is a sketc.' shor',ing the con-
struction of the felt. The model used as a su-tjoct had
17 surface orifice' in a plaie oi its ".orer s-rfice. The
pressure belt was r.ade *-ith 19 ti'.-es, i-ut thic extreme
tube at each edge was not -ised. A sinblL orifice v.as made
in each tube. Ori.fice.s '.err located nt aistP-ces aft from
the leading edge to correspond aoroxi;natel;.- to the surface
orifice locations o-: t..e body. cooper tubin& of 0.040-inch
diameter was used for the cell, *'.ich -hen cor'oleted was
about 3/4 inch wide. 'he m.aximu:., diameter of the r..odel was
approximately 21 inches. The leading edge of the belt
was screwed to the interior surface of the lip, the belt
was then t'7-t to conform snugly with the surface of the
model and was secured at the trailing edge with Scotch
tape. The belt ras located auproxiriatel;' c inches to one
side of the plane of tne surface orifices.
The leads from the nressvre belt and the surface'
orifices nere connected to the sawe culticle manometer
and a simultaneous reading made at an airspeed of approx-
imately 100 miles per hour.
DISCUSSION OF RESULTS
The results of the tests ere shown in figure 3.
Pressures were clotted directly in- inc'hs of alconol,
the plot showing vPriation of pressure with distances
fro.. t'-:e le dinr edge of the body. It can Ce seen that
tiere is ood p~reeme.t between the :rezsure acistribution
measured. wit' the orecouire belt gnd thot qobtained with
the s- 'rfsce orifties. Tt i; Lelieved t'.Pt for m~., inves-
tiati.o, ). the slight loe.s of accuracy incurred bc; the use
of a Deit for mens riL.. or sszure is .ore t.-n offset by
the si.-jlicit;, of its s rt':ct.-re and aopli cacion.
Several factors should oe con-ridered in the fabrica-
tion and use of s. -ch ?. clt. T'ho aet ;iT ra perri.issible
diameter of tl-t. corc-r + L s u eli for :..a-in, the uolt de-
oeids on the dtic-:.et .r a..d s.-oe. of the iody o:. which the
blt is to b"e Ts::.. J Te3;. h.vv et been mr c.e to estab-
li l- t. s ra'. ti];. rn; cs v, 'ture of L-C s:r-nrce probably
affects t-.e -i';] i lit;- cI 3r E -: mea ureai ..t s .Dy the
belt :ieti d. In .'he s L ec't test tl-e air f cr as~ the
body suiface res wer.1li1- to tie .bes cc:,.or ici a. the
belt. it is f:r tl.iEs -~~~ of aoolication t.iat th-e belt
method i i't, Ai'i d. r;.cr "-uild very iikel; he incurred
by oblierie :low ovur L"e telI .
No qtte-Lpt is t.i. ,- hen to de .cri e re: rir.ex n-.ts of
fabric'tio.a jr to rc-in; oot the pr ccioo use3 for the oelt
method. T e test e -r r.ed er.o .-tra i ;s tnit the belt
method used wit.n C.' r-re. o1n .'1il ,ive a Le .,iremar.t of
oressure distiba io cselal aojro;imat irin that obtained
from tie use of s;:rface orifices.
Langley Leuorial Aeroncrlt ic.-l Laboratory,
National Advisory Committee for Aeronautics,
Lagfjleey Field, V..
Digitized by Ihe Iniernel Archive
in 2011 With fuLnding froin
University of Florida, Geolge A. Smalhers Libraries Wilh support from LYRASIS and Ihe Sloan Foundation
hllp: www.archive.org details bellmelhodlormeaOOlang
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