The measurement of pressure distribution may be accomplished rapidly for any number of locations deemed necessary in model or full-scale investigations by use of the "belt" method. Reasonable accuracy may be obtained by careful use of this method

Corson, Blake W., Jr.

English

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• I NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 
ORIGINALLY ISSUED 
February 1943 ae 
Restricted Bulletin 
THE BELT METHOD FOR MEASURmG PRESSURE DISTRIBUTICN 
By Blake W. Corson, Jr. 
Langley Memorial Aeronautical Laboratory 
Langley Field, Va. 
I 
WASHINGTON 
I 
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 unclassiiied. Some of these reports were not tech-
nically edited. All have been 'reproduced without change in order to expedite general distribution. 
L - 244 
https://ntrs.nasa.gov/search.jsp?R=19930093278 2020-06-17T01:41:38+00:00Z
NAT IONAL ADV I SORY COM~ I TTEE FOR AERONAUTIC S 
THE BELT METHOD FOR MEASURING PRESSURE DISTRIBUT I ON 
By Blake W. Corson , Jr . 
SUMMARY 
The measurement of pressure distribu tion may be 
accomplished ra-p idly fo r a ny n'HiJbe r of locat ions deemed 
n ece ssary in model or full - scale investi~ations by use 
of the llb e lt 11 method. Reaso nabl accu r acy may be ob-
tained by careful use of this method . 
HJTRODUCT I ON 
I n wind - tunnel i nvestigation of engi n e cowlings it 
is desirable to obtain a clear picture of p r a ssure dis-
tribution every her0 i n the vicinit y of the engine instal-
lation . The ill1~') orta nce of pressuras within the cowling 
which bear directly on eng ine cooling is obvious . Of 
equal interest are the ~ressures over various regions of 
the co li nb exterior in that t he se affect the internal 
pressures availAble for en~ine cooling , i ~di cate drag 
qualities associ a ted wi tl1 external flow , afld determine th e 
critical comp ressi bili t y speed . 
Full - scale engine nacelle install8tions recently 
test e d tere not provided with surfa ce p r essu re orifices . 
I f such provisions had been made , the time and. expense 
for i n stalling a satisfactory number of uressure ori f ices 
woul~ have been excessive and the time required for con-
necting and disconnecti~g t he ir leads hene v e r the cowling 
had to be removed would have made their use impractical: 
If external pressure distributions were to be me asured , 
it would have to be by a quickly a~o licable method . 
S i l1 c e u r e s sur e r, e a s ·,;l r e ;n e n t s w e r e d e s i r e d a t a l a r g e 
num1) er of points , and in-<ts rau ch as surface p resstre orifices 
were missing , these mea surements could have been made by 
the use of a 11 mouse . 11 Howev r , t he time lost during the 
s hu tdowns that would have been necessa r y for th e relocat i on 
of the mou s e made this method prohibitive also . 
2 
DESCRIP'IIO:~ OF 11 BE LT 11 kETB. OD 
Tha constru cti on of a ~o~se su[gested t~e usa of a 
~elt of small-aiameter coppe= tubes , sweated toge t he r , 
e~ch of wh ich is pr ovided w i~h a si1g le orifice at a point 
where the 1)re ssure measurement is to be r1ade . All of t e 
tubes a re se a led at one end and c onnect ed to man ometer 
l eads a t the ot her . s~ ch a belt may re ad i ly be pl aced at 
any l o cation that t:.e measureh.ent of a pre s su re distribu-
tion is de sir e6. . 
Since the a)Dlication of a belt to the su rf ace of a 
body in effect c hauge s . th5 she~e of the body , it is real -
ized t~at t~e pre ssu re distribution ave~ the b ody n ea r th e 
belt wil l be altered b • it s pr esence . On the ot he r hand , 
the use of t~e belt met hod pe r mit s a means for obtaining 
a p ressure distribution over a la rge area during a si ng le 
r un . Alteration to t ~.e mode ::. is inconseq,ential. The 
belt may be easily moved from one r eg io n to Rnother on the 
mode l and ma~r ~e di scarded entirely upon co mpletio11 of 
p r e ssure - dis t ri bu tion measure1;1ents , leav i ;:g no i m-oedi Lenta 
on the mod el to i:nterfere wit. sub s equent te s t s. 
DESCRIPTIO~ OF TEST 
I 11 order to as c e r t a i r; t .1. e fa l1 sib i 1 it .- and r e 1 i a b i 1 -
ity of this "e t hod f or ~ea surin~ pre ssu r e distribution , 
a brief test was made to det · r 2 i ne the eitent of ~ re eme nt 
between a pr e ssur e distribution mea su re d by the belt 
method and on e measured by the use of s~rface orifices . 
These tests vere co ndu cted i n t he ~ACA propeller - research 
t unn el u si ng a bod~ of revolut io n a s the mod el on which 
the ? ressur e distributions were measu re d . 
A p~otog rau~ of the te l t i n st 8ll ed on the model is 
shown in fi~ure 1 . Fibure 2 is a sketc h showing the con-
structio n of the be lt . ~ he model u sed a s a sub ject had 
17 surface orifices in a plane on its 1~pe r surface . The 
pressure b e lt vas Lade ,ith 1 9 tubes , but the extreme 
t ub e at eac~ edge wa s not use d. A sinbl6 orifice wa s made 
i n eac~ tube . Orifices were loc~ted ~t d ista nce s aft from 
t h e leading edge to correspond a?p roximately to the surface 
orifice locations on the bod~ . Copper tubing of 0 . 040 - inch d i am e t e r w a s u s e d f o r th e ·o e 1 t , ·.v h i c h ''! h en c o r:ro 1 e t e d w a s 
about 3/4 inch wide . Tl: e max i mu, diame ter of the rr:ode l was 
~---------------------
(-J 
I 
f-=1 
au~roxim~tely 21 i nches. The leading edge of the belt 
was screwed to the iLterior surface of t he lip , the belt 
was the:1 1-, io:oe~t to conform snug ly with the surface of t b e 
model and was secu r ed a t t h e trailing edg e with Sco tch 
tape. The belt ras locA.ted approxi mately 6 i n ches to o 1e 
side of the plane of tne surface orif ic es . 
T:'1e leads f ro lll the !Jress,J.re belt a nd the urface 
orifices nere connec ted to the saille ~ultiple manometer 
and a simultaneous readi ng :naf.e at an airspeed of approx-
i mately lCO miles p~r hour . 
DISCUSSION OF RESULTS 
The res~lts of the te sts ere s hown in fi gu re 3 . 
Pressure s were plotted directly in i nc he s o! alcohol , 
t ~ e p lot sho wing variation o~ p re ssure with distances 
fro~ tje leadi ng ed ~ e of the body . It c ~ n be seen that 
t ~e re is g ood a gre e went betryeen th e p ressure dist ri~ution 
me~sured w i t~ the p reasu re bel t and that obt ained vith 
th e s~rface orific e s . It i a be lieve d t~at for maay inves-
ti ~ etions t he sli ~h t lo s s of accuracy incurr e d by the use 
of a be~t for measu ri ~g ~ r e ssure is more t han offs e t by 
the s i !!lU l i c it ;; of i t s s '.; r u c t u r 6 a n d a:o p 1 i c a t i o n • 
Several factors s~ould b e c onsidered in the fabrica-
tion and u se of su ch a bo lt. The illa ximum permiss ible 
dia me ter of tho corpe r ube s used for mak i ng the belt de-
? Bnds on the dia~ete r and sh-pe of the bo dy o~ which the 
bolt ia t o ~e u sdd. No te~ t s have yet been mRde to es~ab­
li nh t ~~ s r elatio, . The c urvPture of the surf ace probab ly 
af ~ ects t~e r&Jia~il it ~ of Jr~ ssure measureme nts by the 
belt method. In the s ~bj ect tests the air f l ow at the 
body surface was o?rallel to the tube s comp ri£i n~ the 
belt. It i s for thi s L:·pe of application t ~at t ~e belt 
method is i ntended . Error would ve ry likely be incurred 
by obli qu e flow over t~e belt . 
No at t e Gp t i ;; n.a d. o ]:-,_ e r e t o de s c r i be r e f in em e :..1 t. s of 
fabric at io ~ or t o ~ oi nt out the possible useo for the oe lt 
method. Tne test d es~ribed demonatrates t h3t tha b elt 
method used with discretio~ nill ~i ve a measu reme n t of 
uressure dist r ibution clo se ly ao~roximating tha t obtained 
fro m the use of su rface orifices. 
Langley Memorial Aeronautical La~o ratory, 
National Ad v isory Co mmit tee or Aeronautics, 
La ng ley Field, Vn . 
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I TlTlE: The Belt Metbod for Measurlnc Pressure Distribution An- n245 (Noae) 
AUTHOR(S): Corson, B. W. -. _, -
ORIGINATING AGENCY: National AdYisory Committee for Aeronautics , Washington, D. C. R.B.-L-244 
PUBliSHED IY: (Same) --_,.-
.... 
Feb ' 43 
ABSTRAct: 
Tbe belt cons Isis of small copper tubes, sweated tocether, each of which Is pro-
vided with a s lncle orifice at a poiDt where the pressure measurement Is to be 
made. Tubes are s ealed at oae end and connected to manometer leads at the 
other. Comparison of pressure measurements obtained with surface orifices 
and a pressure belt Is Illustrated. Agreement Is shown between tbe two methods 
so the supt loes of accuracy by use of the belt Is more than offset by the 
simplicity of lis structure and application. 
All SHEET NO.: R-17-3-7 
AIR nCHNICA1 INDIX 


The Belt Method for Measuring Pressure Distribution

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