Effects of compressibility and large angles of yaw on pressure indicated by a total-pressure tube

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Material Information

Title:
Effects of compressibility and large angles of yaw on pressure indicated by a total-pressure tube
Alternate Title:
NACA wartime reports
Physical Description:
6, 10 p. : ill. ; 28 cm.
Language:
English
Creator:
Humphreys, Milton D
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:
Yawing (Aerodynamics)   ( lcsh )
Compressibility   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: The effects of compressibility and angle of yaw on the pressure measured by a round-nose and a flat-nose total-pressure tube have been investigated. The tests were conducted in the Langley rectangular high-speed tunnel at Mach numbers from 0.3 to 0.9 for angles of yaw from 0° to 180°. The results indicated that no error was incurred in the measurement of total pressure by either tube for angles of yaw from 0° to 10° in the Mach number range investigated. At constant Mach numbers, the round-nose tube had a linear variation of total-pressure error with angle of yaw at angles ranging from 50° to 70°. This characteristic is desirable in yaw heads of the Y-type. The flat-nose tube had a nonlinear variation of total-pressure error with angle of yaw in this range.
Bibliography:
Includes bibliographic references (p. 6).
Statement of Responsibility:
by Milton D. Humphreys.
General Note:
"Report no. L-77."
General Note:
"Originally issued April 1945 as Restricted Bulletin L5C30."
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 - 003638540
oclc - 71834672
sobekcm - AA00006261_00001
System ID:
AA00006261:00001

Full Text

AtA L-77


RB No. L5C30


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WAllTIME'li REPORT
ORIGINALLY ISSUED
April 1945 as
Restricted Bulletin L5C30

EFFECTS OF COMPRESSIBILITY AND LARGE AIBLES YAW
ON PRESSURE INDICATED BY A TOTAL-PRESSURE TUBE
By Milton D. Humphreys

Langley Memorial Aeronautical Laboratory
Langley Field, Va.


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.


DOCUMENTS DEPARTMENr


L -77


7



































Digitized by the Internet Archive
in 2011 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


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T 1 T T.'- -' IC,:!


from toaila 1le Two r -iton nof totle nres.s. e .tuberes- h
tot-.-l-,,n..es ;re t',h"es '.a\ed wit?": "r, ..... .: t.:, i:l-A ..ilr str'ean
s bt Led in thiso llrert huld tte nl of : [,c n
An -L-.' t .;.. IoL1-n ','s3 r,-e.? fore h1: -n c,:.nc-. L ,,i to aet, r-
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11acb n n p.Z;-.s f r:'," 0.5 tj C..q ov r tr.-z ni le-of--,kw r :ange
from 1 to 1iCc 'Two b-,.'ri.. cf ',ta. ali- ,-esslle tu'.e ,e:'
t s F d s r l-nd rl os : ,.,' flat -.ose The- In for:.i;.;ti,?i,
.b~t'a:ier In t.his reTort should f-cilltate ,nal:/3-s cf
flc.w- i rectc.n 2measur'2-:,L.nts 3 .nri otJL-r ac rod,'.iamic
p ronrer ties.








FACA RB 7o. L5C30


APPARATUS :. 0 TODS


The tests were made in the Langley rectangular
bhih-sneed tunnel, which is an induction-tyne tuimel
having sc 4- by 1J-inch. test section. Atmosrheric air
Is inruced to flow through the tunnel by an induction
nozzle located downstream from the test section.
yceot for a small loss of pressure result'in from the
nrssage of air through the screens at the tunnel entrance,
the total pressure at tle test section is approximately
-qual to atmospheric pressure '.I's wind tunnel is
basically similar to the '..A.C.A. hi -h-speed wind tunnel
described in reference 1.

The round-nose and the flat-nose total-pressure
tubes used in this investigation were ie of brass
tb-in- hav'.ig an outside dia*r.eter of 0.125 inch and
walls 0.0254 inch thicli. 'he tubes were constructed
in the form of an L with a h3ad 1 inch l:: at an
angle of 900 to the suprort1-- handle (f:T. 1).

The total-pressure tube was mounted in the center
of the test section with the surporting spindle normal
to the tunnel wall and passing out through a hole of
1
a rroxinately -inch diameter drilled in the wall. The
head o! the tube could be rotat- about the spindle
axis through the : "le-of-- "w r..- and could be locked
In -.-n" desired position.





T total pressure measured above absolute zero with
air at rest

H' pressure indicated b' total-oreseure 'oub

free-stream Dach n,..:, r

I.Ix 'uch number at nose of tube computed on asesm p-
tionsathat flow is adiabatic and that :i' equals
static pressure at nose of tube

n fre :-stream static rrecsure









NACA RB No. L5C30


q free-stream dynamic pressure [2-pV 2

p density, slugs oer cubic foot
" velocity of mean free stream, feet ncr second

angle of yaw of instrument head


PREC ISIO 0


It is believed that practically all the errors to
wiich the quantities measured in this investigation are
subject are of an accidental nature. The variation in
'ach number in the test section narallel and normal to
the tunnel axis is insignificant for these tests. Tunnel
constriction effects should be negllgitile because of
che small size of the total-nressure tube relative to
the tunnel size. Air-flow misalinement and the error
10
in alinement of the total-oress;re tube are within it *

The tree-stream static ,resaure and the error in
total pressure as indicated by the total-pressure tubes
wv re m.easu'.red by: visual observation of liquid-filled
manome ters. Liquids of different densities were used
in the manometers for various range of pressure dif-
ferances to insure large rises of the liquid and thereby
rmunimize the errors in readings. An indication of the
magnitude of the accidental error involved in these
data is given in figures 2(a) and 2(b), each of which
shows the scatter for two tests with the total-nre3sure
tube at an angle of yaw of 650. Check points are indi-
cated by flagged symbols.

The data presented have been correct-ed for t-he
total-pressure loss resulting from the nass-el of the
air through the screens at the tunnel entrance. The
amount of this loss was determined by measurements
-made in the test section and in the low-speed region
ahead of the entrance cone and was checked by computa-
tions of the pressure loss thro-ugh screens.


RESULTS AND DISCUSSION

The variation of total-pressure error, in terms of
total pressure, with Mach number for the round-nose and









MACA RB Pc-. L5C50


for the flat-nose tubes is shown in figures 2(a) and 2(b),
respectively. At constant angles of yaw of 200 or
-~-. ater, the total-oressure error incre-as.ed with
increasing Mach number. The rate of change of the error
wi'th '.ch number increased as the angle of :ow was
increased from 200 to approximately 900, where the rate
of c A,-- of the error was at a maximum. At angles of
yaw from 900 to 1800, the slopes decreased with incr-asilng
angle of yaw.

The variation in ,he total-oressure error with .'ach
number became increasingly irregular in the free-stream
Sch number range from 0.7 to 0.8 for angles of s ,--
between 1100 and 1500 (figs. 2(a) and 2(b)). If the
flow is assumed to be adiabatic and the pressure
measured b{ the tube H' is assumed to correspond to
t?he static pressure of the flow in the vicinity of the
opening in the nose of the tube for these conditions,
the local lMach number T can be computed. The value
of H for a T.ch number of 1.0 would be 0472.
H
It can be seen that the irregularities in the curves
P7 HI
occur near a value of H of 0.472 and are possibly
H
due to the formation or movement of shock.

The variation of total-nressure error, in terms
of free-stream dynamic pressure, with .:h number is
shown in figure 3. For angles of yaw greater th.vi 200,
the total-pressure error had a small, nonlinear variation
with Mach number. This variation became irregular at
the higher angles of yaw and the most pronounced direc-
tional changes occurred near 90. No error was incurred
in the measurement of total pressure by either the round-
nose or the flat-nose tube over the Mach number range
extending from 0.5 to 0.9 for an angle-of-yaw range
from 00 to 100 (figs. 2 and 3).

The variation of the total-oressure error, in
terms of total pressure, with angle of -'ai.v is presented
in figure 4 for several :`."ch numbers. The curves were
obtained by cross-plotting the data presented in fig-
ure 2. The results show that the total-pressure error
increased with increasing the angle of :-w from 20 to
approximately 670 and then decree,--d as the angle of yaw
was increased to 1300.

At an an,-le of yaw of 180, the nrssure measured
at the nose of each total-or.ssure tube was arppro:-irrately








'TACA RB ro. L5C30 5


th-. sa,e for equal FI.'ach num,':ra and .'s be low free-
str. n.i static pressure PC, a..t all sCe ',.i3. T'-,e relation
\ .'r r

p, ,



'"or tither tube at s-n Incli n'-t icon of 1-00 to the aiir
stream is correct within 12 r.-rc.-nt of H-H ov-r
H
th": 2n nu,-'lD':r rc!e svsti -at d. Th'.s -gr e nment
'-.3s cnt 3 a possible r-et..: of dr .et 'r':in.in 3t-.ttic pres-
s'.'re e ns cf a s Zfl in. L .. "L.-At t.,t ..i bL.e nuz.fs l
in :.::3 "inst 1 lat.s L s.

T., :ar. tc ion ',n t t.,l---r,.: s r--- .r.' m", ii terms
0o ti s. .-.c '1 ;; :, 2 "- --'.. .* L.- 9 1 T'i .o i'f -c. l
of "ar "'or c,'oist.az. F.'. -. nu'.]b-: 3 'j s- .n in '"i ureC 5,
a cro' 'lot of tY. ta.. in '-1 ure ..'. e eas the flat-
no's-. t uoe had a nv-.l -1. .1, r- v -i--I tlinn of c ctal-r.res.- 're
e c.'r r d ::. :..le a ;:a v '.- r' :i. ,l' r r-j ,e frci
50'' o L f. 7 cr ,3 ,t tA' n.j :- r.'.e .':', -.u .-rol:, tu-I'.e
bar' t sc c .n -... '. Lat c', t\ tha; r A- nc' i
tuc .0"I D. uj si 1-- fos'r i;se ". -" Lesi'. of ti.'?
Y- .. e''-*t 'ne ; ead a Cin "c n.'.J-n so ti.tLes 1 L
an inel,.1..-d =n.le o.f 12. c l .. 'ine r. r v' ari ai on
in cal ibration f2t::or a0. .il:. r u' a' r -t '.

Ln order to -ive n. in i-. .t in of nos. -'i e af' l
of maTinressi'il ity on ci-.. cal briatc.n f'c tor of a ;a
he-ad, the slo -es of th:- curves of .f;l ure 5(1) L-.re shIown
in r"igure 6 ",r angles of :'-i' b.etveen C0 and 0 T i-'L
curve in,.'icates a ';iial effect of ccor:pre- sibility on
the c a L ration of a vn'J head havin rom-n-:cose tubes
if bhe :-aw h.? a supr rt is as 'urr-.d to iave nr el hl i
infl'u nee.





Tests made to deter-ina the ef'feLts of cor,,pre.3cibiLity
an-' ai-.Tle of :'a& on th, --ressure m-T surged b" A rou id-
nose anr.- a flat-nose total-ure..sure tub'.e ; ndiated that:

1. Total-opr-ssur: t.es. of the t.-n tested' in this
invest iLation would give tru9 total prc.ssurc for anrlgs
of yaw of 0 to 100 for .M.ach numbers from 0.5 to 0.0.








"T.CA RB No. L5C50


2. At constant 1Jach numbers, the round-nose tube
had a linear variation of total-pressure error aith
-r-le of '-aw at ,i.rles ran nog ",-:;. 500 to 700. 'T'
flat-nose tube had a nonlinear variation of the total-
ni-ess-l.re error with angle of yay, in ths range. The
roiund-nose tl'bes set at an included angle of 1200 should
therefore be desirable for use as co -.,--=!ts of a Y-tyro
yaw he*. .- s yaw head should give a linear variation
in calibration factor over an angular range of 100.


.. .n-- i.enorial Aeronautical Laboratory
Ilational Advisorv Comnittee for Aeronautics
'1: i d, Va.


















1. Stack, John: The ?:.A.C.A. High-3S--':i--ind Tr'L2el and
Tests of Six Proneller '-.ctions. NACA Ren. "D. 463,
19Q33.






NACA RB No. L5C30


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NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS.


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