Research abstracts

National Advisory Committee for Aeronautics


Research Abstracts


NO.80


MARCH 29, 1955


CURRENT NACA REPORTS

NACA Rept. 1179 (

A NOTE ON SECONDARY FLOW [N ROTATING.
RADIAL CHANNELS. James J. Kramer and John
D. Stanitz. 1954. ii, 12p. diagrs. (NACA
Rept. 1179. Formerly TN 3013)

A general vector differential equation for the vor-
ticity component parallel to a streamline is derived
for steady, nonviscous and incompressible flow in a
rotating system. This equation is then simplified by
restricting it to rotating radial channels and by
making further simplifying assumptions. This sim-
plified equation is used to solve for the secondary
vorticity, the vorticity component parallel to the
streamline, in three special cases involving different
streamtube geometries; the results are presented in
a.series of figures. The secondary vorticity is
*shown to decrease with decreased absolute angular
velocity of the fluid, decreased inlet total-pressure
gradient, decreased length of relative flow path, and
increased relative velocity.



NACA RM E54D13

A DROP TEST FOR THE EVALUATION OF THE
IMPACT STRENGTH OF CERMETS. B. Pinkel,
G. C. Deutsch and N. H. Katz. March 1955. 8p.
diagrs., photo. (NACA RM E54D13)

The development of brittle high-temperature mate-
rials has focused attention on the impact resistance
of these materials. This report describes a device
for measuring very small values of impact resistance
both at norm and elevated temperatures. The device
is believed to eliminate extraneous energies, such as
the "toss energy" from the impact strength. The
method of testing consists of dropping a hammer
. from increasing heights so that it strikes near the
"' ffrib@ end of a cantilever beam specimen. The energy
of the hammer when the specimen fractures is the
impact strength. Representative values of the im-
pact strengths of several high-temperature materials
are given.



NACA TM 1382

STEADY PROPERLY-BANKED TURNS OF
TURBOJET-PROPELLED AIRPLANES. (La Virata
Corretta Stazionaria Degli Aeroplani Azionati da
Turboreattori). Angelo MIele. March 1955. 33p.
diagrs., tab. (NACA TM 1382. Trans. from Rivista
Aeronautica, v.27, no.l, 1951, p.23-35)


The problem of a jet propelled airplane in a steady
turn is analyzed for the case of parabolic and non-
parabolic aircraft polars. A general solution is...--
obtained and the special cases of max'juntt-ked
turn, maximum angular velo ctritnand minimum
radius turn are then investing ted. -ref compari-
son of the jet and reciprocating prb ~ied airplape.i- -
made. Compressibility effect are considered. -



NACA TN 3336 I t -u -

REVIEW OF EXPERIMENTAL INVESTIGATIONS OF
LIQUID-METAL HEAT TRANSFER. Bernard
Lubarsky and Samuel J. Kaufmann. March 1955.
115p. diagrs., tab. (NACA TN 3336)
Experimental data of various investigators of liquid-
metal heat-transfer characteristics were reevaluated
using as consistent assumptions and methods as pos-
sible and then compared with each other and with
theoretical results. The reevaluated data for both
local fully developed and average Nusselt numbers in
the turbulent flow region were found still to have
considerable spread, with the bulk of the data being
lower than predicted by existing analysis. An equa-
tior based on empirical grounds which represents
most of the fully developed heat-transfer data is
Nu = 0.625 Pe0.4 where Nu represents the
Nusselt number and Pe the Peclet number. The
theoretical prediction of the heat transfer in the
entrance region was found to give lower values, in
most cases, than those found in the experimental
work.




NACA TN 3338.%>

A DYE-T R TECH BIFOR EXPERIMENTAL-
LY qBTAI NG IMPINGE T CHARACTERISTICS
OF AR EI ARY BOR A METHOD FOR
DETER NI m I L SIZE DISTRIBUTION.
Uwe H. v lahn.h las F. Gelder and William H.
Smyers, Jr. 1955. 73p. diagrs., photos.,
tab. (NACA TN 3338)

A dye-tracer technique has been developed from which
the droplet impingement characteristics of bodies can
be determined by colorimetric analysis. The tech-
nique is applicable to various wind tunnels provided
the humidity of the air stream can be maintained near
saturation. A method is also presented whereby the
droplet size distribution of the impinging cloud may
be determined by relating the experimental impinge-
ment characteristics of a body to the theoretical tra-
jectory results for the same body.


"AVAILABLE ON LOAN ONLY.
ADDRESS REQUESTS FOR DOCUMENTS TO NACA, 151 H ST., NW., WASHINGTON 25, D.C., CITING CODE NUMBER ABOVE EACH TITLE
THE REPORT TITLE AND AUTHOR.

^..**3










NACA TN 3359

AN INVESTIGATION OF DRAINS DISCHARGING
LIQUID INTO SUBSONIC AND TRANSONIC STREAMS.
Allen R. Vick and Frank V. Silhan. March 1955.
54p. diagrs., photos., tab. (NACA TN 3359)

Results of an investigation on the characteristics of
drains discharging liquid into an airstream at Mach
numbers from 0.5 to 1.3 are presented in the form of
surface stain patterns, schlieren photographs of the
flow, and drag measurements for drains of circular,
elliptical, and airfoil cross-sectional shapes. Var-
iables whose influence have been investigated include
Mach number, liquid reservoir pressure, drain
extension, angle of sweep, and end shape. Vent
pressure data are presented as differentials between
the free-stream and drain static pressure for various
tube configurations.





NACA TN 3362

ESTIMATES OF PROBABILITY DISTRIBUTION OF
ROOT-MEAN-SQUARE GUST VELOCITY OF
ATMOSPHERIC TURBULENCE FROM OPERATION-
AL GUST-LOAD DATA BY RANDOM-PROCESS
THEORY. Harry Press, May T. Meadows and Ivan
Hadlock. March 1955. 48p. diagrs., 4 tabs.
(NACA TN 3362)

Relations are derived between the peak gust loads
experienced in airplane operations and the probabil-
ity distribution of root-mean-square gust velocity.
These relations are applied in the analysis of opera-
tional data on peak gust accelerations to derive esti-
mates of the probability distribution of root-mean-
square gust velocity. The application of these
results to gust load calculations for other airplane
operations is also considered briefly.






NACA TN 3365

AN ANALYSIS OF ACCELERATIONS, AIRSPEEDS,
AND GUST VELOCITIES FROM THREE COMMER-
CIAL OPERATIONS OF ONE TYPE OF MEDIUM-
ALTITUDE TRANSPORT AIRPLANE. Thomas L.
Coleman, Martin R. Copp, Walter G. Walker and
Jerome N. Engel. March 1955. 31p. diagrs.,
4 tabs. (NACA TN 3365)

Time-history data obtained by the NACA VGH re-
corder from one model of a four-engine civil trans-
port airplane during operations on three routes are
analyzed to determine the magnitude and frequency
of occurrence of gust velocities, gust and maneuver
accelerations, and the associated airspeeds. Varia-
tions of the gusts and gust accelerations with route
and flight condition are indicated. Estimates of the
overall gust and gust-load histories for extended
operations on one route are obtained by supplement -
ing the data from the NACA VHG recorder with
available data from the NACA V-G recorder.


NACA
RESEARCH ABSTRACTS NO. 80


NACA TN 3374

TURBULENT-HEAT-TRANSFER MEASUREMENTS
AT A MACH NUMBER OF 2.06. Maurice J.
Brevoort and Bernard Rashis. March 1955. 20p.
diagrs., tab. (NACA TN 3374)

An axially symmetric annular nozzle was used to ob-
tain essentially flat-plate data on turbulent heat-
transfer coefficients and temperature-recovery fac-
tors. The test results of this paper are for Mach
number 2.06 and for a Reynolds number range of
1.7 x 106 to 8.8 x 107. The heat-transfer-coefficient
results are in good agreement with theoretical analy-
ses and the experimental results of the tests of V-2
rockets. The recovery factors are approximately 0.5
percent lower than data for a Mach number of 2.4.





NACA TN 3375

A THEORY FOR PREDICTING THE FLOW OF REAL
GASES IN SHOCK TUBES WITH EXPERIMENTAL
VERIFICATION. Robert L. Trimpi and Nathaniel B.
Cohen. March 1955. 69p. diagrs., photo.
(NACA TN 3375)

The nonlinear characteristic differential equations
applicable to a quasi-one-dimensional unsteady chan-
nel flow with friction and heat transfer are linearized
and integrated in functional form for the particular
study of small perturbations from ideal shock-tube
flows. If the equivalence of unsteady-flow and
steady-flow boundary layers is assumed, the theory,
evaluated with an equivalent steady-flow turbulent-
boundary-layer skin-friction coefficient, predicts
that the shock attenuates with distance and that aver-
age values of static pressure, velocity, density, and
Mach number in the hot gas increase with time at a
fixed position, while average sonic speed is simulta-
neously decreasing with time. Experimental
measurements of the shock attenuation with distance
and static-pressure variation with time at a fixed
position for diaphragm pressure ratios from approx-
imately 4 to 18 gave good agreement with the theore-
tical predictions.






NACA TN 3377

FLIGHT MEASUREMENTS OF THE VELOCITY
DISTRIBUTION AND PERSISTENCE OF THE
TRAILING VORTICES OF AN AIRPLANE.
Christopher C. Kraft, Jr. March 1955. 32p.
diagrs., photos., tab. (NACA TN 3377)

Measurements have been made in flight of the veloc-
ity distribution and persistence of the trailing vor-
tices of a propeller-driven fighter-type airplane.
The vortices were marked in the atmosphere with
smoke and were penetrated by a jet airplane equipped
with a high-frequency angle-of-attack vane and a sen-
sitive total-pressure instrument. Photographs of the
trailing-vortex filaments were also made.





NACA
RESEARCH ABSTRACTS NO. 80


NACA TN 3380

STUDY OF EFFECTS OF MICROSTRUCTURE AND
ANISOTROPY ON FATIGUE OF 24S-T4 ALUMINUM
ALLOY. H. A. Lipsitt, G. E. Dieter, G. T. Horne
and R. F. Mehl, Carnegie Institute of Technology.
March 1955. 41p. diagrs., photos., 4 tabs. (NACA
TN 3380)

This report presents the results of an investigation
of the statistics of the effects of variation in micro-
structure (extruded and extruded plus recrystallized)
on the fatigue properties of 24S-T4 aluminum alloy
notched specimens tested in both the longitudinal and
transverse directions.





NACA TN 3390

SECOND-ORDER SUBSONIC AIRFOIL-SECTION
THEORY AND ITS PRACTICAL APPLICATION.
Milton D. Van Dyke. March 1955. 50p. diagrs.,
5 tabs. (NACA TN 3390)

Several recent advances in subsonic compressible
flow theory are combined into a unified second-order
theory for two-dimensional airfoils. Solutions are
given for a number of profiles, and are compared
with the results of other theories and of experiment.
A straightforward computing scheme is outlined for
calculating the pressures on any airfoil at any angle
of attack.





NACA TN 3391

FREE-FLIGHT MEASUREMENTS OF TURBULENT-
BOUNDARY-LAYER SKIN FRICTION IN THE PRE-
SENCE OF SEVERE AERODYNAMIC HEATING AT
MACH NUMBERS FROM 2.8 TO 7.0. Simon C.
Sommer and Barbara J. Short. March 1955. 47p.
diagrs., photos., 2 tabs. (NACA TN 3391)

Measurements of average skin friction of the turbu-
lent boundary layer have been made in free flight at
high rates of heat transfer at high Mach numbers.
The results are appreciably higher than zero-heat-
transfer wind-tunnel data. The T' method for lami-
nar boundary layers, slightly modified, is shown to
agree with results of this and other investigations at
widely different Mach numbers and heat-transfer
conditions.






NACA TN 3399

A RAPID APPROXIMATE METHOD FOR THE
DESIGN OF HUB SHROUD PROFILES OF CENTRIF-
UGAL IMPELLERS OF GIVEN BLADE SHAPE.
Kenneth J. Smith and Joseph T. Hamrick. March
1955. 26p. diagrs., 3 tabs. (NACA TN 3399)


3



A rapid approximate method for the design of cen-
trilugal compressors of given blade shape with com-
pressible nonviscous flow characteristics has been
developed using techniques based upon stream-
filament theory. Axial symmetry is assumed, but
meridional-plane forces derived from tangential
pressure gradients are included. The method was
applied to the design of an impeller in order to de-
termine the approximate maximum meridional
streamline spacing that could be used. Three nu-
merical solutions for different streamline spacings
were made using the same hub profile, blade shape,
and prescribed velocity distribution along the hub.
The shroud profiles obtained from the three
solutions, which utilized 3, 5, and 9 streamlubes,
were negligibly different. The approximate comput-
ing time required was 15 hours per streamtube.



NACA TN 3400

ANALYSIS OF ERRORS INTRODUCED BY SEVERAL
METHODS OF WEIGHTING NONUNIFORM DUCT
FLOWS. DeMarquis D. Wyatt. March 1955. 40p.
diagrs. (NACA TN 3400)

Three typical duct flow profiles have been numeri-
cally analyzed to determine the errors introduced by
commonly used averaging methods in the resultant
uniform-flow properties. The analysis covers a
range of subsonic duct Mach numbers, but is con-
fined to flows having uniform static pressure and
total temperature. An averaging method is developed
which yields uniform properties that satisfy the inte-
grated mass and momentum of the nonuniform flow.
In contrast, it is shown that commonly used averag-
ing methods introduce inherent errors which may
markedly affect the validity of duct flow calculations.




NACA TN 3401

LAMINAR BOUNDARY LAYER BEHIND SHOCK
ADVANCING INTO STATIONARY FLUID. Harold
Mirels. March 1955. 25p. diagrs., 2 tabs. (NACA
TN 3401)

A study was made of the laminar compressible
boundary Layer induced by a shock wave advancing
into a stationary fluid bounded by a wall. For weak
shock waves, the boundary layer is identical with
that which occurs when an infinite wall is impulsively
set into uniform motion (Rayleigh problem). A
numerical solution was required for strong shocks.
Velocity and temperature profiles, recovery factors,
and skin-friction and heat-transfer coefficients are
tabulated for a wide range of shock strengths.



NACA TN 3403

ANALYTICAL DETERMINATION OF EFFECT OF
WATER INJECTION ON POWER OUTPUT OF
TURBINE-PROPELLER ENGINE. Albert O. Ross
and Merle C. Huppert. March 1955. 29p. diagrs.
(NACA.TN 3403. Formerly RM E9H17)






4


An analysis is presented to show the effect of evap-
orative cooling of the charge air during compression
on the performance of a turbine-propeller engine
incorporating a centrifugal compressor. Calcula-
tions were made with water as the cooling agent for
compressor tip speeds of 1200, 1500, and 1800 feet
per second. Results indicated that a power augmen-
tation of 200 percent is possible at a compressor tip
speed of 1800 feet per second if sufficient water is
evaporated during compression to saturate the air at
the compressor outlet.




NACA TN 3404

THE COMPRESSIBLE LAMINAR BOUNDARY LAYER
WITH FLUID INJECTION. George M. Low. March
1955. 29p. diagrs., 3 tabs. (NACA TN 3404)

A solution of the equations of the compressible lami-
nar boundary layer including the effects of transpira-
tion cooling is presented. The analysis applied to the
flow over an isothermal porous plate with a velocity
of fluid injection proportional to the reciprocal of the
square root of the distance from the leading edge.
Several examples are calculated, and the stability of
the boundary layer is investigated. It was found that,
on a weight-of-coolant basis, transpiration cooling is
more effective than other methods considered.



NACA TN 3407

INTERACTION OF A FREE FLAME FRONT WITH A
TURBULENCE FIELD. Maurice Tucker.March 1955.
55p. diagrs., 2 tabs. (NACA TN 3407)

Theoretical values are obtained for the root-mean-
square flame-generated turbulence velocities and the
attenuating pressure fluctuations resulting from a
linearized interaction of a constant-pressure com-
bustion front with a field of isotropic turbulence.
The anisotropic flame-generated turbulence is found
to be of about the same intensity as the incident
turbulence. A brief discussion of turbulent flame
speed is given. Directly at the flame front the noise
pressure levels characterizing the pressure fluc-
tuations are fairly intense (59 to 81 decibels) even at
moderate approach-flow turbulence intensities.



NACA TN 3408

ONE-DIMENSIONAL CALCULATION OF FLOW IN A
ROTATING PASSAGE WITH EJECTION THROUGH A
POROUS WALL. E. R. G. Eckert, John N. B.
Livingood and Ernst I. Prasse. March 1955. 29p.
diagrs., photo, (NACA TN 3408)

A method is developed for the determination of the
local wall permeability necessary to obtain a pre-
scribed local distribution of ejected gas or for the
determination of the local distribution of ejected gas
resulting from a given local uall permeability.
Sample calculations are presented for two blind radi-
al passages of a rotating transpiration-cooled turbine
blade. The effects of passage area variation, passage
inlet pressure, and passage inlet Mach number are
investigated.


NACA
RESEARCH ABSTRACTS NO. 80


BRITISH REPORTS




N-36022*

Aeronautical Research Council (Gt. Brt.)
PUBLISHED REPORTS AND MEMORANDA OF THE
AERONAUTICAL RESEARCH COUNCIL. 1954. 8p.
(ARC R & M 2550)





N-36023*

Aeronautical Research Council (Gt. Brit.)
A WIND-TUNNEL INVESTIGATION OF ENTRY LOSS
ON PROPELLER TURBINE INSTALLATIONS.
PARTS I AND I. J. Seddon and A. Spence. 1954.
56p. diagrs., photos., 16 tabs. (ARC R & M 2894;
ARC 11,602; ARC 11,883. Formerly RAE
Aero 2252; RAE Aero 2281)

Part I describes tests on a series of models of annu-
lar entries, with and without propeller in the 5-foot
tunnel, and tests on a set of large circular blade
roots on a full-size nacelle in the 24-foot tunnel.
Part II describes tests on models of a number of al-
ternative ducted spinners for a typical engine, and
for comparison, one annular entry similar to those
tested in Part I. The work is confined to intakes for
direct-flow engines with axial compressors. The
conclusions on propeller losses can be apphed to any
form of annular intake.




N-36024*

Aeronautical Research Council (GI. Brit.)
THE EFFECT OF UNIFORMLY SPACED FLEXIBLE
RIBS ON THE STRESSES DUE TO S ELF-
EQUILIBRATING SYSTEMS APPLIED TO LONG
THIN-WALLED CYLINDERS. E. H. Mansfield and
M. Fine. 1954. 43p. diagrs. (ARC R & M 2832;
ARC 10,983. Formerly RAE Structures 6)

The effect of discrete, flexible ribs has been inves-
tigated and the results have been incorporated mi a
number of graphs which show the effect of rib-
flexibility in a long thin-walled cylinder of arbitrary
shape under end constraint. Some of the results of
these investigations are of a negative character in
that they show that for certain types of end conditions
the effect of rib-flexibility is negligible. But rib-
flexibility is of paramount importance when self-
equilibrating shear-distorting forces are applied to a
cylinder and this report makes the stress distribution
in such a case readily determinable.



N-36025*

Aeronautical Research Council (Gt. Brit.)
AN ANALYSIS OF N.A.C.A. HELICOPTER
REPORTS. R. N. Liptrot. 1954. 61p. diagrs.,
5 tabs. (ARC CP 183)






NACA
RESEARCH ABSTRACTS NO. 80

Theory is compared with flight and model tests in
order to obtain empirical correcting factors which
will enable reliable performance estimates to be
made for new helicopter designs. A survey of gen-
eral theory is followed by an analysis of certain
American reports. Correcting factors for effective
blade drag for tip speed ratio, compressibility, and
stalling of the retreating blade are derived. A
method of calculating the retreating blade tip angle
of attack for twisted blades is presented.



N -36026'

Aeronautical Research Council (Gt. Brit.)
LOAD DIFFUSION IN PLASTIC STRUCTURES.
L. M. Tucker and R. B. Twiss. 1955. 79p.
diagrs., photos., 14 tabs. (ARC CP 186)

This report describes theoretical and experimental
investigations of the inherent advantages, in plastic
structures, of resin bonded shear joints over com-
parable pin joints, and the most efficient material
distribution for load diffusion. Theoretical analysis
and graphical solutions are developed to obtain the
ideal distribution of material for load diffusion;
these have general applicability to structural design.




N-36073'

Royal Aircraft Establishment (Gt. Brit.)
HYDRAULIC FLUIDS, ETC.: THE DECREASE IN
RATE OF FLOW ALONG TUBES OF A COLUMN OF
LIQUID WHEN BROKEN BY AIR GAPS. G. F. N.
Calderwood and E. W. J. Mardles. November 1954.
17p. diagrs., photos. (RAE Tech.Note Chem. 1242)

The loss of performance due to cavitation in a hy-
draulic system has been assessed by comparing
observed times of flow with those calculated by
means of the Poisemtle equation. Several air gaps
of relatively small dimensions impart elastic and
plastic resistance in addition to the normal viscous
resistance so that the apparent viscosity may be
several fold the bulk viscosity. An explanation of the
increased resistance due to air gaps is attempted.



N-36075"

Royal Aircraft Establishment (Gt. Brit.)
USE OF RADIO-ACTIVE ISOTOPES FOR DETECT-
ING FUEL CONTAMINATION OF AIRCRAFT
STRUCTURES. B. F. A. Gatward, H. W. G. Wyeth
and D. J. Nosworthy October 1954. Bp. diagr.,
Lab. (RAE Tech.Note Mech.Eng. 191)

Previous methods of determining the areas of con-
tamination of an aircraft structure from fuel spilt
from the tanks in flight have not been satisfactory as
their application has been difficult and the results
obtained uncertain. This note describes a conven-
ient method of tracing the spread of spilt fuel by
using fuel treated with radio-active compounds. It
records the results of an investigation in which the
method was used successfully. It was found that the
best results were obtained when the radio-activity of
the fuel was approximately 300 microcuries per
gallon.


N-36076'

Aeronautical Research Council (Gt. Brit.)
THE HOT-WIRE ANEMOMETER FOR TURBULENCE
MEASUREMENTS. PART I. B. Wise and D. L.
Schultz. March 24, 1954. 71p. diagrs. (ARC
16,679; FM 1527b; Oxford Univ., Engineerng Lab.
No. 69)

Further investigation of the operation of the hot-wire
anemometer has shown that there are only two sys-
tems which are both statically stable and capable of
improving the frequency response. A description is
given of further experiments which have been made
to verify the theory of operation of the wire, using
both radio-frequency and direct current heating. An
analysis of some feedback systems is given, and it is
shown how these techniques may be used in the
measurement of turbulence at high air speeds.


N-36077-

Aeronautical Research Council (Gt. Brit.)
NEUTRAL HOLES IN LATERALLY LOADED
PLATES HAVING SMALL DEFLECTIONS. R. Hicks.
April 26, 1954. 43p. diagrs., photos. (ARC 16,768;
Strut 1707)

Reinforced holes which do not alter the stress dis-
tribution in a plate are said to be neutral. In this
discussion it is shown that a circular neutral hole
can be cut in a laterally loaded plate providing there
is a choice for the cross-sectional dimensions of the
reinforcement. General expressions are derived
which enable the cross-sectional dimensions of the
reinforcement to be obtained from the expression for
the deflection surface of a similarly loaded plate
which has no hole. For some particular loadsystems
considered, expressions are found for the cross-
sectional dimensions of rings reinforcing circular
neutral holes in plates whose boundaries are circular,
rectangular, triangular, and elliptical. These expres-
sions are used to solve typical numerical examples
and it is found for all the cases considered that the
cross-sectional dimensions of the ring are always
practical.



N-36080'

Aeronautical Research Council (Gt. Brit.)
THE PLANE STRESS DISTRIBUTION IN A PLATE
CONTAINING A REINFORCED ELLIPTICAL HOLE.
R. Hicks. April 26, 1954. lip. diagrs. (ARC
16,769; Strut 1708)

The investigation deals with a reinforced elliptical
hole in a rectangular plate having unequal applied
principal stresses. It is shown that providing the
ratio of the major and minor axes of the ellipse is
suitably chosen, reinforcements of practical dimen-
sions can be designed to give small stress concen-
trations.


N-36081*

Aeronautical Research Council (Gt. Brit.)
VISCOUS EFFECTS ON PITOT TUBES AT LOW
SPEEDS. F. A. MacMillan. June 15, 1954. 8p.
diagrs., 2 tabs. (ARC 16,866; FM 2081)





6


Measurements were made of the pressure in a blunt-
nosed pitot tube in an air stream at Reynolds num-
bers of 15 to 1,000. The results are expressed in
terms of a pressure coefficient. This pressure co-
efficient becomes greater than 1 at low Reynolds
numbers, the increase being about 1-1/2 percent
at a Reynolds number of 50 (based on external tube
radius). No decrease of the coefficient below 1 was
found at any Reynolds number. When the values of
the coefficient are plotted against Reynolds numbers
based on internal tube radius, it is found that the
curves are in closer agreement than when the
external radius is used.



N-36092*

Aeronautical Research Council (Gt. Brit.)
THE FLEXURAL AXIS OF THIN-WALLED SEC-
TIONS THAT HAVE NO PLANE OF SYMMETRY.
D. Williams and B. V. S. C. Rae. 1955. 6p.
diagrs. (ARC R&M 2939; ARC 6871. Formerly
RAE SME 3248)

A method of finding the flexural axis of unsymmetri-
cal thin-walled sections is described that not only
obviates the necessity for first finding the principal
axes of inertia, but also simplifies the whole pro-
cedure.


N-36093*

Aeronautical Research Council (Gt. Brit.)
EXPERIMENTS IN THE COMPRESSED AIR TUNNEL
ON SWEPTBACK WINGS INCLUDING TWO DELTA
WINGS. R. Jones, C. J. W. Miles and P. S. Pusey.
1954. 26p. diagrs., 6 tabs. (ARC R& M 2871.
Formerly ARC 11,354; Perf. 415)

Date aregiven relatingto CL, CD, and Cm at high
values of Reynolds number on wings of triangular
plan form, and at angles of attack from 00 to above
the stall. Increasing the radius of the leading edge
did not yield an improved CL max vs. R curve.
Although the induced drag coefficient on the modified
delta wing is somewhat less than on the original wing,
the minimum-drag coefficient is greater.


N-36094*

Aeronautical Research Council (Gt. Brit.)
PRESSURE PLOTTING AND BALANCE MEASURE-
MENTS IN THE HIGH SPEED WIND TUNNEL ON A
HALF-MODEL OF A 90-DEG-APEX DELTA WING
WITH FUSELAGE. A. C. S. Pindar and J. R.
Collingbourne. 1954. 59p. diagrs., 5 tabs. (ARC
R & M 2844; ARC 12,804. Formerly tAE Aero2335)

Tests were made on a delta wing that had a taper
ratio of 0.143 and a wing section of RAE 102, sym-
metrical, 10 percent thickness/chord at 35 percent
chord. The tests were conducted at a Reynolds
number of 1.8 x 106 and Mach numbers up to 0.93.
These tests were designed to provide data on the
surface pressures over a delta wing at high subsonic
speeds. For comparison, balance measurements
were also arranged. The pressure distributions
were the most accurate and reliable of the results
given.


NACA
RESEARCH ABSTRACTS NO. 80


N-36128*

Aeronautical Research Council (Gt. Brit.)
THE EFFECT OF COMPRESSIBILITY ON ELEVA-
TOR FLUTTER. D. E. Williams. 1954. 9p.
diagrs. (ARC CP 185)

The effect of compressibility on elevator flutter is
investigated by using two-dimensional control sur-
face derivatives for Mach numbers of 0 and 0.7. It
is shown that compressibility may have a consider-
able effect when the stick is fixed, but that the effect
is small when the stick is free.



N-36129*

Aeronautical Research Council (t. Brit.)
APPROXIMATE WALL CORRECTIONS FOR AN
OSCILLATING SWEPT WING IN A WIND TUNNEL
OF CLOSED CIRCULAR SECTION. W. E. A.
Acum and H. C. Garner. 1955. 23p. diagrs., tabs.
(ARC CP 184)

The oscillatory interference upwash for a circular
tunnel is derived from the corresponding steady up-
wash. Corrections to measured derivatives of a
slowly pitching wing are calculated by Multhopp's
lifting surface theory. A satisfactory approximate
method using interference parameters for a small
wing is given, and an extension to rectangular
tunnels is suggested.





N-36203*

Forest Products Research Lab. (Gt.Brit.)
THE KNIFE-TEST METHOD OF ASSESSING BOND
QUALITY IN PLYWOOD. R. A. G. Knight and
L. S. Doman. December 1954. 17p. diagrs.,
photos., 4 tabs. (Forest Products Research Lab.
AMP 26/1; PRP 13/1)

This report describes the procedure of knife-testing
and the origin of the "Master Scale" by means of
which bond quality can be given by numerical assess-
ment. Questions are answered about the test such
as the influence of species and the "force factor, "
and the strengths and weaknesses of the test are
pointed out. An analysis is made of the knife-test
data for variation.





MISCELLANEOUS





NACA TN 3409

Errata on "CHAIN BREAKING AND BRANCHING IN
THE ACTIVE-PARTICLE DIFFUSION CONCEPT OF
QUENCHING." Frank E. Belles and A. L. Berlad.
February 1955.





NACA
RESEARCH ABSTRACTS NO.80


DECLASSIFIED NACA REPORTS



NACA RM A50H24

FLIGHT CALIBRATION OF FOUR AIRSPEED
SYSTEMS ON A SWEPT-WING AIRPLANE AT
MACH NUMBERS UP TO 1.04 BY THE NACA
RADAR-PHOTOTHEODOLITE METHOD. Jim
Rogers Thompson, Richard S. Bray and George E.
Cooper. October 27, 1950. 41p. diagrs., photos.,
tab. (NACA RM A50H24) (Declassified from Con-
fidential, 3.'11/55)

The characteristics of four different airspeed sys-
tems installed in a swept-wing airplane have been
investigated in flight up to 1.04 Mach number by the
NACA radar-phototheodolite method of airspeed
calibration. The variations of static-pressure de-
fect per unit indicated impact pressure with Mach
number and a limited amount of information on the
effect of airplane normal-force coefficient are pre-
sented for each system. The results are compared
with available theory and wind-tunnel tests of the
isolated heads.



NACA RM E50F29

SURVEY OF LESS-INFLAMMABLE HYDRAULIC
FLUIDS FOR AIRCRAFT. Wray V. Drake and
I. L. Drell. September 7, 1950. 64p. 14 tabs.
(NACA RM E50F29) (Declassifiedfrom Confidential,
3/11/55)

A survey of current information on civil and military
development of less-inflammable hydraulic fluids
for aircraft is presented. Types of less-inflammable
fluid reported include: glycol derivative, waterbase,


silicone, ester, and halogenated compound. Spec-
ification requirements, physical and chemical
properties, hydraulic-system test results, and
advantages and disadvantages of various hydraulic
fluids are discussed. For completely satisfactory
service, some modification of currently available
fluids or of present hydraulic-system parts still
appears necessary.







NACA RM E53C12

THE DESIGN OF BRITTLE-MATERIAL BLADE
ROOTS BASED ON THEORY AND RUPTURE TESTS
OF PLASTIC MODELS. Andre J. Meyer, Jr.,
Albert Kaufman and William C. Caywood.
April 6, 1953. 45p. diagrs., photos., tab. (NACA
RM E53C12) (Declassified from Confidential,
3/11/55)

Theoretical design charts based on Neuber's equa-
tions for symmetrically located notches are pre-
sented for estimating the approximate rupture
strengths of blade roots made from brittle materials.
The limit of applicability of the theoretical charts
is shown as determined by' rupture tests of plastic
models. The optimum proportions among overall
root width, neck width, notch radius, and notch
depth are determined from the design charts.
Eighteen different root designs were investigated,
their relative strengths were evaluated analytically
and experimentally and the results were compared.
A dovetail root having the optimum proportions as
established by this investigation was the strongest
root evaluated.


NACA-Langley 3-29-55 4M




UNIVERSITY OF FLORIDA
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