Equipment used for boundary layer measurments in flight

CoA Note No. 4Q

HE HOGESCHOÖI.

VLkGTÜIGBOUWKÜNDE Kanaalstraat 10 - DELFT

U

AUG. 1956

THE COLLEGE OF AERONAUTICS

CRANFIELD

EQUIPMENT USED FOR BOUNDARY

LAYER MEASUREMENTS IN FLIGHT

by

F. M. BURROWS

TECHNISCHE HOGESCHOOL VLKGTUIGBOUWKUNDE Kanaalstraat 10 - DELFT NOTE N O . 2f9

jum,

1956.

T H E C O L L E G E O F A E R O N A U T I C S

C R A N F I E L D

A Note on some E q u i p n e n t u s e d f o r Boundary Layer Measurements i n P l i g h t

P a r t I

The D e s i g n and C o n s t r u c t i o n of a Large L l u l t i t u b e Manometer f o r Use i n P l i g h t

P a r t I I

TvTO F i x e d Head Type Ccoibs f o r Boundary Layer I n v e s t i g a t i o n s

b y

-F»M, BurrovYS, D.C,Ae«

(Prc3pcj7cd u n d e r

-2'

L i s t of C o n t e n t s Page

Summary 3

1.1, Introduction Part I 4

1.2, General Description of the Manometer

h-1.2.1, Choice of Dimension, Manometric 4

Fluids, etc.

1.2.2, The General Arrangement of the 5

Manometer

1.3, Constructional Details

5

1«3«1» The Manometer and Lamphouse 5

1,3.2. The Lower Manifold 7

1,3•3» The Manometer Reservoir

7

1.3.4. The observation Camera Frame 8

1»3.5» Top Tube Connections and Tube 8

Freeze Clamp

1.3.6. The Observer Camera 9

1.3.7. The Installation of the Instrument 9

in the Aircraft

1.4, General Discussion 9

1,4»1« Behaviour of the Instrument in 9

Plight

1.4.2, Pressure Connections to the 10

Manometer

1.4.3. Specimen Results 10

2.1, Introduction Part II 11

2.2, The Transition Indicator 11

2,2.1. General Description . 11

2,3» The Boundary Layer Ccmb 12

2,3.1. General Description 12

2,4. ^7ind Tunnel Tests 13

2.4.1. Experimental Equipment 13

2.4.2. Details of Tests 13

2,5» Specimen Results - 14

-3-JAst of Contents (Contd.)

2,5.2, Boundary Layer Velocity Profiles

2,6, Concluding Remarks

Figures

AcknovTledgements

The author wishes to express his gratitude to I'ir, I'llartin and Mr. Parrer of the Department of Flight at

the College of Aeronautics J Mr. Parrer for M s many helpful suggestions and work in the construction of the manoneter unit, and i,5r, Martin for his patience and craftsmansMp

displayed during the construction of the boundary la^y^er combs,

SUI'IÏARÏ

Some notes are presented relating to the design and construction of a large multitube manometer and to two

'fixed head' type boundary layer combs to be used for the measvirement in flight of the boundary layer characteristics

of a sv/ept back wing. Although the equipment described was designed •with a particular object in view, there is no

reason v/liy the designs should not bo modified as and v/here necessary for the construction of similar equipment,

Page

14

-4-PART I

The Design and C o n s t r u c t i o n of a Large t f c i l t i t u b e Mancaneter

For Use in Flight

1,1» Introduction

In Part I of t M s note brief consideration is given to the design and oonstruotion of a large multitube manometer w M c h has been installed in the rear fuselage of an Avro Lancaster (P,A,474). This aircraft is being used as a test vehicle f or a series of investigations in flight of the behaviour of the three dimensional boundary layer on a swept back wing (mounted as a fin above the mid ujyper fuselage of

the aircraft) at moderartely high Reynolds numbers, and the manoneter described was designed to cope with all the aero-djmamic measurement requirements to be satisfied under test conditions, and to overcome the difficulties associated with making such observations in flight,

Although the instrument is large, there is no reason why its dimensions should not be scaled down to any

size, modifications being made as and where necessary in the particular circumstances»

1 ,2, General Description of the Manometer

1 .•S'.l, Choice of Dimensions. Manometric Fluids etc,

Consideration of the range of static and dynamic pressures to be met in practice together with the headroom and width available in the rear fuselage of the Lancaster led to the choice of a fifty tube manoneter some 7 feet in height, and 30in, wide. It was at first thought that, due to the height restriction of 7 feet, a dense maronetrio fluid would be necessary and so initially provision was made for using carbon tetrachloride {S,G, = 1,599) in the instrument,

The use of carbon tetrachloride as a manonetric fluid does present one or t\7o difficulties. For example,

the use of rubber tubing for fluid pipe lines is out of the question since it rapidly tends to perish under the action of the carbon tetrachloride. Plastic (P,V,C.) tubing may however be used vd.th success but it requires that connections be wired and sealed off by means of shellac varnish to

completely eliminate leaks, A further difficulty encountered in flight is that of the tendency for the manometric fluid

(i,e, carbon tetrachloride) to 'boil' at altitude, due to the reduced atmospheric pressure and ten^aerature and its relation

-5-to the liquid vapour pressure,

For such a large manometer, the reservoir size is naturally large (the actual capacity being approximately 4 gallons) and since the installation v/as within the relatively confined interior of an aircraft fuselage, it was necessary to guard against the toxic effects of carbon tetrachloride upon the operating crew of the aircraft in the advent of tube failure and consequent spillage, by providing an adequate draining system with its outlet to atmosphere. Although, for the initial measurements made using the instrument under discussion the manonetric fluid v/as carbon tetrachloride, it was later found possible to replace t M s fluid by distilled TiTater using f lucre scene as a dye.

Since observations of the manometer are recorded photographically using an P.24 camera, it was necessary to

overcome the problem of illumination. This V7as acMeved by a system of back lighting to be described,

1,2,2, The General Arrangement of the Manometer

The general arrangement of the complete manoneter unit is shown in figs. 2 and 3. The manometer tube bank is positioned at the front end of a lamphouse, the framework of w M c h is extended to form a rigid structure incorporating the P,24 observer camera. The reservoir is mounted on \ DTunners w M c h are attached to the side of the lamphouse, and it may be positioned at any desired height, fixture at the required position being facilitated by a simple clamping arrangement,

The whole assembly forms a very rigid structure and being attached to the aircraft floor via resilient mounts, is free to vibrato as a whole. It has ho\irever been observed that under test conditions, little or no perceptible

vibration of the instrument occurs, except during the 'groiind run up' of the aircraft engines,

1,3. Constructional Details

1,3.1. The Manometor and Lamphouse

An exploded view of the manoneter and lamphouse is shown in fig, 4. Basically the u M t consists of a box framev/ork constructed of 2in x 2in x l/8in steel angle vd-th an additional member of 'T' section let into the front face to provide adequate support for the perspex face and tube bank assembly. All joints are welded v/ith the exception of

was to facilitate the removal of the actual manometer observation face and tube assembly, should t M s prove

necessary, v/ithin the confined interior of the aircraft fuse-lage,

The sides of the box frame were covered vd-th 22 S.W.G, light alloy sheet attached by means of No, 6 P,K, screws,

The back cover for the frame was constructed of 3/8in, plywood and serves as the mount for the lighting unit w M c h consists of 24, 6V, 24W bayonet cap frosted light bulbs. The lighting unit was vrixed in series parallel and supplied from one of the 24V -power circuits available on the aircraft,

To eliminate concentrations of light corresponding to the bulb filaments appearing on the manometer observation face, small diffusers of 2in diameter were fitted over each bulb. These are not shown in fig, 4> but were very similar

to the light traps shown on the top and bottom cover plates, The top and bottom cover plates as attached to the box frame were also of 22 S,Yf,G, light allov/ sheet but vrere provided vd-th heat vents as indicated in fig. 4. To eliminate the possibility of stray reflections from the aircraft fuselage due to light streaming fron the heat vents and its consequent effect upon the observer camera, baffle plates were fitted as indicated in fig. 4, thus constituting a light trap. To obtain a maxim^um degree of diffusion of the available light, the interior of the box assembly was sprayed matt w M t e ,

Three tube supports v/ere constructed of 5/8in x l/4in brass strip and positioned at the top, middle and botton of

the front face of the manoneter frame as indicated in fig. 4. These were drilled along their length vd-th 1 c m . diameter holes to correspond to the manometer tube spacing and then ' split' to form clamping units. Due to variations in the diameter of the tubing used for the manoneter it v/as foimd that to obtain satisfactory clamping, it v/as necessary to vdjre each glass tube to the rear half of the support straps

as indicated in fig. 6, the front of each strap being used to 'back up' the assembly,

The front of the box frame was closed in with two 3/16in, tMck perspex sheets, the 'inner' faces of which

v/ere 'scrubbed' by means of emery cloth to yield a matt finish, They vrere positioned between the three tube support straps on the manoneter frame and attached by means of 2 B.A, counter-sunk head screws. On the outer faces of these t\/o backing sheets a graticule vras engraved, t M s being simply a system of parallel horizontal lines spaced at -^in, intervgls over the entire surfaces of the backing sheets, and coloured

altemate]y black and red for ease of identification. The arrangement of the tube support straps and the tvro backing

sheets vras such that v/hen the glass tubes vrere wired in place they were in contact vd.th the backing sheets throughout their length, and the graticule was thus positioned as close as possible behind the tubes.

Two front cover sheets of l/8in. tMck perspex v/ere fitted over, and in contact with, the glass tube assembly. They were mounted on oak spacing blocks attached to the

manonetex" frame as indicated in fig* 6, and positioned between the tube support straps in the same v/ay as the tv/o perspex backing sheets. Additional clamping of the glass tube bank v/as then acMcved by means of a nuniber of 6 B.A, brass screws passing through from the perspex front covers to the rear of the backing sheets, the screv/s being tightened so as to lightly snudvd-ch the glass tubes. T M s cjrrangement has, so far,

proved to be satisfactory,

1,3.2, The Lov/er Manifold

Interconnection of the manoneter tubes and the

reservoir v/as acMeved by means of the lov/er manifold as shown in fig, 5. T M s v/as constructed of 2in, O.D, x 20 S,¥,G, brass tubing and v/as fitted v/ith 48 stub tubes suitably staggered to facilitate the fitting of connections to the manometer tubes. The remaining tv/o manometer tubes v/ere separately connected, forming a simple 'U' tube unit to be connected to the aircraft airspeed pitot static system for direct indication of the free stream dynamic head,

Since the manoneter tubes v/ere very closely spaced it was necessary to use thin walled P,V,C, tubing (approx-imately 9!ii.m, O.D.) for all flexible connections to the glass tubes, and the connections from the lov/er manifold to the botton ends of the manometer tubes were accordingly made using t M s material together with 'elbov/s' of copper tube fitted as and where necessary to eliminate 'kinking'. The scheme is illustrated in fig, 5.

The lower manifold v/as fitted \d-th a drain plug and inlet tube together v/ith a screv/ed plug v/Mch could if necessary be used to 'bleed off' any entrapped air, and the v/hole

assembly'' attached to the manometer box frame as indicated in fig. 5.

1,3»3. The Manometer Reservoir

The manometer reservoir is constructed of 22 S,Yi/',G. Brass Sheet and measures 15in, x 12in, x 6in, Tv/o bearing

tubes are let into the tank, and the tank can be moved up and dov/n tv/o 3/4in, diEcicter Bright Mild Steel guide irinners which are attaclned to the manometer box frame as shov/n in fig.4.

-8-Pixture of the tank at any desired position on the guide

runners is acMeved by t//o simple 'split collar' screv/ clamps, Connection to the lov/er manifold is made by means of lin, diameter P.V.C. tubing, and to prevent t M s tube 'kinking' it is fitted internally v/ith a close coiled spring of 7/8in. diameter, wound f ran 18 S.¥.G. piano wire, 'Jubilee' clips v/ere used in the attachment of t M s feeder tube to both the reservoir and the lov/er manifold,

1,3»4« The Observation Camera Frame

The observation camera frame was constructed of lin, X 1in, x l/8in, steel angle throughout. It was built as an extension to the manometer box framevrork and was designed to be as rigid as possible, t M s being to ensure that the nanometer unit v/ould vibrate as a v/hole under flight conditions and so not impair the use of the camera as an observer. The arrangement is shov/n in fig. 2,

1,3»5« Top Tube Connections and Tube Freeze Clamp

Due to the close spacing of the glass tubes in the manometer, it v/as necessary to make the top tube connections via a jimction bar as indicated in fig, 7. The thoroughfare tubes in the junction bar were staggered, to facilitate the connection of the rubber tubes fron the required pressure tappings,

The tube freeze clamp is shown in fig* 8, The clamp base v/as constructed of l^in, x 1-|in, x 3/l6in, 'T' section mild steel, attached to the observation camera frame, all joints being welded, A lin, diameter bright mild steel rod was used for the clamping eccentric, spigots being turned on either end of the rod at centres displaced l/4in, from the centre line of the rod, Tv/o trunnion bearings for the spigots v/ere attached to the sides of the top members of the

camera dbservad^ion lYarae and v/ere arranged so that the rod spigot centres v/ere disposed along the centre line of the web of the 'T' section base, and 3/4in, above the flange face, To the end of one spigot a clamping handle v/as attached

(fig. 8 ) .

The rubber tubes from the required pressure tappings were passed through the freeze clamp unit (fig, 8) and by

rotation of the clamping handle, all pressxires to the manometer could be isolated. There is harever a tendency for the

clamping eccentric and base to distort imder load and it is evident that more effective isolation of the pressures at the manoneter could be acMeved if the clar/iping eccentric were to be fitted v/ith a centre bearing in addition to the two truimions,

-9-1,3.6, The Observer Camera

The observer camera v/as basically a standard F,24 camera. It v/as fitted to the manoneter frame at the

position indicated in fig. 2 by means of a sv/ivelling mount, thus permitting the camera to be 'lined up' on the manometer, Since the manometer face is very much greater in height than in breadth, a considerable film v/astage v/ould result from using the full F,24 frame for each observation. To overcome

this a standard F.24 magazine was modified so that thQ. film could be v/ound independently of the camera shutter mechanism. The rear face of the camera v/as suitably masked so that film records could be obtained of approximately one t M r d of the v/idth of the standard P.24 frame v/hich v/as adequate for the purpose required. Considerable saving in the use of

observer camera film v/as thus acMeved,

1.3.7. The Installation of the Instrument in the Aircraft

Five heavy rubber resilient mounts v/ere fitted to the manoneter frame, four at the base of the box frame and one directly under the camera (see fig. 2 ) . The complete installation of the instrument in the aircraft was effected by attaching these mounts to the floor of the rear fuselage,

the general arrangement being shov/n in fig. 1.

The unit as a v/hole including the manometric fluid v/eiglas approximately 350 lbs. and its design, construction and installation was completed in 8 v/eeks,

1,4. General Discussion

1,4.1. Behaviour of the Instrument in Flight

Up to the present, the behaviour of the complete manometer unit .in flight has been most satisfactory. Although

the raancmeter and observer camera unit are attached to the aircraft via resilient mounts, there is little or no

vibration of this assembly in flight and it has been fo\and that, due to the skilful and accurate handling of the aircraft by the pilot, experinental conditions can be set such that the fluctuation of the fluid columns does not exceed l/32in, T M s latter has been deduced from careful observation of the behaviour of the fluid colimins in the manometer during each of the test runs completed so far,

It has been found that the only notev/orthy limitation upon the accuracy of the results obtained is that encountered

-lo-in the read-lo-ing of the film records, for wMlst tarue and

accurate readings of the required pressures may be displayed upon the nanometer, it has so far proved impractical to

attempt to read the film records to an accuracy involving less than 0,05in. of manometric fluid. Since the attainable experimental conditions permit greater accuracy in film

reading, the film reading technique has accordingly received some consideration, although as yet no definite steps have been taken for its improvement,

1.4.2. Pressure Connections to the Manoneter

The 'U' tube u M t built into the instrument (para, 1,3.2) is connected to the aircraft pitot static system and thus provides a direct indication of the free stream dynamic head, i.e, v/hen corrected for the aircraft static pressure error,

T\/o further tubes, one at each side of the manometer face are connected to the aircraft static system and so under test conditions provide a datum to v/hich all measurements may be referred, By t M s means allca/ance is made for the

effect of snail angles of bank occurring during tests and the corresponding settling of the fluid to its gravitational level,

The other available tubes on the manometer are connected in- the usual way to the required pressure sources,

1.4.3. Specimen Results

Tv/o specimen observation photographs of the mano-meter face are shov/n in figs, 9 and 10, The clarity v/ith v/Mch tlie fluid columns are displayed may be seen and the u M f o m i t y and effectiveness of the lighting arrangement is noteworthy. The difficulties encountered, however, in

attempting to read the observation film to an accuracy

-11-PART II

Two Fixed Head Type Conbs for Boundary Layer Investigations

2,1, Introduction

Consideration is nov/ given to the construction of tv/o combs for boundary layer exploration using the 'fixed head' technique. They v/ere designed to meet the needs of the tests, to be performed in flight, on the boundary layer characteristics of a sv/ept back v/ing (see para. 1,l) in v/hich the primary aim v/as to study the behaviour of transition v/ith variation in Reynolds number and incidence,

The tv/o types of comb to be used for this v/ork v/ere designed to measure the boundary layer velocity profile and the total head distribution at, near to, and along the v/ing surface respectively for a fairly v/ide range of experimental conditions in v/hich the flov/ could assiome any characteristics between those of a thin laminar to a tMck turbulent boundary

layer, or more remotely, & layer in separated flov/,

Although it is possible to maJce a svrvey in flight of the boundary layer using a tra.versing gear, such a survey may be much more easily and rapidly completed using fixed heads of the type to be described provided that the flow is reasonably v/ell ordered. In regions v/here the flov/

experiences considerable transverse shear, hov/ever, more elaborate techniques are required for measurement,

In t M s note, separate consideration will be given to each of the two types of comb together v/ith the results of some preliminary test work performed to assess their usefulness,

2,2, The Transition Indicator

2,2,1, General Description

We shall consider first the conb to be used for measuring the total head distribution at, near to, and along

the v/ing siorface, T M s comb will be referred to as the 'trajisition indicator' since from such measured distributions of total head the position of the trejisition front may be readily determined (see fig, 11).

The indicator is made up of tv/o pitot tubes and one static tube (to provide a datum pressure to v/Mch the pressures recorded by both pitot tubes could be referred) arranged as

-12-hypodennic stoel tubing. The ends of the pitot tubes are 'flattened' to yield orifice dimensions of approximately 0,50in, x 0,01 Oin.- 0.012in,, v/Mlst the static tube is of the usual bullet nosed type having six static vents disposed approxinately in line with the ends of the pitot tubes.

The three tubes pass through a hypodermic steel tube of 3n.n. O.D. to v/Mch thin brass fixing straps are fitted to facilitate attachment to the vdng surface,

Adaptors for the pressure leads are fitted to the ends of the pitot and static tubes, all joints being made v/ith soft

solder. The arrangement is such that v/hen the fixing straps are firmly in contact with the ^ving surface, the position of the pitot and static tubes are respectively, resting on, l/4in. above, and -g-in, above the v/ing surface.

Attaclment to the v/ing surface is acconplished by means of cellotape v/hich provides completely adequate rigidity

in fixing although being sonev/hat utilitarian in nature,

T M s arrangement has so far proved to be perfectly satisfactory vmder test conditions, and the transition indicator may be

attached at any desired position on the \/ing surface, to the exclusion of those regions v/here the v/ing surface curvature is large (e.g. close to the leading edge), without destroying the surface finish,

For the particular tests under consideration

(paxa, 1,1) six such transition indicators were constructed,

2,3, The Boundary Layer Comb

2,3.1« General Description

For measurement of the boundary layer velocity profiles a comb v/as designed a.s shov/n in fig. 13. Five such combs v/ere constructed and each consists of eleven pitot and tv/o static tubes (to provide datum pressures) disposed as shov/n in fig. 13» o M y those pitot tubes in the immediate vicinity of the v/ing s\xrface having flattened ends. The pitot and static tubes v/ere constructed of 1n,m» 0,D, hypodennic

steel tubing and mounted in tv/o faired brass pedestals. The pedestals v/ere provided with feet for attachment to the v/ing

surface,

A thin brass strap of streamlined section v/as

attached to the comb at approximately 1 ,l/4in, dovmstream of the leading edge (tube orifice line) and serves both as a

brace and datum fixing for the tube assembly. The arrangement is such that when the base of this strap is held in contact v/ith the v/ing surface, the tube centres are above the -vving

-13-surface at the respective heights shov/n. Contact between the stra.p base and the ^7ing surface is effected by means of a sma.ll moveable brass stirrup which may be positioned as shov/n in fig, 13.

Adaptors for the pressure leads were fitted to the downstream ends of the pitot and static tubes, end as with the transition indicators all joints v/ere made using soft solder,

The comb is attaclied to the v/ing surface at the desired position with cellotape w M c h provides all the rigidity required under test conditions,

2,4. "v7ind Tunnel Tests

2.4.1. Experimental Equipnent

To assess the usefulness of both the transition indicator ajid the bo\andary layer comb, sane sitnple experiments were made using the boundary layer flow on a flat plate,

These experiments v/ere perfonned in the College of Aeronautics Güttingen IVind Tunnel, T M s tunnel is of the return flov/, open v/orking section tjrpe, the jet being of elliptic cross section v/ith dimensions of the major (horizontal) and minor (vertical) axes of /jOin, and 27in. respectively. All pressiore mea.surements were made using a multitube manometer inclined at 30° to the horizontal,

A flat plate of 20in, chord constructed from light alloy v/as supported betv/een end plates in the tunnel a,s shown in fig, 14. T M s plate v/as some 0.375in. in thickness and v/as everyv/here aerodynamic ally smooth. Its leading and

trailing edges v/ere elliptic in cross section, and there was provision for inclining the plate at snail incidences to

the mainstream,

For the purpose of comparing the boundary layer velocity profiles -as meas-ured by the combs with those resulting from a standard pitot traveraj a pitot tube of 0,030in, 0,D, was mounted on a traversing head fitted v/ith micrometer adjustment in the vertical plane, T M s was

arranged as shown in fig, 14.

2.4.2, Details of Tests

\7ith the flat plate set at zero incidence to the mainstream and v/ith free transition, the velocity distribution in the boundary layer at 11,5in, fron the leading edge of the plate v/as detemined using the traversing head, for tunnel

-14-specds of 80ft/sec. :ind 130ft/sec, respectively. Por compari-son, sinilcir distributions v/ere also measured using a boundary layer co.ib positioned alongside the traversing pitot as sho^im in fig, 15. , .

To determine the position at w M c h transition from laminar to turbulent flow was occurring, a transition indicator v/as positioned in turn at a number of stations spaced 2in, apart along the plate and the distribution of total heaji near to and along the plate surface detemined for a tunnel speed of 130ft/sec,

For the piirpose of assessing the behavioiir of the boundary layer conb in a tMck fully turbulent boundary layer,

a l/8in, diraneter transition v/ire v/as fitted 1,5in, fron the leading edge of the plate» The velocity profiles at 11,5in, from the loading edge v/ere ner-sured accordingly, both v/ith the comb lined up v/ith the free stream, end also yav/ed through + 30° (in intenrals of 10°), t M s latter being intended to simulate the effect of transverse floiv,

2,5» Specimen Results

2.5.1. Bounda.ry Layer Trrjisition

Prom the pressturos recorded by the two pitot tubes on the trajisition indicator, raeasiored relative to the datura static, the distribution of total head along and l/4in, above the plate surface was determined. The results obtained are shov/n in fig, 16, and are plotted as the variation of (u./u ) v/ith distance along the plate surface (v/hero u. is the

velocity in the boiondary layer, and u is the free stream velocity),

It can be seen that throughout the traverse the raised pitot (i.e, at l/4in. from the plate surface) v/as at no tine immersed in the boundary layer and thus recorded no

total head loss. The siJi-face pitot readings do hov.'ever shov? quite clearly the narked reduction in total head v/hich occtirs as the tube passes fron the turbulent into the laminar boundary layer and it caji be seen that in t M s particular" case trans-ition to fully turbulent flow occurs over a. region vrfiich is approxi:iatcly 4in, in length,

2.5.2, Boundary Layer Velocity Profiles

The various boundojry layer velocity profiles

neasured are shov/n in figs, 17-21, The agreement between ' the profiles as measured by a standard traverse and those

-15-the tunnel speeds considered, v/ith -15-the exception of those cases in v/hich the conb was yav/od relative to the free stream direction. Under those latter conditions it can be seen that the profile is seriously affected, even v/hen the angle of yav/ of the comb is as small as 10°,

The test shov/ed that, even v/ith such small pitot tubes, there was no serious lag in the manoneter readings for changing flov/ characteristics, T M s is a prime requirement for measurements to be made in flight since a time limit is inposed by the ability of the pilot to hold steady any given set of experimental conditions,

2,6, Concluding Remarks

Up to the present only a fev/ tests have been performed in flight using both the boundary layer combs and

trajisition indicators positioned on the svirface of a sv/ept back v/ing» The behavioxir of the conbs and transition

indicators has hov/ever been extremely good under all conditions of flight encountered so far, as a result of v/hich a compre-hensive boundary layer survey is being made on the above v/ing for a range of Reynolds numbers and incidences, the

incidences being restricted to a range (0° - 10°) in v/hich the changes of flov/ direction at the \djig surface are knov/n from tuft observations, to be very snail,

TUBE CONNECTIONS NOT SHOWN IN F\ILL.

r

n

§

o

- o l

TOP COVER PLftTE WITH HEAT VENTS & LIGHT TRftPS

SIDE COVER PLATE

SUPPORT STRAP FOR GLASS T U B E S .

PERSPEX FRONT COVER

M A N O M E T E R T U B E S S O . O F F

BftCK COVER. MOUNTING 2 4 . feV. a4W. 'FROSTED* LIGHT BULBS.

S I D E COVER P L A T E .

RESERVOIR SUPPORT

RUNNERS-RESERVOIR.

RESERVOIR C L f l M P SCREWS.

B A S E SUPPORT BRACKET.

R E S I L I E N T M O U N T S .

MANOMETER MAIN FRAME. PERSPEX SACKING SHEET.

r<^

i PERSPEX SHEET

9 M.M. DIA.GLR5S TUBE.—

TUBE SUPPORT STRAP

SCREW PLUG.

P.V.C. TUBING.

ELBOW. I'xao.S.W.G. COPPER TUBE. DRAIN PLUG.

TUBE SUPPORT STRAP.

PERSPEX FRONT COVER

GLASS TUBES.

PERSPEX BACKING SHEET

SUPPORT STRAP CLAMP SCgEW.

WIRE FIXING FOR GLASS TUBES.

OAK SPACING BLOCKS.

MANOMETER FRAME.

/P.V.C. TUBING. JUNCTION BAR.I

ELBOW. I-20.S.W.6. COPPER

TUBE-TUBE SUPPORT

STRAP-MANOMETER FRAME.

it PERSPEX SHEET. 9.M.M. DIA. GLASS TUBE.

CLAMPING ECCENTRIC CLAMP BASE. PRESSURE LEADS CLIP BRACKET. MANOMETER FRAME. C L A M P HANDLE-ECCENTRIC SPianT

TAPERED PACKING STRIP

TRUNNION BEARING.

CLAMP HANDLE CLIP.

FIGURE 9. THE M A N O M E T E R FACE.

(NOTE: THE UNFILLED 'U' TUBE

UNIT M A Y BE SEEN AT THE E X T R E M E

RIGHT HAND SIDE).

FIGURE 10. THE M A N O M E T E R

FACE UNDER TEST CONDITIONS.

S T A T I C . .

R A I S E D P I T O T . S U R F A C E P I T O T .

L f t M I N A R . TRW><SITION. T U R B U L E N T .

FLOW IN T H E BOUNDARY LAVER.

o o « o ^ O'fc a-% V E L O C I T Y P R O T I U E A T A.R.

il

I

1

o o * , o-^ o-fc o.« ri V E L O C I T V P R O F I L E fVT B . B .

©.

s.

F I G . n . DIAGRAM SHOWING PRINCIPLE OF

TRANSITION LOCATION USING RAISED AND

SURFACE PITOT TUBES.

STATIC T U B E I.M.M.DIA., [SEE BELOW).

TWO PITOT T U B E S I M M . DIA. WITH ORIFICE" DIMENSIONS AS SHOWN

.TUBES PARALLEL TO EACH OTTHER B E T W E E N ' A R ' A ' B B '

%. SPLAYED OUT ( A S SHOWN LOWER L E F T ) BETWEEN ' B t f ft'CC.'.

PRESaUHe U6AD ADAPTORS.

• • ^ ' ' - ^ ^

P ft"

T „ Z

V I E W ON ' A A ' .

•» CIRCULAR PITOT T U B E S . I . M . M . O I A

B R A S S STRAP.

a. ST « T I C T U B E S . I . M . M . O I A .

T U B E MEICHTS FROM SURFACE O'OIO O-OIS" o o a o * o - o s o ' o - i o o T o-zoo'. O-SOO' f * T « T l c ) . o • * o o ' . 0 - T O O ' . 1 -ooo'. I • SOÖ'. Z • OOo'.fSTWTIc). 3 ooo". P R E S » U R E L E A D BPWPTOWB. B R A S S P E D E S T A L S . M O V E A B L E BKRSS STIRRUP. ORIFICE D I M E N S I O N S A S FOR TKAMSITION INOICWTOR P I T O T S .

-TKAVEgSING GEAK SUPPORT. ^.,_ MICROMETER A D v l U S T m G H E R D . -- E N D P L A T E S . F L A T P L A T E . F I G . 1-^ . ftKKANGEMENT OF FLRT PLATE! & T R A V E R S I N G GELRK IN W I N D T U N N E L .

FIGURE 15. ARRANGEMENT O F T H E BOUNDARY LAYER COMB, TRANSITION INDICATOR, TRAVERSING P I T O T AND F L A T P L A T E IN WIND TUNNEL.

DtqTANCE FROM LKHDINO EDSE.: INCHES. F l f t . Ifc. F R E E T R A N S I T I O N ON R - A T l-LJ^TE. FROM T R A N S I T I O N 1 N D I C H T 9 R REJ^DINftS.

o «

0-5

DISTANCE FROM PLATE SmrFACE. INCHES.

BOUNDAKV LA/ER /ELOcnrv PROFILE AT n a ' FROM L.C o r FLAT PLftTE. TUNNEL ftRECO; » o ' / * E C . . *TANW _ ^ W D TRAV . 0 ^ ^ tRfeE. ^ O-fc 0%

u..

DISTANCE FROM PLATE SURFACE. INCHES.

BOUNDARY LAYER V ELOCITV PROFIUE AT 11-5' FROM L.E. OF FLAT PLATE. TUNNEL « P K E O : 7 ISO'/SCO RAVERSE OMB. f

J

D I S T A N C E A B O V E P L A T E S U R F A C E . I N C H E S . T H I C K T U R S U L E N T B O U N D f l R V LWYCR V E L O C I T V P R O F I L E AT I I S " ; F R O M L . E . O F F L A T P L P H X . A DIA. T R A N S I T I O N W I R E F I T T E D O * Ofc FiG.ia u.. I-O O S 0 7 0 - 5 O -D I S T A N C E A B O V E T H I C K TU1 F U A T E KBULEPTT S U R F A C E S O U N D A R -L A V E R V E -L O C I T Y P R O F I -L E A T l i s ' F R O M L E A D I N G E D G O F F L A T P L A T E . . é ' o i A . T R A N S I T I O N W I R E FIT-• » FIT-• F R O M L . E . O F P L A T E . T U N N E L S P E E D : I S O ' / S E C . A 4 k — A SSUft; R O -ntrnt

J

-A

J

1