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OCR for page 493
Propeller Wake Analysis by Means of PIV
F. Di Felice (Istituto Nazionale per Studi cd Esperienze di Architettura Navale, Italy)
G. Romano (Rome University, Italy)
M. Elefante (Centro Esperlenze Idrodmamlcne Marrna MlLtare, Italy)
ARs7.]RAcr
An experimental mve tigation of 6he propeller
wake m c cavitation tmmel has been perfommed using
Particle Imcge Velocimet y PPV) he hyd odynamic
md geomehiccl mve tigation of 6he wake md its
evolution hcs been pomted o t he bkde viscous
wake, developmg from th blcde surfae bo mdary
Icyers, the hailmg vo tex sheets, due to 6he radicl
g adient of 6he bo md circulation, ad the velocity
fluctuation distributions me identffied md discussed
he near wake geomet y is descobed th ough 6he
bendmg of the bkde wake sheets, 6he slipsheam
conhation md 6he tip vortex trajectory md viscous
i te~ations ~ the near field 6he effects of tmbulent
dfffusion md isc ms dissipation, which c mse c rapid
spaebroadenmg of 6he velocity g cdients m 6he
t~ailmg edge wake, me clso examined in 6he far wake
th d velopment of the slipsheam instability md 6he
brekdown of the hub md tip vortices are outlmed
IN7.~0DUCPION
he experimentcl inve tigation of the propeller
wake holds a impo t mt role for the desigm md 6he
pe formance crurlysis of ship propulsion ~ modern
desigm, to reduce propeller-mduced hull vibrcti ms,
efficiency decay md noise generction, due to
cavitation, 6he~e is c contmoous hend towards m
increcsed complexity of 6he bkde geometry his
compl :xity is primarily due to the low cspect mtio a d
to th sk w of marine propellers, which cmse shong
thee-dimensiom~l effects 7berefore, 6here is c rising
i te~est on detailed data of the velocity flow feld
aro md 6he bkdes md in the wake he kmowledge of
th velocity field m 6he wake em~bles to check locclly
th desigm requi ements For example, this c m be done
by comparing the mecsmed bkde section d cg
coefficients ad bo md cl coktion wi6h 6hose provided
by desigm dish~butions Kobayashi 1982, Koyamc
1986 md Jesmp 1989) Moreover, the kmowledge of
6he position of the t~aili g vo t :x sheets is necessary to
evaluate 6he atual wake-induced velocity feld aro md
6he blades md to determme 6he propeller
pe fommances
Velocity mecsurements are clso c tool for 6he
development md the validation of m mericcl codes
md flow modeling Mo t cunent m mericcl methods
for propeller mvestigations are based on potenticl flow
6heories md simplffied wake models More complex
md ref ned m odels of viscous flows Kobayashi 1981,
Jessup 1989, Amdt md Mcines 1994), of 6he hub
effects V mg 1985), of 6he t~ailing vortex shets md
of tip roll-up pmcess are ~equi~ed for inmecsmg 6he
a uray of m mericcl p~edictions
Measur ments by Lcser Doppler Velocimeby
LDV have been c t ming point in the a~ly is of 6he
6 ee-dimensiom~l complex flow aro md rotors md
propellers, providmg cmong 6he others, q mtitative
i formation on the roll-up process, 6he slip tream
conhation md 6he tip vertex evolution Mm 1978,
Kobayashi 1982, Cenedese et cl 1985, Jessup 1989,
he :mck md Jes mp 1998) LDV hcs th cactility of
velocity di~ection recogmition, high spaticl resolution,
good fi equency resp mse md of c non inh usive probe
However, most of 6he p~evious LDV crurlyses me
focused on cross-sections of 6he wake md c f w
examples are avaibble concernmg 6he evolution of 6he
wake dow sheam of 6he slipsheam conhation (Stelk
et cl 1998) 7his is mcinly due to the fat th~t 6he
LDV techmique cllows m efhcient d~tc aquisition et c
pomt m time (dffferent propeller ~evolution agles)
mdhence a ecsyrecomtruction ofthefl w feld in c
cross-secti m, while the longit dim~l survey ~equi es c
time consuming weep over m my points
In 6he p~esent study, the a~lysis of the propeller
wake is pe fommed by usmg the 2D Particle Imcge
Velocimeby techmique PP , which cllows c p we ful
mvestigation of 6he radLcl md axicl velocity
components in the lo git dim~l pkme PIV
mecsurements, es p~eviously done by Cotroni et cl
OCR for page 494
(1999), are taken in phase with the blade angular
positions in order to resolve the evolution of the wake
during the propeller revolution. Wake characteristics
and tip vortex spatial fluctuations, leading to the
breakdown farther downstream, are pointed out
considering three adjacent windows starting from the
blade trailing edge to about 1.5 propeller diameters
downstream.
The propeller used in the present experiment is the
same investigated by Cenedese et al. (1985) and by
Stella et al. (1998)0
Although some wake detail is strictly dependent on
both propeller geometry and loading conditions, the
results of this investigation will be discussed with
emphasis on those flow features of a general content.
EXPERIMENTAL SET-UP
The present PIV measurements were performed at
the Italian Navy Cavitation Tunnel (C.E.I.M.M.~. The
test section is a square, closed jet type
(0.6mxO.6mx2.6m). Perspex windows on the four
walls enable the 90° optical access required for PIV.
The nozzle contraction ratio is 5.96 and the maximum
water speed is 12 m/s. The maximum free stream
turbulence intensity in the test section is 2% in the
regions behind the wake of the shaft supports, while it
reduces to 0.6 % in the propeller blade inflow at a
radial position equal to 0.7 R (R being the propeller
radius). The flow uniformity of the axial and the
vertical components is within 1%.
The sketch of the instrumentation set-up is shown
in figure 1. The propeller model is mounted on a front
dynamometer shaft. This arrangement of the propeller
and the length of the test section, which is about 15
| Tunnel cohere l Free stream velocity
|~r~oo1~|
Propeller | — |]
r.p.m I
Test section
C:
| Ends l
_4
| Synchronizer ~
, ~ Crosscorrelat ion l
Camer a '
[~ Laser sheet Fl ow di r ect i on
~ ~7
,~,~,~,2,'~,~,~'H~'e,''~,'''~,~,~'L,'''~,,,e,r,~,~,~'''''' ~'~'~'~'~
, ~ Set laser parameters
~`me I
| Or Cuber |
Figure 1: Experimental set-up
times the propeller diameter, allows the slipstream to
develop freely in the downstream direction as in a real
operative condition. An encoder, with a resolution of
0.1 °, mounted on the dynamometer shaft, feeds a
special signal processor which sends a trigger signal
to a special synchronizing device for each propeller
angular position. The synchronizer provides a TTL
trigger signal to a cross-correlation camera
(1018x1018 pixel), and to a double cavity Nd-Yag
laser (200 mJ per pulse at 12.5 Hz), to allow image
acquisitions for each propeller angular position. The
digital cross-correlation video camera, allows the
recordings of two separate images (one for each laser
pulse) within a few microseconds at a maximum frame
rate of 15 Hz. By using cross-correlation, the
directional ambiguity is completely removed.
The instantaneous velocity fields were acquired
from a distance up to 700 mm from the side window,
using a 60 mm lens with 2.8 f-number and imaging an
area of about 100 x 100 mm2.
The tracer particles are one of the critical aspects
of the PIV technique, especially in case of large
facilities. Being the technique based on the
measurement of the particle displacement, it is
fundamental that the seeding accurately follows the
water flow velocity (Hunter and Nichols 1985,
Melting 1986, Mayers 19914. This requires particles
having a diameter on the order of some ~m. At the
same time, it is mandatory to achieve a high uniform
seeding density in the region of interest, at least 15
particle pairs per interrogation window (Keane and
Adrian 1990), in order to accurately perform
auto/cross correlation analysis. To this purpose, the
water in the tunnel was initially filtered, and then
seeded with 10 lam silver coated hollow glass spherical
particles with high diffraction index and density of
it /
~~ 1
~ :
I'm
1
Figure 2: Tested propeller model.
~~ ~~-~
OCR for page 495
about 2 g/mm3
The four blade propeller model (figure 2) is
skewed, with a uniform pitch (pitch/diameter = 1.1) a
forward rake angle of 4° 3" and a diameter of 227.2
mm.
PIV measurements were carried out with a
propeller angular velocity n=25 rps and an upstream
water speed Uinf=4.25 m/s, corresponding to an
advance ratio J= Uinf /(nD) of 0.748, in moderately
high loading condition. In such conditions, the
propeller shows tip vortex hub cavitation which was
maintained outside of the measurement windows to
avoid camera blooming. The blade Reynolds number
Rn=(C0.7Vo.74/v' where c0.7 and V0.7 are respectively the
chord length and the velocity at r/R=0.7, was equal to
1.12 106. The cavitation number ov=(P-pv)/q' being P
the absolute ambient pressure, Pv the vapour pressure
and q the stagnation pressure of the propeller upstream
flow, was 9.3.
The PIV system was arranged to measure, in the
mid longitudinal plane of the propeller, the axial and
vertical velocity components simultaneously in the
tunnel frame. In view of the symmetry of the propeller
inflow and of the steady conditions, when the light is
located on the vertical radius (along the z-axis), the
axial component of the velocity and the vertical one
correspond respectively to the axial and the radial
components in the propeller moving frame. To
investigate the propeller wake at least 1 diameter
farther downstream of the stream tube contraction, the
measurements have been performed over 3 adjacent
windows by traversing the camera (with an accuracy of
about 0.1 mm) as shown in figure 3. The initial
reference position is fixed with an accuracy of about
0.5 mm by imaging a special target device.
Trajectory of
vortices '~
~~ ' _
5{ Axis of the
L .^roneller shaft
I ~
1 1 ~ .
, ~ 7-
Light sheet
plane
Flow
direction
~Tip- `3
\ Vortices
~ sections ~
Investigation Camera
windows
Figure 3: Measurement planes
IMAGE ANALYSIS
The acquired images were analysed using an
algorithm in which the window off-set correlation
method has been implemented (Westerweel 19974.
Furthermore a recursive processing method is used by
implementing a hierarchical approach in which the
sampling grid is continually refined and also the size
of the interrogation windows is reduced during the
iterations. In Figure 4 the iterative process starting
from windows of 128 px2 to the final one 16 px2 is
presented. In the last iteration the windows are also
overlapped to obtain a better reconstruction of the
whole flow field especially in the regions with strong
gradients. This procedure has the added capability of
applying interrogation windows with size smaller than
the particle image displacement increasing both the
dynamic range and the spatial resolution of the
measurement technique.
The effectiveness of this recursive algorithm,
allows the analysis using sub-windows up to 16 px2,
with a limited number of spurious determinations (less
than 7% of the total number using sub windows of
16X16 pixel).
To eliminate the remaining spurious vectors,
always present and due to the lack of particles in the
interrogation windows or noise in the background of
the images, each data set is subjected to a validation
procedure to detect and replace spurious displacement
vectors. Four different kinds of validation techniques
have been implemented:
a local median-filtering method, to identify
displacement vectors that deviate by a prescribed
amount in magnitude or direction, from adjacent
vectors (Westerweel 19944;
a cross-correlation Signal to Noise Ratio (SNR)
validation, where the highest correlation peak is
compared with the second one, and validated if the
ratio is greater than a predefined value d= 1.2
(Keane and Adrian 1992) or even lower according
to the seeding density;
a displacement range validation, which rejects
vectors outside a certain velocity range;
a geometric validation, which rejects vectors
within a certain predefined area, useful when solid
surfaces are within the area of investigation.
Different flags are associated with the spurious
vectors from each one of the previous four different
types of validation. Therefore, in the following
statistical analysis the rejection criterion can be
selected as a combination of some as well as all of
them for filtering the data to be used for statistics
computation.
OCR for page 496
I 28 Fx~
1~ lterstloc
64 ~x~
2~ lter~loc
16 ~x~ 500/o overlap
last lter~loc
Figur e 4: Multig id 6 drpti s wmdow offYst ccrrektion method di pl6 sment sctor f eld 6t dffferent
Iteratmn teps
For 6he res 4t presented m 6he followmg 6 fincl
window siv4 of 24 px~ has ben 6dopted 6s the best
compromise of spurious sctor reduction 6md spati61
resolution that in the prese t case is equivalent to
2 4X2 4 mm
For 6 gi sn propeller 6mgle. 65 p6 irs of im rge h6 4
been 6 qmired to eval rte statistic61 q mtities A gles
from 0° to 85° h6 s been consideled with 6 step of 5°
for 6 total 6mo mt of 6bout 4000 prirs of images for
th considered wmdows Sbtistic evaluation has been
pe formed considering only slocity sctors thrt f if ii
simultarr40usly 611 the filter 6bo s pecffied
MEASUREMENT UNCERTAINTY
th 6 cur6 y of 6he PIV techmique is out of the go61
of 6he present work 6md this 6 spect is 6 compl :x topic
wi6h mamy op n points A debiled 6rmlysis of 6his
6 pect cam be fo md m Rrffel et 61 (1997) in 6he
following, th mam 6sressments r~scess6 y to qualffy
6he present results 6 e leported
The uncertainty on docity measurements by
meams of 6 PIV system is mamly due to th error on
p6 ticle di pl6 ments evaluation which cam be
consideled less thm 1/106 of 6 pi el for the plesent
imag arulysis61goribm Intemmsof slocityism6he
order of I m/s Perk lockmg enors, mainly due to
p6 ticle image siYs, has been Iv5duced, 6s much 64
possible, by using im rge defccusmg techmiques
E rcrs due to noiYs were impo tamt only m flow
egiom where light reflecti ms fi om the c6 ibtmg hub
or fiom the bkde smf6 e wsre plesent E sn if
enor~sous w~ctors 6 e elimim~ted 6md repkced by
mte polrti m durmg po t-processing, sometimes
spurious w~ctors 6re validated 6md sifect 6he stati tics
This effect is relevamt especi611y for the second order
statistics
OCR for page 497
The accuracy of the statistical estimations
definitely depends on the number of acquired samples
and on the shape of the velocity probability
distribution function. The probability density function
in the tip vortex core and in the blade wake markedly
differs from the Gaussian. Furthermore, a lack of data
and less samples available for statistics have been
observed in these regions. In figure 5 the total number
of samples used for statistical computations is plotted
at a given angle for the first measurement window
PIV provides an explanation for this phenomenon: the
strong centrifugal forces in the vortex core reduce
dramatically the probability to have useful particles
required for the measurement as can be seen in figure
6 where a single PIV image is shown. The tip vortex
location can be easily identified as a black hole in the
image of about 40 px in diameter. This problem has
been noticed also for LDV measurements and the
same explanation, as before, is suggested. However,
only PIV provides a direct justification of such a
problem. In the same figure, the dimension of the
interrogation window used for the analysis is shown.
The first outcome of such aspect is that the tip vortex
velocities are underestimate.
By using the t-Student distribution (for which the
confidence interval is +1.96:krms /~(N-1), with
N=65), it is possible to estimate the uncertainty on a
velocity component to be about 1/4th of the measured
rms and hence equal to 0.025 m/s (at the measurement
points far from the tip vortex and the blade wake).
~ I:
~ ~ 7~5 17
Figure S~ San~'le:s distribution. 0=~;3
· 60
556
~ _7
~ sO
In the tip vortex core and near to the blade (where
the highest velocity gradient are encountered), only a
few data are available to compute statistics which
result in low accuracy estimation especially for the
second order statistics
PROPELLER WAKE ANALYSIS
An example of an instantaneous flow field obtained
in the first measurement window for a revolution angle
O=0° is shown in figure 7. For graphical reasons the
vectors have been skipped of a factor two and the
upstream velocity has been subtracted in order to point
out the flow perturbation induced by the propeller.
Two tip vortices due to the actual blade and to the
previous one, as well as the wake released by the
blade, are recognised. The strong flow acceleration
near the hub due to the presence of the hub vortex is
also observed.
The mean velocity obtained over 65 image pairs
for the same angle shows similar features, thus
indicating that the flow field is dominated by the
propeller revolution. In figure 8 the whole measured
flow field is given. Due to graphical reasons, the
contour plots for the U and V components, non-
dimensional by the upstream velocity Uinf are shown
in a mirrored layout. In the diagram the error, due to
the camera positioning in the overlapping region of the
three measurement windows near the hub, can be also
Figure 6: PIV single exposure image. The tip
vortex location is identified due to the lack of
particles in the vortex core which is compared
with the interrogation window
OCR for page 498
-0 .2
-0 .3
-0 .4
-0 .5
=" -0 .6
-0 .7
-0 .8
-O .9
noticed.
_____ ~_-——~ ~ \ ~
are_ I, A;
V ^~./ /, .....
or-- I - - I- I ' 'bit' \ ' t \\''`\~' ~ ~ ~ I, \ '
0.25 0.5 0.75
1
x/R
Figure 7: Instantaneous perturbation velocity field of the propeller (upstream
velocity Uinfremoved).for O=0
The traces of six tip vortices are evident in the
measurement plane. The tip vortex velocity iso-
countours show a typical Rankine vortex pattern: the
U distribution is similar to the V distribution after
rotation by 90°.
The viscous wake due to the boundary layer on the
blade is represented by a defect in the velocity. The
velocity defect is strong at the trailing edge of the
blade and is rapidly smoothed and faded downstream.
As shown by Stella et al. (1998), the velocity defect is
stronger at the blade root due to the larger thickness of
the blade profile near the hub. The blade wake almost
disappears within one diameter downstream, whereas a
strong deformation, due to the higher axial velocity at
the inner radius bends the blade wake. The strong
acceleration of the radial velocity component near the
hub reveals the strong roll up process of the hub
vortex (which is cavitating just outside the
measurement area). It also contributes to the wake
deformation convecting downstream the flow field.
This type of information is also evident in figure 9
where the modulus of the in plane velocity
((U2+V24~/2/Uinf), and the streamlines are shown. The
strong deformation of the streamlines due to the effect
of the tip vortices and the hub vortex is highlighted.
In figure 10, the vorticity generated by the
propeller, non-dimensional by the upstream velocity
and the propeller diameter, is given. In such a figure
the streamlines obtained by subtracting the upstream
velocity are also shown: they highlight the effect of the
tip vortex roll-up. In figure 11, the evolution of the
vorticity field for the revolution angles 20°, 40°, 60°
and 80° are shown. The following considerations can
be done:
The trailing vorticity, shed from the blade trailing
edges consists of two layers of opposite sign which
remain distinct in the wake. This is mainly due to
the presence of the blade boundary layer which
separately generates the two sheets.
The blade wake continuously spirals around the
vortex core which enlarges downstream
OCR for page 499
- The tip vo tex vorticity dfff sion is why strong up
to x/R=1 es also shown in figure 12, where She
me m vorticity of the tip vo tex is plotted along She
dosst~recm distance Such remit is similar to
those obtained by Jessup (1989) for the mskew d
propeller 411 9
- As soon es the blade wake is released md before it
is dissipated, c shong deformation takes place At
Croat x/R=1 the wake of the actual bade feels She
action of She tip vo tex of the previous one which
starts to defomm the wake At x/R=1 5 She wake of
the actua I blade interacts wish th tip Fort :x of She
previous one For x/R > 2 the wake of th actual
blade looses the Imk wish its tip vort:x md is
rolled up by She previous bade tip vortex
Figure 13 shows She di tribution of the turbulence
mtemity au md c. for th measured velocity
components for q=0°, while figure 14 shows th
evolution of av for O=20°,40°,60°,80° Even if She
confidence of She statistical e timator is limited, due to
th fact that has been evaluated only own 65 samples,
some importmt features of She wake cm be
recombed
The turbulent wake released by She bhde is quickly
dissipated md diffused d wnsheam The same process
of wake defommation md broadening, due to the action
of She tip vortices md of the hub vo tex, observed m
th vorticity plots, is also seen m She turbulence level
distributions Newx6heless, new i formation are
obtained by 6 is second order statistics:
- The effect of hub vo tex roll up m She wake is why
importmt md et x/R=2 the t lad wake, ii king She
tip vortex to She hub vo tex, almost d6scppe s
especially for the at, di tribution
- Turbulence diffusion from She hub vortex occurs m
the l ongitudincl evo hit ion e pec id ly for c. es
expected due to the hub vo tex orientation
- Some small scale turbulence, more evid nt m She
c, distribution, generated probably et the lecdi g
edge of the bade, is quickly dissipated
downstream withm one prop llemadius
- The effect of noise in She images, due to She
cavitating hub is pouted o t by the intense spikes
in She turbulence level di tribution
- Velocity fluctuations et She tip vortex core increase
while this is convected d wnsheam This aspect is
rented to She vortex breckdow in tability which
effects She velocity fluctuations th ough paticl
o sc il lit ions of th c m e Fur6herm ore , the pattem of
the turbulence dishdbution suggests that the tip
vortex oscillation occurs m some preferential
direcriom
The tip vortex fluctuations, lecdmg to She
t ret down, c m be pointed out also by evaluating She
stmdard deviation of the spatial fluctuations of tip
vo tex core wish reap cl to She metn et c given
longit dirul position The result, given m figure 15,
shows that the cmplit de of She spatial fluctuation is
mcrecsi g dow sheam md that She amplitude of
h msverscl fluctuations has c higher g owth mte m
respect to the lo git dmal This reach is similar to
chose obtained by Cot om et cl (1999) for c different
propeller md seems to be c g nercl fectme of She
helical vo tex system behaviour
A other impo tmt feature of She tip vortex ystem
mstioility, pointed out by P V, is She separation of She
four tip vortex hajectories after the section of
maxim m contraction ~ figure 16 She evolution of She
tip vort:x tmjecto y for different revolution males is
shown Ah er She connection, md cppmximately et She
same kc ,h m where She tip vo tex interacts with She
wake of the subsequent bade, here is c clear
separation of the trajectory of She tip vo tices due to
She different bodes Furthermore, es pointed out m She
same figure, She locati m of She tip vo ti es m She
measurement plume at different males pomts out She
03 .11 won of the whole sheam tube This is loosing its
axisymmet y md bird periodicity but in the fi st
phase of She t ret dow still maintains the phat with
She propeller revolution Such behnviour also provides
m exphrmtion of She bade sub harmonics pressme
fluctuations sometime e perienced by the hull
Such measur merits are in perfect ag cement with
She flow vis disations obtained m incipient cavit Lion
given m figure 17 The tip vo tex trajectory t par dion
is drictly rel ded to the hub vo tex defommation which
moves from a Ime into a pi al This behaviour is
mai dy due to mutual tip-hub vortex interaction as
demonshated by thei simultaneous generation The
starting point of the instability could be the crossed Id
wake mteracti m as proved by the fact that when
red t ~ g the loading condition 6 is interaction is
sh ted dow sheam as do the l He tkdow
CONCLUSIONS
The PIV tech iq~x was used in a cl coating water
tunnel to investigate the sp dial md tempor d evolution
of She wake of a four bode marme propeller m a
mffomm i flow Both indmtmeous md averag d
velocity fields are achieved, the fader tfter phst
sampling averaging own She stme regular position of
She propeller bade The experimental results, in terms
of velocity md vo ticity fields, reveal some of She
different contributions to She complex propeller flow
field:
OCR for page 500
1. The viscous part of the wake generated by the
boundary layers on the blade surfaces.
2. The potential part of the wake deriving from the
vortex sheet at the blade trailing edge.
3. The slipstream contraction of the wake along the
downstream direction and the beginning of its
broadening after the contraction
4. The cross-blade interaction which seems to be the
starting point of the breakdown process.
5. The behaviour of the tip and hub vortex in the
instability of the helical vortex system.
The PIV technique, both for the careful control of
the set-up adopted in the present experiment and for
the image analysis algorithm implemented, allows a
good spatial resolution (of the same order of
magnitude as in LDV) to be obtained. PIV has proved
to be a suitable means of investigating the complex
flow field in the wake of a propeller giving additional
and complementary information in comparison to the
LDV technique.
Acknowledgements.
The authors are grateful to the CEIMM personnel and
to Mr. Di Florio who supported the PIV
measurements. This work was sponsored by Italian
Ministero dei Trasporti e delta Navigazione in the
frame of INSEAN research plan 2000-2002.
REFERENCES
Arndt, R., Maines, B. "Viscous effects in tip vortex
cavitation and nucleation", Proc. of the 20th
Symposium on Naval Hydrodynamics, 1994.
Biggers, J.C. ,Orloff, K.L., "Measurements of the
helicopter rotor-induced flow field", Journal of
American Helicopter Society, Vol.20, no. l, 1975.
Cenedese, A., Accardo, L., Milone, R. "Phase
sampling techniques in the analysis of a propeller
wake ", Proc. of the International Conference on Laser
Anemometry Advances and Application, Manchester
UK 1985~
Chesnack C., Jessup S., (1998), Experimental
characterization of propeller tip flow, 22th Symposium
on Naval Hydrodynamics, Washington D.C.
Cotroni A., Di Felice, F., Romano, G. P., Elefante M.
"Propeller Tip vortex Analysis by means PIV", 3rd
International Workshop on PIV, Santa Barbara CA,
(1999)
Hunter, WW, Nichols, CE., "Wind Tunnel Seeding
Systems for Laser Velocimeters." NASA Conference
Publication 2393, Workshop, March 19-20, 1985,
NASA Langley Research
Jessup, S.D. "An experimental investigation of viscous
aspects of propeller blade flow". Ph.D. Thesis. 1989
The Catholic University of America, Washington
D.C..
Keane R.D., Adrian R.J., "Theory of cross-correlation
analysis of PIV images", Applied Scientific Research,
Vol.49, 1992, pp.191 -215.
Keane R.D., Adrian, R.J., "Optimization of Particle
Image Velocimeteres". Part 1: Double pulse system.
Meas. Sci. Tech., 1, pp. 1202 1215, 1990
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A.
o
-0.5
' at,
1~.~.
Figure 8: Longitudinal (U) and radial (V) component distribution for ~ =0°
1.1
0.91
0.70
0.49
0.28
0.07
HI I I I
~ upstream
1 .06
0.83
0.59
0.35
0.1 2
-0.1 2
-0.3 5
-0.59
-0.83
- 1 .06
OCR for page 502
1 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
1
-n
0.5
O
-0 .5
-1
__
1 1 1 111 1 1 111 1 1 111 1 1 1 11 1 1 111 1 1 111 1 1 1 11 1 1 1 11 1 1 111 1 1 111 1 1 1 11 1 1 1 11 1 1 111 1 1 111 1 1 1 1
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8
x/R
Figure 9: Modulus of the inplane velocity with streamlines
. ...................... ....... .....................
-50 -43 -36 -29 -22 -1 5 -8 1 8 1 5 22 29 36 43 50
.,::- ~—
Ed__ ~
,,--. ,~.0 (. ,;;.
~-;~- >~ w ~~ ~~ ~
~~''~ ma'-' ~-~-~-3 ~-----2=~---- >--^-----~$P~'-'--3~''''''~''—
_,,,,,, \, NO ~ ,,,,----',
''''I ~ --' Am' - - - - ---~3~ -~ ~~''~
x/R
Figure 10: Non dimensional vorticity distribution and streamline in the frame moving with the
upstream flow for O=0°
OCR for page 503
o "I ~ ~ !!!~
-0.1 <- 1 ~
~ ~~ L ~ ~°°
-1 1 ~ I I I
0 1 x/R 2 3
~ IRE oo
-1 1 ~ I I I
0 1 x/R 2 3
~ IRE oo
-1
-1 1 ~ I I I
0 1 x/R 2 3
~ IRE oo
-1 1
0 1 x/R 2 3
Figure 11: Marcy evolution far 0= 20°.40°,60°,80°
OCR for page 504
-160 r
-170
-180
-190
. _
>
x -200
> -210
Q
F -220
-250
/
1 \, \,
o. o
,..
-230 o
-240 o ~
0.5 1
o
~ to.- --
o
a,....
o ~,,o ~ ,..:.
o
OCR for page 505
-1 1
. ~ - .
. ~ ::::
.
~ OS O.~6 O. 10 O.~14 O. 1~:8 ~ 2~2 1
~ O.5 1 :~11t ~2~5
13 0~:5
Alto
Solo
600
Soo
4 ~ ~
;~14'
Figure 14: ov distribution evolution at ~ = 20°, 40°, 60°, 80°
