ARCHIEF
Lab. y. Scheepsbouw'kund
Technische Hogeschoot
Deift
Some Investigations on Propeller Open-Water
Characteristics for Analysis of
Self-Propulsion Factors
March 1977
MITSUBISHI HEAVY INDUSTRIES, LTD.
1. Introduction
In the analytic method of model-ship correlation,
open-water characteristics of a propellei play an important
role in coupling the resistance and the propulsive
per-formance as pointed out by one of the authors0t. Namely,
self-propulsion factors are derived from resistance and self-propulsion test results by using the propeller
open-water characteristics for the model and power calculations
are made coupling the resistance and self-propulsion
fac-tors by using the propeller open-wate charactei istics
estimated for the ship. lt must be needed, therefore, that
the flow characteristics on blade surface of a propeller
in open-water condition are similar to that in behind
condition both for ship and model, in order to obtain
the consistent self-propulsion factors through the method
mentioned above.
As far as a full scale propeller is concerned, the most
important problem is how to estimate the open-water
characteristics of it, since it is scarcely possible to conduct
open-water tests in full scale. At present, open-water characteristics, which are corrected for the Reynolds
number and surface roughness of a full scale propeller
from its model test results or obtained directly by the
model tests at the standard Reynolds number, are used
for the power calculation. BecaUse it is unquestionable
that the boundary layer flow on the blade surface of
full scale propeller is fully turbulent due to its extremely high Reynolds nLlmbers, the higher the Reynolds number
n open-water tests is, the better to avoid the laminar
effects upon them.
On the other hand, the most important problem for
Some Investigations on Propeller Open-Water Characteristics
for Analysis of Self-Propulsion Factors
Kinya Tamura*
Takao Sasajlma**
The choice of propel/er characteristics for the analysis of se/f-propulsion test results is one of the most important problems to be solved in the process of standardizing the model-ship correlation method. Two methods are wide/y used. i.e. the one is to use the propeller open-water characteristics at the same Reynolds number as in self-propulsion tests [method (1)1, and the other is to use the propel/er open-water characteristics at the standard Reynolds number [method (2)1.
To study which method is preferable, the boundary layer flow on propeller blades was visualized both in open-wa ter and behind
conditions by using the oil-film method. Test results showed that the method (1) was rather preferable to method (2), even though the area of turbulent boundary layer on blades was a little larger in behind condition than ¡n open-water condition at the same Reynolds number. However, due to the complexity of the flow track patterns of oil-film, it seems pretty hard ro conclude it definitely.
Further to achieve the same boundary layer flow on propeller blades both in open-water and ¡n behind conditions, turbulence stimulators were applied to a propeller, with which open-water and self-propulsion tests were carried out. The self-propulsion
factors thus obtained were almost the same as those obtained by the method (1). This result also supports the method (1). Further study, however, is necessary to reduce the drag of turbulence stimulators before adopting them to model propellers as a routine practice.
the analysis of self-propulsion factors, i.e. wake fraction w,0 and relative rotative efficiency er, is the selection of propeller revolutions or Reynolds number, at which the
open-water tests are to be carried out, since the
self-propulsion tests are usually conducted in the range of
Reynolds number where transition from laminar boundary
layer to turbulent one does occur. Two methods are
widely known, i.e..
method (1): Open-water tests are to be carried out at
the same propeller revolution as that corresponding to the normal speed in self-propulsion tests and also at the same temperature as that in the self-propulsion
tests. This comes from the consideration that turbulence
in up-stream will not affect the flow characteristics
on the blade surface of a propeller so much.
method (2): Open-water tests are to be carried out at
the revolution corresponding to the standard Reynolds
number, which is usually higher than that in
self-propulsion tests. This comes from the consideration that turbulence in up-stream will affect
the flow
characteristics to large extent.
Some model basins including the Nagasaki Experimental
Tank have adopted the method (1), while other model
basins have adopted the method (2). The experimental
study by Watanabe2 has supported the method (1) from
the view point of consistency of the analyzed data. However, further studies have been pointed out to be
necessary for standardizing the model-ship correlation
method.
In order to study which method is better, the authors
intended to investigate the effect of turbulence in
up-Manager, Resistance and Propulsion Research Laboratory, Resistance and Propulsion Research Laboratory,
stream upon propeller flow characteristics and
visualiza-tion of the boundary layer flow on the blade surface
were conducted applying the oil-film method3. Further,
to have the same boundary layer flow characteristics on
the blade surface both in open-water and in behind
conditions, the application of turbulence stimulators on
blade surface was examined.
2. Consideration of Flow Characteristics on Blade Surface of Propellers
As stated in the previous section, it is important for the analysis of self-propulsion factors, i.e. Wm and er, tO obtain the open-water characteristics of the propeller,
the flow characteristics of the blade surface of which
in open-water tests are the same as that in the
self-propulsion tests.
Watanabe(2) discussed this problem from the practical
point of view based on the results of the repeated self-propulsion tests of a 7m tanker model through a year.
In this repeated tests, even though the water temperature
changed from i 2°C to 26°C (which corresponds to the
change of Reynolds number Re(K°) from 21x105 to
30x1 5> and the open-water characteristics of the propel-ler correspondingly changed considerably, wm and er
analyzed by the method (1) were scarcely affected by
the change of the water temperature. Thus his data
implies that the method (1) is preferable to the method (2).
Strictly speaking, however, the method (1) is based
on a presumption that the effect of turbulence in up-stream, i.e. in wake, on the extent of turbulent boundary layer is almost negligible and that the turbulence ¡n wake does not always affect the boundary layer in the same
way as the increase of the Reynolds number does. So
if the effect of turbulence in wake on propeller
charac-teristics were larger than test errors, the difference of
propeller characteristics between in open-water test arid
in behind test conditions would result in the scatter of
model-ship correlation factors, which is to be avoided as
much as possible, ¡n order to achieve the higher accuracy
of the estimation method of the ship performance.
This situation can be explained through the relation between the blade section drag of a propeller and the
Reynolds number, as schematically shown in Fig. 1, since
the blade section drag of a propeller directly reflects
the boundary layer condition on propeller blades. In
case of the method (1), the propeller characteristics which
correspond to CD,7 ) is used in the analysis of
self-propulsion factors instead of those corresponding to
CD,)ÇP, i.e. the following relation is assumed.
CDm)5p Cjj.rn)o at Re(K)5 = Re(K)0
while the method (2) assumes the relation
CD,m)sp Cj.i,,,n)s atRe(K)5 <Re(K)5
But, since the Reynolds number of self-propulsion tests changes for every ship model, it seems much more
con-sistent to use the open-water characteristics corresponding
to CD fl)o as an approximation than those corresponding
to CDm)st.
Co.n')o Open-water test at the same Re(K)OS that for self-propulsion tests
Co. n Ist Open-water test at the standard Re(K)
Co, o ISP Self- propulsion test
Co. ,n Its Open and self-propulsion tests by use of a propeller *,th turbulent
St tnu lators
Co.n,)t Open-water and seIf-propulson tests for fully turbulent propeller
Surface flOw
Co.n,)s Open-woter and self-propelled pant for full scale propeller a o a o o, o E E E L) Re(K)= O72(O77t)2
Fig. 1 Pictorial explanation of scale effect of blade section
drag of propeller
Furthermore, better agreement of the boundary layer
flow condition on the blade surface will
be obtainedbetween in open-water and in behind conditions, if
turbulence stimulators are successfully applied to a
pro-peller. The corresponding blade section drag will be
Cjjm)t in Fig.
i.
Present study is motivated to see the effect of turbu-lence of the flow in wake upon the flow characteristIcs of
the blade surface by using the flow visualization technique,
which has been extensively studied by Meyne4. Also
the effect of turbulence stimulators on self-propulsion
factors was studied.
3. Flow Visualization of Propeller Surface Flow 3.1 Flow Visualization Technique
Flow visualization of the propeller surface flow has
been tried since the beginning of the studies on the scale effects of propeller characteristics. Allan5 and Berr$6
of the National Physical Laboratory used an ink or a
deep black aqueous solution of dye released from line holes drilled on the blade surface to see the boundary
layer flow on the blades ¡n operating condition.
In the recent extensive studies of the boundary layer flow on propeller blades, Meyne4 tried several kinds of
flow visualization techniques and also solved the boundary
layer equations for rotating disks in both laminar arid
turbulent cases. Based on his studies, he showed that the flow visualization technique using a soft paint gives reasonable results, as summarized in the following..
(1) The region of turbulent and alminar boundary layer
can be easily distinguished from the flow track angle of
the soft paint relative to the circumferential line, which
RelK)p R(K)st Re(K)s
Propeter : Ae/Ad 0.55 p = 0.6 Z 5
° In case of laminar boundary layer
Leading edge. Track of oil-film nR =Contt T railing edge
results from the difference of the hydrodynamic (fric-tional) force and the centrifugal and Coliori's forces in
the boundary layer. In case of a circular disk, the deviation
of the flow track of the soft paint from the
circum-ferential line is about 11 degrees in turbulent boundary
layer, while 40 degrees in laminar boundary Iayer8.
(2) In the open-water condition, there remains the laminar
boundary layer on the pressure side of a propeller at
the Reynolds number Rc)K) < (8-10)x105, which is far
above the standard Reynolds number widely accepted, i.e. Rc(K) = (4-5)x10, while the transition begins around the Reynolds number Re(K) = (2-3)x105 on the suction
side.
The method employed by Meyne has been used
recent-ly by others9'°1. Among them, Minsaas of the Ship
Research Institute of Norway9 tried to visualize the
boundary
layer flow on the
propeller blades both inopen-water and in behind conditions and concluded that
the boundary layer condition on blades is almost the same
in both conditions, though the turbulence is slightly greater in latter case. This result also support the adequacy
of the method (1).
Table 1 Flow track angle of oil-film
measured
calculated (4)
Laminar boundary layer, = tan' 10.0349 00) Turbulent boundary layer,
= tan 10.00137 00)
In the Nagasaki Experimental Tank, the authors used the oil-film method3 as the flow visualization technique,
which is categorized in the same kind of soft paint
method employed by Meyne. After several preliminary tests, the following material and combination were selected.
Engine oil: Titanium: Grease
= 10: 10: 1 for V> 10 rn/s
=10:10:0.6
forV<lOrn/s
where, V is the velocity relative to the 0.7 radius of the
blade. The mixture after well mixed up, was applied to
the blade surface thinly in two ways, i.e. it was spread
up to 20% of the chord length from the leading edge for two blades, and to whole surface of other blades.
To check the results by Meyne, the flow track angle
of the oil-film was measured and compared with the values
obtained by the simple calculation for a circular disk
given by Meyne, as shown in Table 1. The flow angle of the track of oil-film showed the same tendency as
those obtained by calculation. So the part of laminar and turbulent boundary layer was found to be distinguished
easily by the track of oil-film.
ReIK) Slip Surface 0.5 0.7 0.9
Back 46 33.2 18.2 o (laminarI (M) 60 52.5 39 o (C) 58 52 31 4.3 x i0 0.1 00 53.5 42.5 24.0 Face Iturbulent) 10.0 11.0 14.0 (C) 4.2 (61.91° 3.30 (56.0) 1.90)83.30) Back 00 36.7 29.5 17.6 o (laminar) (M) 40.0 40.0 35.0 ° (C) 52 45.8 31.5 5.7 x iO 0.3 Face 0°
-
39 23 o (turbulentl IM)-
9.0 13 ° (C)-
3.1 (53.7) 1.8 138)Table 2 Principal particulars of models
3.2 Boundary Layer Flow of a Propeller in
Open-Water Condition
3.2.1 Effect of Reynolds Number on Boundary
Layer Flow
At first, boundary layer flow on the blade surface of
propellers in open-water condition was visualized to see
the effect of Reynolds number on the extent of the
turbulent boundary layer.
Model propeller A, originally designed for a container
ship, and B, for a tanker, were used in this test. The
particulars of these propellers are shown in Table 2.
Figs. 2 through 5 show the track of oil-film ort the back and face side of the model propellers A and B, tested at the slip ratio of 0.3. Tests at the Reynolds
Items A B C D Model propeller D (ml 250.00 233.33 177.63 p 1.0500 0.6000 0.7143 0.7975 Ae/Ad 0.8500 0.5500 0.6649 0.6210 tic) 0.7R 0.03500 0.06000 0.05665 0.07183
Section M-5 MAU-5 MAUw-6
Model Ship Im) 8.000 6.250 /Bmld 6.000 5.912 Ch 0.8019 0.8130 Ship (ml 240.0 285.0
Type SR 61 Cb-Series 157,000DWT Tanker
in o tests
K d f
Propeller open-water tests :
Effect of slip ratio and
Reynolds number on the
boundary layer flow of the
propeller blades
Propeller open-water and behind tests :
Effects of Reynolds number on the boundary layer flow of the propeller blades with and without turbulent stimulators
Propeller open-water and self-propulsion tests Effect of turbulence stimulators on self-propulsion factors 2.26 4.52 6.78 9.09 12.11 15.11 18.24 Re(K) x105
Fig. 2 Effect of Reynolds number on boundary layer flow of model propeller A
1.42 X105
4.27 X iO
5.69 X 1O
Re(K)
Fig. 5 Effect of Reynolds number on boundary layer flow of model propeller B
(Suction side : Slip ratio = 0.3)
number lower than 7x105 were conducted in the towing tunnel. From these photographs, sketches were made, as
tank, while others were conducted in the cavitation shown in Fig. 6, illustrating the extent of the turbulent
2.26 4.52 6.78 9.09 12.11 15.11 18.24
Re(K) ><1O
Fig. 3 Effect of Reynolds number on boundary layer flow of model propeller A
(Suction side : Slip ratio = 0.3)
Fig. 4 Effect of Reynolds number on boundary layer flow of model propeller B
boundary layer as far as distinguished clearly by the
tracks. Observation of these patterns of oil-film is
sum-marized as follows.
(1) Generally speaking, the area of turbulent boundary
layer increases with increase of Reynolds number on both
sides, but the rate of increase is not always linear with
the Reynolds number.
Suction side Pressure side
L.E Re(K)2.26 x lO 4.52 l0 6.78 x l0 12.11 x 8.24 x l0 Propeller B T.E. TE.
Re(K) l42l0
427x105 5.69 x IFig. 6 Effect of Reynolds number on extent of turbulent
boundary layer : Slip ratio = 0.3
Suction side
Pressure side
Propeller
About 40% of the blade surface remains laminar at
the standard Reynolds number generally accepted, i.e.
Re(K) = (4-5)x105.
lt is worth noticing that there still remains the region
of laminar boundary layer on the blade surface at a Reynolds number as high asRe(K) = 18x106.
The region of the turbulent boundary layer on the
blade surface strongly depends upon the geometry of
propellers.
3.2.2 Effect of Slip Ratio on Boundary Layer Flow Since the development of the boundary layer strongly
depends upon the pressure distribution on the body, it
can be easily imagined that the slip ratio has considerable
effect upon the boundary layer flow of propellers. So the track of oil-film on the blades was also examined at different slip ratios, using model propellers A and B.
Figs. 7 and 8 show the test results. Also sketches were
made for both propellers to see the turbulent extent, as shown in Fig. 9, by the zone between the lines and the trailing edge in each sketch.
lt is clearly shown that, with increase of the slip ratio,
the turbulent area increases on the suction, while decreases
on the pressue side. And it is also shown that the effect of the slip ratio on the boundary layer flow is quite large: for instance, in case of propeller A almost the same area
of turbulent boundary layer is obtained on the suction side by the increase of Reynolds number Re(K) from 4.5x105 to 18x106 at the slip ratio of 0.3 and by the
increase of the slip ratio from 0.3 to 0.5 at the Reynolds
number Re(K)
of 4.5x10.
3.3 Boundary Layer Flow of Propeller in Behind Condition
Boundary layer flow of a propeller in self-propulsion
test condition, i.e. in behind condition, which is the main concern in this study, was examined by using the model propeller C. This model propeller is a scale model of the
propeller designed for a
Ch = 0.8
tanker used ¡n theFig. 7
Effect of slip ratio on boundary layer flow
of model propeller A Re(K) = 4.5 x iO5
systematic series tests by SR 61 Committee in Japan. The
principal particulars are shown in Table 2.
Fig. 10 shows the test results in comparison with those
obtained in open-water tests. Due to the turbulence in
wake, track of oil-film shows the complicated patterns.
Especially the non-uniformity of the velocity field in
wake, which results in the change of slip ratio at each phase angle of a propeller, did affect the flow track of
oil-film, so it is quite difficult to evaluate the extent of
turbulent zone, except the zone where the turbulent
boundary layer is kept throughout one revolution of the
propeller.
In these tests, the extent of turbulent boundary layer on the suction side, thus estimated, was a little larger in
behind condition than that in open-water condition, but
Suction side
Pressure side
Open-water tests
Re(k) 4.5 * IO
Suction side Pressure side
Model propeller A - Slip ratio r 0.1 Slip ratio r 0.3 Slip ratio r 0.5 Behind tests LE Re(k) 2.85x io Re(k) 45xIO
Suction side Pressure side
Model propeller B
Fig. 9
Effect of slip ratio on extent of turbulent boundary layer
Fig. 10
Comparison of track of oil-film
on blades of model propeller C
in open-water and behind test
conditions
Re(K) = 3.25 x Slip ratio
= 0.50
Slip ratio 0.1 0.5
Fig. 8 Effect of slip ratio on boundary layer flovv of
model propeller B Re(K) = 2.85 x 10
M
on the pressure side, the difference was little. But this
difference is considered to be a negligible effect upon propeller characteristics, so it might be said that the
method (1) is rather preferable.
4. Effect of Turbulence Stimulators on Propeller
Characteristics and Self-Propulsion Factors
4.1 Turbulence Stimulation by Studs
Following the idea that the flow characteristics on the blade surface should be the same both in open-water and
in behind conditions for the analysis of self-propulsion
factors to get the consistent W7 and Cr, turbulence
stimulators were applied to model propellers.
As turbulence stimulators, cylindrical and square studs were used and the size and the pitch of the studs were
designed using the data by Tagori01), to achieve the fully turbulent flow behind the studs. Table 3 shows the
dimension of the turbulence stimulators for model pro-pellers, C and D. Model propeller C was used to study
the effectiveness of the design method of studs using the flow visualization technique and model propeller D was used in self-propulsion tests. As an example, square and
cylindrical studs applied to the model propeller D are
shown in Fig. 11.
Figs. 12 and 13 show the flow visualization test results
for model propeller C both n open-water and in behind
conditions respectively at two different Reynolds
num-bers.
Though the flow track of oil-film shown in the
photographs at the lower Reynolds number is not so clearon the suction side, by the careful observation of the
track, it was ensured that on the blade surface behind turbulence stimulators fully turbulent flow was achieved
both n open-water and in behind conditions in the range
Table 3 Dimensions of turbulence stimulators
Cylindrical studs
Square studs
Fig. 11 Turbulence stimulators applied on the blade surface of model propeller D
of Reynolds number for self-propulsion tests. 4.2 Effect of Turbulence Stimulators on
Self-Propulsion Factors
As mentioned in the previous section, the fully
tu,bu-lent flow on propeller
blades was confirmed both inopen-water and in behind conditions by the use of turbu-lence stimulators. So the self-propulsion tests were con-ducted using the model propeller D to see the
self-propul-sion factors when the same boundary layer flow is
achieved on propeller blades both in open-water and in behind conditions. Model propeller D which was designed
for a157,000DWTtanker was chosen because the Reynolds
number of the propeller Re(K) at the self-propelled
condition was relatively small.
Fig. 14 shows the propeller open-water test results of the propeller D with cylindrical and square studs. In this figure, open-water characteristics of the propeller without
studs at the same Reynolds number as that of
self-propulsion tests and at the standard Reynolds number
)del propeller b'
ØIi
Cylindrical studs Square studs Design condP (mm) 3.0 dorb (mm)
\.
1.0 n = 10.45rps b'(mml 0.5 CN
N
Re(Kl =2.60 x 10' h(mml boss -O.4R 0.25N
O.4Rtip
0.18 P (mm) 3.0 3.0 d orb (mml 0.83 1.0 n 10.Orps b (mm) 0.5 D Re(K) = 1.88 10 h (mml boss - 0.4R 0.9 0.53 0.4R - tip 0.4 0.265Behind tests Open-water tests Behind test Open-water tests Suction side Suction side
are also shown. As expected, the effect of the cylindrical and square studs on propeller characteristics was found
to be the same. In both cases, however, due to the excessive drag of studs the thrust coefficients decrease,
while torque coefficients increase from those without
studs. Namely, the blade section drag of this case
cor-responds to CDm)rs instead of CD,fl),. in Fig. 1.
Self-propulsion tests of the tanker model were carried
out using the model propeller
D with
and withoutcylindrical studs and analyzed by using the open-water
characteristics of the same propeller with and without
Pressure side
Fig. 12 Comparison of track of oil-film behind turbulence stimulators of model propeller C
Re(K) = 2.91 x
Pressure side Fig. 13 Comparison of track of oil-film behind turbulence stimulators of
model propeller C
Re(K) = 3.91 x 1O
studs respectively, which were obtained at the same
Reynolds number as that in self-propulsion tests. Fig. 15 shows the comparison of the self-propulsion
factors, i.e. w,0 and Cr. In the case of the model propeller
with turbulence stimulators, wm and er are a little lower than those in the case of the propeller without turbulence
stimulators. However, these difference are within the
standard errors of repeated self-propulsion testsas already
shown by Watanabe(2), even though the Reynolds number
at the self-propulsion tests was considerably lower than
0.3 5 06-030 a a o 04- 0.2-l'O 0.9 065 0.55 .0 09 06 05 025 020 0.15 0.10 0.05 n
I
Model propeller D ep 0.12 0.14- Re(K)
l.67zl0 Without studs 442X105 Do1,71 X IO Square studs 194X105 Cylindrical studs
Fig. 14 Open-water characteristics of model propeller D
with and without turbulence stimulators
5700QDW Tanker
Model propeller D
Reynolds number at self- propulsion test Without studs
-- -- With cyliridricol studs
Standard Reynolds number
Bollost Load. 1% Trim Aft
Full Load. Even Keel
016 0.18
Fn
Fig. 15 Comparison of self-propulsion factors
the reference, self-propulsion test results which were con-ducted by using the propeller without turbulence stimula-tors were analyzed using the open-water characteristics
of the propeller at the standard Reynolds number and
also shown in Fig. 15. In this case, the difference in
w,,t is little, but the difference in er is quite large in
comparison with those analyzed by using the open-water
characteristics of the propeller obtained at the same Reynolds number as that of self-propulsion tests.
Thus it can be said that within the present accuracy
of self-propulsion tests, self-propulsion factors analyzed
by using the propeller open-water characteristics at the
same Reynolds number as that in self-propulsion tests are
more reasonable. But from the view point that the flow characteristics on the blade surface should be the same
in open-water and behind conditions to obtain the
con-sistent self-propulsion factors, application of turbulence stimulators to model propellers is preferable. There might be a possibility that the self-propulsion factors would
change to a certain extent by using the propeller with
lower thrust coefficients than those pre-determined. So
further study to reduce the effect of the drag of
turbu-lence stimulators upon propeller characteristics without
exerting bad influence upon the turbulence stimulation
is necessary.
5. Concluding Remarks
Some investigations were made in the Nagasaki Ex-perimental Tank to see which is reasonable, method (1) and method (2), for the analysis of self-propulsion factors.
Namely,
method (1): Open-water characteristics for the analysis
of self-propulsion factors are to be obtained by
open-water tests at the same Reynolds number as that in
self-propulsion tests.
method (2): Open-water characteristics for the analysis
are to be obtained by open-water tests at the standard
Reynolds number, which is usually higher than that
in self-propulsion tests.
As a first step of the investigation, flow visualization of the boundary layer flow on the blade surface of a propeller in both conditions were tried. Then, to obtain the same boundary layer flow on the blade surface in both conditions artificially, turbulence stimulators were applied to a propeller, with which self-propulsion tests
were carried out and the results were discussed in
com-parison with those obtained by the methods (1) and (2). The results of these investigation are summarized in the following.
As far as the boundary layer on blades which is
kept turbulent throughout one revolution of a propeller in
behind condition concerns, it is a little larger than that in open-water test condition. This difference is considered
to exert negligible influence upon propeller characteristics
and it may be said that the method (1) is preferable to the method (2). But due to the complexity of the flow track patterns of oil-film on propeller blades in behind condition due to non-uniformity of the wake, it seems
pretty hard to derive definite conclusion from this kind
of flow visualization tests.
By applying properly designed turbulence stimulators
on blades of a model propeller, fully turbulent flow is
achieved behind stimulators both in open-water and in behind conditions in the range of Reynolds number for
0.2
O 0l 0.3 0,4 05
self-propulsion tests.
Self-propulsion factors, obtained by using the
open-water characteristics of a propeller having the same
boundary layer flow as that in behind condition by apply-ing turbulence stimulators are almost the same as those
obtained by the method (1) within the accuracy of
self-propulsion tests. This result supports the method (1) is preferable to the method (2).
To obtain the consistent self-propulsion factors, it
seems better to use open-water characteristics of a propeller
having the same boundary layer flow on propeller blades by applying turbulence stimulators. In the tests reported
here, there occurred the large change of propeller
charac-teristics due to the drag of turbulence stimulators, so
Tamura, K., Speed and Power Prediction Technique for
High Block Ship Applied in Nagasaki Experimental Tank,
Proc. STAR ALPHA Symposium, SNAME, Washington, D.C., 1976
Watanabe, K., Repeated Self Propulsion Tests on A Tanker Model, Journal of the Society of Naval Architects of Japan, Vol. 121, 1967
131 Murai, H., Hirata, Y., and Mikashima, Y., Study on
Swept-Back Wings in Parallel Walls (ist Report), The Memoi jet of the Institute of High Speed Mechanics, Vol. 21, No. 210, 1965/66
141 Meyne, K., Untersuchung der Propel lergrenzsch ichtsströmung
und der Einfluss der Reibung auf die Propellerkenngrossen, Jahrbuch der Sciffsbautechnischen Gesellschaft, 66 Band, 1972
(5) Allan, J. F., Formal Discussion to Subiects 1 & 5 (Scale
Effect of Propellers and Self-Propulsion Factors(, Seventh
References
further studies are necessary to reduce the drag of
turbu-(ence stimulators without reducing the effect of turbulence
stimulation before adopting them as a routine practice.
Flow visualization tests carried out here gave additional
result concerning the scale effect of propeller open-water
characteristics.
There remains laminar boundary layer on the blade
surface of a propeller up to
Re(K) = 18x105,
which 5far above the standard Reynolds number generally
ac-cepted. Propeller open-water tests at, higher Reynolds
number will be necessary, in future, to establish the
method to predict propeller characteristics of a full scale
propeller more accurately.
International Conference on Ship Hydrodynamics,
Scandi-navìa, 1954
Berry, L. W., Boundary Layer Flow on Model Propeller,
The Journal of Photographic Science, Vol. 10, 1962
Cochran, W. C., The Flow Due to a Rotating Disk, Proc.
Cambr. Phil. Soc., 1934
Banks, W., H. and Gadd, G. W., A Preliminary Report on Boundary Layers on a Screw Propellers and Simpler Rotat-ing Bodies, NPL-Report SH 27: 1962
Minsaas, K., Scale Effect of Model Propellers, The Ship Research Institute of Norway
Suzuki, I., Effects of Turbulence Stimulators on Propeller Blades upon Propeller Open and Self-Propulsion Tests, SRC Technìcal Note, Vol. 2, 1974
Tagoi i, T., On the Effect of Various Turbulence Stimulators and Resistance of these Stimulators Own, Journal of the Society of Naval Architects of Japan, Vol. 110, 1960
