Full Scale Ship Performance, 24th - 25th October 2018, London, UK

Investigation on Full Scale Performance of the Propeller Boss Cap Fins (PBCF)
K Kimura and S Ando, Akishima Laboratries(Mitsui Zosen) Inc,, Japan
S Ono, Y Tanaka and S Takeuchi, MOL Techno-Trade, Ltd. (MOL Tech), Japan
N Asanuma, Mitsui O.S.K. Lines, Ltd. (MOL), JapanSUMMARY
The propeller boss cap fins (PBCF) is well known to be one of the most successful energy-saving devices for ships.
More than 3,300 sets have been sold since its first introduction in 1987.
In this paper, SPIV measurements and CFD computations were carried out in order to investigate the reasons for thedifference in the energy saving effects of PBCF in model test and in full scale data. It was confirmed to evaluate the fullscale energy saving effect of PBCF by taking into account the propeller inflow in the real ship. As these results, it wassuggested that EFD and CFD analysis using simulated full scale ship wake is effective to estimate the energy saving
effect of PBCF in full scale. And the effect of energy saving was confirmed to increase in combination with PBCF andother ESD. Also, it was confirmed that the effectiveness of the combination of PBCF and other ESD for EEDI
improvement. Furthermore, it was confirmed that PBCF is an effective device to reduce the underwater radiation noisefrom the cavitation test.

NOMENCLATURE
DJnPropeller diameter (m)Advance coefficient
Rotation speed (rps)
Thrust coefficient=
Torque coefficient

Propeller efficiency

=

=

∙

Propeller Reynolds number



P
1.

Ship Reynolds number=-1
Ship Speed (m s )Kinematic viscosity (N s m-2)
Density of water (kg m-3)
Pressure (N m-2)=

INTRODUCTION

The propeller boss cap fins (PBCF) is well known to be
one of the most successful energy-saving devices forships. More than 3,300 sets have been sold since its first
introduction in 1987. However, the reasons for thedifference in a gain in propeller efficiency between fullscale and model scale by installing PBCF have not beenclarified.

Figure 1: Propeller Boss Cap Fins(PBCF)© 2018: The Royal Institution of Naval Architects

The investigation and development of PBCF wereoriginally performed by Ouchi et al [1,2,3]. They
confirmed that thrust increases and torque decreases, thus
the efficiency increases with the introduction of PBCF.
The measured increase of the efficiency in their modelexperiments was from 1 to 2%. Nojiri et al. reported theresults of more systematic experiments regarding four,
five and six-bladed propellers. The measured increase of
the propeller efficiency was from 1 to 1.5% [4]. On theother hand, Ouchi reported the results of full scale
analyses for 12 different vessels, in which the averageenergy-saving effect of PBCF was 5.4% [3]. Hansen et al.
reported that the analysis of the sea trials showed 3.5%
and 4% reduction in shaft horsepower in ballast and infull load condition [5]. Nojiri et al. also showed theresults of full scale analyses for 16 different vessels, inwhich the energy-saving effect ranges from 2 to 10%with the average being approximately 5% [4]. Those
results suggest that the energy saving effect of PBCF islarger in full scale than in model scale. Kawamura et al.
reported results of CFD computations were carried out inorder to investigate the reasons for the difference in theeffects of PBCF in model test and in full scale data [6,7].
They presented the computed effect in the propeller
efficiency, which around 2% is still smaller than thereported value in sea trial and fleet data.
The authors have also been studying the possibility ofExperimental Fluid Dynamics(EFD) and Computational
Fluid Dynamics(CFD) on the performance evaluation of
PBCF and propeller [8,9]. In precious study, the authors
discussed the various validations for the effect of PBCF,
and we confirmed that the effect of PBCF in a uniform
flow and an imaginary wake was qualitatively wellestimate, but the difference in effect for the propeller
efficiency between full scale and model scale were notsufficiently explained. So, the authors performed EFD
and CFD regarding PBCF operating behind simulated
full-scale ship wake, and discussed the reason of thedifference in the gain between the full scale and model
scale. Furthermore, we were carried out the experiments

Human Factors, 26th – 27th September 2018, London, UK

on the combined effect of PBCF and other energy saving
devices (ESD). The measurement results demonstrated
the effectiveness of the combination of the PBCF andother ESD for EEDI improvement. And we described the
reduction effect of underwater radiation noise by PBCF.

2.

PBCF PERFOMANCE IN FULL-SCALE

2.1

REVERS PROPELLER OPEN TESTThe reverse propeller open test(rev-POT) of PBCF
without/with simulated full-scale ship wake was carriedout in the cavitation tunnel at Akishima Laboratory. The
arrangement of reverse propeller open test was shown in
Figure 2.

Table 1:Stereo PIV system configuration
CamerasCamera lensMeasurement
area
Laser
Seeding
Particles
PIV analysis

2.3

ImagerProX 2M(1600×1200pixel,each being asquare of side 7.4μm)
Ai AF Zoom-Nikkor 24-85mm
f/2.8-4D IF)
W300mm×H300mm
DPIV-L200 200mJ
Silver Coated Hollow Glass
Spheres:diam 14μm
Lavision FlowMaster DaVis8.1.3

MODEL PROPELLER

The practical high-skew marine propellers were appliedin the several model tests. Figure 4 and 5 shows theprincipal particulars of the model propeller P664R andP668R. The model of PBCF was designed for the several
model propellers.
MPNo.P664R
Propeller Diameter(M)

Number of Blades
Mean Pitch Ratio
Expanded Area Ratio
Boss Ratio
Turning Direction

0.25
5
0.80
0.50
0.18
Right

Figure 2: Reverse Propeller Open Test (rev-POT)
Figure 4: Model Propeller P664R
2.2

FLOW MEASUREMENT

The difference of flow pattern without/with the PBCF
behind simulated full scale ship wake was measured byusing the stereo particle image velocimetry (SPIV). And
it is discussed that the influences of simulated full scale
ship wake for PBCF. The SPIV set-up is shown in Figure 3 and the SPIV system configuration was shown in
Table 1. The SPIV set up consisted of two CCD cameras
located in both sides of the cavitation tank and the NdYaG laser to generate the light sheet to the measurement
plane. The area of measurement was W300×H300mm[10].

Figure 3:Arrangement of Stereo PIV System

MPNo.P668R
Propeller Diameter(M)
Number of Blades
Mean Pitch Ratio
Expanded Area Ratio
Boss Ratio
Turning Direction

0.25
6
1.10
0.85
0.19
Right

Figure 5: Model Propeller P668R

2.4

FULL SCALE SHIP WAKE SIMULATION

In assessing the ESD performance of the full scale ship,
the flow field of stern is very important. Figure 6 shows
the CFD analysis results of wake distribution in model
Re =107 and full scale ship Re=109. It was confirmed thatvery different wake between model and full scale wasobtained, as full scale ship wake against model wake [11].
Therefore, to estimate the energy saving effect of PBCF,
the propeller inflow is very important and it is necessary
to consider full scale ship wake. So, we estimated two
type of Full scale ship wake distribution at the propeller
plane in the towing condition.
The full scale ship wake flow in cavitation tunnel was
simulated by a wire mesh screen method which was
installed upstream the propeller. The arrangement of wire
mesh screen in cavitation tunnel was shown in Figure 7.

© 2018: The Royal Institution of Naval Architects

Full Scale Ship Performance, 24th - 25th October 2018, London, UK

Table 2 : Test Condition
Thrust(N)

P664R

200

○

400

○

○

600

○

○

800

a) modelb)shipFigure 6: Comparison of wake distribution between
model Re =107 and s full scale ship Re=10 9.
The wire mesh screen method is usually used for thesimulation of ship wake on the cavitation test. This
simulation method is very effective in reproducing thedesignated ship wake distribution in cavitation tunnel.

Figure 7: Arrangement of Wire mesh screen

P668R

○

Figure 9 shows the measurement results of the propeller
slipstream of P668R without and with PBCF in uniform
flow. It wase confirmed that the strong hub vortex behindthe propeller boss in without PBCF. On the other hand, it
was confirmed that the hub vortex was disappeared with
PBCF. Figure 10 shows the measurement results of thepropeller slipstream of P668R without and with PBCF in
full scale ship wake A. It wase confirmed that the hub
vortex behind the propeller boss in full scale ship wake A
was stronger than uniform flow in without PBCF. And, it
was confirmed that the hub vortex was disappeared with
PBCF.

a)

Thrust 600N without PBCF

Two type of simulated full scale ship wake in cavitation
tunnel was shown in Figure 8. Ship-A wake is the fullform ship and ship-B wake is the relatively slender ship.

b) Thrust 600N with PBCF
Figure 9:Comparison of Velocity(left) and Vorticity(right) distribution behind P668R in uniform flow.
a) Ship Wake Ab) ship Wake B

Figure 8: Simulated wake distribution in cavitation
tunnel.

2.5

FLOW MEASUREMENT RESULTS

To confirm the effect of performance improvement of
PBCF, the propeller slipsteam was measured using SPIV.
The test condition was shown in Table 2. The constantloading method is employed for the reversed POT.

© 2018: The Royal Institution of Naval Architectsa)Thrust 600N without PBCF

Human Factors, 26th – 27th September 2018, London, UKa)Thrust 600N with PBCF

a)

Thrust 600N without PBCF

Figure 10: Comparison of Velocity(left) and Vorticity(right) distribution behind P668R in Ship Wake A.

Figure 11 shows the comparison of the energy-saving
effect of PBCF. The energy-saving effect of PBCF was
obtained around 2 to 3% in uniform flow. The energysaving effect of PBCF was achieved more than 4% inship wake A, almost same magnitude of energy saving
effect of PBCF in full scale.

b) Thrust 600N with PBCF
Figure 12:Comparison of Velocity(left) and Vorticity(right) distribution behind P664R in uniform flow.

a)uniform flowa)Thrust 600N without PBCFb) ship wake A
Figure 11: Comparison of the energy-saving effect of
PBCF for propeller P668R.

Figure 12 shows comparison of velocity and vorticity
distribution behind propeller boss cap of P644R in
uniform flow. Figure 13 shows comparison of velocity
and vorticity distribution behind propeller boss cap of
P644R in ship wake B. As with case of propeller P668R,
it was confirmed that the hub vortex was disappearedwith PBCF in unifoem flow and in ship wake B.figure 14
shows the comparison of the energy saving effect of
PBCF for P664R. The energy-saving effect of PBCF was
obtained around 2 to 3% in uniform flow. The energysaving effect of PBCF was achieved more than 3% inship wake B, almost same magnitude of energy saving
effect of PBCF in full scale.

b) Thrust 600N with PBCF
Figure 13: Comparison of Velocity(left) and Vorticity(right) distribution behind P664R in Ship Wake B.

a)uniform flow

© 2018: The Royal Institution of Naval Architects

Full Scale Ship Performance, 24th - 25th October 2018, London, UKb) ship wake Ba) without PBCF
Figure 14: Comparison of the energy saving effect of
PBCF for Propeller P664R.

b) with PBCF

Figure 16: Comparison of streamline behind propeller
P668R in Ship wake A.

Thus, it was confirmed that the difference in effect forthe propeller efficiency between full scale and model
scale was reduced by taking into account the full scale
ship wake. To estimate the energy saving effect of PBCF
in full scale, it is important to be close the load of thepropeller to the condition in full scale. Especialy, the inflow distribution of propeller is very important to estimate the energy saving effect of PBCF in full scale.
a)
2.6

Thrust 600N in uniform flow

CFD Calculation

The present work uses OpenFOAM OpenSource CFD
tool to compute the incompressible flow field around thepropeller and PBCF in reversed POT. In this study,
pimpleDyMFoam is an unsteady solver for incomepressible fluids on a moving mesh using the PIMPLE(merged PISO-SIMPLE) algorithm with AMI (Arbitrary
Mesh Interface) techniques. The governing equations are
the Reynolds-Averaged Navier-Stokes equations and the−model was used for turbulence modelling.
Figure 15 and Figure 16 shows the comparison of
streamline behind propeller boss cap for propeller 668R
in uniform flow and in ship wake A. The hub vortex
behind propeller boss cap was generated and the efficiency loss has occurred without PBCF. On the other hand, it
was confirmed that the hub vortex was disappeared andthe energy saving effect was achieved by PBCF. And theenergy saving effect in ship wake A is increased
compared with uniform flow.

b) Thrust 600N in Ship Wake A
Figure 17: Comparison of Vorticity distribution aroundpropeller P668R without(left) and with(right) PBCF.

a) Thrust 600N in uniform flow
Figure 18:Comparison of Vorticity distribution aroundpropeller P664Rwithout(left) and with(right) PBCF.

a) without PBCFb) with PBCF

Figure 15:Comparison of streamline behind propeller
P668R in uniform flow.

© 2018: The Royal Institution of Naval Architects

Furthermore, the comparison of isosurface of vorticity
distribution around propeller was shown in Figure 17
and Figure 18. From these results, it was confirmedthat the hub vortex in ship wake A was larger than in
uniform flow and the hub vortex was disappeared by
PBCF. Especially, it was recognized that PBCF is
better ESD to decrease the efficiency loss by the hub
vortex.

Human Factors, 26th – 27th September 2018, London, UK

3.
COMBINED EFFECT of PBCFOTHER ENERGY SAVING DEVICE.

AND

Due to global warming and exhaustion of fossil fuels,
measures in the maritime industry to reduce greenhousegas (CO2) and to cope with fuel consumption regulations
are becoming important issues. Therefore, the development of the high-performance energy-saving device is
expected. The experiments regarding the combined effectof PBCF and typical ESD were conducted in the large
towing tank at Akishima Laboratory. It is confirmed
about the influence of the interaction between PBCF andother ESD. Figure 19 shows the combination was used in
the experiments, which PBCF, PBCF with Rudder BulbFin(RBF), PBCF with Duct and PBCF with Duct and
RBF.

c)

without PBCFd) with PBCF
Figure 21: Velocity(left) and Vorticity(right) distribution
behind propeller with Ducta) PBCFb) PBCF+RB

c) PBCF with DUCTd) PBCF with Duct and RB

Figure 19: Combination of PBCF and typical ESD

a)Figure 20 and Figure 21 shows the comparison of velocity and vorticity distribution behind propeller wasmeasured by SPIV. In both conditions without and withduct, the hub vortex is generated by rotating propeller.
And, it was confirmed that the hub vortex was disappeared by PBCF. Since these experiments regarding
the combined effect of PBCF and typical ESD werecarried out in the model wake, it is expected that theenergy saving effect is further improved in the full scale
wake. Figure 22 shows the comparison of the energy
saving effect of combination between PBCF and typical
ESD by considering the energy saving effect in full scale
wake. By combining PBCF and other ESD, it waspredicted that more energy saving effect was achieved
and more than 6% gain was obtained in case of
PBCF+DUCT+RBF.

without PBCF

Figure 22: Comparison of the energy saving effectof combination between PBCF and typical ESD.
4.
b) with PBCF
Figure 20: Velocity(left) and Vorticity(right) distribution
behind propeller without DuctUNDERWATER RADIATION NOISE

From the influence of radiation noise from the merchantships to marine life attracted global attention, thedevelopment of underwater radiation noise reduction
techniques have been important. Especially, the various© 2018: The Royal Institution of Naval Architects

Full Scale Ship Performance, 24th - 25th October 2018, London, UK

cavitation generated from propeller is main noise sourcefrom the ship, the reduction of these cavitation isimportant. The experiment regarding the underwaterradiation noise was conducted in cavitation tunnel at
Akihima Laboratory. Figure 23 shows the results ofcavitation observation without and with PBCF. It was
confirmed that the hub vortex cavitation was disappeared
by PBCF. Figure 24 shows the comparison of the soundpressure level (SPL) between condition without and with
PBCF. In PBCF equipped condition, the underwaterradiation noise was confirmed to be reduced by around
5db in range from 100 to 1kHz. As a result, it was
confirmed that PBCF is an effective device to reduce theunderwater radiation noise.

5.

SPIV measurements and CFD computations were carriedout in order to investigate the reasons for the differencein the energy saving effects of PBCF in model test and infull scale data. It was confirmed to evaluate the full scaleenergy saving effect of PBCF by taking into account thepropeller inflow in the real ship. As results, it was suggested that EFD and CFD analysis using simulated fullscale ship wake is effective to estimate the energy saving
effect of PBCF in full scale.
And the effect of energy saving was confirmed toincrease in combination with PBCF and other ESD. Also,it was confirmed that the effectiveness of the combination of PBCF and other ESD for EEDI improvement.
Furthermore, it was confirmed that PBCF is an effective
device to reduce the underwater radiation noise from thecavitation test.

6.

a)without PBCFb) with PBCF

© 2018: The Royal Institution of Naval Architects

ACKNOWLEDGEMENTS

The authors would like to express their gratitude to Dr.
Chiharu Kawakita at Fluid Control Research Group,
Fluids Engineering & Hull Design Department, National
Maritime Research Institute for his cooperation andsupport to the study.

7.

REFERENCES

1.

K Ouchi, Ogura M, Kono Y, Orito H, Shiotsu T,
Tamashima M, Koizuka H,’A research andDevelopment of PBCF (Propeller Boss Cap
Fins) –Improvement of Flow from Propeller
Boss –‘, Journal of Society of Naval Architectsof Japan 163:66-78, 1988.

2.

K Ouchi, Tamashima M, Kawasaki T, Koizuka
H,’A Research and Development of PBCF
(Propeller Boss Cap Fins) : 2nd Report:Study on
Propeller Slipstream and Actual Ship
Performance’. Journal of Society of Naval
Architects of Japan 165:43-53, 1989.

3.

K Ouchi,’Effect and Application of PBCF
(Propeller Boss Cap Fins)’. Journal of MESJ
27(9):768-778, 1992.

4.

T Nojiri, N Ishii, H Kai,‘Energy Saving
Technology of PBCF (Propeller Boss Cap Fins)
and its Evolution’. Journal of JIME 46(3): 350358, 2011.

5.

Hansen H R, Dinham-Peren T, Nojiri T,’Modeland Full Scale Evaluation of a 'Propeller BossCap Fins' Device Fitted to an Aframax Tanker’.
Second International Symposium on Marine
Propulsors smp'11, Hamburg, Germany, 2011.

Figure 23: Comparison of cavitation observation without
and with PBCF for propeller..

Figure 24: Comparison of the reduction effect of PBCF
for the underwater radiation noise.

CONCLUSIONS

Human Factors, 26th – 27th September 2018, London, UK

6.

T.Kawamura, K. Ouchi2, S. Takeuchi,’ Modeland full scale CFD analysis of propeller boss
cap
fins
(PBCF)’,Third
International
Symposium on Marine Propulsors, smp’13,
Launceston, Tasmania, Australia, May 2013

7.

T.Kawamura, K. Ouchi, T Nojiri, ‘Model andfull scale CFD analysis of propeller boss cap
fins (PBCF)’,Journal of marine science andtechnology 17(4), 469-480, 2012-12-01

8.

K Kimura. et al.，’Study on Unsteady Cavitating Flow Simulation around Marine Propeller
using a RANS CFD code’, CAV2009 ，Michigan, USA, 2009.

9.

S Ando, et al., ‘Study on the Hybrid Method of
CFD and Bubble Dynamics for Marine
Propeller
Cavitation
Noise
Prediction’,
CAV2108, Baltimore, USA, 2018.

10.

K Kimura, S Ando, S Matsuda, ‘Developmentof Advanced Flow Visualization Technology
using PIV and CFD’, Mitsui Engineering &Shipbuilding Co Technical Review No.212,
2014.

8.

AUTHORS BIOGRAPHY

basic design and R and D works and on ship’s
performance in rough sea, in Mitsui O.S.K. Lines, Ltd.
Susumu Takeuchi holds the current position of technicaladvisor for PBCF Department at MOL Techno-Trade,Ltd.
He is responsible for R&D and sales of PBCF at MOL
Techno-Trade. His previous experience includes shipplanning, designing and construction of new-building
vessels in Mitsui O.S.K. Lines, Ltd.
Norimichi Asanuma holds the current position ofgeneral manager for Technical Innovation Team,Technical Division at Mitsui O.S.K. Lines, Ltd.
He is responsible for R&D of technologies for reducing
environmental impact like PBCF. His previous
experience includes ship planning, designing andconstruction of new-building vessels and maintenance ofexisting vessels in Mitsui O.S.K. Lines, Ltd.

Koyu Kimura holds the current position of Director of
Research&Development Division at Akihima Laboratories (Mitsui Zosen) Inc.
He is responsible for R&D and design of hull form,
propeller, ESD at Akishima Laboratory. His previous
experience includes hull form, propeller design and R&D
on propeller cavitation noise in Akihima Laboratories(Mitsui Zosen) Inc.
Satoko Ando holds the current position of AssistantManager of Marine Engineering & Hydrodynamics
Department at Akihima Laboratories (Mitsui Zosen) Inc.
She is responsible for R&D and design of propeller, ESD
at Akishima Laboratory. Her previous experience
includes propeller design and R&D on propeller
cavitation noise in Akihima Laboratories (Mitsui Zosen)
Inc.
Shirou Ono holds the current position of generalmanager-technical of PBCF Department at MOL
Techno-Trade, Ltd.
He is responsible for R&D and sales of PBCF at MOL
Techno-Trade. His previous experience includes ship
basic design and R&D on ship in Mitsui Engineering &Shipbuilding Co., Ltd.
Yoshikazu Tanaka holds the current position ofmanaging director at MOL Techno-Trade, Ltd.
He is responsible for R&D Promotion and PBCF
development. His previous experience includes ship

© 2018: The Royal Institution of Naval Architects