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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 927
Study on the Prediction of Flow Characteristics Around a Ship Hull
K.-S.Min, J.Choi, D.Yum, K.Chung, B.Chang, S.Chung, B.Han
(Hyundai Heavy Industries, Korea)
ABSTRACT
A long term R & D Program on the prediction of flow characteristics around a ship hull has been established with the
aim of preparing a sufficiently accurate computational method for practical applications. This program is composed of 3-
stage studies. The 1st stage study on the investigation of the state-of-art of CFD technology has been carried out. For this
purpose, 4 CFD codes were selected. Using the selected codes, numerical computations have been performed for 5
different ships in 4 different ship types together with the experimental measurements. The comparisons between the
experimental results and the results of computation show that present CFD technology needs to be further improved for
practical applications.
INTRODUCTION
In order to improve the hydrodynamic performance of a ship, it is necessary to have the knowledge on the flow
characteristics around a ship hull and to utilize the knowledge in design. Two methods are available to predict the flow
characteristics—one is the experimental method, that is, model test, and the other is the computational method so called
computational fluid dynamics (CFD). The experimental method is to measure the items related to the flow characteristics
by model tests. This traditional method has long been used and has one definite advantage that comparatively accurate
results could be obtained. In general, however, this method needs longer time and higher cost. Furthermore, there are
some items which could not be measured by model tests. Those are disadvantages of the experimental method. The
computational method is to calculate the characteristics using nowaday's highly developed computers and CFD codes.
This method not only is economical in time and cost, but also could estimate some characteristics which are not possible
to be measured by model tests. Those are advantages of this method. In general, however, the computational method does
not have sufficient accuracy and reliability yet for the practical applications. This is the fatal disadvantage of the
computational method.
In order to improve the CFD technology for the prediction of flow characteristics around a ship hull, related studies
have been actively carried out in the world and International CFD Workshops have been held three times (Larssen 1980,
Larssen et al. 1991, Kodama 1994). Following the worldwide trend and necessity, Hyundai Maritime Research Institute
(HMRI) has established the long term R & D Program on this subject and has carried out the study. The ultimate goal of
the research program is to prepare a sufficiently accurate prediction method for the practical applications and to
efficiently utilize the method for the actual design and performance analysis.
This program is composed of 3 stage studies as follows:
- the 1st stage study: Investigation of the state-of-art of CFD technology
- the 2nd stage study: Improvement of CFD technology to the level of practical application
- the 3rd stage study: Study for the actual utilization
This paper deals with the 1st stage study of HMRI's long term R & D program and includes the following contents:
- Selection of CFD codes
- Calculation of flow characteristics
- Measurement of flow characteristics
- Comparison between test results and the results of calculation
- Evaluation
Therefore, the primary purpose of this study is in the validation of present CFD technology. After the full evaluation
of the 1st stage study, the future direction of the CFD study shall be established.
For the sake of universal validity in the result of the study, 5 different ships in 4 different ship type have been
selected as the object ships such as very large crude oil carrier and large-size bulk carrier as the
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 928
full slow-speed ship type, LPG carrier as the full medium-speed ship type, large-size container carrier as the fine medium-
speed ship type and naval ship as the fine high-speed ship type. Those ships were actually built and delivered in 1990's.
For the computational analysis, total 4 CFD codes were selected, that is 3 well-known commercial codes and HMRI
code. The three commercial codes are STAR-CD, FLUENT and SHIPFLOW. Initially, CFDSHIP_IOWA code was
included. However computation by CFDSHIP_IOWA code has not been progressed satisfactorily, and it was decided not
to include in this paper.
Enormous amount of computations and measurements have been carried out. Due to the limited space, however,
only the brief summary shall be presented and discussed in this paper.
NUMERICAL METHODS
The details and formulations of the numerical methodologies for CFD are well known and extensively documented
in many literatures. Hence, only main features of the methodologies will be described in this paper.
First of all, the dual coordinate systems have been adopted as shown in Fig. 1. The global coordinate system (x, y, z)
is defined to represent the flow patterns around hull as positive x in the flow direction, positive y starboard, and positive z
upward where the origin is at the bow and undisturbed free surface; while the local coordinate system (x′, y′, z′) to
enhance the usefulness of calculated wake patterns in the propeller designs where the origin is at the center of propeller.
The physical quantities in the paper are nondimensionalized by ship length between perpendiculars (LPP), ship speed
(UO), and fluid density (ρ).
Fig. 1 Coordinate System
Viscous flow
The numerical procedure presented in this paper deals with incompressible flows. The basic equations that govern
the flow are to describe the instantaneous conservation of mass and momentum. The time-dependent conservation
equations can be expressed in tensor notation as:
(1)
(2)
where Ui P, Re, are the velocity, piezometric pressure, Reynolds No., and Reynolds stress respectively.
In order to predict turbulent flows via the equations, it becomes necessary to make closure assumptions about the
Reynolds stress, because the equations do not constitute a closed set. The turbulence models and process of expressing the
Reynolds stresses in terms of the known quantities can be categorized into Reynolds stress model (RSM) and eddy
viscosity model (EVM).
In RSM, the partial differential equations for the Reynolds stresses are formulated and solved. The RSM includes the
effect of some important factors, such as the streamline curvature and the body force etc, on the characteristics of the
turbulence, but requires additional computation to solve the partial differential equations for the each components of the
stress. Furthermore it is still necessary to model some of terms in their equations. Alternatively algebraic stress model
(ASM) using the algebraic equations instead of the partial differential equations, on the assumption that convective and
diffusion terms in RSM is linearly dependent on the turbulence kinetic energy k, can be applied to several engineering
fields.
In the EVM, based on the Boussinesq's hypothesis, the Reynolds stresses are represented as mean velocity gradients.
The EVM are classed into zero, one, and two equation models according to the number of partial differential equations.
The most widely used model in engineering applications is the k-ε model in conjunction with the wall function
instead of the fine meshes near the wall surfaces.
In solving flow patterns around 3-dimensional bodies, it is convenient to use the boundary fitted Coordinate system.
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The partial differential equation to transform the physical domain into the computational domain must be solved,
governing equations also be transformed. This transformation can be divided into two ways: one is that both geometrical
and physical variables are transformed. The other is that only geometrical variables are transformed. From the
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 929
viewpoints of numerical procedures, the partial transformation is simpler, but invokes numerical errors when the
discrepancy between the flow stream and physical coordinate is large.
To solve the governing equations, the flow domain is subdivided into a finite number of cells and these equations are
changed into algebraic form via the discretization process such as Finite Difference Method (FDM), Finite Volume
Method (FVM), Finite Analytic Method. (FAM), Finite Element Methods (FEM) and so forth.
However, the governing equations are nonlinear and coupled forms of the continuity and momentum equations. And,
hence it is necessary to use an iterative procedure: SIMPLE (Semi-Implicit Method for Pressure-Linked Equations),
Artificial compressibility Methods, and PISO (Pressure Implicit with Splitting Operator) etc. The SIMPLE is one of the
most widely used procedures, but is less economical than the more recent PISO, especially in unsteady problems, because
with SIMPLE the iteration is required at each time step.
Before solving the equations, the grid inside flow domain must be generated. The grid pattern can be categorized
into structured and unstructured grids. The structured grids do not require special attention to define the connectivity
between cells because there is one-to-one correspondence between adjacent faces of neighboring cells. The unstructured
grids allow mesh mismatch on the interface between adjacent cells and/or blocks, thus locally enhancing the numerical
resolutions where required.
Potential flow
The flow is assumed steady, irrotational and incompressible. The potential of the disturbed velocities ( ) is
defined by equation (3) and will satisfy the Laplace equation (4):
(3)
(4)
On the hull boundary the normal velocity must be zero, and on the free surface boundary a similar relation holds.
This kinematic condition may be written as:
(5)
where h(x, y) is equation for the wavy surface.
A dynamic free surface condition may be obtained from the continuity of the stresses across the free surface. This
condition degenerates to the simple statements that the pressure must be atmospheric at the surface, and without the
generality this pressure may be set zero. Neglecting surface tension and applying the Bernoulii equation the dynamic free
surface boundary condition may be written:
(6)
Finally, the velocity is undisturbed at infinite:
(7)
These free surface boundary conditions are nonlinear and they have to be applied at an initially unknown surface.
Iteration procedure, using the solution on linearized boundary conditions, are generally adopted.
SELECTION OF CODES
For the sake of universal validity of this study, total 4 codes were selected, that is 3 well known commercial code
(STAR-CD, FLUENT, SHIPFLOW) and HMRI code. The characteristics of each code has been summarized in Table 1.
Table 1 Characteristics of CFD Codes
Characteristics HMRI STAR-CD FLUENT SHIP FLOW
Governing equation NS NS NS Zonal
Turbulence model KE MKE MKE KE
Near wall WF WF WF WF
Spatial discretization FVM FVM FVM FAM
Grid system S US US S
Variable layout SG NG NG SG
Velocity-pressure coupling SIMPLE PISO SIMPLE SIMPLER
NS: Full NS
Zonal: Potential/Integral/Full NS
KE: Standard k-ε
WF: Wall function
S: Structured
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SG: Staggered
MKE: Modified k-ε
US: Unstructured
NG: Non-staggered
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 930
EXPERIMENTAL METHOD
The model tests were conducted at the deep-water Towing Tank of HMRI. The size of the tank is 210x14x6 m in
length, width, and depth, respectively, with maximum carriage speed of 11m/s. The contents of the model tests,
measuring items, and data acquisition conditions to investigate the flow characteristics around a ship are shown in Table 2.
Table 2 Model Tests and Data Acquisition Conditions
Tests Measuring items Sampling rate Measuring time (sec)
Resistance Resistance 30 40
Local velocity Pressure 50 5
Wave Hull - -
Local 100 2
Global - 40
Hull pressure Pressure 20 15
Flow line Flow line - -
All the tests, except the resistance test, were carried out at the fixed model condition with zero sinkage and trim, and
were conducted at the design speed. During the measurements of wave elevation and local velocity, the model was moved
into the port by 300 mm for the gauges to be accessible.
Test description
During the resistance test the model was provided with no appendages and free in vertical motion except Destroyer
model ship. In the case of Destroyer model ship, the resistance tests were performed at the conditions with appendages
and without appendages. The towing point was located at LCB and KB.
For the global wave elevation measurements, the longitudinal cut method was utilized. Four wave gauges of
capacitance type with 50 mm interval were tied up in one unit, so that four lines of wave elevation data were obtained in a
single run. This holder was moved along a truss attached at the sidewall of the tank. Triggering signal is provided by an
optical switch at 4.62 m ahead of F.P. to identify the location. For the local wave elevation measurements, the probe of
servo-needle type was attached at a traversing mechanism and inclined by 45° to be accessible. To measure the wave
elevation along the hull surface, three persons read the wave profile and the average was taken.
For the local velocity measurements, a rake with five 5-hole Pitot tubes was used. The 5-hole Pitot tube had spherical
tip with 6 mm in diameter and the angle between axes of center hole and side holes was 30°. Each tube was connected to
a pressure transducer. The kinematic calibration range of the Pitot tubes was ±30° of pitch and yaw angle. If the flow
angle to be measured was out of the calibration range, the data was discarded. The measurements were carried out across
the centerplane to confirm the symmetry of flow.
The vertical holes to the hull surface with 3 mm in diameter were pierced for the measurements of the hull pressure.
The holes were on the keel line and on the station 2 and station 1 with 20 mm spacing.
The flow lines on the hull were visualized using paint. The paint was an appropriate mixture of dye, oil paint, wax,
and thinner. The optimum mixing rate will be obtained from the try-and-error.
Uncertainty analysis
The uncertainty analysis for the resistance test was performed by the recommendation of the 22nd ITTC resistance
committee. For the other tests, the bias and precision errors of the gauges; and precision errors of the measurements were
investigated. The accuracy of the model geometry (L, B, d) is (1, 1, 1) mm. The bias and precision errors of the gauges
are listed in Table 3. The residual flow of the tank is 0.001 m/s. In case of the wave elevation measurements of the hull
surface, the main error source comes from the human eye. The accuracy is within ±1.5 mm. The average value of the
standard deviations of the measurements for the local wave elevation and the hull pressure are 0.2 mm and 9.764 N/m2,
respectively.
Table 3 Error Sources of Instrumentations
Instrumentation Bias limit Precision index
Velocity (m/s) 0.001 0.0015
Dynamometer (N) 0.1 -
Thermometer (°C) 0.24 0.16
Wave probe (mm) 0.3 0.7
Traverse (mm) 0.1 1
Pressure transducer (psi) 0.00625 0.0057
SELECTION OF THE OBJECT SHIPS
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The object ships selected for measurements and numerical analyses comprise 300,00 TDW VLCC, 170,000 TDW
bulk carrier, 6,300 m3 LPG carrier, 4,200 TEU container carrier and 5,000 tonne destroyer. These five ships have
representative hull forms of full slow-speed, full medium-speed, fine medium-speed and fine high-speed ship, respectively.
Fig. 2 shows the body plans and side profiles of the ships. Table 4 and Table 5 show the principal
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 931
particulars of the objected ships and model propellers, respectively.
300,000 TDW VLCC is the KTTC (Korea Towing Tank Conference) standard ship for the study of flow
characteristics around the hull (Kim et al. 1999, Van et al. 1998 a-b, Choi et al. 1999). This ship is very similar to the ship
which was selected as the one of the test cases for the Gothenburg 2000, a workshop on CFD in ship hydrodynamics.
Other ships are either HHI (Hyundai Heavy Industries) standard ships or actual ships manufactured at HHI in 1990's.
Model ships were made of wood. In order to generate turbulent flow, the studs of cylindrical shape (3.2 mm in
diameter, 2.5 mm in height and 25 mm interval) were located at St. 19.5 and middle of the bulb for the ship models
having bow bulbs. For the destroyer model with no bulb, turbulent stimulators were located at 50 mm off the bow.
The scale ratio (λ) of the model ships is 47.56, 36.815, 14.959, 37.441, and 27.6 for 300,00 TDW VLCC, 170,000
TDW bulk carrier, 6,300 m3 LPG carrier, 4,200 TEU container carrier, and 5,000 tonne destroyer, respectively.
Table 4 Principal Particulars of the Object Ships
6,300 m3 LPG
300,000 TDW 170,000 TDW 4,200 TEU 5,000 tonne
VLCC bulk carrier carrier container carrier destroyer
LPP (m) 320.00 278.00 98.40 259.90 138.00
LWL (m) 325.50 283.00 99.69 265.80 138.00
B(m) 58.00 45.00 15.70 32.20 17.40
T(m) 20.8 16.5 6.0 11.5 4.7
S (m2) 27320 19044.1 2208.8 10742.4 2201.9
∇(m3) 312737.5 174274 7030 59526 5273
LCB (m, fwd+) 11.136 8.765 0.948 −4.277 −2.048
CB 0.8101 0.8443 0.7584 0.6185 0.4673
CP 0.8118 0.8465 0.7723 0.6499 0.6070
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 932
Fig. 2 Body Plans and Side Profiles
RESULTS AND DISCUSSIONS
The selected CFD codes and the flow characteristics to be calculated or measured have been summarized in Table 5.
Computations and measurements have been conducted according to Table 5 for each of 5 different ships, and a vast
amount of information for the flow characteristics have been prepared. Among them, the following characteristics shall be
presented selectively:
- resistance
- profile wave elevation
- local resistance
- velocity distribution
- limiting streamline
- pressure distribution
- wake (at the propeller plane)
Table 5 CFD Codes and Characteristic to Be Calculated or Measured
Characteristics H C F S M
○
○ ○ ○
○
Resistance Viscous
○
○
Wave X X X
○ ○
Overall X X X
○ ○
Wave Elevation Profile X X X
○
○
Local X X X
○
○
Global X X X
○
Local resistance X X X X
○ ○
○ ○ ○
Limiting streamline
○
○ ○
○
Velocity distribution ∆
○
○ ○
○ ○
Pressure distribution
○
○ ○
○
Boundary layer X
○ ○ ○ ○
○
Wake
In Table 5, the symbols of H, C, F, S, and M represent HMRI, STAR-CD, FLUENT, SHIPFLOW codes, and model
test, respectively
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 933
Resistance characteristics
Resistance and self-propulsion tests were conducted according to the ITTC Standard Procedure. Form factors were
determined using the resistance values measured at the low speed region. Resistance itself has been nondimensionalized
to resistance coefficients. Therefore, the total resistance coefficient for the model ship (CTM) can be represented by the
sum of viscous resistance coefficient (CVM) and wave resistance coefficient as shown in equation (8).
(8)
In equation (8), k and CFM represent form factor and frictional resistance coefficient, respectively.
In computational analysis, viscous resistance could be considered to be composed of two stress components which
are perpendicular and tangential to the ship hull, respectively. When two stress coefficients perpendicular to and
tangential to the hull are denoted by CVP and CVF, viscous resistance coefficient can be obtained as follows:
(9)
In equation (9), cvpx and cvfx are the perpendicular stress coefficient and the tangential stress coefficient acting on the
unit section of the hull, and can be expressed as follows:
(10)
(11)
The resistance coefficients obtained in this way have been summarized in Table 6. Table 7 shows the comparison of
resistance characteristics between test result and computed result. As shown in Tables 7 and 8, there are considerable
difference between computed and measured results. Futhermore, the results of computation are not consistent.
Particularly, the computed results of wave resistance by SHIPFLOW code differ from the test result very much. Even if
the contribution of wave resistance to total resistance at design speed is generally less that 2% for full slow-speed ships,
the reason of this discrepency should be investigated and improved. For practical purpose, any prediction method should
have at least ±3%, or preferably ±2% accuracy and precision.
Table 6 Comparisons of Resistance Characteristics between Model Tests and Numerical Calculations
Kind of Ship Method CVM CW CTM
300,000 TDW VLCC M 100.00 100.0 100.0
H 95.34 - -
C 98.93 - -
F 105.03 - -
S 93.23 1126.19 104.40
170,000 TDW bulk carrier M 100.00 100.00 100.00
H 99.17 - -
C 115.41 - -
F 78.08 - -
S 89.99 776.60 98.52
6,300 m3 LPG carrier M 100.00 100.00 100.00
H 83.97 - -
C 95.44 - -
F 103.99 - -
S 90.80 134.91 108.46
4,200 TEU container carrier M 100.00 100.00 1000.00
H 107.93 - -
C 98.65 - -
F 109.87 - -
S 103.39 343.33 120.99
5,000 tonne destroyer (without appendages) M 100.00 100.00 100.00
H 145.96 - -
C 96.71 - -
F 100.72 - -
S 100.66 93.67 97.64
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 934
Table 7 Resistance Characteristics (Model Scale)
CFM×103 CVM×103 CW×103 CTM×103
Kind of Ship Test Condition Method
300,000 TDW VLCC LM=6.728 m Model test 3.174 3.841 0.042 3.883
VM=1.156 m/s HMRI 3.662 - -
Re=0.73x107 STAR-CD 3.800 - -
FLUENT 4.034 - -
Fn=0.142
SHIPFLOW 3.581 0.473 4.054
170,000 TDW bulk carrier LM=7.551 m Model test 3.006 3.737 0.047 3.784
HMRI 3.706 - -
VM=1.272 m/s
Re=0.97×107 STAR-CD 4.312 - -
Fn=0.147 FLUENT 2.918 - -
SHIPFLOW 3.363 0.365 3.728
6,300 m3 LPG carrier LM=6.578 m Model test 2.976 3.705 2.475 6.180
VM=1.995 m/s HMRI 3.112 - -
Re=1.03×107 STAR-CD 3.536 - -
Fn=0.249 FLUENT 3.853 - -
SHIPFLOW 3.364 3.339 6.703
4,200 TEU container carrier LM=6.942 Model test 2.821 3.038 0.240 3.277
VM=2.018 m/s HMRI 3.279 - -
Re=1.40×107 STAR-CD 2.997 - -
Fn=0.239 FLUENT 3.338 - -
SHIPFLOW 3.141 0.824 3.965
5,000 tonne displacement destroyer (without LM=5.0 m Model test 2.952 3.340 2.545 5.885
appendages) VM=2.981 m/s HMRI 4.875 - -
Re=1.10×107 STAR-CD 3.230 - -
Fn=0.425 FLUENT 3.364 - -
SHIPFLOW 3.362 2.384 5.746
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 935
Wave profile
Fig. 3 shows the comparison of wave profile between measured result and computed result by SHIPFLOW code. As
shown in Fig. 3, two results agree well except in the forward part and the aft part. As well known, however, even the
linearized potential theory predicts wave profile very well. For the regions apart from the hull, particularly in the wake
region, the computed result shows the exaggerated wave elevation for all kinds of ship.
Fig. 3 Comparison of Profile Wave Elevation
Fig. 4 Longitudinal Distribution of Local Viscous
Resistance Components by HMRI Code
Local resistance
Fig. 4 shows the local resistance coefficients predicted by HMRI code. Since it was not possible to be calculated by
other codes, comparisons could not be made. However, it could be deduced that the component due to perpendicular to
ship hull is dominent in the foreward and aft parts while the component due to friction is dominent in the middle region.
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 936
Velocity distribution
Fig. 5 shows the axial velocity distribution for 300,000 TDW VLCC at the longitudinal position of station 1(x=0.95).
Due to rapid change in hull shape, there exists low speed region in aft part. This region could be well measured by
experiment. In general, however, the computations do not show this region clearly. Particularly, the compution by HMRI
code shows comparatively thicker boundary layer thickness and slower velocity gradient.
Fig. 5 Axial Velocity Contours of 300,000 TDW VLCC at the Station 1 (x=0.95)
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 937
Limiting streamline
Fig. 6 shows the measured and the computed limiting streamlines for 6,300 m3 LPG carrier. It is clearly shown in
Fig. 6 that the measured streamlines are directed downward in the forward part and upward in the aft part. However, the
angle of computed streamlines with respect to free-surface is not as steep as that of measured in the forward part. In the
aft part, the computed stremlines are concentrated to the propeller shaft region rather than direced upward (particularly,
those from HMRI and SHIPFLOW codes). Furthermore, the computations by STAR-CD and FLUENT codes show flow
separation in the wide region of aft part. The results from SHIPFLOW code also show this phenomenon weakly.
However, this separation phenomenon has not been shown in the results of paint test. The method of paint test is not
sufficient to validate the separation and further study is necessary.
3
Fig. 6 Limiting Streamlines for 6,300 m LPG Carrier
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 938
Pressure distribution
Pressure measurements on the hull suface have not been carried out yet, except on the keel line. However,
computations have been performed for all CFD codes. Fig. 7 shows the comparison of pressure distribution on the keel
line for 3 selected ships and Fig. 8 shows the computed pressure contours on the hull for 170,000 TDW bulk carrier. In
general, the characteristics of pressure distribution is in accordance with the direction of the limiting streamlines. It is
shown in Fig. 8 that rapid pressure changes occur in the forward and aft parts where hull shape changes rapidly and that
the rate of pressure change is greater in the forward region than in the aft region.
Fig. 7 Pressure Contours on the Hull for 170,000 TDW Bulk Carrier
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 939
Fig. 8 Pressure Distribution on the Keel Line
Wake (at the propeller plane)
Fig. 9 and 10 show the axial velocity contours (wake) and velocity vectors on the propeller plane for 170,000 TDW
bulk carrier and 4,2000 TEU container carrier. It is not easy to make a definite comparison between the measured and the
computed results with these figures. Therefore, the radial distribution of mean axial velocity, that is, the circumferentially
averaged radial distribution of axial velocity has been prepared, because this information is used in the actual propeller
design. It has been found that there are rather big differences between the test results and the computed results which
could not be accepted in the practical purpose.
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Fig. 9 Axial Velocity Contours and Velocity Vectors on the Propeller Plane for 170,000 TDW Bulk Carrier
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STUDY ON THE PREDICTION OF FLOW CHARACTERISTICS AROUND A SHIP HULL 940
Fig. 10 Axial Velocity Contours and Velocity Vectors on the Propeller Plane for 4,200 TEU Container Carrier
CONCLUSIONS
The flow characteristics around a ship hull were investigated through the numerical and experimental methods. For
the numerical analysis, four CFD codes (STAR-CD, FLUENT, SHIPFLOW and HMRI) were used. These numerical
results were compared with those of model tests. The object 5 ships were actually built in 1990's.
In general, the comparison between numerical analyses and model tests showed rather large discrepancies and lack
of consistency both quantitatively and qualitatively. Further improvements in the accuracy and the precision of the codes
are necessary in order to be used for the practical applications in the prediction of flow characteristics and hull form
design. And it is also necessary to know the flow characteristics in the full scale of a ship by the numerical and
experimental methods.
Among the four selected codes, only SHIPFLOW can treat the free surface effect using the potential flow theory
based on the Rankine panel method. Large differences between analyses and model tests were especially shown for wave
pattern around the stern of a ship. The effects of the free surface to the flow characteristics around a ship will be more
clearly concluded later after further analyses using the free-surface viscous code based on RANS equations.
As was mentioned in the Chapter of Introduction, the 2nd and the 3rd stage studies will be carried out based on the
results of present study.
REFERENCES
Choi, J.E., Seo, H.W., Han, B.W., ‘Experimental Study on the Flow around a Full Slow-Speed Ship', Proc. of JAKOM'99, 4th Japan-Korea Joint
Workshop on Ship & Marine Hydrodynamics, Fukuoka, 1999.
Kim, W.J., Kim, D.H., Van, S.H., “Calculation of Turbulent Flows around VLCC Hull Forms with Stern Frameline Modification”, Proc. of the 7th
International Conference on Numerical Ship Hydrodynamics, Nantes, 1999.
Larsson, L. (editor), “SSPA-ITTC Workshop on Ship Boundary Layers”, SSPA Publication No. 90, 1980.
the authoritative version for attribution.
Larsson, L., Patel, V.C., and Dyne, G., “Ship Viscous Flow—Proceedings of 1990 SSPA-CTH-IIHR Workshop”, Flowtech International AB,
Gothenburg, Sweden, 1991.
Kodama, Y. (editor), “Proceedings of CFD Workshop Tokyo 1994”, Tokyo, Japan, 1994.
Van, S.H., Kim, W.J., Kim, D.H., Lee, C.J., “Experimental Study on the Flow Characteristics around VLCC with Different Stern Shape”, Proc. of the
3rd International Conference on Hydrodynamics (ICHD), Seoul, 1998.
Van, S.H., Kim, W.J., Yim, G.T., Kim, D.H., Lee, C.J., “Experimental Investigation of the Flow Characteristics around Practical Hull Forms”, Proc. of
3rd Osaka Colloquium on Advanced CFD Applications to Ship Flow and Hull Form Design, Osaka, 1998
Representative terms from entire chapter:
ship hull
